Flower Planting Calendar: Month by Month

Knowing when to sow each flower makes all the difference. Get it right and your garden flowers from spring through to the first frost. Timing matters more than any other factor. Sow too early and seedlings rot in cold, wet soil. Sow too late and plants run out of growing season to reach flowering size.

The UK growing season stretches longer than many gardeners realise. Sweet peas go in during February. Tulip bulbs plant in November. Every month has something to sow or prepare. This calendar covers annuals, perennials, biennials, and bulbs with sowing times tailored to British conditions. For vegetable sowing times, see our separate seed sowing calendar.

A spring border in full bloom — tulips, daffodils, and primroses peak in April

Understanding flower types

Before working through the calendar, it helps to understand the four main categories. Each type has different sowing windows and lifecycle patterns.

Hardy annuals complete their lifecycle in one season and tolerate frost. Sow them directly outdoors from March. Examples: cornflowers, calendula, nigella, poppies, and sweet peas. Many self-seed freely, returning year after year without replanting. The RHS seed sowing guide covers soil preparation in more detail.

Half-hardy annuals also complete their lifecycle in one season but are killed by frost. Start them indoors from April and plant outdoors only after the last frost in late May. Examples: cosmos, zinnias, marigolds, and nicotiana.

Biennials take two years to flower. Sow in summer of year one, they overwinter as foliage, then flower and set seed in year two before dying. Examples: foxgloves, wallflowers, sweet William, and honesty. A cottage-style garden relies heavily on biennials, as our cottage garden planting plan explains.

Perennials live for three or more years, dying back in winter and returning each spring. Most are sown February to June or divided in autumn. Examples: delphiniums, lupins, echinacea, and lavender.

Last frost dates across the UK

Last frost dates determine when half-hardy plants can go outdoors safely. This is the single most important date in the flower planting calendar. Getting it wrong means losing weeks of work to a single late frost.

These dates are averages over 30 years. Individual years vary. When in doubt, wait an extra week. A week’s delay in planting costs far less than replacing frost-killed seedlings.

Gardener’s tip: Track your own last frost date each year and log it. After three or four seasons, you will have a personal micro-climate record more accurate than any regional average.

Winter: January and February

The garden is quiet but there is useful sowing to do indoors. These early starts give slow-growing flowers a head start on the season.

January

Indoors: Sow sweet peas in root trainers at 12-15C. January-sown sweet peas produce the strongest plants and earliest flowers.

Why we recommend root trainers over standard seed trays for sweet peas: After 30 seasons of growing sweet peas, root trainers consistently produce stronger plants than standard trays. The deep, individual cells let roots grow straight down without curling — plants grown in root trainers reach 30cm before those in trays reach 15cm. Sown in January and planted out in March, they typically flower two to three weeks ahead of April-sown plants. Also sow pelargoniums (bedding geraniums) at 18-20C for summer bedding. If you are new to sowing seeds indoors, both crops are forgiving and straightforward.

Outdoors: Nothing to sow. Prepare beds for spring by clearing debris and adding organic matter. Order seeds from catalogues while choice is widest.

February

Indoors: Continue sowing sweet peas if not started in January. Sow lupins, delphiniums, and hollyhocks at 15-18C for flowering in their first year. Start begonias and lobelia at 18-21C — they are slow growers that need an early start.

Outdoors: In mild areas, sow hardy annuals under cloches from late February. Cornflowers, calendula, and larkspur germinate at soil temperatures as low as 7C if the soil is well drained.

Spring: March to May

This is the peak sowing season. More flowers start in these three months than in the rest of the year combined.

March

March is when the flower garden comes alive. Soil temperatures climb above 7C in most of England, opening the door for direct outdoor sowing of hardy annuals.

Outdoors: Sow cornflowers, calendula, nigella (love-in-a-mist), annual poppies, larkspur, and sweet peas directly where they are to flower. Rake the soil to a fine tilth, scatter seed thinly, and cover lightly. These hardy annuals tolerate frost and produce flowers by June.

Indoors: Sow cosmos, marigolds, nicotiana, and antirrhinums (snapdragons) at 18-21C in seed compost. These half-hardy types need 6-8 weeks indoors before planting out. Also sow dahlia seeds at 18C for bedding-type plants, or start tubers in pots for earlier flowers.

Bulbs to plant: Put gladioli corms, ranunculus tubers, and anemone corms into the ground from mid-March. Plant 10cm deep in well-drained soil.

March sowing — cornflowers and calendula go directly into prepared soil

April

The busiest sowing month. Almost everything can start now, and early March sowings begin to show strong growth.

Outdoors: Continue sowing hardy annuals. Add clarkia, godetia, candytuft, and Virginian stock to the list. Sow wildflower seed mixes on prepared ground. Direct-sow sunflower seeds from mid-April when soil reaches 10C.

Indoors: Sow zinnias, ageratum, and rudbeckia (annual types) at 18-21C. Start statice and strawflowers for drying. Prick out March-sown seedlings into larger pots. Begin hardening off the earliest indoor sowings by placing them outside for increasing periods each day.

Perennials from seed: Sow achillea, echinops, echinacea, scabious, and salvia at 15-18C. These germinate within 14-21 days and can flower in their first year from an April sowing.

May

May bridges indoor and outdoor growing. Half-hardy flowers move outside after the last frost.

Outdoors from late May: Plant out all half-hardy annuals once the last frost has passed. Cosmos, zinnias, marigolds, nicotiana, and bedding dahlias can finally go into borders. Harden off for 10-14 days first to prevent transplant shock. Direct-sow nasturtiums and morning glory where they are to flower.

Successional sowing: Sow a second batch of cornflowers, calendula, and nigella outdoors. This extends the flowering season by 3-4 weeks, ensuring colour right through to September. Successional sowing is the simplest trick for a longer display.

Late May tasks: Plant out dahlia tubers that were started in pots, and sunflower seedlings raised indoors.

Summer: June to August

Summer shifts from sowing to maintaining. Deadhead spent flowers to encourage repeat blooming, and sow biennials for next year’s display.

June

Biennials to sow now: Sow foxgloves, wallflowers, sweet William, honesty, Canterbury bells, and hesperis (sweet rocket) in seed trays or a nursery bed. These will grow through summer and autumn, overwinter as rosettes, and flower next spring and summer.

Outdoors: Last chance to direct-sow hardy annuals for late-summer flowers. Sow calendula, cornflowers, and candytuft by mid-June. Sow biennials like hollyhocks in pots for next year.

Maintenance: Deadhead roses after their first flush for repeat flowering. Stake tall-growing plants like delphiniums and dahlias before they flop. Begin liquid feeding container-grown flowers fortnightly with a high-potash tomato feed.

A July border at peak bloom — dahlias, cosmos, and rudbeckia reward careful spring planning

July

The maintenance month. Focus on deadheading, watering, and enjoying the display.

Deadhead rigorously. Removing spent flowers redirects the plant’s energy from seed production to new blooms. Cosmos, dahlias, sweet peas, and roses all respond strongly to deadheading. Cut sweet peas every 2-3 days and they will flower until October.

Sow for autumn colour: Start autumn-flowering wallflowers and winter pansies in pots. Sow spring-flowering forget-me-nots and primroses for naturalising under trees.

Water newly planted perennials deeply during dry spells. Established perennials rarely need watering if they have a good layer of mulch. For plants that handle drought well, see our guide to drought-tolerant plants.

August

The pivot month. Summer flowers are at their peak, but autumn preparation begins.

Collect seed: Gather ripe seed from annuals and perennials for free plants next year. Calendula, nigella, cosmos, and honesty all produce easy-to-collect seed. Dry seed in paper bags for 2 weeks before storing in a cool, dry place.

Sow hardy annuals for early spring flowers: Sow cornflowers, calendula, and sweet peas outdoors in late August. Autumn-sown hardy annuals develop strong root systems over winter and flower 4-6 weeks earlier than spring-sown plants the following year.

Prune lavender after flowering finishes, cutting back one-third of growth. This maintains shape and prevents the woody, leggy growth that shortens a lavender plant’s life.

Autumn: September to November

The focus shifts to bulb planting and preparing for next year’s display.

September

Hardy annuals: Continue autumn sowing of cornflowers, calendula, and sweet peas where winters are mild. In exposed or northern gardens, wait until March.

Bulb planting begins. September is ideal for daffodils, crocuses, alliums, and muscari (grape hyacinths). The RHS bulb planting guide covers depth and spacing for all common species. Plant at a depth of 2-3 times the bulb height. Group bulbs in clusters of 7-15 for natural-looking drifts. Daffodil bulbs need to go in before the end of October for reliable root development.

Divide perennials: Split congested clumps of geraniums, asters, heleniums, and hydrangeas. Dividing perennials in early autumn gives roots time to establish before winter dormancy. Replant divisions immediately and water well.

October

Peak bulb planting month. Get daffodils, hyacinths, alliums, and crocuses in by the end of October. Tulips are the exception — plant them from mid-October to late November. Late planting reduces the risk of tulip fire disease.

Lift tender bulbs: Dig up dahlia tubers, gladioli corms, and cannas after the first frost blackens foliage. Dry for two weeks and store in barely damp compost at 5-10C in a frost-free location.

Plant bare-root perennials and shrubs from October onwards while the soil is still warm. Bare-root roses, in particular, establish faster than container-grown plants when planted between now and March.

November

Last chance for tulip bulbs. Tulips planted in November often perform better than those planted earlier because soil temperatures have cooled sufficiently. Plant 15-20cm deep in free-draining soil.

Prepare next year’s beds: Clear spent annuals, dig in compost, and mark where spring bulbs are planted to avoid disturbing them.

Outdoors: Nothing to sow. The sowing year is effectively over until January.

December

No sowing and very little planting. December is for planning. Browse seed catalogues, order early, and sketch out next year’s planting scheme. Clean and store seed trays and pots. Review what flowered well and what to change.

If the ground is not frozen, you can still plant tulip bulbs in early December as a last resort. They will flower, though slightly later than those planted in October or November.

Quick-reference planting table

This table summarises the key sowing and planting windows for the most popular UK flowers. Indoor sowing assumes a warm windowsill or heated propagator at 15-21C.

Flowers for beginners

If you are new to growing flowers from seed, start with the most forgiving species. These germinate reliably, tolerate mistakes, and produce flowers quickly.

Five easiest flowers from seed:

1. Nasturtiums — sow directly outdoors in May. Germinate in 10-14 days. Flower within 8 weeks. Thrive in poor soil.
2. Calendula — sow outdoors March to May. Tough and fast. Self-seeds for free plants every year.
3. Sunflowers — sow April to May. Fast-growing and tall. Children love them. Our guide on when to plant sunflowers covers timing in detail.
4. Cornflowers — sow March or September. Drought tolerant once established. Long-lasting as cut flowers.
5. Cosmos — sow indoors in April. Flowers non-stop from July to October if deadheaded regularly. The single best cut flower for beginners.

All five attract pollinators. For a deeper list of plants that support bees and butterflies, see our wildlife section.

Gardener’s tip: Sow more than you need. Seeds are cheap and germination is never 100%. Thin seedlings to the correct spacing once they are 5-10cm tall. The thinnings of many species (calendula, nigella, cornflowers) can be transplanted elsewhere in the garden.

Extending the flowering season

A garden that flowers from March to November needs three techniques working together.

Successional sowing: Sow the same species every 3-4 weeks from March to June. This produces waves of bloom rather than a single peak. Calendula, cornflowers, and nigella are ideal for this approach.

Deadheading: Removing spent blooms before they set seed forces the plant to produce more flowers. Cosmos, dahlias, sweet peas, and roses respond well to regular deadheading. A deadheaded cosmos plant produces two to three times more flowers than one left to set seed.

Autumn sowing of hardy annuals: Plants sown in August and September overwinter as seedlings and flower 4-6 weeks earlier the following spring. This fills the gap between spring bulbs finishing in May and summer annuals hitting their stride in July.

Combine all three with spring bulbs and summer perennials. Your garden can hold colour for eight months or more. For broader spring gardening tasks, our seasonal checklist covers everything from lawn care to pruning.

Planting tulip bulbs in November — the work you do now produces next spring’s colour

Now you’ve mastered the flower planting calendar, read our guide on sowing seeds indoors for the next step.

Frequently asked questions

When should I start planting flowers in the UK?

Start sowing hardy flowers indoors from February and outdoors from March. Soil temperature needs to reach 7-10C for outdoor sowing. That is mid-March in southern England, early April in the north. Sweet peas and hardy annuals are the first to go out.

What flowers can I plant in March UK?

March is ideal for sowing hardy annuals outdoors including sweet peas, calendula, cornflowers, poppies, and nigella. Start half-hardy types like cosmos and marigolds indoors on a warm windowsill. Plant out summer-flowering bulbs such as gladioli and ranunculus.

What is the difference between hardy and half-hardy annuals?

Hardy annuals tolerate frost and sow directly outdoors from March. Half-hardy annuals are killed by frost and must start indoors, going outdoors only after the last frost in late May. Common hardy types include cornflowers and poppies. Common half-hardy types include cosmos, zinnias, and dahlias.

When is the last frost date in the UK?

Last frost dates vary by region across a 4-6 week window. Southern coastal areas see last frosts in late April. The Midlands and most of England clear frost by mid-May. Northern England and Scotland can see frost until late May or early June. Check local records for your postcode.

Can I sow flower seeds in autumn?

Yes, many hardy annuals sow in September for earlier flowers the following spring. Cornflowers, calendula, and sweet peas all benefit from autumn sowing. Spring-flowering bulbs like tulips and daffodils plant from October to November. Autumn sowing produces stronger root systems over winter.

What is the easiest flower to grow from seed UK?

Nasturtiums are the easiest flower to grow from seed. Sow directly outdoors in May, 2cm deep. They germinate in 10-14 days and flower within 8 weeks. Sunflowers, calendula, and cornflowers are also very simple. All four tolerate poor soil and need minimal care.

Which flowers come back every year without replanting?

Perennials return each year once established. Reliable UK choices include lavender, geraniums, delphiniums, echinacea, rudbeckia, and Japanese anemones. Some annuals also self-seed freely, including nigella, calendula, foxgloves, and aquilegia, creating a natural cycle without replanting.