TL;DR
Any container that holds soil and has drainage holes grows food. The constraints are size, sun, and water. Most vegetables need 6+ hours of direct sun and daily watering. A 5-gallon bucket grows a tomato plant, a potato crop, or a kale plant. Ten 5-gallon buckets in a sunny spot can meaningfully supplement diet with fresh vegetables.
Container Selection
Drainage is non-negotiable. Roots need oxygen. Soil saturated without drainage becomes anaerobic and roots die. Every container needs holes in the bottom.
Minimum useful sizes:
| Container | Volume | Best For | |-----------|--------|----------| | Quart pot (6-inch diameter) | 1 qt | Herbs only | | 1-gallon container | 1 gal | Lettuce, radishes, spinach, green onions | | 3-gallon container | 3 gal | Kale, chard, carrots, beets | | 5-gallon bucket | 5 gal | Tomatoes (small varieties), peppers, beans, cucumbers | | 7-10 gallon container | 7-10 gal | Large tomatoes, large peppers, potatoes | | 15-gallon grow bag | 15 gal | Potatoes (multiple plants), dwarf corn |
DIY containers: Standard 5-gallon buckets from hardware stores or restaurant supply work perfectly. Drill 4-6 drainage holes in the bottom. Food-grade buckets are preferable but any bucket works for ornamental production; for edibles, food-grade or virgin HDPE (marked with the recycling symbol "2") is preferred.
Soil for Containers
Never use garden soil in containers. Garden soil compacts in containers, reducing drainage and aeration. It often contains weed seeds and pathogens.
Standard container mix:
- 50% high-quality potting mix (commercial all-purpose potting soil)
- 25% perlite (improves drainage and aeration)
- 25% compost (improves nutrition and water retention)
Budget alternative:
- 2/3 any available compost or topsoil
- 1/3 coarse sand or perlite
For moisture retention (important in hot climates): Add a handful of coco coir to the mix — it absorbs 10× its weight in water and releases it slowly.
Fertilizing containers: Container plants deplete nutrients within 4-6 weeks as they're watered out. A liquid fertilizer (fish emulsion, liquid compost tea) applied every 2-3 weeks maintains productivity throughout the season.
Crops Suited to Containers
Excellent Container Performers
Tomatoes: Determinate (compact) varieties are best for containers: Patio, Celebrity, Bush Early Girl. Indeterminate varieties can grow in 10-gallon+ containers with a sturdy stake or cage but require more care. Expect 10-20 lbs per 5-gallon container from a determinate variety in a good season.
Peppers: All peppers grow well in 5-gallon containers. Less sensitive to container size than tomatoes. Expect 20-40 peppers per plant depending on variety.
Bush beans: Excellent in 3-5 gallon containers. Plant 4-6 seeds per 5-gallon container. Expect 1-2 lbs of beans per plant.
Kale and Swiss chard: Continuous harvest for months from a 3-gallon container. One of the best value container crops for nutrition per container.
Lettuce, spinach, arugula: Grow in wide, shallow containers (12+ inches wide, 6 inches deep). Harvest outer leaves continuously. In hot weather, shade cloth extends the growing season.
Green onions: Extremely productive per inch of container. 20+ scallions per linear foot of container space.
Cucumbers: Grow vertically on a trellis against a wall. 5-gallon container minimum. Expect 10-20 cucumbers per plant.
Challenging But Possible
Potatoes: Grow in purpose-built potato bags or 15+ gallon containers. The method: fill 1/3 with soil, plant seed potatoes, add soil as plants grow (hilling). Expect 5-10 lbs per 15-gallon container.
Dwarf/mini corn: Requires multiple containers for pollination (shake plants when tassels shed pollen). 5+ plants minimum. 15-gallon containers. Possible but labor-intensive.
Dwarf squash varieties: Bush summer squash varieties in 10+ gallon containers can work. Full-sized winter squash need ground space.
Poor Container Performers
Melons: Very large vines, very high water demand, difficult to support in containers.
Full-sized corn: Needs space for wind pollination; container isolation makes pollination unreliable.
Perennial crops: Established perennials (asparagus, rhubarb, artichoke) need large, permanent containers and aren't worth the effort for first-year production.
Watering Container Gardens
The most common failure mode in container gardening is inconsistent watering. Containers dry out rapidly — especially small containers on hot, sunny days.
Daily check is the standard. Touch the soil. If the top inch is dry, water. If it's still damp, skip.
How to water: Water slowly until water drains freely from the drainage holes. This ensures even moisture throughout the container. Quick surface watering doesn't penetrate to the roots.
Signs of underwatering: Wilting (often reversible if caught early), dry, shrunken-looking plants, soil pulling away from container edges.
Signs of overwatering: Yellowing lower leaves, root rot (mushy, dark roots if you remove the plant), persistently soggy soil that smells sour.
Self-watering containers have a reservoir in the bottom that plants wick water from. They dramatically reduce watering frequency and are worth using for any container crop if you have the option.
Extending the Season
Containers can be moved — use this advantage.
Early spring: Start containers indoors or in a protected space 4-6 weeks before the last frost. Move outdoors after frost risk passes.
Fall frost: Move containers of still-productive plants indoors during frost, then back out when temperatures rise. Extends the growing season by weeks.
Cold frames: A simple cold frame (wooden box with a clear lid) over containers can extend growing in fall by 4-6 weeks and start production 4-6 weeks earlier in spring.
Overwintering perennials: Perennial herbs (rosemary, thyme, chives) in containers can be moved into a cold garage or unheated shed to overwinter and brought back out in spring.
Sources
- University of Maryland Extension - Growing Vegetables in Containers
- Cornell University Cooperative Extension - Container Vegetable Gardening
Frequently Asked Questions
What size container do vegetables need?
Smaller crops (lettuce, herbs, radishes, green onions): 6-8 inch depth minimum, 1-gallon pot. Medium crops (kale, chard, bush beans, beets, carrots): 12-inch depth minimum, 3-5 gallon container. Large crops (tomatoes, peppers, cucumbers): 12-18 inch depth, 5-10 gallon container minimum. Potatoes: special bags or 15-gallon containers. Container size directly determines yield — always go larger than minimum if space allows.
How often do containers need to be watered?
Container plants typically need watering once per day in warm weather (twice daily in very hot, dry conditions) and every 2-3 days in cool, cloudy weather. Containers dry out far faster than in-ground gardens. The finger test: push a finger 1-2 inches into the soil; if dry, water. In extreme heat, large containers may need watering morning and evening. Self-watering containers (with reservoir systems) significantly reduce watering frequency.
Can you grow enough food in containers to matter nutritionally?
Yes, meaningfully, for vitamins and variety — less so for total calories. A 10-gallon tomato pot can produce 20-30 lbs of tomatoes per season. A 5-gallon kale pot can provide continuous harvests of vitamin-rich greens for months. For pure caloric contribution, 5-gallon potato bags can produce 5-10 lbs of potatoes per bag. Container growing supplements a stored-food diet with fresh vitamins; it rarely replaces caloric staples.