How to Sow Seeds

Sowing Seeds

With the cold Spring of 2018 you may be a little behind with your seed sowing…

The good news is, they will soon catch up and many seeds such as Zinnia’s actually resent been sown too early.

After a quick germination, they quickly die off as they sit in cold damp soil…

April is ideal, the sky is bright, the sun is warm, lets get started!

You’ll need seed trays, pots, bottom trays, potting compost, vermiculite or horticultural grit, clear dome lids, and plant labels.

Sowing Seeds, Propagation, Seed Trays, Domed lids and Heat Mats

Buy new shop bought compost, Your heap at home will never get hot enough to kill off those weed seeds when breaking down and you do not want to end up nurturing a tray of nettles!

There are dedicated seed sowing composts available but here at Swan Cottage we use cheaper Multi Purpose Compost mixed with 10% horticultural grit for drainage.


Always use as fresh a seed as you can manage if you can, germination levels are significantly better – there is a reason it all gets sold off at the end of Summer!

Like most people I started gardening as a hobby, with a full time job my methods are adapted to be the most time efficient, so rather than spend time pricking out seedlings I like to sow sparingly into individual cells giving each plant space to grow.

By the time you need to pot on plants are not as fragile and the job less time critical.

Read the instructions on the packet (or check online), some seeds need a period of cold or darkness to germinate, others must have lots of light or even heat.

Seeds with a thick seed coat, such as Sweetpeas and Cernithe benefit from a soak overnight, the water needs to permeate the seed coat before the seed will wake from its slumber.

Getting started

Fill your cell seed tray with your seed sowing mix, firm and water. Place in a tray of water to moisten but not soak.

  1. Moisten compost mix until it is thoroughly damp, but not dripping wet.
  2. Fill seed trays or cells to the top with soil, tapping firmly against the table as you go, so the soil settles and there are no trapped pockets of air.                                                  IMG_5956
  3. Get your label ready, you forget very quickly what you have sown so write them first.
  4. Sow seeds according to the instructions, a general rule is a seed should be sown twice as deep as it is large. Make a small hole with a pencil or dibber. ‘Dust like’ seeds are sown on the soil surface and often benefit from light to germinate.
  5. Sow 1 or 2 seeds to each cell, you will remove the weakest if both germinate, this can be quite tricky with seeds such as foxgloves.IMG_2990
  6. Cover with a light dusting of the compost mix or vermiculite if you have it.
  7. Place freshly sown trays in a tray of water to soak them from underneath, overhead watering can dislodge those carefully sown seeds.IMG_5878
  8. Cover moist seed trays with a clear plastic dome to help keep a humid moist environment. It makes a significant difference to germination rates!
  9. Place seeds in a constantly warm (not hot) environment, about 65 degrees. Heated propagation mats are brilliant and with the plastic domes mentioned above, germination can accelerate from 3 weeks to 3 days!  IMG_3163
  10. Check trays daily, and once seeds have sprouted, remove from the heat mats to a bright space such as a greenhouse, conservatory or bright windowsil.
  11. Check seedlings daily and water from underneath when the soil appears dry.
  12. No matter how carefully you sow, extra seeds will appear and you must remove these extra seedlings, if you don’t your seedlings will be cramp and crowded and won’t have the space to grow on well.
  13. Some seedlings resent root disturbance such as Larkspur and Gypsophilia so the extra sowings should be composted but other seeds such as Verbena or Foxgloves are really robust little plants and the extra sowings can easily be rescued and potted on.Swan Cottage Flowers Seed Sowing and Propagation Workshop and Classes
  14. As young plants grow, they need to be fed. Following the label instructions, add the correct amount of liquid seaweed to your watering can and add this to your watering trays. [For more information see my post on Feeding and Plant Tea’s]
  15. Eventually your seedlings will outgrow their trays, either pot on into a larger pot, or if if the risk of frost is over you can start the hardening off process.
  16. Set trays in a sheltered spot outside, increasing the amount of time they are out each day. This helps the young plants acclimatise to outdoor temperature fluctuations so they don’t have a shock.


Watch out for greenfly, slugs and snails as your newly plants will be full of delicious sappy growth! They can be mown down overnight!

If you would like to learn more, first hand, sign up for one of our workshops

I’d love to meet you!

Zoe x

Zoe Woodward, Swan Cottage Flowers, Dahlia Day 2017

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