Sowing biennials

Sowing Biennials

Many cottage garden favourites, such as foxgloves and honesty, are biennial plants. These usually have a two-year lifecycle, but that doesn't mean they're complicated to grow. Let's look at how and when to sow some of the most popular biennials.

Biennials live for two years. They produce leaves in their first year and flower in the second. Sometimes, they take a further year to flower and become a 'triennial', so don't worry if your biennial doesn't flower in its second year.

Biennials are best sown in midsummer (middle to end of June) – this may feel counterintuitive, but this is when they naturally go to seed – and planted out in autumn.

Examples of biennials:

• sweet Williams (Dianthus barbatus)
• honesty (Lunaria annua)
• wallflowers (Erysimum)
• foxglove (Digitalis purpurea)

Biennial seeds should be raised outside as it's too hot in the greenhouse at this time of year; I use a shady spot on a table behind my greenhouse. I cover mine with a lid to prevent them from being eaten and to keep the moisture in to help germination.

I'm sowing Digitalis purpurea 'Apricot Delight'. I'm using a half-size seed tray. The seeds are tiny, like dust, so it's easy to sow too many. I'm using peat-free multipurpose compost as peat-free seed compost can be quite hard to find in the UK. You can sieve the compost to make it finer and remove any large particles.

How to Sow Biennials

1. Fill a half-size seed tray with peat-free compost and gently tamp down to get an even surface.
2. Stand the tray of compost in a tray containing about an inch of water for around half an hour to an hour to let it absorb water from below. This avoids disturbing the compost and ensures it's evenly moist compared to using a watering can with fine rose.
3. Take the tray out once the top is moist and scatter the seeds very thinly on the surface. You probably won't need to sow the whole packet.
4. Put the clear lid over the top to retain humidity and stop anything from disturbing the seeds.
5. Put in a cool shady spot outside – I'm using a table behind my greenhouse.
6. Watch for germination and as soon as you see germination, remove the lid. Prick out later in the summer and grow on in pots before planting out in the autumn if plants are big enough, in their final positions in the border.

Don't Worry if Your Biennials Don't Look Good for Quite a While

Biennials only put on leaves in their first year and may start to look a bit untidy in the autumn and winter. Don't give up on them – underneath the ground, the roots are developing and preparing the plant for next year's flowering.

A Note on Peat Free

Don't worry if your peat-free compost feels a little dry when it comes out of the bag; this isn't necessarily a reflection of quality.

• Compost is often bagged on the dry side to reduce weight, which reduces transport costs and associated carbon footprint.
• A thorough watering, either before sowing if you're using it for seeds or after potting if you're potting plants on into it, will rehydrate the compost.

Top Tips for Growing Peat-Free

1. Water little and often – double-check before watering by sticking a finger into the compost: peat-free compost may look dry on top when in fact it is still moist lower down, and may not need watering yet. Stop watering as soon as you see water starting to drain out of the bottom of the pot.
2. Feed containers regularly, such as using a liquid seaweed feed.
3. Don't worry about any mushrooms that may start to grow in your peat-free compost – these are harmless and won't affect your plants.