When you're short on garden space, or want to grow vegetables in a greenhouse, a grow bag is one way to make growing produce painless. The convenient grow bag contains enough soil to support growing vegetable plants without requiring you to prepare containers or dig in the garden. To grow cucumbers in grow bags you only need to make a few changes to the standard process for in-ground or container-grown plants, and you should have fresh cucumbers for slicing or pickling in a matter of months.
Place your grow bag in a full-sun location, either outside or in your greenhouse, where the sun shines directly for at least six hours each day. This location also needs to be suitable for water runoff and drainage. Place one bag for every two cucumber plants you want to grow.
Set up a trellis or staking system at the location of your grow bags at least 5 feet tall. If possible, or desired, you can place your grow bags next to a fence the cucumber can climb up instead of a trellis so long as the full sun will not be blocked.
Cut three, 1/2-inch diameter drainage holes along both long sides of the bag close to the bottom of the bag, but not on the bottom of the bag. Avoid perforating the base of the bag or you may expose your plant's roots to soil sickness from drainage that cannot leave out from under the bag.
Cut two holes equal in diameter to the seedling pots spaced 1 foot apart across the top of the bag. Scoop out a small amount of soil from each hole to make it deep enough to fit the roots of your seedlings.
Slip the pot away from your cucumber seedling's roots gently and place one seedling into each hole. Make the seedling as deep in the bag as it was in the pot. Press any disturbed soil in around the root ball of your seedling so it is firmed up around the roots.
Water your cucumber seedlings enough to moisten the soil without making it soggy. The soil in grow bags will dry out quickly, so plan to water every day or every other day, using more water as the plants grow larger.
Feed the cucumber plants with an all-purpose vegetable fertiliser at the strength recommended for container plants. Follow the directions on the fertiliser package for application methods and how often you should be fertilising.
Although less economical, you can cut open the top of one grow bag and the bottom of a second grow bag and stack the two for a larger growing space for your two plants. Just be sure to poke drainage holes into both bags.
Check over your cucumber plants weekly for signs of powdery mildew, a white dusty coating on the leaves of your plants, and treat with an edible safe fungicide as soon as possible.