Learn which plants thrive in your Hardiness Zone with our new interactive map!

How to Grow Vegetables in a Small Greenhouse

By Cindy Hill ; Updated September 21, 2017

A small backyard greenhouse is a dream come true for most home gardeners, providing space to start seeds and shelter tender perennials. You can also grow vegetables in your greenhouse, extending your gardening season with early spring and late fall crops of salad greens, radishes and peas. A small greenhouse can expand the spring-crop season through summer with shade cloth or let you grow heat-loving melons and eggplants in cooler climates.

Salad Vegetables

Stack concrete blocks in pillars to convenient heights within the greenhouse and lay plank boards over the blocks to create a seed-starting and vegetable growing bench.

Mix four parts potting medium with one part compost and water mixture with rainwater. Fill seed trays and 4-inch pots, using a trowel. Do not compact the soil mix.

Plant seeds for leafy green salad vegetables in seed trays at the depth and spacing recommended for each variety on its seed packet. Plant seeds for radishes and baby carrots individually in 4-inch pots. Lightly water in the seeds.

Water seed trays and pots as frequently as necessary to keep soil moist until they have germinated and developed their first true leaves. Water twice a week thereafter, adding a dose of liquid soluble fertilizer every other week through the growing season.

Transplant leafy green salad vegetables to individual 4-inch pots when they have reached 3 inches in height.

Start successive rounds of salad vegetable seeds every two weeks to ensure a continual supply from your small greenhouse. Hang shade cloth inside the south side of the greenhouse and open doors and vents when daytime temperatures inside the greenhouse exceed 75 degrees Fahrenheit to continue salad vegetable harvest through the summer. Remove the shade cloth in early autumn.

Heat Loving Summer Plants

Mix one part compost to four parts potting medium and water well with rainwater. Shovel mix into mounds on greenhouse floor, approximately 2 feet high by 3 feet in diameter, placed on 6 foot centers.

Plant melon, squash and cucumber seeds at a depth of 2 inches, four to five seeds per mound, in each mound. Cover with soil. Plant tomato, pepper or eggplant seeds at a depth of 1 inch, three seeds per mound, then thin to one plant per mound after seedlings emerge.

Fill hanging baskets with potting mixture and hang in greenhouse where they will not block light from heat-loving plants below. Plant cucumber and cherry tomato seeds in soil in hanging baskets 1 inch deep, three seeds per basket.

Vent the greenhouse by opening doors, lifting plastic cover edges or opening any vents when interior temperatures exceed 95 degrees. Water plants frequently, adding liquid soluble fertilizer once every other week.


Things You Will Need

  • Hobby-size greenhouse
  • Water source
  • Soil-less potting medium
  • Compost
  • Liquid soluble fertilizer (fish emulsion or compost tea)
  • Shade cloth
  • Plastic milk jugs
  • Black paint
  • Seed-starting trays with interior mesh drainage liner
  • 4-inch pots
  • 1-gallon nursery pots
  • Trowel
  • Concrete blocks
  • Plank boards
  • Vegetable seeds for selected varieties
  • Hanging baskets


  • Start cold-hardy vegetable seeds midsummer outdoors in a cool shady location or in your greenhouse if you are using shade cloth for summer-grown salad crops.

About the Author


A freelance writer since 1978 and attorney since 1981, Cindy Hill has won awards for articles on organic agriculture and wild foods, and has published widely in the areas of law, public policy, local foods and gardening. She holds a B.A. in political science from State University of New York and a Master of Environmental Law and a J.D. from Vermont Law School.