Timing is everything with flowers. Sow at the right moment and seeds germinate fast and grow strong; sow too early or too late and they sulk or never quite flower. This calendar gives you the simple answer for every popular flower — when to start it indoors, when to sow outdoors, and when it blooms — so you can plan colour from spring right through autumn.
It works for a temperate climate (UK and Northern Europe). Gardening somewhere milder or colder? Shift everything by a week or two around your local last-frost date. Every timing here comes from the sowing data on our own seed packets, so it matches what you will actually grow.
How to read the calendar
The flower sowing calendar
| Flower | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunflower | ||||||||||||
| Sweet pea | ||||||||||||
| Cosmos | ||||||||||||
| Zinnia | ||||||||||||
| Nasturtium | ||||||||||||
| Snapdragon | ||||||||||||
| Larkspur | ||||||||||||
| Dahlia |
Timing is drawn from our packet data (planting period, indoor or direct method and peak season), shown for a temperate climate — adjust a week or two for your local last frost.
Sowing through the year
The big sowing window
Most flowers start now. Direct-sow hardy annuals such as nasturtium, larkspur and cornflower as the soil warms, and start tender types like zinnia, cosmos and sunflower indoors for an early, strong start.
Sow, succeed, bloom
Keep sowing fast annuals for late colour, and sow biennials like foxglove and sweet william now to flower next year. Deadhead spent blooms regularly and the display keeps coming all summer.
Last sowings and saving seed
Sow hardy annuals and sweet peas now for sturdy, early plants next spring, and start some perennials. As flowers fade, collect and dry seed from your favourites for next year.
Plan and start early
The garden rests, but a warm, bright windowsill does not. Start slow growers like lisianthus and pelargonium early, and use the quiet weeks to plan next year's borders and get your seed order in.
Popular flowers at a glance
Our best-selling flowers with their sowing window — tap through to the seeds.
Frequently asked questions
When should I start sowing flower seeds?
Most begin in March. Start tender flowers such as zinnia, cosmos and sunflower indoors, and direct-sow hardy annuals like nasturtium, larkspur and cornflower outdoors once the frost has passed.
Which flowers can I sow in autumn?
Hardy annuals such as cornflower, larkspur and poppies, plus sweet peas, can be sown in autumn for stronger, earlier-flowering plants the following year.
Do flower seeds need light to germinate?
Many fine seeds do — sow them on the surface and barely cover. Larger seeds can be covered to about twice their depth.
What is the difference between starting indoors and direct sowing?
Starting indoors gives tender or slow flowers a warm head start before you plant them out; direct sowing suits hardy annuals that grow quickly where they are sown.
