Choose and prepare the growing space
In-ground beds, raised beds and containers compared, with bed sizes, safe lumber, fill ratios, container sizes and the math for buying soil by volume.
Start here Essentials
This module asks you to choose one growing space and work out what it needs: its size, its fill and the questions to ask before you build. Everything marked Go deeper is optional on a first pass.
- Choose in-ground, raised beds or containers. Read the comparison table against your sun hours, soil result, weekly hours, body and rules. The comparison.
- Size it. Beds: set width from your reach and depth from your crops, and cross off railroad ties, old lumber and metal beds of unknown make. Containers: match each pot to the size table, confirm drainage holes and fill with soilless mix. Beds, containers.
- Work out the fill. Put length, width and depth in the bed calculator. Two parts topsoil to one part compost is the most common ratio. For pots, divide total gallons by 7.48 for cubic feet. Ask the supplier for test results and settling. Filling a bed.
- In-ground: call 811, then smother the sod with cardboard and compost. Preparing in-ground soil.
- On a balcony, deck or roof, ask the building owner in writing what it can carry before you fill anything.
Minimum time: about 30 minutes, plus any calls or messages. Done when: your method, size and fill amount are written down.
1. Three growing spaces and what decides between them Understand
A vegetable garden grows in one of three kinds of space. An in-ground bed is the existing soil, cleared and improved where it lies. A raised bed is soil lifted above the surrounding grade, usually held in by a frame of wood, metal, block or stone; University of Maryland Extension's Growing Vegetables in Raised Beds describes the usual bed as 2 to 4 ft across, 2 to 12 in tall and as long as you like. A container is any vessel with a bottom, from a 1-gallon pot to a half barrel, filled with a soilless mix and cut off from the ground.
The choice is rarely about which is best in general. It follows from facts you gathered in the first three modules:
- Sun (Module 2). If the only spot with enough sun is a patio, a balcony or a driveway, the ground there is not an option. Containers and raised beds can go where the light is.
- Soil (Module 3). A lead result, unknown fill or soil you cannot work moves you toward clean soil in raised beds or containers. EPA ties specific actions to specific lead levels; the lead section of Module 3 has both EPA's and Cornell's tiers.
- Water and time (Module 1). Raised beds and containers dry faster than the ground. Containers in summer can need water every day.
- Your body. Raised beds bring the soil up to you. If kneeling or bending is hard, height is a design input, not a finish.
- Rules. Leases, homeowners' associations and community gardens may limit structures. Ask in writing before you build, and keep the reply.
The table compares the three on the points that usually decide it. Each row names its source; where sources are silent, the row says what follows from the physical setup.
| In-ground bed | Raised bed | Container | |
|---|---|---|---|
| Soil control | You work with the soil you have; a soil test (Module 3) tells you what it needs | You choose the fill. Over soil, roots can still grow down into the ground below (UMD) | Complete: bagged soilless mix only (Penn State Extension) |
| Startup cost | Lowest in materials; compost and labor | Frame and fill; UMD lists building materials and labor as the main disadvantage | Pots and mix; low for a few pots, adds up for many |
| Drainage | Whatever the site has; clay drains slowly | Drains well, lowering the risk of waterlogging (UMD) | Depends on drainage holes; every container needs them (UMD) |
| Watering | Least frequent; roots reach a large volume of soil | Dries faster; the taller the bed, the more often you water (University of Minnesota Extension) | Most frequent; at least daily in hot months (Penn State) |
| Spring warmth | Slowest to warm | Warms sooner in spring (UMD, UMN) | Warms fastest; dark pots can overheat roots (UMD) |
| Access | Kneeling and bending | Brought to working height; can be built for wheelchair users (UMN) | Can be raised on stands or tables |
| Lead or poor soil | Depends on the test result and tier | Clean fill over a barrier; EPA's practice for higher levels | EPA's page allows containers at every lead level |
| Permanence | Can change shape each year | Relatively permanent; frames decay and need replacing (UMD) | Movable; can follow the sun or come in for winter |
| Usually fits | Larger gardens on sound soil (the Lindqvist garden, Plot 14) | Poor or contaminated soil, lawns, wet sites, limited mobility (the Okafor garden) | Balconies, patios, renters, small trials (Marisol's balcony) |
Preference Many gardens mix the three: beds for the bulk of the crops, a few pots of herbs by the door. Nothing in the table forces a single choice.
2. Raised beds: width, height and materials
Width: set by your reach
A bed is as wide as you can reach to the middle without stepping in. Stepping in compacts the soil, and compaction crushes the pores that roots and water use (Module 3 explains why). UMD names that benefit directly: the planting area is not walked on, so less compaction and erosion occur.
The published widths differ a little, because they measure different things:
| Source | Width | Height |
|---|---|---|
| University of Maryland Extension, Growing Vegetables in Raised Beds | 2 to 4 ft across | 2 to 12 in typical. On hard surfaces: at least 8 in for leafy greens, beans and cucumbers; 12 to 24 in for peppers, tomatoes and squash |
| University of Minnesota Extension, Raised bed gardens | Up to 2.5 ft if you reach from one side; up to 5 ft if you reach from both | About 27 in is generally comfortable for wheelchair users; low sides suit young children and cost less |
| Oregon State University Extension, EM 9308 | Not given | 28 to 34 in for wheelchair-accessible beds |
Convention A 4-ft bed reached from both sides is the common middle of these figures. Test it Your own reach decides. Kneel or stand beside a strip of lawn, reach in comfortably without leaning your weight on your hand, and mark the spot. Double it for a bed you can walk around; use it as is for a bed against a fence or wall. A bed against a wall that is 4 ft wide puts its back row out of reach.
Length is free. UMN points out that several shorter beds make crop rotation easier than one long bed, because each bed can carry one plant family for a year (Module 5 covers rotation). Leave paths wide enough for you and a wheelbarrow; UMD's examples use 2-ft paths covered with wood chips, bark or another mulch.
Height: what it buys and what it costs
Over open ground, a bed does not need to be tall, because roots continue into the soil below. On a hard surface such as pavement or crushed stone, the bed is the whole root zone, so UMD's minimum depths by crop apply. Taller beds are easier on knees and backs. They also cost more to fill and dry out faster, as UMN notes. The fill math in the next section shows how fast height adds volume: a 4 x 8 ft bed holds 32 cubic feet at 12 in deep and 72 cubic feet at 27 in.
The two wheelchair figures differ (27 in from UMN, 28 to 34 in from Oregon State). Ask the authority The person who will garden from the chair is the authority here. Build a test height with blocks or a table before you build the bed.
Lumber and other frame materials
Wood is the most common frame because it is cheap and easy to cut. It also rots, because raised beds stay wet. The materials question gardeners ask most is whether treated wood is safe for food. The answer has changed over time, which is why older and newer sources disagree.
Pressure-treated wood is lumber with a liquid preservative forced into it under pressure. The old residential preservative was chromated copper arsenate (CCA), which contains arsenic. UMD states that CCA's use for outdoor residential structures was discontinued in 2004, and Oregon State University Extension's Pressure-treated wood for raised bed construction in Oregon (EM 9879) says it has been over 20 years since CCA was used for wood sold to the general public. Current residential treatments are copper-based. EM 9879 names copper azole (CA-C), micronized copper azole (MCA) and alkaline copper quaternary (ACQ); UMD calls MCA the most widely available in the East.
Physical principle Oregon State's study measured what actually moves. Starting in 2021, researchers built two raised beds of untreated Douglas-fir and two of Douglas-fir treated with CA-C for ground contact, each about 4 x 10 ft from 2 x 12 lumber, in a home garden in the Willamette Valley. They grew the same crops in all four, including lettuce, carrots, beets, radishes, kale, tomatoes and peppers, and tested soil at three distances from the boards and the harvested crops. Over four growing seasons:
- Soil copper rose only within 1 inch of the treated boards, by roughly 20 to 68 ppm over the untreated beds, and stayed within the natural range for local soils.
- There was no extra copper 3 to 4 inches from the boards or in the center of the beds.
- There was no increase in copper in any of the vegetables or herbs.
- After six seasons, the untreated beds showed serious decay in their lower boards; the treated beds were mostly intact.
Read the study for what it covers: one site, one preservative, clay soil (EM 9879 notes clay and organic matter bind copper), four seasons. Its own conclusion is addressed to Willamette Valley gardeners. Oregon State says to use only lumber treated with preservatives approved for residential use and rated for ground contact (the label or end tag on treated lumber states its intended use), and to choose cedar, redwood, concrete block or stone if you are not comfortable with any copper movement. Its page also gives advice on handling cut ends; read it there.
Sources do not all agree. The New York Soil Health lead fact sheet (Cornell) advises avoiding treated or painted wood, railroad ties and telephone poles in gardens where lead is a concern. UMD suggests painting or staining treated wood, or using stone or brick, if MCA worries you. Preference Current treated lumber rated for ground contact, untreated rot-resistant wood, and non-wood frames are all positions some extension source supports. Choose by your own comfort, budget and how long you want the bed to last.
Three materials have no such disagreement:
- Railroad ties. Oregon State says old railroad ties are not recommended because their industrial preservatives are not intended for garden or residential use. UMN warns against them too.
- Old lumber. UMN says to avoid old lumber. Oregon State explains why: salvaged lumber more than 20 years old may be CCA-treated, and manufacturers do not recommend CCA for this use.
- Some metal beds. UMN cautions that some prefabricated metal beds sold online have been found to contain lead. If you buy one, ask the seller what the metal and coating are, and keep the answer.
Other frame materials have their own notes. UMD lists decay-resistant woods (cedar, redwood, black locust, several oaks, Osage orange) and cheaper untreated spruce, pine and fir that rot sooner. It considers concrete blocks generally safe while they stay intact, while noting that some contain fly ash and that little research exists; it calls the choice personal. UMN notes that bricks can raise soil pH, and that fabric grow bags behave more like containers than beds.
3. Filling a bed and buying fill by volume
What goes in
A bed over open ground is usually filled with a blend of topsoil (mineral soil, with its sand, silt and clay) and compost. The sources give different ratios:
| Source | Bed over soil | Bed on a hard surface |
|---|---|---|
| University of Minnesota Extension | About 2/3 to 1/2 topsoil and 1/3 to 1/2 plant-based compost | Not given |
| University of Maryland Extension, Soil to Fill Raised Beds | Compost and topsoil at 1:2 or 1:1; or compost and soilless mix at 1:1 | Compost and soilless mix at 1:1; topsoil up to 20 percent by volume in beds at least 16 in deep |
| Oregon State University Extension, EM 9308 | Up to 25 percent compost by volume; break up the original soil surface first | Not given |
So compost runs from up to a quarter (Oregon State) to as much as half (Maryland, Minnesota). Convention Two parts topsoil to one part compost sits inside the Minnesota and Maryland ranges and is the most common single figure. We do not average Oregon State's limit into it; if you follow EM 9308, use its figure.
Two shortcuts are on every list of what not to do:
- Not compost alone. Oregon State's EM 9308 says plainly not to fill raised beds with compost alone. That page does not give its reasons, and we do not supply our own.
- Not potting mix alone in a bed over ground. UMN says potting soil, fine for pots and seedlings, dries out too quickly in raised beds. UMD's hard-surface mix uses soilless mix only together with compost.
Buying topsoil
UMD notes that topsoil sales are not regulated in Maryland, and the same is true in many places. Its advice for buying in bulk: go to a reputable dealer, ask for soil test results and the soil's origin, and look before delivery. Good topsoil is dark and crumbly with an earthy smell. Pass on soil that is very sandy or very clayey, smells foul, or shows grayish mottling or a chalky, sticky or rough texture. UMD also warns that bagged "organic soil" products often contain no mineral topsoil at all, only materials such as wood waste, bark fines, compost and peat.
If lead was the reason for raised beds, the supplier's test results matter twice. The Cornell fact sheet defines clean soil as under 63 ppm lead. Ask for the lead figure, not only the nutrient report. Once the bed is filled, UMD suggests testing again a year later, after the components have mixed and reacted.
Measuring volume
Fill is sold by volume: bags in cubic feet, bulk loads in cubic yards. Oregon State's EM 9308 notes that landscape suppliers sell by the cubic yard and that bags of compost often hold 1 to 2 cubic feet. The arithmetic needs three conversions, all from the National Institute of Standards and Technology's Handbook 44, Appendix C:
- Cubic feet of a rectangular bed = length (ft) x width (ft) x depth (in) / 12.
- A cubic yard is 27 cubic feet, so cubic yards = cubic feet / 27.
- One gallon is 231 cubic inches, and one cubic foot is about 7.48 gallons. (Oregon State's EC 1561 uses the practical version: one and a half 5-gallon buckets is about 1 cubic foot.)
| Bed (ft) | Depth | Cubic feet | Cubic yards | 1.5 cu ft bags |
|---|---|---|---|---|
| 4 x 8 | 6 in | 16 | 0.59 | 11 |
| 4 x 8 | 12 in | 32 | 1.19 | 22 |
| 4 x 8 | 16 in | 42.7 | 1.58 | 29 |
| 4 x 8 | 27 in | 72 | 2.67 | 48 |
| 3 x 6 | 12 in | 18 | 0.67 | 12 |
Bag counts are rounded up. Past about a cubic yard, compare the price of bulk delivery with bags; the trip count and the lifting matter as much as the price.
Bag labels and settling
A bag's printed volume is the maker's figure. Fill claims on the label are a separate thing. Miracle-Gro's product page for its 1.5 cubic foot organic raised bed soil, as one example, says two bags fill a 2 x 2 ft bed 6 in deep. That bed's geometric volume is 2 cubic feet; two bags are 3 cubic feet, about 50 percent more. Product-specific The extra allows for settling, the loss of volume as loose fill packs down and organic matter breaks down, and how much a product settles depends on the product. We cite this label only as an example of a claim, not as a recommendation.
The course's bed and soil calculator computes geometric volume only and does not add a settling allowance. Ask your supplier how much their product settles and add that yourself. Expect to top up beds over time; Oregon State's EM 9308 says to refill raised beds as needed.
Compost on an existing bed Go deeper
For compost spread on top, EM 9308 gives a quick rule: one 1-cubic-foot bag covers 12 square feet at 1 inch deep. Its rates are 3 to 4 inches of compost worked into the top 8 to 12 inches for a new vegetable bed, and a quarter inch to 1 inch a year for an existing one, which it calls the most to add each year. The calculator's top-dress field does this math.
4. Preparing in-ground soil
An in-ground garden, or a raised bed on open ground, usually starts as lawn or weeds. Sod is the turf layer: grass with its roots and the soil they hold. You can remove it or kill it in place.
Before you dig
Contact 811 Before You Dig a few business days ahead. The service is free, and the Common Ground Alliance counts planting a garden as digging, because some utility lines are buried only inches deep.
Killing the turf in place
University of Maryland Extension describes smothering: in fall or early spring, cover the turf with plain cardboard (no wax, tape removed) or several overlapping layers of newspaper, and spread 2 to 4 inches of compost on top to hold it down. The grass dies and decays in place, adding organic matter. UMD's two pages give different times, 6 to 8 weeks on Soil to Fill Raised Beds and 8 to 12 weeks on Growing Vegetables in Raised Beds. Test it Plan on the longer figure and check under a corner before planting. A tarp or weed barrier fabric pinned down does the same job and comes off when the vegetation is dead.
After smothering, UMD gives two ways to plant. No-till: plant straight into the compost, and roots grow down through the decaying turf, with fewer weed seeds brought up. Minimum-till: drive a garden fork into the soil, rock it back and forth, move 6 to 8 inches and repeat, without lifting and flipping the soil.
Removing the sod Go deeper
If you cannot wait, UMD's method is to slice the turf off horizontally with a spade and compost it. This is heavy work. Penn State Extension's guidance on gardening with fewer aches says to lift with your hips and knees and keep the load close; cut the sod into pieces you can carry.
Adding compost and working the soil
For a new in-ground bed, Oregon State's EM 9308 calls for 3 to 4 inches of compost worked into the top 8 to 12 inches. In later years, a quarter inch to 1 inch a year. UMD's figure for raised beds on an existing garden is 2 to 4 inches mixed into the top 4 inches. Convention Use the soil test from Module 3 to decide on lime or fertilizer; compost is not a substitute for a recommendation.
Physical principle Oregon State's EC 1561 warns that tilling, especially wet soil, damages structure and speeds the loss of organic matter. It suggests a digging fork in clay. Work the ground when it is moist, not wet.
For scale: 1 inch of compost over 200 square feet is 0.6 cubic yards (EC 1561), so a quarter inch over the same area is about 0.15 cubic yards.
5. Containers
We do not assess whether a balcony, deck or roof can carry the weight of containers, wet soil and water. That is a question for the building owner or a structural engineer. Ask before you load the space, ask in writing, and keep the answer. Anything attached to a railing is a separate question for the owner too. Nothing on this page, including the volumes below, answers either one.
Size by crop
Container size limits the root system, and the root system limits the plant. University of Maryland Extension's Types of Containers for Growing Vegetables sets minimums by plant size; Penn State Extension's Container Vegetable Gardening: Four Keys to Success gives widths for the largest crops.
| Plant size | UMD minimum | UMD examples | Penn State |
|---|---|---|---|
| Large (one plant per pot) | 8 to 10 gal of mix, 12 to 16 in deep | Tomato, pepper, eggplant, cucumber, winter squash | Tomato: at least 20 in wide. Pepper and eggplant: 14 in. Pots at least as tall as wide |
| Medium | 4 to 6 gal, 8 to 12 in deep | Dwarf tomato, pepper and eggplant; summer squash; cabbage family; beans; beets; carrots; chard | Not given |
| Small | 1 to 3 gal, 4 to 6 in deep | Basil and other herbs, radish, scallions, spinach, salad greens, peas, beans | Smaller pots for herbs and greens |
The sources disagree in two places. UMD lists winter squash as a container crop; Penn State says sweet corn, watermelon, winter squash and zucchini are better suited to the ground. And Penn State's tomato pot is much bigger than UMD's minimum. A pot 20 in wide and at least 20 in tall holds about 6,280 cubic inches, which is about 27 gallons at 231 cubic inches per gallon, against UMD's 8 to 10. Penn State's 14-in pepper pot, 14 in tall, works out to about 9 gallons, close to UMD. Convention UMD's numbers are minimums; Penn State's tomato figure is closer to what a full-size tomato fills. Penn State suggests dwarf, bush or determinate varieties for containers, and UMD puts dwarf tomatoes in its medium class.
Drainage, material and mix
- Drainage holes are required. UMD says every container except a self-watering type needs holes or slits in the bottom, and that many sold pots lack them, so check. Penn State explains why: waterlogged mix keeps oxygen from roots.
- Gravel in the bottom does not help. UMD states that rocks, gravel or pot shards in the bottom do not improve drainage and can raise the water table in the pot. Raise pots on feet or a brick instead, and empty saucers after watering.
- Material changes watering. UMD notes that clay, ceramic, concrete and wood pots dry out faster than plastic or metal, and that dark colors can heat roots enough to injure them. Penn State adds that heavy pots resist tipping under top-heavy tomatoes.
- Use a soilless mix, a blend of materials such as sphagnum moss, composted bark, perlite, vermiculite or coconut coir, not garden soil. Penn State says garden soil is heavy and dense in a pot and keeps it from draining, and that finished compost can make up to 50 percent of the mix.
Watering and feeding
Penn State says most container vegetables need water at least once a day in hot summer months, and that each watering should continue until water runs out the bottom. It also says container plants need more fertilizer than plants in the ground, since roots cannot reach beyond the pot; Module 9 covers feeding. Test it Lift a pot after watering and again the next afternoon: the difference in weight is a direct reading of how much it dried.
To buy mix for a set of pots, add up the gallons and convert: total gallons / 7.48 = cubic feet. The pot's rated size is its capacity to the brim; you fill to just below the rim, so the real need is a little less.
6. See it See it
Both examples use the course's fictional cases. Test results are invented for teaching.
The Okafor garden: two beds on former lawn. The Okafors' yard tested at 140 ppm lead (Module 3; fictional). That falls in Cornell's 100 to 199 tier, which asks for raised beds with clean soil, and below EPA's 200 ppm tier. With two young children, they chose raised beds of purchased fill over landscape fabric. The site gets 7 hours of measured sun in May.
They built two cedar beds, each 4 x 8 ft and 12 in deep. Both sides of each bed are reachable, so 4 ft is within UMD's range and Ada can reach the middle from either side. Because the fabric separates the fill from the yard soil, they did not strip the sod; they mowed short and laid fabric inside the frames. The volume:
- One bed: 4 x 8 x 12 / 12 = 32 cubic feet. Two beds: 64 cubic feet.
- 64 / 27 = 2.37 cubic yards.
- At 2 parts screened topsoil to 1 part compost: 42.7 cubic feet (1.58 cubic yards) of topsoil and 21.3 cubic feet (0.79 cubic yards) of compost.
- In 1.5 cubic foot bags, 64 / 1.5 = 42.7, so 43 bags. At that size they priced bulk delivery instead.
EPA's 16 in of clean soil over fabric is its practice above 400 ppm, so it does not set their depth.
- Known: bed size, depth and volume; the ratio they chose and its sources (UMN, UMD); the yard result (fictional).
- Assumed: that the geometric 64 cubic feet is enough. This is the Okafors' assumption; the calculator adds nothing for settling.
- Open: whether the delivered fill matches the supplier's description, including lead under 63 ppm. The supplier settles it with test results, which the Okafors requested in writing before delivery. Also open: how much the fill will settle, which the supplier's guidance and a top-up next spring settle.
Marisol's balcony: six containers. Marisol Vega rents an apartment with a west-facing balcony that gets 5 hours of direct afternoon sun. She has six containers: two 10-gallon, two 5-gallon and two 2-gallon. Her crops: cherry tomato, pepper, lettuce, basil and radish.
She matched each pot to UMD's table. The two 10-gallon pots meet the large-crop minimum and take the cherry tomato and the pepper. A 5-gallon pot takes lettuce, and the other takes basil. The two 2-gallon pots take radishes. Her 10-gallon tomato pot is smaller than Penn State's 20-in tomato width, so she chose a cherry tomato labelled determinate. All six pots have drainage holes; she checked, and drilled none. She uses a soilless mix with compost and skipped the gravel.
Mix needed: 2 x 10 + 2 x 5 + 2 x 2 = 34 gallons. 34 / 7.48 = 4.5 cubic feet, or 3.03 bags of 1.5 cubic feet, so four bags, with some left for topping up. She carries water in a 2-gallon can, which matters on a hot west balcony where Penn State expects daily watering.
- Known: the six container sizes; the crops; 5 hours of afternoon sun; the lease clause requiring the landlord's written approval for anything attached to the railing.
- Assumed: that the balcony can carry six pots of wet mix. This is Marisol's assumption, and the one that matters most.
- Open: the balcony's load limit. The building owner settles it; Marisol asked the landlord in writing about the load and about the railing, and nothing goes on the railing until the reply arrives. Also open: whether 5 hours of afternoon sun is enough for the pepper, which her own season settles.
Free demonstrations
- Pressure-treated wood for raised bed construction in Oregon (Oregon State EM 9879): the study beds, where the soil was sampled, and photos of untreated and treated boards after six seasons.
- Soil to Fill Raised Beds (University of Maryland): four site scenarios, from thick turf to pavement, each with its own fill recipe.
- Raised bed gardens (University of Minnesota): bed types, widths, materials and the fill ratio, with photos of each frame material.
- Types of Containers for Growing Vegetables (University of Maryland): the full size-by-crop list and the drainage rules.
7. Practice Practice
Minimum: Choose a space, size it, work out the fill with the calculator, and send the supplier and building-owner questions; skip the beds sheet. Time: about 45 minutes, plus calls or messages to a supplier and, if you rent, to your landlord. Materials: a tape measure, your sun map from Module 2, your soil result or sample status from Module 3, a notebook or phone, and the bed and soil calculator.
- List the deciding facts. Write your measured sun hours, your soil result or "not tested," your weekly hours, any body constraint, and any rule from a lease, association or garden.
- Read the comparison table against your list. Mark each row in your favor or against. Choose a space, or a mix of spaces, and write one sentence on why.
- Measure your reach if you chose beds. Set width at double your reach for a bed you can walk around, or your reach for a bed against a wall. Set height from your crops (UMD's figures on hard surfaces) and your body.
- Choose frame material and write which source supports it. Cross off railroad ties, old lumber and any metal bed whose maker cannot tell you what it is made of.
- Compute fill. Enter beds, length, width and depth in the calculator. Write the cubic feet, cubic yards and bag count. Choose a ratio and write its source. For containers, add up gallons and divide by 7.48.
- Ask the supplier for test results (with lead, if lead was a reason for the beds), the soil's origin, and how much the product settles.
- If containers go on a balcony, deck or roof, send the building owner a written question about the load before you fill them.
- Go deeper Record each bed or container in the beds sheet of the garden plan: name, size, depth, sun hours and fill. Add the fill purchase to the amendments sheet.
8. Your garden Your garden
9. Check your work Check your work
Criteria
- Can you name the facts (sun, soil, water, body, rules) that decided your space?
- Can you reach the middle of every bed without stepping in?
- Is each bed deep enough for its crops, by UMD's figures if it sits on a hard surface?
- Is the frame material free of railroad ties, old lumber and unidentified metal?
- Is your fill volume computed geometrically, with the ratio's source written down and settling asked of the supplier?
- Does every container meet the size for its crop and have drainage holes?
- If containers go on a balcony, deck or roof, have you asked the building owner in writing?
Worked example
The Okafors (fictional) meet every bed criterion: 4-ft beds reached from both sides, 12 in deep over fabric, cedar frames, 64 cubic feet computed with the 2:1 ratio sourced, and the supplier asked for test results and settling. Their beds sheet lists both beds with "screened topsoil and compost, 2:1" in the fill column and the fill status as unresolved until the supplier replies.
Marisol (fictional) meets the container criteria for size and drainage. The balcony criterion is met in the sense that counts: she asked in writing. The answer is not in yet, and her record says so rather than assuming it.
Common mistakes
- A 5-ft bed against a fence. UMN's 5-ft figure is for a bed reached from both sides.
- Buying by the bag label's fill claim and then comparing it with a geometric calculation. Use one method, and know which one you are using.
- Filling a bed with potting mix or compost alone. UMN says potting soil dries too fast in beds; Oregon State says not to fill with compost alone.
- Building with free old lumber of unknown age. Over 20 years old, it may be CCA-treated.
- Gravel in the bottom of pots. It does not improve drainage.
- Treating a container's gallon rating as its root room when the pot is wider than it is deep or tapers sharply. Check the depth against UMD's figures too.
- Loading a balcony first and asking later.
What is still unresolved
This module does not settle whether a balcony, deck or roof can take the load; the building owner or a structural engineer does. It does not settle what is in a given load of fill; the supplier's test results, or your own sample sent to a lab, settle that. It does not tell you how much a product settles; the supplier does. Which crops go in which bed, and how many plants fit, is Module 5. How often each space needs water is Module 8.