Sowing Hardy Annual Seeds

It’s an exciting time in the garden. Spring flowers are blooming, bulbs are finally poking their noses through the earth and some early flowering shrubs are decorated with jewel like blossom too. It’s quite exciting indoors too this month! I’ve been sowing seeds indoors for a few weeks now. For Looking Good in the Garden on Friday I think my seedlings are the stars this week. Hardy Annual seeds can be started off outdoors in early autumn and from mid spring onwards. Here’s how…

How to Direct Sow Seeds

Hardy Annuals can be sown direct (in the spot you want them to flower) from mid spring when our days become warmer, night temperatures increase a bit and the soil has started to warm up too. The exact time depends on the weather conditions where you live and apparently you can check if the time is right by resting the cheeks of your bare bottom on the ground for a moment or two. If it’s too cold you will know… apparently! I prefer not to shock our neighbours so I keep a close watch on the bare earth and when weed seedlings appear like a rash then the time is right. I’ve found that when daytime temperatures are consistently in excess of 10°C my annual flower seeds germinate well.

If you prefer direct sowing your seeds or simply don’t have the time or patience for indoor sowing then you speed things up a bit. Just covering your seed bed with a cloche, a sheet of polythene or even some empty compost bags will help to warm the soil up and keep the rain off until you are ready to sow. It will probably be April before conditions are right here so that’s why I’ve made a start indoors. I just can’t wait!


Here’s some simple cloches I saw in a vegetable garden recently. The ground still needs more preparation to break down the size of the soil particles because seedlings simply wouldn’t be able to push their way through these huge clods. Cloches or even a sheet of pastic or empty compost bags are a great way to quickly warm up a patch of ground to get it ready for sowing seeds. Creating a seed bed is easy and quick with a rake when the soil is dryer, warm and crumbly. Ideally soil needs to be quite fine to allow tiny seeds to force their shoots through to the surface. Here’s a bed I prepared by digging over to remove weeds and roots. I left it to dry for half a day then raked it thoroughly braking up the clods. The following day I raked it again producing what’s known as a fine tilth.


How to Sow Seeds Indoors

Sowing seeds indoors and getting great results is really easy as long as you follow a few basic guidelines. You don’t need any chemicals or expensive equipment. Please note that good hygiene is essential to prevent seedings damping off and dying.larkspur-long

  1. Use clean seed trays or module trays. If possible use new ones or scrub out your old ones with hot water and a drop of bleach. I love terracotta pots and old wooden seed trays but for starting seeds I have found that plastic is best.
  2. Use a nice fresh new bag of seed compost (there are many to choose from… a light compost with small particles is much cleaner and easier to handle and your seeds will easily be able to push their way through)
  3. Fill your seed trays or module trays to the top with compost and firm applying even pressure so that the surface is level. This will help your seedlings germinate evenly.
  4. Wash and dry your hands thoroughly (sorry… hygiene again!) then scatter a pinch of seed thinly across your seed tray or sow just a few seeds per cell. Resist the urge to go over the same tray again with more seeds. Most seeds will germinate and that tiny pinch will produce a lot of lovely plants for your garden.
  5. Cover the seeds with sieved compost. Use a garden sieve or an old plastic colander for this. If the seeds are roughly 2mm long then cover them with 2mm of compost, if they are 3mm then cover them with 3mm of sieved compost and so on.
  6. Label each tray with the date and name of plants sown. If you use a pencil or permanent marker pen you’ll be able to read the label in a few weeks time! This is especially useful if you sow several similar plants. The photo below shows Salvia viridis… you wouldn’t know which seedlings were blue and which were pink, white and blue without the labels.
  7. Stand the seed tray in a clean tray of fresh slightly warm water until the surface of the compost is moist. The water will draw the seeds into the compost and the surface will sink a little.
  8. Allow excess water to drain way from the soaked seed trays then cover them with a plastic lid or a sheet of cling film to keep the moisture in. Most hardy annuals need a a warm (16°C-20°C) dark place to start the germination process. A boiler room, airing cupboard or even a corner of a warm room in your home is ideal. If it’s not dark just cover your seedlings with a dark towel or something similar.
  9. Check your seeds every day for shoots then remove the plastic lid/clingfilm and move the tray to a cool light place such as a windowsill or greenhouse when it looks like most have germinated. Hardy annual seedlings can cope with much lower temperatures once they begin to grow.
  10. Allow the tiny seedlings to grow on and water from below when the compost looks dry. When they are large enough to handle pot up into larger cell or small pots and feed each week to encourage root growth.
  11. Acclimatise your young plants to conditions outside by hardening them off. Move them outside each day for a week so they become used to the cooler temperatures. Once they are hardened off (foliage becomes tougher/not as soft) and you are sure there is no chance of frost then it’s safe to plant them out.
  12. Woo Hoo! Pat yourself on the back and pour yourself a gin and tonic. You’ve done it!
    Many Hardy Annuals take just 12 weeks from seed to flower so you can look forward to some beautiful flowers like this in just a few weeks time.



6 Monday Flowers





13 thoughts on “Sowing Hardy Annual Seeds

  1. Very timely post. I have some seeds and containers ready bought and am just waiting until the end of the month to sow them otherwise it will be too cold to plant them out. My sweet peas are already through though. I read somewhere that they are actually hardy and can be planted out in a mind spell earlier than the non-hardy annuals – is that really true?

    1. Sweet Peas are quite hardy. You can actually sow them in autumn and grow them on through winter in an unheated greenhouse ready for planting out in spring. Usually they need warmth and long days to initiate growth but there are some that have been bred to grow during the short days of winter such as Winter Elegance Mixed. Commercial flower producers need the early blooms but for most gardeners sowing as usual in Feb and planting out nice big healthy plants in April will produce great results. Half Hardy Annuals such as Cosmos and Zinnia won’t stand cold at all so they shouldn’t be planted out or sown direct until after the last frosts in your area when the soil has warmed up. If you have a quick look at my shop on this website you’ll see that I’ve divided the seeds into Hardy Annuals and Half Hardy Annuals which may help you see which plants belong to which group. I haven’t sown any Half Hardy seeds yet as it’s still a bit cool and dark plus I like to get my Hardy Annuals going first.

  2. I want Sweet Peas, just like yours, and I want Scabious ( I hope they have a prettier name somewhere), just like yours. I’ll just take your garden!

    1. I know that feeling Cady. I feel the same each time I shop at a garden centre or nursery and about every garden I visit! It’s healthy to try something new I think and it’s human nature to want more!

  3. Just noticed I put mind spell instead of mild spell – I wonder what that would be?
    Thanks for all the advice – you will no doubt read about my success or otherwise on my blog later on.

  4. Helpful advice accompanied by delightful pics – can’t wait to get started, just didn’t feel like it as it has been cool enough up to now but we’re in for good weather now. Happy spring days 🙂

  5. Such detailed instructions. I’ve started seeds for years, but I need to review the basics to get better results. Thanks. Always good to have a little refresher.

    1. There are lots of ways to sow seeds … this is the most successful for me. Good luck with your seed sowing this year Leah!

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