Seed Starting and Transplanting
I always recommend that you have a basic idea of where your baby plants will end up! Also give some thought to how many plants you want to end up with to plant out in the garden. This will determine how many seeds to sow.
When sowing seeds indoors, the goal is to have seedlings that will be ready to transplant at the right time in spring or fall. To do this, you will need to know the following:
- The last expected frost date for your growing zone OR the first hard frost in your growing zone. Use the internet to find your USDA growing zone by zip code.
- The temperatures your seedlings need for successful germination and transplanting.
- The number of weeks from sowing to setting-out size.
Information for numbers 2 and 3 should be on your seed packet.
Once you have this information, count backwards from the frost-free date through the number of weeks needed to germinate and grow on the seedlings, located on your seed packet. Then sort your seed packets into groups by recommended germination temperature (also found on the seed packet), so you will know which ones you can sow together.
Then determine how many seeds to sow.
Sowing Seeds in Flat Trays
If you are using flat trays, estimate 2 seeds for every plant, then sow the seeds as follows for every 25 square inches of tray:
- Up to 25 large seeds
- Up to 50 small seeds
- Up to 75 tiny seeds
Sowing Seeds in Planting Pot Cells
- Place 1 (or, if desired, 2) seeds into the hole in each cell.
- Consult your seed packet for any special instructions about light, darkness, or temperature.
- If you have sown multiple seeds into a cell, keep only the strongest seedling in each cell. Use scissors to cut away the other seedling(s) at the base of its stem.
Successful Seed Sowing Requires the Following (regardless of tray type):
- Choose a good quality seed starting mix, moisten it by scooping it into a plastic bag and adding water, and then fill the seed tray with the mixture to about 1/4″ of the brim. Gently tamp the soil down so it’s even and smooth.
- Make shallow holes in the grow mix, using a pencil or your fingers. Holes should be 1/4″ deep for small seeds or 1/8″ deep for tiny seeds. Large seeds can just be poked into the medium without making a hole.
- Pinch the holes closed over the seeds. A good rule of thumb is to cover the seeds to twice their thickness.
Please note, any seeds that need light to germinate should not be covered. Make sure the seeds have good contact with the soil by tamping down gently.
- Water the flat by placing it in a pan of lukewarm water until the top of the medium is very moist.
- Cover the flat with a sheet of clear plastic wrap or place it in a plastic bag. Make sure the plastic does not touch the surface of the soil. Place the flat in a protected location.
- Check the moisture of your little seed babies every day. If it feels dry, bottom-water it again as in step 5 above.
- After the seeds sprout, remove the plastic.
Transplanting Seedlings from a Seed Flat:
Seedlings grown in a seed flat quickly become overcrowded and should be transplanted when they have developed 2 sets of true leaves. Bottom water the seedling flat 1 hour before transplanting.
- Make a large hole in the center of a pot using a pencil or your fingers.
- Gently remove seedlings from the flat, I like using a chopstick or pencil using a fork to loosen the soil and pry the seedlings apart. A small soil ball should cling to the roots. Please Note: Handle seedlings by the leaves or the soil ball, not by the stems.
- Place the root ball into the hole you have made. Gently firm the soil around the roots, then fill in the hole so that the soil surface is level in the pot. Cover only the roots and the base of the stem, not the leaves.
- Label the pots with the name of the plant.
- Thoroughly soak the pot from the bottom, the same way as for a seedling flat.
- Seedlings may droop right after transplanting. If that happens, keep the soil quite moist and out of sunlight for a few days.
As your seedlings grow:
The two leaves that appear on a brand-new seedling (often with part of the seed clinging to them!) are not true leaves. They will wither and drop off after the true leaves emerge.
Increase the light levels to prevent the seedlings from stretching (this is where the plant looks “leggy”) You may choose to use a plant light, or kitchen counter lights, or even a bright window. Whatever you choose, know that your tiny plants need LIGHT.
Watch your seedlings carefully. If some of them fall over and have a brown base even though the leaves look healthy, they may be “damping off.” Reduce watering and improve air circulation to prevent this. If seedlings have shriveled leaves or bent stems, they are probably too dry, and need a thorough soak.
Plants are ready for the garden when they have at least 2 sets of true leaves or are between 2 and 4 inches high. By the time their roots are growing out the base of the container, it is time to transplant.
Watering and Mulching:
Water your seedlings thoroughly as soon as they have been planted. This helps to ensure good contact with the soil and helps to eliminate any air pockets in the soil.
After watering, mulch around the plants. Here in Southern Utah where our soils are lacking in nutrients, I always recommend a mulch high in organic matter.