How to Plant Seeds in a Mini Greenhouse

Written by patrick armstrong
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How to Plant Seeds in a Mini Greenhouse
Using small indoors greenhouses to start tropical vegetable seeds dramatically improves yield at harvest time. (tomato plant image by Crisps85 from

For most people, a year's growing season is not twelve months long. Late fall, winter and early spring are plants' times for dormancy and death, and these months typically don't command gardeners' attention. For some resourceful and adventurous growers, however, these months are a time for growing indoors. These folk grow herbs in small pots and start next year's crops, like tomatoes and peppers, in mini greenhouses. These small greenhouses present their own challenges, but when managed successfully, extend the growing season by months.

Skill level:

Things you need

  • Vegetable seeds
  • Mini greenhouse
  • Potting soil
  • Garden trowel

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  1. 1

    Choose a mini-greenhouse. The smallest and cheapest variety is the windowsill greenhouse, which usually comes with a plastic base and a clear plastic top, and biodegradable pots made from woven or moulded materials. Larger greenhouse varieties require more floorspace but allow plants to grow more before transplant. The largest mini-greenhouses provide enough space for some plants to grow completely indoors. Choose the design best suited to the plants' overall growth plan.

  2. 2

    Purchase vegetable seeds. Warm-weather plants, like peppers and tomatoes, benefit the most from extended indoor growing time. These plants have hot, humid conditions in their native locales, and small greenhouses will mimic these conditions well.

  3. 3

    Purchase high-quality potting soil. Potting soil allows for good initial root growth, has superior nutrient levels and stays evenly moist. Buying topsoil or manure or digging soil from outside will significantly hamper a plant's ability to grow indoors. Potting soil is labelled as such at garden centres and home improvement stores.

  4. 4

    Fill the pots with potting soil, leaving half an inch of open space at the top. For larger pots and greenhouses, a garden trowel will be the best tool for the task. Windowsill pots are easiest to fill with spoons from the kitchen. Once the pots are filled, add enough water to wet the soil. This will cause the soil to settle, so add more potting soil to make up the difference and keep the pots full.

  5. 5

    Plant the seeds at the proper depth, according to the instructions on the seed packet. Label the pots to make identification easy when the seedlings are ready to transplant. A marker and masking tape is a good way to label the pots. Water the pots again to make sure all the soil is evenly moist.

  6. 6

    Cover the windowsill pots with the clear plastic top, or if using a larger system, place the pots in the greenhouse. Move the pots to a window with direct sunlight, preferably a south-facing window.

Tips and warnings

  • Let air circulate once a day by opening the greenhouse to the surrounding air. This will allow for gas exchange and will minimise the chances of mould taking hold in the potting soil.
  • Windowsill greenhouses won't need much watering because the system is nearly sealed and water vapour can't escape.
  • Rotate the mini-greenhouse 180 degrees every day or so to keep the plants growing straight. Otherwise, the plants will bend towards the window in one direction only and will have strange and detrimental shapes when they are transplanted.
  • Not all "biodegradable" pots will degrade in a timely fashion. When it comes time to transplant, gently remove or break up as much of the pot as possible without damaging the roots.

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