Young seedlings are very delicate just after germination. Wind gusts can blow them over, animals can damage them, and extreme weather conditions can kill them. For these reasons, many gardeners prefer planting germinated seeds indoors, even if they eventually plan to replant them outdoors.
For this initial planting, use a pot, cup, or other container that’s about 16-20 ounces (the size of a Solo Cup). Place the seedlings somewhere they’ll get plenty of sunlight, which is crucial for strong growth. A south-facing window is ideal. Remember to rotate the containers periodically to prevent the plants from leaning, but don’t relocate them frequently, as movement can stress young plants out.
Alternatively, you can plant your germinated seeds outside and in the container that they’ll grow to full size in. This limits the number of times you’ll need to transplant them (which causes stress) and allows them to adjust to their permanent environment right away. In fact, some plants that grow extremely fast (such as beans) are best started outside.
Steps for Planting Germinated Seeds
It’s important to plant seeds as soon as they germinate because their roots need nutrients from soil and their stems and leaves need sunlight. Before planting, make sure the new roots are 1.5 to 2.5 centimeters long. Follow these steps when learning how to plant germinated seeds into soil.
Step 1: Prepare Your Growing Medium
Fill your container almost to the top (about 1 centimeter below the pot’s edge) with your desired growing medium. Good choices for germinated seeds include coco coir (made from coconut husks) products such as coco coir blocks or a coir and potting soil blend. Coco grow cubes, which are made of coco coir fiber and pith, are another great option. Their water retention abilities and fibrous structure allow seedlings to develop strong root systems. Plus, like all coir products, they resist most bacteria, fungus, and mold growth that other growing mediums can be prone to.
If you’re using a compact coco coir block as your growing medium, you’ll need to soak it in a large bucket first to allow it to decompress. Slowly add the amount of water indicated on the packaging’s directions (which might seem like a lot, but coir can hold up to five times its volume in water) and wait until the coir absorbs it. When the block starts to crumble, you can mix it up with your hands. Then, it’s ready to use for planting germinated seeds.
Regardless of the medium you use, moisten (but don’t soak) it before placing the seeds, and pack it firmly within the container to avoid gaps.
Step 2: Create Holes for the Seeds
Make a half-inch to an inch-deep indentation in the soil for each germinated seed. Your finger up to one knuckle or the end of a pen work well for creating the holes.
Step 3: Place Seeds in the Soil
Very gently place each germinated seed, root down, into your growing medium, so the top of the seed husk is just below the soil’s surface. Make sure you don’t touch the white taproot, which can damage it, or squeeze the seed too hard in the process. You can use a pair of tweezers to move each seed safely.
Step 4: Cover the Seed
Cover the germinated seed gently with a thin layer (just a couple of millimeters) of growing medium. Avoid packing or pressing on the soil. Use a plant sprayer or mister to moisten the surface if it’s not already damp, and place the container in a well-lit area.
If you’ve followed these directions for how to plant germinated seeds properly, the seedlings should emerge within a week to 10 days, if not sooner. Sometimes they’ll break through the soil within mere hours or a couple of days. If more than a week passes, however, without any sign of seedlings, they probably didn’t survive the planting process.
Caring for Your Seedlings
After your germinated seeds sprout through the soil, you still have to be vigilant in caring for them to ensure they survive and their growth isn’t stunted. Check your growing medium each day to make sure it remains slightly moist. When it begins to dry, spray it with a mister. If you’re using coco coir as your growing medium, remember that it holds more water than traditional soil and won’t require watering as frequently. You might also need to supplement nutrients.
Seedlings benefit from good airflow, so you might set up a fan nearby (but not directly on them). This may not be as critical a step if you’re planting in coco coir, which has naturally aerating properties.
If you haven’t planted your seedlings in their final location, you’ll probably need to transplant them into larger pots after about a month of growth. At this point, the plant should be strong enough to survive repotting and continue growing outdoors.Â
Make the transition gradually, however, in a process called hardening off. Let the seedlings acclimate by spending a few hours each day in a protected area outside that is shielded from the wind and direct sun. Remember to bring them inside at night. Expose the young plants to increasingly more sun and wind, for longer periods, over a week to 10 days.Â
Just because a seed has germinated doesn’t mean you’ve missed your planting window. In fact, many fruit, vegetable, herb, and flower species do best when planted after sprouting. By learning how to plant germinated seeds properly, you can ensure a healthy, strong crop.