Seed Starting Handbook

Seed Starting Handbook
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Seed Starting Handbook

Seed Starting Guide from Park Seed

Find instructions for planting and germinating seeds. Want to make it easier? Download the From Seed to Spoon app to calculate dates for you. You'll get tips on trouble shooting and videos to guide you along your growing journey, too. 

Sowing Seeds Indoors

Check the back of your seed packet for instructions about sowing. If indoor sowing is recommended, follow the directions below. If outdoor (direct sowing) is preferred, see a section called, Sowing Outdoors.


Sow your seeds so that the seedlings will be ready to transplant at the right time in spring. To do this, you will need:

  1. The last expected frost date for your area (search online for "US frost free dates").

  2. The temperatures your seedlings need for successful transplanting (consult the seed packet).

  3. The number of weeks from sowing to setting-out size (consult the 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. 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. If you are using the Bio Dome or Park-Starts, estimate about 1.25 to 1.5 seeds for every plant you want. (You will need only 1 or, for some varieties, 2 seeds per bio sponge.)

If you are using seed trays, estimate 2 seeds for every plant, then broadcast-sow the seeds as follows for every 50 square inches of tray:

  • Up to 50 large seeds
  • Up to 100 small seeds
  • Up to 150 tiny seeds

Sowing Seeds in Park's Bio Dome or Park-Starts

The easiest way to start seeds is with Park's Bio Dome, which is a humidity-controlled seed starter with a bottom tray; a Styrofoam planting block; either 60, 40, or 18 plugs; and a clear plastic dome with vents. You may also use Park-Starts, which is a Styrofoam planting block with 18 plugs set into a shallow tray.

  1. Place 1 (or, if desired, 2) seeds into the hole in each plug, or place tiny seeds on the top of the plug, uncovered.
  2. Mix a weak fertilizer solution according to the directions on the free fertilizer packet included with your Park-Starts or Bio Dome. Fill the base of the tray with this solution, so that the planting block floats.
  3. When you have sown every plug in the unit, place the Bio Dome or Park-Start in a protected place (such as the top of the fridge or on a kitchen counter). Consult your seed packet for any special instructions about light, darkness, or temperature.
  4. As the seeds sprout, adjust the air circulation in the Bio Dome by sliding the vents in the cover. If using Park-Starts, place plastic over the whole unit if needed for greater humidity until the seeds sprout. Always keep the base of the tray filled with water.
  5. If you have double sown the seeds, keep only the stronger seedling in each plug. Use scissors to cut away the other seedling at the base of its stem.

Note: If you are using Park-Starts or the 60-cell Bio Dome, you can transplant the seedlings, plug and all, when the first or second true leaves appear. If using the 40 or 18-cell Bio Dome, the seedlings can grow larger and stouter before transplant. If weather delays your transplanting, the seedlings' roots may emerge from the bottom of the plugs. Simply prop up the planting block to allow some air around the roots until you can transplant. Don't allow the roots to dry out.

Go to Growing On section for detailed information on growing and transplanting your seedlings.

Sowing in Seed Flats

  1. Choose a good quality seed starting mix, moisten it by scooping it into a plastic bag and adding water, and then fill the seed flat with the mixture to about 1/4" of the brim. Smooth it down.
  2. Make shallow furrows 1" apart in the grow mix, using a pencil or your fingers. Furrows should be 1/4" deep for small seed or 1/8" deep for tiny seed. Large seed can just be poked into the medium without making a furrow.
  3. To sow seed evenly in the furrow, tap the seed packet lightly as you move it over the furrow. If too many seeds fall too close together, separate them with a pencil point.
  4. Pinch the furrows closed over the seeds. A good rule of thumb is to cover the seeds to twice their thickness. Note: Seeds that need light to germinate should not be covered. Consult your seed packet for instructions.
  5. Water the flat by placing it in a pan of lukewarm water until the top of the medium is very moist.
  6. 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 sowing medium. Place the flat in a protected location.
  7. Check the moisture of the sowing medium every day. If it feels dry, bottom-water it again as in step 5 above.
  8. After the seeds sprout, remove the plastic.

Transplanting Seedlings Indoors from a Seed Flat

Note: If you are using the Bio Dome or Park-Starts, skip these steps and go to Growing On.

Seedlings grown in a seed flat quickly become overcrowded and should be transplanted when they have developed 2 sets of true leaves. Transplant them into small pots or One-Steps as follows:

  • Bottom water the seedling flat 1 hour before transplanting.
  • Moisten the soil in the pots or the One-Steps, and set them into your tray.
  • If using pots, make a large hole in the center using a pencil or plant label. (One-Steps have pre-cut holes.)
  • Gently remove seedlings from the flat, using a fork or tongue depressor to loosen the soil and pry the seedlings apart. A small soil ball should cling to the roots. 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 with fertilizer solution, from the bottom, the same way as for a seedling flat.
  • If seedlings droop right after transplanting, keep the soil quite moist and out of sunlight for a few days.

Growing On

Growing garden sized plants may take anywhere from a week to several months, depending on the species. Follow the instructions on your seed packet.

The two leaves that appear on a brand-new seedling (often with part of the seed clinging to them!) are not leaves at all, but cotyledons. They will wither and drop off after the true leaves emerge.

Increase the light levels to prevent the seedlings from stretching. Plant lights are ideal, but under-the-counter kitchen fluorescents will do if the seedlings are placed close to the bulb. Plant lights provide optimum growing conditions for seeds and seedlings.

As the seedlings grow, watch them 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.

Give growing seedlings a drier medium and less frequent, more concentrated feedings. Let the surface of the soil become dry to the touch between waterings (lower layers should still never dry out). Feed once a week using a water-soluble fertilizer.

If plants get too tall before transplanting time, just pinch them back.

Transplanting Scheduling

It's best to transplant your seedlings into the garden or final container before they begin to bloom. If your seedlings begin to set buds before transplant time, pinch the buds off.

Plants are ready for the garden when they have at least 2 sets of true leaves and/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.

Hardening Off

This is the process of acclimatizing seedlings to outdoor conditions. Place the Bio Dome, Park-Start, or tray of seedlings in a shaded outdoor spot, protected from wind. Keep the seedlings well-watered, and move them back inside after a few hours. The next day, let them remain outdoors longer. The third day, move them to a sunnier spot. When they get through a day outdoors without wilting, they are ready for transplanting.

Planting Out

Before transplanting, smooth the surface of the soil with a rake. Then, in early morning or on a cloudy day (if possible), place the transplants, a few at a time, on top of the soil, in the design you want. Do this quickly, so they do not dry out before planting.

Watering and Mulching

Once you transplant your seedlings, immediately water them thoroughly. This not only keeps them hydrated, but also helps eliminate air pockets and promotes good root/soil contact. Soak the whole bed for large plantings and create a small mud puddle around a single plant.

After watering, mulch around the plants. Mulch is a protective layer of material that helps preserve soil moisture, keeps soil temperature more constant, and prevents weeds from sprouting. Good organic mulches include old leaves and pine needles, bark, dry grass clippings, or wood shavings. Spread mulch several inches deep over the soil between the plants, pressing gently around the base of the stems. Inorganic mulches such as landscape fabric may also be used.

Sowing Outdoors

Seeds that are very large, grow quickly, or form a taproot should be sown outdoors, where they are to be grown. Your seed packet will tell you which sowing method each type of seed prefers.

Most seeds are sown in spring, although some cool season vegetables and perennial seeds can be sown in late summer. Some seeds (particularly perennials) need sowing in late fall, so that they can experience a cold period during winter and be ready to germinate in spring. To do this, sow the seed slightly deeper than you would do in spring. Protect the sides of the bed with boards to prevent seeds washing away. Apply a protective mulch as soon as the ground freezes.

Weather Watching

The key to direct sowing is to pick the right weather. Use the frost dates for your area as a guide, and try to select a day that is not too windy or wet, so the seeds will not wash out.

Seed Bed Preparation

Unless you have already prepared the soil thoroughly, turn it over 6 to 8 inches deep.


Sowing depths vary for each type of plant; see seed packet for instructions. Make a furrow to the depth you need, sprinkle the seeds into the furrow, and firm the soil down over them. Some very fine seeds (such as Lettuce) will scarcely need covering at all.

Care After Sowing

Until seeds have sprouted, keep the seed bed moist, never allowing it to dry out. Water with a fine spray nozzle or watering can to avoid washing out the seeds.

As seeds germinate, the seedlings may grow too close together. Thin them, following the instructions on seed packet. If you do not thin the plants, all of the plants will suffer.

Ongoing Garden Care

Once your plants are growing outdoors in the soil, make sure to give them attention all season long.

During the first 3 weeks after transplanting indoor-sown seedlings, check the soil moisture weekly by feeling the surface of the soil beneath the mulch. Give the garden at least 1 inch of water or irrigation a week throughout the growing season.

Fertilize plants according to specific needs. If the foliage begins to yellow, the plant needs more nutrients.

Seed Tape

Seed tape is an easy way to start seeds in exactly the space you wish. It’s great for sowing straight rows of plants, designing pattern plantings, and more. The tapes hold the seeds in place until they sprout, and the water you apply to the soil gradually dissolves the tapes.

Prepare to sow the seed tape exactly where you want your plants to grow. Cut the tape to fit the space you wish to plant. Lay the tape on top of the soil, or in a slight furrow, and sprinkle soil lightly over the tape so that it is covered completely. Do not bury the tape more than 1/4 inch deep and water the tape in well.