Its time to think about sowing biennials for a display next year.
Biennials are those plants we grow that flower in their second year from sowing after which we traditionally rip them out and replace them with summer bedding; foxgloves and forget-me-nots are perhaps the two most popular.
The plant world does not always follows the definitions we make for it and the range of plants we traditionally call biennials are not all strictly that: there are probably three different groups to be aware of.
Firstly the true biennials are those plants that no matter how early we sow them will not flower until their second year. These are some of our best known cottage garden favorites including Canterbury Bells, foxgloves, forget-me-nots, honesty (Lunaria annua) and some of the mulleins such as Verbascum olympicum. I sow now, but for really large plants you could have started in April or May.
Some of these plants, such as forget-me-nots (Myosotis) are perennial in the wild but in gardens are not. Some other plants that fall into my second group can survive as short lived perennials in our gardens, but perform much better in their first flowering season and are therefore better grown as biennials. One such is Hesperis matronalis or Sweet Rocket which is like honesty but taller, deliciously scented and longer flowering.
Perhaps the best known plants in this second group of so-called biennials are the wallflowers. If you sow too early they may start flowering at the end of their first summer and not be of use the following spring. Between now and the end of June is the best time to start these off depending on where you live. The aim is to have large bushy plants ready to plant into their flowering positions in autumn at the time you are busily planting spring flowering bulbs. The Siberean Wallflower, Erysimum hieraciifolium, flowers later than the others and should not be sown until the end of June to avoid premature flowering.
Iceland Poppies (Papaver nudicaule) is another of these short lived perennial to grow as biennials. Sow these before the end of the month and you will have good strong flowering plants next summer.
Another odd-ball biennial, but one of my favorites, is Salvia sclarea var. turkistanica ‘Alba’. If sown in early spring it can flower the same summer, but the bold plants we need are made by sowing in early summer and allowing them to form robust grey leaved rosettes in their first year which will run up to flower the following early summer.
Lastly, the third group of plants to think of as biennials are some that most gardening books treat as perennials. Amongst these are the Iceland Poppies which I have already talked about, but another is Anchusa azurea which is at its best in its first summer and thereafter not worth keeping. But there are others – some are perennials we can grow so easily from seed that they are worth treating as biennials. Doronicums are the best example that comes to mind – these offer starry yellow flowers in spring along with tulips, but thereafter are not worth giving border space. But the one plant I always treat this way is the lupin.
Lupins are so easily raised from seed and will flower magnificently the following summer, but once they go to seed they look ugly, they quikly become infected with mildew and take up a lot of space. Throw them all out and start from fresh each year and thereby take to opportunity to play with different colour combinations.
The best way to grow biennials is in rows in your vegetable garden and to move them into position in the autumn. My problem is that I do not have such a free space and have to grow all my biennials in pots. This makes biennials a real chore as they need daily watering throughout the summer. I think it is worth it, but for lazy gardeners some of the most well known biennials will do the job for them. Foxgloves, honesty and above all forget-me-nots will seed themselves around. All we need to do is weed out the ones we don’t need.
I see biennials as a luxury in my garden. They are not permanent theme plants, but bring spontaneity and change, albeit at a cost of time and effort. I tend to dot them around the edges of borders and along paths where they bring early season colour and reinforce the garden’s design.