Sow annual flowers from seed under cover or outdoors from this month onwards for a brilliant display of summer colour that lasts right through the year.
Half-hardy annuals include some real beauties like golden yellow rudbeckia, delicate nicotiana, feathery-leaved cosmos and zingy zinnias. They won’t tolerate frost, so you can’t sow them outside just yet.
Instead, sow them in trays or modules of good quality seed compost and set them on a bright windowsill or on the shelf of an unheated greenhouse to germinate (if you can give them gentle extra warmth from a heated propagator they’ll come up much quicker). Once they germinate, grow them on until the last frost has passed and you can harden them off and plant outside around 15cm apart.
Hardy annuals are cheerful and easy-going and put up with a little chilly weather. They include native flowers like cornflowers, love-in-a-mist and calendula, and some more exotic blooms including sunflowers, Californian poppies and the beautifully sultry Cerinthe major ‘Purpurascens’ with steely blue-grey leaves and slate-purple flowers.
You can sow them indoors like half-hardy annuals for an earlier display of flowers, or just take the easy option and sow them directly outside from this month onwards. It helps if you cover the soil with clear polythene or a cloche about two weeks ahead of sowing to warm it up a little, helping the seeds to germinate more quickly (keep the cloche on for a couple of weeks after seedlings come up to keep them growing on strongly).
Never let your seedlings dry out, watering them daily while they’re establishing, and defend them against slugs which will munch their way through a whole swathe of your babies when you’re not looking. They should burst into glorious flower from June onwards: with regular dead-heading, the display will continue until the first frosts come around again.