GardenNotes #724

Vegetable Gardening in Containers

Outline:   Cool season vegetables
                 Warm season vegetables
                 Additional information

For basic information on container gardening, refer to CSU Extension Fact Sheet #7.238, Container Gardens

Container vegetable production is somewhat more demanding than growing flowers and other ornamentals in containers. Quality of most vegetables is based on the soil’s ability to provide a constant supply of water and nutrients. Vegetables become strong flavored, stringy, and tough under dry or low fertility conditions. With the limited root spread in a container, the gardener must frequently and regularly supply water and fertilizer. In growing container flowers, minor lapses in daily care may interrupt flower production, but flowering eventually resumes with returned quality care. With container vegetables, minor lapses in daily care may significantly reduced produce quality.

Cool Season Vegetables

Cool season vegetables prefer the cool growing temperatures (60º to 80º) of spring and fall. Most are intolerant of summer heat. They do tolerate light frosts. Leafy and root vegetables prefer full sun, but are tolerant of partial shade. They are intolerant of reflected heat during the summer season.

Spring crops are typically planted two to four weeks before the average spring frost date. Along the Colorado Front Range, spring planting times are mid-April to early-May. Most are replanted in mid-July to mid-August for a fall harvest.

The quality of these vegetables is directly related to their ability to grow rapidly in a good soil mix under frequent light fertilization and a constant supply of water. Crops become strong flavored if they become dry.

Vegetable	Minimum Container Size*	Minimum Direct Sunlight Per Day	Remarks
Beets	8" deep	8 hours	Best in cool temperatures, grow a spring and fall crop. To give space for root development, thin greens to 3". A consistent supply of water and nutrients promotes the rapid growth essential for quality produce.
Broccoli Cabbage Cauliflower Kale Collards	10" deep 5 gal/plant	8 hours	Best in fall production (plant mid July for fall harvest along the Colorado Front Range). Minimum spacing per plant is 18" by 18". A consistent supply of water and nutrients promotes rapid growth and is essential for quality produce. Heavy feeder, requiring frequent light fertilization. Crops develop a strong flavor if the soil gets dry.
Carrots	8"-12" deep	8 hours	Best in cool temperatures, grow a spring and fall crop. Use short root varieties, like Short & Sweet or Scarlet Nantes. Roots will crack and be strong flavored if the soil gets dry. Thin early to 2"-3" apart. Foliage is rather decorative.
Chard	8" deep	6 hours	Space to 6+" between plants in a row. Harvest outer leaves allowing plants to continue to grow. Makes an excellent "cut and grow again" crop. Colored varieties are very decorative. Responds to frequent light fertilization. A consistent supply of water and nutrients promotes the rapid growth essential for quality produce.
Kohlrabi	8" deep	8 hours	Best in cool temperatures, grow a spring and fall crop. A consistent supply of water and nutrients promotes the rapid growth essential for quality produce. Never allow soil to become dry. Kohlrabi is a heavy feeder, requiring frequent, light fertilization
Lettuce (leaf)	8" deep	6 hours	Grow as a spring or fall crop; avoid hot summer temperatures. Use softhead or leaf types. As the young crop grows, thin to 9" spacing; crowding (competition for space, water and nutrients) reduces quality. A consistent supply of water and nutrients promotes the rapid growth essential for quality produce. Responds to frequent light fertilization. Lettuce become strong flavored if the soil become dry, during hot weather, and with crowded plants
Onions (green)	6" deep	8 hours	Onions require a consistent supply of water. Never allow soil to become dry. Thin the crop by harvesting young plants. Plant in early spring. A consistent supply of water and nutrients promotes the rapid growth essential for quality produce.
Peas	8" deep	full sun	Not well suited to container gardening. Best in cool temperatures, grow a spring and fall crop. Use dwarf, edible-pod or snap types for salads and stir-fry. May be grown in hanging baskets or trellised. Needs good air circulation to avoid powdery mildew.
Radish	8" deep	8 hours	Best in cool temperatures, grow a spring and fall crop. A consistent supply of water and nutrients to promote rapid growth is essential for quality produce.
Spinach	8" deep	6 hours	Best in cool temperatures, grow a spring and fall crop. A consistent supply of water and nutrients promotes the rapid growth essential for quality produce.
Turnips	8" deep	8 hours	Best in cool temperatures, grow a spring and fall crop. When large enough to make greens, thin to 4" allowing roots to develop. A consistent supply of water and nutrients promotes the rapid growth essential for quality produce.

* Larger container sizes will make crop easier to care for, providing a bigger supply of water and nutrients.

Warm Season Vegetables

Warm season vegetables prefer warmer summer temperatures (70º to 95º) and are intolerant of frost. They are typically planted after the average spring frost date as summery weather moves into the areas. Along the Colorado Front Range, planting time would be mid-May to early June.

Vegetable	Minimum Container Size*	Minimum Direct Sunlight Per Day	Remarks
Beans	8" deep	full sun	In a long box 12" wide, plant bush beans or trellis pole beans. TBeans have a high water requirement during blossoming. Beans drop blossoms with dry soil or excessive wind.
Cantaloupes Muskmelons	5+ gal/plant	full sun	May be trellised to conserve space. Compact varieties preferred for container gardening. With male and female blossoms, may need hand pollination. Needs good air circulation to minimize powdery mildew.
Cucumbers	8" deep 3+ gal/plant	full sun	Grow bush-types in hanging baskets or on a trellis (vines grow 18-24" long). Grow strong vining-types on trellis. Needs good air circulation to minimize powdery mildew. Young plants are very sensitive to wind burn.
Eggplant	8" deep 4-5 gal/plant	full sun	One plant per container. Needs night temperatures above 55º for pollen development.
Peppers	8" deep 2-5 gal/plants	full sun	One plant per container or space to 14"-18" in row. Needs night temperatures above 55º for pollen development. Decorative, attractive plant with fruit.
Summer Squash (Zucchini)	36" by 36" space 8" deep	full sun	Compact varieties more suited to container gardening. Great in a whiskey barrel size container. One plant will produce 6 or more fruit per week. Has male and female blossoms. May need hand pollination. Needs good air circulation to minimize powdery mildew. Keep fruit picked for continued production.
Tomatoes	12" deep 2-5 gal/plant depending on variety (plant size)	full sun	Varieties vary in mature plant size from determinate (bush) types to large, indeterminate vines over 6 feet tall. Patio types (small vines) are great for container gardening and may be grown as hanging baskets or trellised. Standard garden types require a larger container (like a whiskey barrel) and trellising. Needs night temperatures above 55º for pollen development. Crowding cuts yields and increases disease potential. Blossom end rot (black sunken area on bottom of fruit) is a symptom of inconsistent watering or a soil that does not have enough water storage.

* Larger container sizes will make crop easier to care for, providing a bigger supply of water and nutrients.

Additional Information CMG GardenNotes on vegetable gardening:

#711 Vegetable Garden: Soil Management and Fertilization

#712 Sample Vegetable Garden Seed Catalogs

#713 Block Style Layout in Raised Bed Vegetable Gardens

#714 Irrigating the Vegetable Garden

#715 Mulches for the Vegetable Garden

#716 Water Conservation in the Vegetable Garden

#717 Growing Tomatoes

#718 Early Blight of Tomatoes

#719 Vegetable Garden Hints

#720 Vegetable Planting Guide

#721 Sample Planting for Raised-Bed Garden

#722 Frost Protection and Extending the Growing Season

#723 Growing Vegetables in a Hobby Greenhouse

#724 Vegetable Gardening in Containers

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Authors: David Whiting, Carol O’Meara and Carl Wilson: Colorado State University Extension.

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