Building Soil for Your Dirt Locker Slope: A Regional Guide

In this guide 1. Why the soil in your Dirt Locker matters 2. How to identify your native soil: clay, sandy, rocky, or loam 3. Soil, compost, and fill products you can buy, explained 4. Best soil ingredients for Dirt Locker hillside planting 5. What not to put in your fill: peat moss, bark, sand, and more 6. How to buy bulk or bagged soil 7. Regional guide: soil, native plants, and local suppliers by region 7.1 Ecoregions and USDA zones at a glance 7.2 Pacific Northwest 7.3 California (eight subregions) 7.4 Desert Southwest 7.5 Rocky Mountains and Intermountain West 7.6 Texas and the Southern Plains 7.7 Midwest and Great Lakes 7.8 Southeast and Appalachian Piedmont 7.9 Northeast and Mid-Atlantic 8. Where to buy: local suppliers first, big box checklist 9. Frequently asked questions 10. Works Cited 1. Why the soil in your Dirt Locker matters The soil you fill your Dirt Locker with decides how quickly native plants root in, and those roots are what hold your slope once the system has done its first job. Dirt Locker is an erosion control and hillside gardening system built from recycled, food-grade milk jugs. It installs without heavy equipment or permitting, and the jugs are shaded from the sun as plants grow in over time, leaving a planted habitat and a strong foundation for the slope. Most installs need fill brought in: bagged or bulk topsoil, compost, or a soil conditioner. This guide covers which soil to buy for your region and native ground, which ingredients are worth adding, what to leave out, and where to shop, with local and regenerative suppliers listed first. Plant lists favor natives with a mix of root depths and textures. University of Rhode Island research on roadside slopes found that deep-rooted species anchor a slope while fast-spreading species stop surface erosion and slow runoff, and that when root mass sits in a shallow mat, failure is likely beneath the mat ("Potential Solutions"). Pairing a deep taproot, a fibrous grass root, and a woody shrub root on the same slope covers both jobs. 2. How to identify your native soil: clay, sandy, rocky, or loam A jar test on the ground under your slope sorts it into sand, silt, and clay, and that ratio tells you what the fill in your Dirt Locker needs to do. Dig 6 to 8 inches down, clear out stones and roots, half fill a quart jar with soil, cover it with water, and shake. Sand settles in a minute or two, silt after about an hour, and clay can take hours to days (WSU Extension Lewis County). Divide each layer's height by the total height to get percentages, then find the match on a soil texture triangle (Jeffers). Loam falls at roughly 30 to 50 percent each of sand and silt and 20 to 30 percent clay (Phipps). The jar test shows texture only. A lab test through your county extension office shows nutrients and pH (Phipps). Native plants usually do better in lean soil. The Colorado Native Plant Society notes that natives often grow well in unamended ground, that very rich soil can leave them overgrown or short-lived, and that sandy or rocky soil benefits from about 3 percent compost by volume while clay takes about 10 percent compost plus 15 percent small aggregate for in-ground planting (CoNPS). Arizona extension makes a similar point for desert natives, which generally do not need manure, fertilizer, or compost added (Cochise County Master Gardener Newsletter). Starting recipe for the fill. Because the pockets hold mostly imported soil, a reasonable starting mix is 70 to 80 percent screened loam-type topsoil, 10 to 20 percent finished compost, and 5 to 15 percent coarse mineral on clay or wet sites only. This is a range built from the sources above, not a lab-tested formula, so confirm it with a soil test and your county extension office. Native soil How it behaves on a slope What the fill should do Clay Holds moisture and swells, so water sheds as runoff and roots can drown (Medford) Add finished compost for structure and a small share of coarse mineral such as pumice or small aggregate. Skip sand, which packs with clay into a dense, concrete-like mix (Chalker-Scott). Rocky or sandy Drains fast and changes temperature quickly (Phipps); holds few nutrients Use a loam-based topsoil plus compost to hold moisture and nutrients. Leave out extra grit or perlite. Loam Balanced drainage and water holding (Jeffers) Top up with a modest amount of compost and leave everything else out. Match the fill to the slope. Linda Chalker-Scott's research on amended planting holes found that backfill that differs sharply from the surrounding soil can hold water at the boundary and keep roots circling inside the rich pocket instead of moving into native ground (Chalker-Scott, "Myth of Soil Amendments"). Her advice applies most to trees and shrubs in planting holes, but the same texture contrast can appear between Dirt Locker fill and the slope behind it. Keep the mix in the same texture family as your native soil, with compost as a modest share. 3. Soil, compost, and fill products you can buy, explained Yards and garden centers sell the same few products under many names, and only some belong in a Dirt Locker pocket. What it is In the Dirt Locker pockets Subsoil dug from grading and construction sites, usually unscreened and low in organic matter, sometimes with sand, rock, or stone (Total Landscape Care; Hello Gravel) No. It is sold to raise grade and is never the layer plants root into (Hello Gravel). Natural surface soil. Composition and quality vary widely (UF/IFAS), so ask for screened material and its texture. Yes, as the mineral base. Choose a texture close to your native soil. Decomposed organic matter that feeds soil microbes and improves drainage and water retention (Pokorny) Yes, as the organic share. Look for STA certified or OMRI listed. A regulatory term. Colorado treats it as a synonym for soil amendment and excludes compost and treated manures sold without conditioner claims (8 CCR 1202-4). The bag can hold peat, wood chips, compost, manure, biosolids, or minerals (CSU Extension). Only after you read the ingredient list. The word alone says nothing about what is inside. Cow, horse, or poultry manure composted with high-carbon material. Salt levels run higher than in raw manure (CSU Extension), and chicken or steer manure can carry antibiotic residue (UC Master Gardener handout). Sparingly or not at all. Native plants do better in lean fill. Spent mushroom-farm substrate; see the ingredient table above. A small share on mildly acidic soil only. Topsoil with compost added. Colorado defines planting mix as a material suitable for holding and growing plants that may include small amounts of fertilizer (Colorado Department of Agriculture). GreenWaste's bulk planting mix blends compost, topsoil, and sand (GreenWaste). Often the closest ready-made match to the starting recipe. Ask for the soil-to-compost ratio and whether it contains peat or bark. A cross between potting soil and garden soil that often contains more peat (UC Master Gardener handout); raised-bed soils are meant to be light and well drained (Iowa State Extension) Usually no on a slope. Accept it only if topsoil is the first ingredient. Usually soilless, built on peat or coir with perlite and compost (UF/IFAS Pasco) No. It is made for containers. Treated sewage sludge. The main concerns are heavy metals, pathogens, and salts, and CSU advises only Grade 1 biosolids (CSU Extension). Ask the supplier and pass if unsure. Mixes made to a specification for stormwater projects (GreenWaste) Only if a landscape supplier recommends one for your slope. Surface cover Surface only, never mixed into the fill. Mineral components Pumice in small amounts; skip sand on clay. See the ingredient table. A ready-made bulk garden blend plus screened topsoil is the simplest route: blend them yourself at the ratios in the starting recipe and adjust for your native soil. 4. Best soil ingredients for Dirt Locker hillside planting Finished compost does most of the work, and each ingredient below solves one specific problem. Ingredient What it does Best use Watch for Finished compost Feeds soil microbes and improves drainage and water retention, though it breaks down faster than peat (Pokorny) The main organic ingredient in every mix Buy mature, screened compost. Producers in the Seal of Testing Assurance program publish maturity, stability, heavy metal, and pathogen results (City of Boise), so ask for the report. Pumice Heavy volcanic rock that stays mixed in and keeps air space longer than perlite (Grow Organic). Desert Survivors uses pumice or volcanic cinder in its native plant mixes (Desert Survivors). Clay, and any slope that needs drainage Supplier guidance runs about 10 to 30 percent of the mix (LGR). Use less on loam. Perlite Lightweight expanded volcanic glass for aeration and drainage (Grow Organic) Pockets that stay too wet Light enough to migrate to the surface (Grow Organic), so pumice is the safer pick on a steep slope. Coconut coir The closest replacement for peat (Pokorny) Holding water in fast-draining sand Shipping uses fossil fuel. Blend it with compost instead of using it alone. Mushroom compost High organic matter and strong water holding, with high soluble salts (Chatterson) Small amounts on mildly acidic soil low in organic matter (RHS) Spent mushroom compost can carry up to 30 percent chalk and may contain peat (RHS). Skip it on alkaline ground, around seedlings, and for salt-sensitive plants (Wang). Kelp meal A trace mineral source with negligible nitrogen, phosphorus, and potassium; about 1 pound per 100 square feet (CSU Extension) Micronutrients Not a fertilizer on its own. Fish meal, fish bone meal Dried, ground fish by-products; fish meal runs roughly 8 to 10 percent nitrogen and 6 percent phosphorus (San Diego Master Gardeners) Slow nitrogen and phosphorus on lean fill Strong smell. Fish bone meal analysis varies by brand, so read the bag. Alfalfa meal Plant-based nitrogen at about 2-1-2, released moderately fast (Sideman) A mild nitrogen boost Skip it in fill that is already fertile. Blood meal Very quick-release nitrogen at 12-0-0 (Sideman) Only when a soil test shows low nitrogen Can burn plants (CSU Extension). Bone meal Phosphorus source at roughly 15 percent, slow release (Pandian) Only when a soil test shows low phosphorus Attracts animals (Espace pour la vie), which can dig up a new planting. Treat blood, bone, fish, and alfalfa meals as optional. Native prairie plants tolerate infertile soil and often do better without fertilizer, which mostly feeds fast-growing weeds (Savoy Prairie), so let a soil test decide whether any are needed. 5. What not to put in your fill: peat moss, bark, sand, and more Six materials show up in bagged soils and old gardening advice, and each one works against a planted slope. Peat moss. Peat is low in nutrients, acidic, and does little for soil microbes, and harvesting it releases carbon that bogs have stored for more than 10,000 years while destroying habitat (Pokorny). Peat is also hard to wet on its own, which is why bagged mixes add wetting agents (UMass Extension). Read labels, because peat turns up in garden soils and some mushroom composts (RHS). Heavy bark, wood chips, and sawdust mixed into the fill. As microbes break down low-nitrogen wood, they temporarily pull nitrogen out of the soil, and fine particles mixed into soil do this most (OSU Extension). A North Carolina gardening column lists hardwood bark, sawdust, and wood chips among materials that do not improve clay (Blackwelder). Coarse chips laid on the surface are a different use, and OSU recommends that use (OSU Extension). Check that they stay put on your slope. Sand added to clay. Sand has to make up nearly half the volume before a mix behaves like sandy soil, and smaller amounts produce a denser mix (Chalker-Scott). A gravel layer "for drainage." Coarse material under finer soil slows water and creates a perched water table above it (Soil Myth Busting). Potting, raised-bed, and moisture-control mixes. These are often soilless, built on peat or aged bark (Mississippi State Extension), and may include fertilizer prills, wetting agents, and polymer gel (UMass Extension). The pockets need mineral soil. Fill that is too rich. Natives grown in very fertile soil can end up overgrown or short-lived (CoNPS). 6. How to buy bulk or bagged soil Bulk soil is easier to inspect and usually cheaper per cubic yard, and bagged soil makes sense when a truck cannot get near the slope. Bulk. Bulk material is sold by the cubic yard (27 cubic feet) and delivered by dump truck or picked up from a yard. You can see and feel it before it goes on the hill, and municipal and regional composters often sell tested compost directly. The City of Boise, for example, listed bulk compost at $5.43 per cubic yard for 2025 agreements, with test results posted (City of Boise). Raleigh's Yard Waste Center sells compost that is both OMRI listed and STA certified (City of Raleigh). Plan a drop spot near the slope, then move material up by bucket or wheelbarrow. Bagged. Bags are easier to carry up a steep slope and to buy in small amounts, but you cannot see inside before you open one (Epic Gardening). A bag labeled "garden soil" can range from topsoil with compost to mostly bark, so read the ingredient list. Questions to ask a bulk supplier What is in this product by volume, and is it screened? Is it STA certified or OMRI listed, and can I see the latest test report? Has it been tested for persistent herbicides? Testing is optional in some states (NC DEQ). Does it contain peat, bark fines, or wood? Do you carry a loam or sandy-loam topsoil to blend with it? To size an order, multiply the fill volume of one Dirt Locker unit by the number of units, convert to cubic feet, and divide by 27 for cubic yards. Add a margin for settling. 7. Regional guide: soil, native plants, and local suppliers by region Each region below lists the soils you are most likely to meet, how to adjust the fill, native plants that cover a range of root types, and local suppliers to try before a big box store. This version covers the lower 48 in eight regions and does not yet cover Alaska, Hawaii, or Florida. Two cautions apply everywhere. Established vegetation cannot hold a steep slope when other landslide forces are present, and the University of Washington's Miller Library advises expert input for serious slope problems (Miller Library). Also, plant notes combine the cited sources with general growth habits, so confirm each species and local ecotype with your state native plant society or the Native Plant Information Network before you buy. 7.1 Ecoregions and USDA zones at a glance The eight regions loosely follow the EPA's ecoregions and the 2023 USDA hardiness zones, so use whichever system you know best. Ecoregions group land by similar geology, landforms, vegetation, climate, and soils. The EPA divides North America into 15 broad Level I regions, 50 Level II regions, and 182 Level III regions (EPA). USDA zones are narrower: they rank only the average coldest winter temperature, in 10-degree bands with 5-degree half zones, and the 2023 map uses 1991 to 2020 data (Britannica). Zones say nothing about rainfall, summer heat, or soil, so use them alongside the soil advice above. Guide region EPA Level I ecoregion Example Level III ecoregions Approximate USDA zones Pacific Northwest Marine West Coast Forest; Cascades slopes sit in Northwestern Forested Mountains Coast Range, Puget Lowland, Willamette Valley (Wikipedia) 8a to 9b, with 10a pockets on the coast (Bob Vila) California Mediterranean California; Sierra and Cascades in Northwestern Forested Mountains; southeast in North American Deserts Central California Valley, Central California Foothills and Coastal Mountains, Sierra Nevada (Gardenia) 5a to 11a statewide; see the California subregions below Desert Southwest North American Deserts Sonoran Basin and Range, Chihuahuan Deserts, Mojave Basin and Range About 6b at high elevation to 10b in the low desert Rocky Mountains and Intermountain West Northwestern Forested Mountains; basins in North American Deserts Southern Rockies, Northern Rockies, Idaho Batholith, Wyoming Basin About 3b to 7b Texas and Southern Plains Great Plains; Eastern Temperate Forests in the east Texas Blackland Prairies (Wikipedia), Edwards Plateau, Cross Timbers About 6b in the Panhandle to 10a near the Gulf Midwest and Great Lakes Eastern Temperate Forests; Great Plains in the west; Northern Forests in the far north Central Corn Belt Plains, Western Corn Belt Plains, Driftless Area, Northern Lakes and Forests About 3b to 7a Southeast and Appalachian Piedmont Eastern Temperate Forests Piedmont, Blue Ridge, Southeastern Plains (Izel Plants) About 6a in the mountains to 9a on the coastal plain; most of the Piedmont sits near 7b to 8a Northeast and Mid-Atlantic Eastern Temperate Forests; Northern Forests in northern New England Northeastern Highlands, Northeastern Coastal Zone, Atlantic Coastal Pine Barrens About 4a to 8a, colder in far northern Maine Treat the zone ranges as approximate. Look up the exact zone for your ZIP code on the USDA Plant Hardiness Zone Map, and find your ecoregion on the EPA ecoregion maps by state. Alaska, Hawaii, and Florida are not covered yet. 7.2 Pacific Northwest (western Washington and Oregon) Ecoregion and zone. EPA Level I: Marine West Coast Forest, with Cascades slopes in Northwestern Forested Mountains. USDA zones: about 8a to 9b, with 10a pockets on the coast. Soil and fill. Steep slopes and regular rain make erosion the main risk in western Washington (Green Kirkland Partnership). Use a loam-based topsoil with a modest share of finished compost, keep peat out of the mix (Oregon State is the source for the peat concerns above), and avoid compacting wet fill. If a soil test shows acidic soil low in organic matter, a small amount of mushroom compost can suit it (RHS). Plant Habit and root role Vine maple (Acer circinatum) Woody-root shrub used for slope stabilization, including on eastern-facing slopes (Green Kirkland Partnership) Red-osier dogwood (Cornus sericea) Controls erosion at stream edges and other wet sites (Rose) Red elderberry (Sambucus racemosa) Shallow-root shrub palette (Green Kirkland Partnership) Snowberry (Symphoricarpos albus) Thicket-forming shrub for erosion control (Green Kirkland Partnership) Sword fern (Polystichum munitum) Evergreen fern from a woody rootstock that works as a groundcover in shade (Hampton) Spike bentgrass (Agrostis exarata) Native grass with a fibrous root system, suggested for King County erosion plantings (Hampton) Cascade barberry (Mahonia nervosa) Evergreen groundcover (Hampton) Local and regenerative sources King County native plant nursery list and the UW Miller Library list of PNW native sources, including MsK Rare and Native Plant Nursery in Shoreline. Cruising Climate, a Port Townsend native plant nursery and regenerative landscape design studio. Corner Nursery in Chimacum, which stocks Pacific Northwest natives and bulk compost. SeaCoast Compost, a biodynamic compost made from fish carcasses, crab and shrimp shells, cow manure, and red alder, sold in bulk and bags. East Multnomah SWCD Conservation Directory for Portland compost and native plant retailers, and the Marion SWCD supplier list for the Salem area. 7.3 California (eight subregions) California spans USDA zones 5a to 11a (Gardenia), and the Jepson eFlora divides the state into 35 bioregions (Jepson eFlora). For soil and plant choices, eight practical subregions work better than one statewide answer. Subregion Conditions and zones Fill approach Slope plants North Coast and Klamath (Eureka, Fort Bragg, Crescent City) Zones 8b to 10a; cool summers, heavy rain, frequent fog (Gardenia) Loam-based topsoil with modest compost; avoid compacting wet fill Coyote brush, coffeeberry, ceanothus, manzanita (UC Master Gardeners of Marin) Cascades and Modoc Plateau (Redding to Alturas) Cold winters and dry summers; roughly zones 5a to 8b (approximate) Lean, well-drained fill with little compost Antelope bitterbrush, greenleaf manzanita (Hampton) Sierra Nevada foothills and high Sierra (Auburn, Placerville, Tahoe) Zones 5a to 9a; late frosts and short seasons at elevation (Gardenia) Lean loam with compost near the low end of the starting recipe Greenleaf manzanita, antelope bitterbrush (Hampton) Great Central Valley (Sacramento to Bakersfield) Zones 8a to 10a; hot dry summers, cool damp winters (Gardenia) Loam-based fill with modest compost; slopes appear mainly in the foothills and levees California buckwheat, coyote brush, western redbud, elderberry Central Coast and San Francisco Bay (Napa, Santa Cruz, San Jose) Zones 9a to 10b with strong microclimates (Gardenia); much of the soil is slow-draining clay (UC Master Gardeners of Marin) Compost plus a small share of pumice; skip sand Coyote brush, California buckwheat, coffeeberry, coastal sagebrush, California fescue, creeping sage South Coast, Channel Islands, and Peninsular Ranges (Santa Barbara to San Diego) Zones 9b to 11a; very mild winters, dry summers, marine layer (Gardenia) Loam-based fill with compost for water holding; add pumice only on clay Coastal sagebrush, California buckwheat, lemonade berry, toyon, matilija poppy, bladderpod (Hampton) East of the Sierra and Great Basin (Bishop, Mono Basin) Cold winters and low rainfall; roughly zones 5b to 8a (approximate) Lean, fast-draining fill Antelope bitterbrush, eastern Mojave buckwheat (Hampton) Deserts (Mojave and Colorado Desert: Palm Springs, Imperial Valley) Zones 9b to 11a; extreme summer heat (Gardenia) Follow the Desert Southwest advice: pumice or cinder, compost added yearly, no mushroom compost Desert willow, desert ceanothus, eastern Mojave buckwheat, bladderpod (Hampton) On clay, the California NRCS guidance behind the Marin advice calls for deep, spreading root systems and a mix of groundcovers, perennials, shrubs, and trees (UC Master Gardeners of Marin). Hampton notes that root structure is not well documented for many California natives and recommends mixing several plant types on a slope (Hampton). Plants that work in most subregions Plant Habit and root role California buckwheat (Eriogonum fasciculatum) Low shrub with deep, spreading roots (UC Master Gardeners of Marin) Manzanita (Arctostaphylos spp.) Woody shrub on the NRCS slope list (UC Master Gardeners of Marin) Coffeeberry (Frangula californica) Woody shrub on the NRCS slope list (UC Master Gardeners of Marin) Ceanothus (Ceanothus spp.) Woody shrub on the NRCS slope list (UC Master Gardeners of Marin) Coyote brush (Baccharis pilularis) Spreading groundcover shrub (UC Master Gardeners of Marin) California fescue (Festuca californica) Native bunchgrass with fibrous roots (Hampton) Coastal sagebrush (Artemisia californica) Shrub recommended for southern California erosion plantings (Hampton) Local and regenerative sources CNPS Santa Clara Valley list of native plant sources, which includes Las Pilitas Nursery, Oaktown Native Plant Nursery, and Mission Blue Nursery. The Watershed Nursery in Richmond, which reports 100 percent native inventory, and Mostly Natives Nursery in Tomales. Tarweed Nursery in Los Angeles, which grows local natives from nearby seed and cuttings. The Theodore Payne Foundation erosion control page and the CNPS guidance on planting hot, dry slopes. StopWaste's directory of Bay Area bulk compost sources and GreenWaste's Zanker Landscape Materials Yard in San Jose, which sells OMRI listed compost. 7.4 Desert Southwest (Arizona, New Mexico, southern Nevada and Utah) Ecoregion and zone. EPA Level I: North American Deserts (Sonoran Basin and Range, Chihuahuan Deserts, Mojave Basin and Range). USDA zones: about 6b at high elevation to 10b in the low desert. Soil and fill. Arizona soils carry very little nitrogen or organic matter (Cochise County Master Gardener Newsletter), and caliche, a cemented calcium carbonate layer, can limit how far water moves into the soil below (NMSU). When a planting cannot get through caliche, University of Arizona Extension suggests adding enough soil to give about two feet of rooting depth (UA Extension). Warm summers and alkaline soil break organic matter down fast, so plan to add compost every year (Yavapai County Extension). Use sandy-loam topsoil with modest compost and pumice or volcanic cinder, and skip mushroom compost and peat. Plant Habit and root role Spike dropseed (Sporobolus contractus) Native grass; NRCS lists its Cochise germplasm for erosion control (NRCS) Arizona cottontop (Digitaria californica) Native bunchgrass of oak woodland, chaparral, and semi-desert grassland (NRCS) Desert zinnia (Zinnia acerosa) Low native shrublet found at 2,300 to 6,200 feet (NRCS) Velvet mesquite (Prosopis velutina) Native tree with deep roots, grown at Desert Survivors (KGUN 9) Local and regenerative sources Desert Survivors in Tucson grows bioregionally native plants and builds its soil mixes with pumice or volcanic cinder. Borderlands Nursery and Seed, Native Seeds/SEARCH, and Flagstaff Native Plant and Seed are listed on the same regional nursery directory. Soilutions in Albuquerque sells bulk compost, soil, and mulch. University of Arizona Extension's Managing Caliche in the Home Yard. 7.5 Rocky Mountains and Intermountain West (Colorado, Utah, Wyoming, Idaho, Montana) Ecoregion and zone. EPA Level I: Northwestern Forested Mountains (Southern Rockies, Northern Rockies, Idaho Batholith) and desert basins such as the Wyoming Basin. USDA zones: about 3b to 7b. Soil and fill. Colorado soils are generally low in organic matter and alkaline, and the Colorado Native Plant Society recommends about 3 percent compost by volume for sandy or rocky ground and 10 percent compost plus 15 percent small aggregate for clay (CoNPS). Because the pockets hold mostly imported soil, stay near the low end of the compost range in the starting recipe, skip mushroom compost and peat, and start with a soil test through your CSU Extension office. Plant Habit and root role Little bluestem (Schizachyrium scoparium) Deep-rooted native grass with seasonal color (Rivendell) Indian grass (Sorghastrum nutans) Deep-rooted native grass common in restoration (Rivendell) Switchgrass (Panicum virgatum) Tall bunchgrass; one seed supplier reports roots of nine feet or more in mature plants (Nature's Seed) Rubber rabbitbrush (Ericameria nauseosa) Native shrub profiled by Front Range Wild Ones (Wild Ones Front Range) Rocky Mountain juniper (Juniperus scopulorum) Evergreen woody native profiled by Wild Ones (Wild Ones Front Range) Chokecherry (Prunus virginiana) Thicket-forming native shrub profiled by Wild Ones (Wild Ones Front Range) Red twig dogwood (Cornus sericea) Native shrub for moister pockets (Wild Ones Front Range) Native sedges (Carex spp.) Fibrous-rooted, grass-like cover (Wild Ones Front Range) Local and regenerative sources Harlequin's Gardens in Boulder, a native plant nursery that reports neonicotinoid- and pesticide-free plants. Western Native Seed in Coaldale, and the Colorado Native Plant Society vendor list. High Plains Environmental Center in Loveland and Wyoming Plant Company in Casper. A1 Organics, a Colorado composter with STA certified compost that processes Denver's curbside compost. City of Boise compost for the Treasure Valley. 7.6 Texas and the Southern Plains Ecoregion and zone. EPA Level I: Great Plains (Texas Blackland Prairies, Edwards Plateau, Cross Timbers), with Eastern Temperate Forests in the east. USDA zones: about 6b in the Panhandle to 10a near the Gulf. Soil and fill. Texas soils change within short distances: one Wildflower Center answer describes heavy clay at the base of a hill and three feet of sand at the top (Hampton), Central Texas seed collections record limestone-based clays such as Crawford clay (Wildflower Center Seed Bank), and eastern sites can be sandy loam (Tomme). Run the jar test, match the fill to your texture family, and skip mushroom compost on chalky limestone soils. The City of Austin's guide to choosing landscape products covers compost, amendments, native plants, and slopes. Plant Habit and root role Little bluestem (Schizachyrium scoparium) Fibrous-rooted bunchgrass suggested for a Fort Worth clay slope (Wildflower Center) Indiangrass (Sorghastrum nutans) Tall bunchgrass recommended for full-sun clay slopes (Larson) Texas sedge (Carex texensis) Grass-like cover recommended for full-sun clay slopes (Larson) Bluewood (Condalia hookeri) Thicket-forming shrub with a taproot and deep root system (Texas Master Gardeners) Southern dewberry (Rubus trivialis) Trailing native on the Houston chapter's erosion list (Hampton) Local and regenerative sources The Natural Gardener, Garden-Ville, Geo Growers, Countryside Nursery, and McIntire's Garden Center are Central Texas shops focused on organic practice and native or hardy species. Garden-Ville says it still loads bulk product at all its locations (Angi). Native Plant Society of Texas, based in Fredericksburg, for chapter plant sales. New Earth produces bulk compost, topsoil, and mulch in Houston and San Antonio. 7.7 Midwest and Great Lakes Ecoregion and zone. EPA Level I: Eastern Temperate Forests (Central Corn Belt Plains, Driftless Area), Great Plains in the west, and Northern Forests in the far north. USDA zones: about 3b to 7a. Soil and fill. Midwest tallgrass prairie soils are typically deep silty clay loams and silt loams formed from glacial till or loess, with high nutrient content (USGS), and the black soils of the Corn Belt were built under prairie plants (Missouri Department of Conservation). The native plants below are adapted to fertile ground but tolerate lean soil and often do better without fertilizer (Savoy Prairie), so keep the fill close to a loam with a modest compost share and leave out the fertilizer meals unless a soil test calls for them. Plant Habit and root role Switchgrass (Panicum virgatum) Tallest root system of the group; one seed supplier reports nine feet or more in mature plants (Nature's Seed) Big bluestem (Andropogon gerardii) Deep-rooted prairie bunchgrass; the same supplier reports five to seven feet (Nature's Seed) Indian grass (Sorghastrum nutans) Deep-rooted bunchgrass, five to seven feet by the same report (Nature's Seed) Little bluestem (Schizachyrium scoparium) Finer-textured bunchgrass for drier, leaner pockets (Bright Lane Gardens) Canada wild rye (Elymus canadensis) Fast-growing cool-season grass that works as a nurse plant while slower grasses root (Bright Lane Gardens) Red fescue (Festuca rubra) Fibrous-rooted grass for partial shade and moister spots (Bright Lane Gardens) Lead plant (Amorpha canescens) Deep-rooted native shrub found on Iowa glacial lake banks (Kircus) Native prairie roots typically reach 6 to 15 feet (Linn County, Iowa), which is why a mix of grasses at different depths does more than turf. Local and regenerative sources Prairie Moon Nursery in Winona, Minnesota, which sells over 700 non-cultivar native species, and Prairie Nursery in Westfield, Wisconsin. Taylor Creek Restoration Nurseries in Brodhead, Wisconsin, and Midwest Groundcovers in St. Charles, Illinois. The Wisconsin native plant nursery list and the Iowa State list of Midwest native plant nurseries. For soil, ask your city or county compost site for STA certified compost, and use the supplier questions in the bulk and bagged section. 7.8 Southeast and Appalachian Piedmont Ecoregion and zone. EPA Level I: Eastern Temperate Forests (Piedmont, Blue Ridge, Southeastern Plains). USDA zones: about 6a in the mountains to 9a on the coastal plain, mostly 7b to 8a in the Piedmont. Soil and fill. The Georgia Piedmont's red clay formed from intensely weathered rock, is mildly acidic, and holds few nutrients, and its original topsoil has eroded in many places and will take centuries to rebuild (Georgia Native Plant Society). Clay particles hold moisture and swell, which threatens roots with drowning (Medford). Clemson Extension says most South Carolina soils need organic amendments (Jeffers). Use compost-enriched loam, keep sand out, and skip peat. A small amount of mushroom compost can suit mildly acidic clay (RHS). Plant Habit and root role Little bluestem (Schizachyrium scoparium) Fibrous-rooted bunchgrass for full-sun clay (Larson) Indiangrass (Sorghastrum nutans) Tall bunchgrass for full-sun clay (Larson) Bushy bluestem (Andropogon glomeratus) Bunchgrass for full-sun clay (Larson) Texas sedge (Carex texensis) Grass-like groundcover (Larson) Hairawn muhly (Muhlenbergia capillaris) Grass suggested for a sunny Washington, DC slope (Medford) Inland sea oats (Chasmanthium latifolium) Grass suggested for a sunny Washington, DC slope (Medford) Canada wildrye (Elymus canadensis) Grass suggested for a sunny Washington, DC slope (Medford) The Wildflower Center's general advice for red clay is to pair fibrous-rooted grasses with shrubs and perennials that spread by runners into thickets (Larson). The Georgia Native Plant Society's Piedmont guide lists shrubs for that role. Local and regenerative sources Mellow Marsh Farm in Siler City, North Carolina, grows Southeast natives from seed collected in the Carolinas and Virginia and sells to individuals as well as wholesale. Piedmont Plants Nursery in North Carolina and Cottage Garden Natives in Lithonia, Georgia, both native-only. The Georgia Native Plant Initiative recommended nursery list and Plant Virginia Natives retail partners. City of Raleigh Yard Waste Center for OMRI listed, STA certified compost, and Earth Farms in Dallas, North Carolina, for organic soil and compost near Charlotte. 7.9 Northeast and Mid-Atlantic Ecoregion and zone. EPA Level I: Eastern Temperate Forests, with Northern Forests in northern New England. USDA zones: about 4a to 8a, colder in far northern Maine. Soil and fill. Questions from Northeast gardeners to the Wildflower Center most often involve sandy, gravelly, or rocky banks, such as a sandy gravel bank in Connecticut (Kircus) and sandy slopes in New York and Massachusetts (Bossart; Ruggles). Sand with no organic matter benefits from compost before planting (Garrett). Use loam-based fill with moderate compost, skip peat, and avoid enriching the fill beyond what the plants need. Plant Habit and root role Little bluestem (Schizachyrium scoparium) Top performer with purple lovegrass in University of Rhode Island roadside trials (Phys.org) Purple lovegrass (Eragrostis spectabilis) Named with little bluestem among the best choices in the same trials (Phys.org) Switchgrass (Panicum virgatum) and sideoats grama (Bouteloua curtipendula) Grasses suggested for a quick-draining Lake Ontario bank (Bossart) Broomsedge bluestem (Andropogon virginicus) Grows in dry, sandy soil (Kircus) Eastern woodland sedge (Carex blanda) Evergreen sedge for sun or part shade (Kircus) Kinnikinnick (Arctostaphylos uva-ursi) Evergreen shrub for rocky or sandy sites (Kircus) Sweet fern (Comptonia peregrina), fragrant sumac (Rhus aromatica), lowbush blueberry (Vaccinium angustifolium) Shrubs suggested for slopes in New York (Bossart) Local and regenerative sources Native Plant Trust's Nasami Farm in Whately, Massachusetts, which grows New England natives from sustainably harvested seed. Pinelands Nursery in New Jersey, which propagates plants from seed collected in New Jersey, Virginia, and New York, and Toadshade Wildflower Farm in Frenchtown, New Jersey. Mass.gov's list of native plant sources, including Blue Stem Natives in Norwell and Tree Talk Natives in Rochester, and the Wild Seed Project directory. Black Earth Compost in Gloucester, Massachusetts, which sells compost and compost-soil blends in bulk, and Organic Recycling in Goshen, New York, for bulk topsoil and compost across the region. 8. Where to buy: local suppliers first, big box checklist Start with local suppliers, and use a big box store only for what they cannot cover. Local first. These sources know the local soil and are the best place to ask which compost and plants suit it. State native plant society plant sales and member nursery lists, such as those linked in each region above. Soil and water conservation districts, which keep supplier directories and often run native plant sales. The East Multnomah SWCD and Marion SWCD directories in Oregon are examples. Municipal and regional composters that sell tested compost, such as Boise, Raleigh, and A1 Organics in Colorado. Independent nurseries and landscape supply yards that stock native plants and bulk soil. If you must use a big box store, check these first Choose products labeled topsoil, garden soil, or compost. Skip potting mix, raised-bed mix, and moisture-control mix, which are usually soilless (Mississippi State Extension). Read the ingredient list and look for the word "soil" near the top. Peat moss is a very common filler in bagged garden soil (House Digest). Look for round fertilizer prills and gel crystals in the bag. They signal synthetic slow-release fertilizer and water-retention polymers, which belong in containers rather than in slope fill (UMass Extension). On compost, look for the OMRI Listed or STA Certified mark. The STA program requires approved labs, frequent testing, and disclosed results (US Composting Council). Buy compost and topsoil separately and blend them on site at the ratios in the starting recipe. Ask the garden desk whether the store can order bulk soil from a local yard. Pass on dyed mulch and any bark or wood product meant for the fill. 9. Frequently asked questions Short answers to the questions Dirt Locker customers ask most. Each answer points back to the section above that explains it. What soil should I use inside my Dirt Locker? A good starting mix is 70 to 80 percent screened loam-type topsoil, 10 to 20 percent finished compost, and 5 to 15 percent coarse mineral such as pumice on clay or wet sites only. Keep the mix close to your native soil texture, and confirm it with a soil test and your county extension office. Can I use fill dirt in a Dirt Locker? No. Fill dirt is subsoil sold to raise grade, it is low in organic matter, and it is not meant for planting. Use screened topsoil and compost instead. Is peat moss good for hillside planting? No. Peat is low in nutrients, hard to wet when dry, and harvesting it releases stored carbon and destroys bog habitat. Compost is the usual replacement, and coconut coir can help hold water in sandy fill. Can I use potting mix or raised-bed mix? Usually not. Potting mixes are mostly soilless and built on peat or bark, and raised-bed mixes often contain more peat than garden soil. Slope fill needs mineral soil. Should I add sand to clay soil? No. Sand has to make up nearly half the volume before a mix behaves like sandy soil, and smaller amounts make a denser mix. Add finished compost and a small share of pumice instead. Do I need blood meal, bone meal, kelp, or fish meal? Usually not. Native plants tolerate lean soil and often do better without fertilizer. Kelp meal adds trace minerals, and blood, bone, and fish meals supply nitrogen or phosphorus, so add them only if a soil test shows a need. Can I mix wood chips or bark into the soil? No. Wood and bark mixed into soil temporarily tie up nitrogen as they break down. Coarse chips work as a surface mulch if they stay in place on your slope. How do I find out what soil I have? Run a jar test: fill a jar half full of soil and water, shake it, and measure the sand, silt, and clay layers as they settle. A lab test through your county extension office shows nutrients and pH. Where should I buy soil and compost? Start with local suppliers such as native plant nurseries, soil and water conservation districts, municipal composters, and independent landscape yards. At a big box store, choose topsoil or compost over potting mix, read the ingredient list, and look for STA Certified or OMRI Listed compost. How much soil will I need? Multiply the fill volume of one unit by the number of units, convert to cubic feet, and divide by 27 for cubic yards. Add a margin for settling. Which native plants work best on a slope? Use a mix of root types: deep-rooted grasses and taprooted shrubs for anchoring, plus fibrous grasses and spreading groundcovers for surface cover. The regional guide lists plants by region and, for California, by subregion. Should I choose plants by ecoregion or USDA zone? Either works. Ecoregions group land by geology, soils, vegetation, and climate. USDA zones rank only winter cold, so use zones alongside the soil advice. Will plants alone stabilize a steep slope? Not always. Established vegetation cannot hold a steep slope when other landslide forces are present, so get expert advice for serious slope problems. 10. Works Cited MLA 9th edition. All web sources were accessed 2 Nov. 2026. Entries without a title use a short description in place of one. Suppliers and directories follow the research sources. Research and extension sources "Bagged Potting Mixes and Garden Soils for Home Gardeners." UMass Amherst Extension, University of Massachusetts Amherst, www.umass.edu/agriculture-food-environment/home-lawn-garden/fact-sheets/bagged-potting-mixes-garden-soils-for-home-gardeners. Bob Vila. "Understanding USDA Plant Hardiness Zones." Bob Vila, www.bobvila.com/articles/hardiness-zones/. Blackwelder, Darrell. "Clay Soil Is Not a Lost Cause." Salisbury Post, salisburypost.com/?p=453287. Bossart, Anne. "Plants for a Sandy Slope in NY." Ask Mr. Smarty Plants, Lady Bird Johnson Wildflower Center, m.wildflower.org/expert/show.php?id=6861. Bossart, Anne. "Plants to Hold a Slope in Northern New York." Ask Mr. Smarty Plants, Lady Bird Johnson Wildflower Center, w.wildflower.org/expert/show.php?id=4997. Bossart, Anne. "Plants to Hold a Slope in NY." Ask Mr. Smarty Plants, Lady Bird Johnson Wildflower Center, w.wildflower.org/expert/show.php?id=5603. Bright Lane Gardens. "The Best Native Grass for Erosion Control and Natural Shorelines." Bright Lane Gardens, brightlanegardens.com/native-plants/erosion-control/native-grass-for-erosion-control. Britannica. "Plant Hardiness Zones." Encyclopaedia Britannica, www.britannica.com/print/article/2238667. Chalker-Scott, Linda. "The Myth of Soil Amendments." Washington State University Extension, Puyallup Research and Extension Center, Puyallup.WSU.edu/wp-content/uploads/sites/403/2015/03/soil-amendments.pdf. Chalker-Scott, Linda. "The Myth of Soil Amendments Part II: 'If You Have a Clay Soil, Add Sand to Improve Its Texture.'" Washington State University Extension, Puyallup Research and Extension Center, Puyallup.WSU.edu/wp-content/uploads/sites/403/2015/03/soil-amendments-2.pdf. Chatterson, Sarah. Spent Mushroom Substrate on Landscape Plant Establishment. Thesis, University of Delaware, udspace.udel.edu/bitstreams/f1b041db-170f-497f-98a0-d8c3aa1193ef/download. City of Austin Watershed Protection Department. "Making Informed Choices When Choosing Landscape Products." City of Austin, 2018, austintexas.gov/sites/default/files/files/Watershed/growgreen/2018LPT/Making_Informed_Choices_when_Choosing_Landscape_Products.pdf. City of Boise. "Purchase Request." Public Works: Curb It, Compost, www.cityofboise.org/departments/public-works/curb-it/compost/purchase-request-form/. City of Raleigh. "Raleigh Yard Waste Center Receives National Recognition." City of Raleigh, raleighnc.gov/landfill-and-reuse/news/raleigh-yard-waste-center-receives-national-recognition. Cochise County Master Gardener Newsletter. University of Arizona Cooperative Extension, Oct. 2001, ag.arizona.edu/cochise/mg/sites/cals.arizona.edu.cochise.mg/files/newsletter/Oct01.pdf. Cochise County Master Gardener Newsletter. University of Arizona Cooperative Extension, Oct. 2005, cales.arizona.edu/cochise/mg/sites/cals.arizona.edu.cochise.mg/files/newsletter/Oct05.pdf. Colorado Department of Agriculture. "8 CCR 1202-4: Fertilizer, Soil Conditioner and Plant Amendment Rules." 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Espace pour la vie, espacepourlavie.ca/en/natural-fertilizers. "Evaluating Your Soil Texture." Washington State University Extension, Lewis County, Feb. 2023, wpcdn.web.wsu.edu/extension/uploads/sites/82/2023/02/Evaluating-Your-Soil-Texture-1.pdf. Gardenia. "California Planting Zones: Growing Zones Guide." Gardenia, www.gardenia.net/guide/california-planting-zones-growing-zones-guide. Gardenia. "Shade-Loving Native Perennials for Central CA Foothills & Coastal Mountains." Gardenia, www.gardenia.net/guide/recommended-shade-loving-native-perennials-for-central-california-foothills-coastal-mountains. Garrett, Dean. "Ground Covers for Sandy Hill in New York." Ask Mr. Smarty Plants, Lady Bird Johnson Wildflower Center, m.wildflower.org/expert/show.php?id=644. Georgia Native Plant Society. "Landscaping with Native Plants in the Georgia Piedmont." Archived 16 Jan. 2009, UNT Web Archive, webarchive.library.unt.edu/web/20090116093131/http:/www.gnps.org/pdf/GNPSls.pdf. 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Extension for Real Life, extension.msstate.edu/blogs/extension-for-real-life/how-choose-potting-soil. Missouri Department of Conservation. "Helton Prairie." Missouri Department of Conservation, mdc.mo.gov/discover-nature/places/natural-areas/helton-prairie. Nature's Seed. "Xeriscaping Slopes & Hillsides: Erosion Control That Looks Good." Nature's Seed, naturesseed.com/resources/lawn-and-turf/xeriscape-slopes-erosion-control/. New Mexico State University Cooperative Extension Service. "Growing Plants in Caliche Soils." Guide A-151, pubs.nmsu.edu/_a/A151.pdf. North Carolina Department of Environmental Quality. "Commercial Compost Testing." NC DEQ, www.deq.nc.gov/about/divisions/environmental-assistance-and-customer-service/recycling-and-materials-management/organics-recycling-and-composting/commercial-compost-testing. Pandian, Vijai. "Common Organic Fertilizers for Home Gardeners." 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