Is It Possible To Overgrow Vegetable Seedlings In A Greenhouse?

To ensure the success of seedlings, it is essential to control the temperature and humidity in greenhouses. Fill clean seed trays or pots with the seed-starting mix, leaving space at the top for watering. Protect seedlings from overheating and avoid using starting seeds suitable for direct sowing. Avoid using old seeds, failing to account for “days to maturity”, starting seeds at the wrong time, forgetting to stratify seeds, starting seeds in native soil, and sterilizing your seed-starting soil.

Plug trays or peat pellets are great for starting seeds but require transplanting after the seedling has developed its second set of true leaves. Seedlings can be placed in an unheated garden greenhouse when they are still tiny, such as when they are in their seed starting trays or pots. It is important to keep up with maintenance care, thin out weak seedlings, prick out those growing too big for their seed starting trays, and maintain a minimum of 5°C/41°F.

To harden off seedlings, slowly introduce them to outdoor light levels for an hour and then bring them back in. If using fleece/row cover when transplanting, you don’t need to harden them off at all. However, transferring seedlings too early may risk them being damaged by late frosts or setting their progress back with adverse weather conditions.

When seedlings grow too big, pot up, fertilize, remove flowers, and water when the soil starts to dry out. Hardening off a plant means slowly acclimating it to a new environment so that they don’t go into shock, suffer damage, or even die.