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How to Sow Seeds in 10 Easy Steps (With Pictures)

Eugene is an avid gardener and has been passionate about growing things for over 40 years.

How to Sow Seeds in 10 Easy Steps (With Pictures)

You can buy "ready made" plants in a store, but it can be much more fun and a lot less expensive to grow them yourself from seed. The magical phenomenon of a seed's germination and transformation into an adult plant is entertaining for both adults and children alike!

In this guide we'll discuss

  1. Collecting seeds (from poppies)
  2. Trays and other containers for sowing seeds in.
  3. Which growing medium is best
  4. Details on sowing seeds
  5. How you should look after seeds once they're sown
  6. Getting ready for planting out
  7. What are the easiest flowers to grow from seeds
  8. Seed germination and seedling problems
  9. Alternative methods of propagating plants

Is it easy to grow plants from seeds?

Seed sowing is a basic horticultural skill. Many flowers, trees, and vegetables are easy to grow from seed if you take a little bit of care. Minimal equipment is needed and all you need to do is provide the basic requirements for germination; warmth, moisture and oxygen.

One obvious advantage of growing plants from seed is that it is much cheaper than buying them. Also many plants produce lots of seeds which can easily be harvested and sown, and you can collect more seeds than would ever be included in a store-bought packet.

What you'll need:

  • the seeds themselves
  • containers: you can use discarded plastic cups, trays or boxes
  • seed compost (potting soil made especially for starting seeds)
  • a spray mister (empty spray bottles are ideal)
Oriental poppies: I harvested seeds from these in the late summer.

Oriental poppies: I harvested seeds from these in the late summer.

Steps for Sowing

These are the basic steps, but check the seed packet for specific details on sowing depth, germination temperature and when to sow.

Step 1: Harvest Seeds From Flowers and Vegetables

The seeds I sowed were collected or harvested from flowers in the autumn after flowering.

  1. Pick a dry day for collection.
  2. Shake seeds into a paper bag or envelope (not a plastic bag, which will retain moisture and promote mold). Some plants have pods which are just another shape of ovary. You can split these open yourself and collect the seeds, but some pods are "spring loaded" and twist and split open themselves, flinging seed everywhere, so collect those seed before this happens.
  3. Store seeds in a cool, dry place until you're ready to sow them.

When are seeds ready to be collected?

Collect seeds when the ovaries (seed pods) are ripe. You'll know this because they'll usually have become crisp, dried-out, and beige in color. Sometimes, with plants like marigolds, the ovary will split open, revealing bunches of seeds. Other flowers have a capsule-like ovary. A tell-tale sign that seeds are ready is that you can hear them rattle inside when you shake the seed pod.

Will flowers grown from seed be like their parents?

Not necessarily. Flower varieties are often bred to have certain attributes such as large, abundant or colorful blooms or nicely shaped petals. Quite often if you sow seeds, the flowers produced will revert to what the original wild version looked like. We'll learn more about this later.

Seed-containing ovary of a poppy plant. Seeds can be harvested on a dry day when pods have lost their green color and dried out.

Seed-containing ovary of a poppy plant. Seeds can be harvested on a dry day when pods have lost their green color and dried out.

Step 2: Collect Trays or Pots and Drill Holes If Needed

You can sow seeds in a proper seed tray bought from a store. Alternatively, you can make do with a cookie tin, flower pot, empty food container, or something like that. If there are no holes in the bottom of the container, make some with a 1/4 inch drill bit or a nail. Space the holes a few inches apart. This allows water to drain from the container and prevents it from collecting, which would make the seed compost overly wet.

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You can also sow seeds individually in plant trays like the ones annual plants from stores are sold in. The advantage of these is that seedlings don't need to be transplanted later. If you have lots of seeds and not enough trays, sow a couple in each compartment in the tray in case one doesn't germinate.

Many containers can be used for sowing seeds. Add holes for drainage.

Many containers can be used for sowing seeds. Add holes for drainage.

Step 3: Fill the Container With Sterile Seed Compost (Seed-Starting Potting Mix)

Use a sterile seed compost like this seed starting potting mix from Amazon if possible. You can also use a multipurpose seed/potting compost, but don't use soil dug up from your garden, as this will be lumpy, contain lots of pests and diseases, and dry out quickly. Some plants aren't "fussy" about what they grow in, and if you have lots of harvested seed, you can try sowing it in soil which you have crumbled up so that it's nice and fine. From my experience however, it's best to buy proper compost to maximize the chances of germination.

Fill the seed tray with seed compost.

Fill the seed tray with seed compost.

The seed tray doesn't need to be totally filled because seedlings will eventually be transplanted.

The seed tray doesn't need to be totally filled because seedlings will eventually be transplanted.

Step 4: Moisten the Surface of the Compost

Moisten the surface of the compost with a mist spray. I just use an empty recycled window or shower cleaner bottle (carefully washed out before using). You can use a watering can but unless its sprinkler rose has small holes, it will flood the compost. Don't use a watering can to wet the compost pre-germination if it becomes dry, or to water delicate young seedlings, because too much water will wash away seeds or flatten seedlings.

Wet the surface of the soil with a mister. Mine was recycled and cleaned thoroughly.

Wet the surface of the soil with a mister. Mine was recycled and cleaned thoroughly.

Step 5: Sprinkle the Seeds Evenly Over the Compost

Sprinkle small seeds over the compost from the palm of your hand using your finger. Don't cover small seeds with soil, as it can smother them. Larger seeds can be placed one by one on the compost and then covered with a sprinkling of compost. Much larger seeds (such as sweet corn, sunflowers, and tree nuts) can be pushed down below the surface of the compost about 1/4" / 6 mm.

Sprinkle seeds evenly over the compost surface. Small seeds don't need to be covered. Larger seeds can be covered with a thin layer of compost.

Sprinkle seeds evenly over the compost surface. Small seeds don't need to be covered. Larger seeds can be covered with a thin layer of compost.

Larger seeds can be covered with a thin layer of compost. A flower pot acts like a pepper pot and is useful for sprinkling compost

Larger seeds can be covered with a thin layer of compost. A flower pot acts like a pepper pot and is useful for sprinkling compost

Step 6: Cover the Seed Tray and Place It in a Warm Spot

Cover the seed tray with a piece of glass, a magazine, a slate, a piece of plastic, plywood or whatever. This prevents the compost from drying out and keeps the seeds in the dark, which aids germination. However seeds may alternatively require diffuse light for germination, so again, consult the seed packet or Google for specific details.

Seeds sprout best at a temperature above 64F (18C). In the northern hemisphere, it's best to sow seeds in early spring around February or March so the plants can have a full growing season. If you live in a climate with cold winters, it may be too cool for germination, so you can place the tray in a plant propagator (or alternatively locate it in a hot press close to a hot water tank or near your furnace/boiler).

Check the seed tray after a couple days, and then keep checking it for signs of germination. The trick is catching them in time: some seeds sprout quite quickly (within days) while others take weeks.

Cover the seed tray. I used a scrap piece of thin plywood which worked nicely.

Cover the seed tray. I used a scrap piece of thin plywood which worked nicely.

Requirements for seed germination.

Requirements for seed germination.

Step 7: Uncover the Seedlings Once They Germinate

It's very important to uncover the seedlings and expose them to light once they germinate, otherwise they will rapidly become straggly, with overly long, thin stems.

  1. If the plants are sensitive to frost, they will need to be kept indoors in full sun, in a greenhouse, or under a cold frame. During severe frosts, seed trays should be brought indoors or covered with insulation to protect them from freezing.
  2. Place the seed tray on a windowsill where it should get enough light.
  3. Turn the tray each day so the seedlings are evenly lit.
  4. Keep the compost moist with a spray mister. This is essential, especially if the seeds are at or close to the surface, as those tiny roots can dry out rapidly when exposed to warm sunshine or warm air in a room.
  5. Check daily and water if necessary. Once seedlings have a few pairs of "true leaves," they're ready for the next step.

Tip: Avoid strong sunshine on trays of small seeds sown outdoors. The surface of compost can rapidly dry out, especially if it's windy, and the seedlings may perish. It's probably best to keep them out of direct sunlight until a few pairs of leaves appear.

The seeds germinated after about a week and reached this size after 18 days.

The seeds germinated after about a week and reached this size after 18 days.