Vegetable Gardening in Containers

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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 reduce produce quality.

Cool Season Vegetables

Cool season vegetables prefer the cool growing temperatures (60°F to 80°F) 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.


Table 1.
Cool Season Vegetables
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 three inches”.
  • A consistent supply of water and nutrients promotes the rapid growth essential for quality produce.

Broccoli
Cabbage
Cauliflower
Collards
Kale

10” deep

5 gallons per plant

8 hours
  • Best in fall production (e.g., plant mid July for fall harvest along the Colorado Front Range).
  • Minimum spacing per plant is 18 inches by 18 inches.
  • 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 two to three inches apart.
  • Decorative foliage.
Chard
8” deep
6 hours
  • Space to six or more inches 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 growth essential for quality produce.
  • Never allow soil to become dry.
  • Kohlrabi is a heavy feeder, requiring frequent, light fertilization.
Leaf Lettuce
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 nine-inch 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 four inches, 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 (70°F to 95°F) 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. Warm season crops need full sun.


Table 2.
Warm Season Vegetables

Vegetable
Minimum Container Size*
Minimum Direct Sunlight Per Day
Remarks
Beans
8” deep
full sun
  • In a long box 12-inch wide, plant bush beans or trellis pole
  • Beans have a high water requirement during blossoming.
  • Beans drop blossoms with dry soil or excessive wind.
Cantaloupes
Muskmelon
s
5+ gallons per 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+ gallons per plant
full sun
  • Grow bush-types in hanging baskets or on a trellis (vines grow 18-24+ inches 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 gallons per plant
full sun
  • One plant per container.
  • Requires night temperatures above 55°F for pollen development.
Peppers
8 deep
2-5 gallons per plant
full sun
  • One plant per container or space to 14 to 18 inches in row.
  • Requires night temperatures above 55°F for pollen development.
  • Decorative, attractive plant with fruit.
Summer Squash (Zucchini)
8 deep
36 by 36 space
full sun
  • Compact varieties more suited to container gardening.
  • Great in a whiskey barrel size container.
  • One plant will produce six 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 gallons per plant depending on cultivar (plant size)
full sun
  • Cultivars 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.
  • Requires night temperatures above 55°F 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 (too wet or too dry) or inadequate pot size.
*  Larger container sizes will make crops easier to care for, providing a bigger supply of water and nutrients.


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Authors: David Whiting (CSU Extension, retired), with Carol O'Meara (CSU Extensoin, Boulder County) and Carl Wilson (CSU Extension, retired).

  • CMG GardenNotes are available online at www.cmg.colostate.edu
  • Colorado Master Gardener/Colorado Gardener Certificate Training is made possible by a grant from the Colorado Garden Show, Inc.
  • Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating
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  • Copyright. 2010-14. Colorado Master Gardener Program, Colorado State University Extension. All Rights Reserved. CMG GardenNotes may be reproduced without change or additions, for nonprofit educational use.

Revised October 2014

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