How to Grow Cucumbers With Tomatoes in a Greenhouse

Updated February 21, 2017

Cucumbers and tomatoes, both warm-season, summertime plants, are straightforward and highly successful in home gardens. Both types of plant require bright, warm sun, long growing seasons, and adequate warmth and nutrition. As vining plants, both tomatoes and cucumbers require plenty of space and support from veggie cages or trellis system. As warm-season plants, cucumbers and tomatoes need protection in cold climates and winter. Provide that protection with a greenhouse, but make sure you still give the plants the conditions they need for growing.

Start tomatoes and cucumbers at any time in a greenhouse. For winter growing, make sure you have a workable fan, heater, thermometer and artificial lights in the greenhouse. Plant tomatoes and cucumbers in pots for easy movement within the structure, both for yourself and the plants. Prepare 3- to 5-gallon pots with drainage holes by filling them three-quarters full with a mixture of half quick-draining potting soil and half organic compost. According to package directions, add 10-10-10 fertiliser to the potting soil before planting.

Plant tomatoes and cucumbers in shallow holes to give their roots access to air and water. Put only one seedling in each pot. Pack in amended soil around their roots, then water them with 2 inches of water. Place a veggie cage in each pot for eventual support.

Place all pots in areas that get full sun exposure and make sure none of the plants will shade any others. Place the tomatoes at 24 to 36 inches, in rows at 4 to 5 feet. Place the cucumbers in a section 5 feet away from the tomatoes, at 2 to 3 feet, in rows at 5 feet. All of these plants require full light all day and will fail if they grow in the shade of another plant.

Turn on the heater and thermometer for winter and maintain temperatures of 18.3 to 23.9 degrees Celsius for ideal tomato and cucumber growing. Water the plants weekly with 2 inches of water and spray them with the hose at least once a week to build humidity in the greenhouse. Turn on the fan for air circulation and pollination. Keep windows and doors closed to retain humidity in the building. Use the artificial lights to supplement natural daylight as the days grow shorter.

Feed potted cucumbers and tomatoes more often than you would in the garden. Give the plants water-soluble 20-20-20 or 15-30-15 fertiliser once a week with their watering, starting halfway through the growing season. This feeding encourages blooming, fruiting and a larger harvest.

Things You'll Need

  • 3- to 5-gallon pots
  • Quick-draining potting soil
  • Organic compost
  • Fertiliser
  • Veggie cages
  • Felt ties
  • Heater
  • Thermometer
  • Fan
  • Hose
  • Artificial lights
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