5. Control the temperature and humidity. Make sure the room temperature is regulated as well, ideally between 65 degrees and 70 degrees Fahrenheit for most seeds (consult your seed packet for specific instructions). An easy way to boost the temperature is to place a humidity dome over the plants or a heated mat under the plant trays. Make sure to maintain adequate moisture levels; soil should be damp, but not drenched. No fertilization is required during the germination period. If you are using any artificial heat, remove it when after the seeds sprout their first leaves.
6. Start thinning. Once your tiny plants start to sprout, it's time to show some tough love. Thinning might seem like a waste of a healthy plant, but it is a necessary step to help your seedlings become strong and healthy. To thin, clip the weaker sprouts at the soil level, as pulling them out can damage the delicate root systems. At this point, give the seedlings a half-strength fertilizer that is specific for houseplants about every two weeks.
7. Upgrade your containers. When several inches high, it's time to carefully transplant your seedlings into bigger containers. Try using some peat pots, as they are biodegradable and can be planted straight into the garden when outdoor conditions are appropriate.
8. Acclimate your plants to the outdoors. The final step is to transition your plants into the garden, a process called “hardening off.” After the threat of frost has passed, take your little seedlings outside for about an hour, in an area that is sheltered from the sun and wind. Gradually increase this time and exposure to the outdoors over a two-week period until, finally, your little plants are ready to be planted into the garden—ideally on an overcast day. (If you purchased seedlings from a store, ask the seller whether or not they were hardened off, though assume so if the plants were outside when you bought them.)
9. Transplant your plants into the garden. Whether you are planting seeds directly into the soil or transplanting seedlings, consult your seed packet for sowing depth and spacing. (or, as a general rule, dig a hole that is twice as wide and deep as your transplants). Handle your seedlings carefully because, essentially, they are delicate babies.
10. Care for your new plants! Seedlings and directly-sown seeds require TLC once they are in the garden. Watering them regularly is important as they are in their infancy and not yet "established." Protect them from wind and predators (birds are notoriously munch on freshly planted seeds). Mulching around plants, once established, is a helpful way to increase moisture retention, too.