How to grow annual flowers indoors

Do it:


Takes just:

30 minutes

At its best:

Jun, Jul, Aug

It's easy to succeed with annual flowers. Follow your seed packet's instructions but use your own judgement, too. Sowing temperatures vary between varieties; it's roughly 18-24 degrees celsius for half-hardy annuals and 8-16 degrees celsius for hardy annuals. Use clean pots or trays, and start a new bag of multi-purpose compost. Hardy annuals often resent root disturbance so if you sow these indoors, sow them in cells that can then be transplanted without disturbing the rootball.

You will need

Seed packets

Clean pots or seed trays

A bag of multi-purpose compost

Pea sticks



When seedlings have their first true leaf plus a pair of seed leaves, carefully prick them out into small individual pots or seed trays. Grow on in warmth for a few days, then move to a cooler windowsill.

Direct sun is essential. Warmth-loving/delicate kinds are best on a patio; traditional hardy annuals thrive in the open garden. In a poor summer or cold location, salpiglossis, eustoma or large-flowered zinnias do best under glass or in a polytunnel.

Annuals need fertile soil enriched with a little well-rotted compost and general fertiliser, such as blood, fish and bone. They don't need lashings of manure which will make them grow large and ungainly. Use a multi-purpose compost for containers, and apply liquid tomato feed weekly from June onwards.

Cut flowers need straight stems, so support is essential for taller species. The individual stems up to canes, push 60-90cm twiggy pea sticks along rows, or grow small groups through a  perennial support cage.

Unless you cut all annual flowers as they grow, you must remove spent blooms to prevent plants setting seed - otherwise they'll stop flowering. Snip off fading flower-heads regularly to trigger a fresh flush of buds.


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