Growing Biennials from Seed

Now is the time to sow Biennial Seeds. But what exactly are they and why do we need to sow them in summer?

What are Biennials?

Biennials are hardy plants which are grown from seeds sown this summer. They produce roots and foliage this year then burst into life next spring with masses more foliage, long stems and lots of flowers in late spring and early summer. Sown this summer they have eight to ten months to grow into super strong, healthy plants.

Why Grow Biennials?

Biennials are brilliant for early blooms next year. Most of them flower from May until July so they fill that annoying gap between spring bulbs and summer flowering perennials. Some biennials go on flowering for much longer. In our garden Wallflowers  Erysimum cheiri begin flowering in March, Sweet Rocket Hesperis matronalis very often starts flowering in April and goes on until August and Honesty Lunaria annua produces beautiful decorative seed pods which we like to leave on the plants as long as possible.

When’s the best time to Sow Biennials?

June, July and August are the best months to sow biennial flower seeds. The aim is to produce healthy, vigorous young plants that can be planted into their flowering position in September or October at the latest here in the UK before the cold weather hits.

How to Sow Biennial Seeds.

I usually follow the traditional method for sowing biennials by sowing them directly into a well prepared seedbed. It’s easy to let them grow and develop over summer then transplant the young plants to their flowering position in autumn. I also sow seed indoors in modules to keep them away from the wild creatures rampaging through our garden. We have visiting ducks and squirrels, mice and voles, slugs and snails. I love most of our wild visitors but it really annoys me if they eat my freshly sown seeds or my squeaky fresh young seedlings! Also, I’ve found that tiny seeds like Foxgloves Digitalis purpurea benefit from a little more care indoors. Once the plants are nicely established they are more able to resist attack and can be planted outdoors.

For a more detailed growing guide including how to prepare a seedbed please see How to Grow Foxgloves

Which Biennials are Best for Cut Flowers? 

Many Biennials produce long strong stems which are great for cutting. Here are some of my favourites:

  • Sweet William, Dianthus barbatus
  • Foxgloves, Digitalis purpurea
  • Sweet Rocket Hesperis matronalis
  • Honesty, Lunaria annua
  • Iceland Poppies, Papaver nudicaule
  • Wallflowers  Erysimum cheiri

You’ll find that each plant group mentioned above has many named varieties. There are lots to choose from! Some of them are dwarf varieties bred especially for bedding plants and to look good in a pack at the garden centre. They are not ideal for cut flower production but they are brilliant for a splash of colour in your garden and for your pots and containers. In the photo below you can see that the dwarf Forget-me-Not is a perfect partner for Tulips in large containers. It makes a lovely little bedside posie too but won’t really make the grade if you’re growing cut flowers to sell in bunches. It pays to choose carefully!

There are other much taller varieties which are much better for cut flowers and those are the plants I like to grow in my own garden. To make it easy for you here are some of my NEW Biennial Seed Collections with long stemmed flowers which I know grow particularly well together. I’d appreciate your thoughts on them if you have time to have a look and send me a comment.



Of course there are many combinations of Biennials that work really well together and the earliest biennial flowers (Wallflowers & Forget-me-Not) grow beautifully with Tulips too.

I know we’re only just getting started with summer 2017 and 2018 seems like a long way off right now… but I’m taking a little time to plan ahead and sow some Biennials now,  so by spring next year my garden will be full of beautiful flowers. For the cost of a few packets of seed you can grow lots of plants too. You’ll be so appreciative of your own foresight, there will be masses of blooms for cutting and plenty left for bees and butterflies to enjoy!

Are you planning to grow biennials for next spring?
Which are your favourites?

Happy Gardening Gillian 🙂





7 thoughts on “Growing Biennials from Seed

  1. Gillian the photos of the flowers are beautiful and all the flowers are divine. Thank you for reminding me that I have to plan the biennial planting already. Thank you very much for all the information. Greetings from Margarita.

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