10 Steps to Seedling Success
You might start seeds to save money. Or maybe you want to grow a plant variety that’s not typically available for sale as a transplant. Whatever the reason, starting plants from seeds is definitely doable, no matter your gardening experience. Master the basics, and you’ll find that growing your own seedlings can be a rewarding pursuit.
1. Select a container.
Your seed-starting containers should be clean and measure at least 2 to 3 inches deep with drainage holes. Options include plastic pots, cell packs, peat pots, plastic yogurt cups, newspaper, even eggshells. You can buy a seed-starting kit, but don’t invest a bundle until you’re confident you’ll be starting seeds every year. If you start seeds in tiny containers, you’ll need to transplant seedlings into slightly larger pots once they have their first set of true leaves. Keep in mind that flats and pots take up space, so make sure you have enough room for all the seedlings you start.
2. Start with soil.
Sow seeds in bagged, sterile seed-starting mix. Don’t use garden soil. Moisten soil with warm water before filling seed-starting containers.
3. Double-check planting depth.
Sow seeds to the depth recommended on the seed packet. The rule of thumb is to cover seeds with soil equal to three times their thickest point – but be sure to read the seed packet planting instructions carefully. Some seeds, including certain lettuces and snapdragons, need light to germinate and should rest on the soil surface. After sowing your seeds, use a spray bottle to wet the soil again.
4. Water carefully.
Always use room-temperature water when watering seedlings. Let chlorinated water sit overnight so chlorine can dissipate. Don’t use softened water. It’s important to keep soil consistently moist, but avoid too much water, which encourages disease. Avoid splashing water on leaves. An easy way to avoid this – as well as overwatering – is to dip your containers in water and allow the soil to absorb moisture as needed. Some seed-starting kits supply a wicking mat that conducts water from a reservoir to dry roots. This is probably the most goof-proof method of watering seedlings. Whatever you do, don’t miss a watering. It will kill seedlings.
5. Keep moisture consistent.
Cover your container to help trap moisture inside. Seed-starting systems typically come with a cover. You can also use a plastic bag or plastic wrap. Remove covers as soon as seeds sprout.
6. Maintain soil temperature.
Seeds need warmth to germinate – warm soil, not warm air. Most seeds germinate at 78° F. A waterproof root zone heating mat keeps soil at a constant temperature. Alternatively, you can stash seed trays on top of a refrigerator or other warm appliance until seeds sprout. Following germination, air temperature should be below 70° F. Seedlings can withstand air temperature as low as 50º F, provided that soil temperature remains 65° to 70° F.
7. Feed young seedlings.
Fertilize after your seedlings develop their second set of true leaves, applying a half-strength solution weekly. At the four-week mark, apply full-strength fertilizer every other week until transplanting.
8. Supply enough light.
Inadequate light leads to leggy, tall seedlings. In southerly locales, you likely can grow stocky seedlings in a bright south-facing window. In the northern two-thirds of the nation, even a south-facing window may not provide enough light to produce non-leggy seedlings. Ideally, seedlings need 14 to 16 hours of direct light for healthiest growth. A sign your light is insufficient is if seedlings begin bending toward the window. While you may correct the bend by turning pots, the problem is that once stems elongate you can’t shorten them. When using artificial light, try an illuminated plant stand or choose a full-spectrum fluorescent bulb or one each, cool and warm. Suspend lights 2 to 3 inches above seedlings.
9. Move the air.
Air circulation prevents disease and helps develop strong stems. Run a fan near seedlings to create air movement. Avoid blasting seedlings directly.
10. Harden off seedlings before transplanting.
Before being planted outdoors, seedlings need to be acclimatized to their new – and harsher – surroundings. This process is called “hardening off.” Click here to learn more.