Biennials usually form a rosette of foliage in their first year, harnessing sunlight and storing energy to allow them to burst into bloom in their second, before they set seed and die.
They’re easy and cheap to grow from seed, and many are native to the British Isles. In general, biennials are sown in late spring or early summer, so they have a generous amount of time to bulk up before flowering the following year. Sow them each year to ensure you have a regular supply to plant out in the garden, or in containers. Make sure you have an area set aside to overwinter half-hardy or tender biennials, like nicotianas.
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Check out some of the best biennials to sow and grow, below.
In its first year Angelica sylvestris produces rosettes of large leaves that look great in borders as a foil for other plants. In their second year bunched flower buds appear on deep purple stems that expand into umbrella-shaped inflorescences, attracting masses of pollinators. Grow Angelica sylvestris in full sun or partial shade, in moist, well-drained soil. Angelica gigas and Angelica archangelica are lovely alternatives.
Height x spread: 100cm x 50cm.
Arctic poppies are some of the toughest flowers you can grow, despite their diminutive appearance. Though they’re actually short-lived perennials, you can grow them as biennials by direct sowing them from May to July to flower the following year. Grow them in full sun in well-drained soil and deadhead them to prolong flowering.
H x S: 30cm x 30cm.
There are lots of beautiful foxglove varieties you can grow from seed, and they’ll often self-seed, so all you need to do is transplant the seedlings to where you want them. Most foxglove species are biennial, including our native Digitalis purpurea. Discover some of the best foxgloves to grow.
Commonly known as sweet William, Dianthus barbatus is a cottage garden favourite that has been bred countless times to produce numerous cultivars with varying flower colours and patterns. Sow the seeds in April or May, then plant out in autumn for flowers the following year. Usually a short-lived perennial or biennial. Choose a spot in beds, borders or containers that will provide them with full sun and grow them in a gritty, well-drained soil.
H x S: 50cm x 50cm.
Aquilegias are short-lived perennials, but they can be grown as biennials by sowing them in mid- to late summer for flowers the following spring. The best spot to grow them is in a dappled or partially shaded spot, in moist, well-drained soil. They make fabulous cut flowers, too, and this action of cutting off the flowers will help to promote further flowers.
This fabulously scented biennial thrives in sunny and shady spots. It can be sown from early spring to mid-summer to flower next summer, and will self-seed, too, so is a good option for a low-maintenance garden – just pull up any unwanted seedlings when young. Grow Hesperis matrionalis in moist, well-drained soil and don’t forget to cut a few flowering stems for vases or small posies.
H x S: 100cm x 45cm.
Teasels, like Dipsacus fullonum and Dipsacus pilosus, are excellent plants for wildlife gardens, providing flowers for pollinators, followed by seeds that are loved by garden birds like goldfinches. Grow these true biennials in full sun or partial shade, in moist, well-drained soil. Teasels will self-seed, too.
H x S: 180cm x 80cm.
Though a short-lived perennial, Nicotiana sylvestris can be grown as a half-hardy annual, or overwintered and treated as a biennial. The fragrant, elegant flowers close up during the day and open again at dusk to scent the evening air, so they’re perfectly suited to night gardens with plants like sweet Williams and night-scented stocks. Plant them in moist, well-drained soil with a bit of shade to protect them from the hottest summer sun.
H x S: 150cm x 60cm.
Hollyhocks are typically perennials, however, they often fall victim to fungal rust attacks, which disfigures the leaves and spoils the appearance of the plant. Treating them as biennials often allows you to get the best from them in their first year of flowering, before the disease really hits. You can also grow resistant varieties, and with their striking, pollinator-friendly flowers, they’re worth the effort. Grow in full sun in moist, well-drained soil.
H x S: 180cm x 25cm.
Honesty, Lunaria annua, can be grown as an annual or biennial, though it’ll give its best flowering performance if grown as a biennial. It makes a lovely addition to a shady wildflower garden, where the flowers will lure in bees and butterflies. After they’ve finished flowering, translucent, disc-shaped seedpods are produced that look lovely in floral arrangements. Leave some seedpods, though, to allow it to self-seed.
H x S: 90cm x 30cm.
True biennials and short-lived perennials
Some of the biennials you come across, for example on the websites of seed companies, aren’t actually true biennials, but short-lived perennials. Such perennials are often better suited to growing and treating as biennials, because their best performance is in their first year of flowering, after which the flowering performance diminishes.