What Flowers to Plant in March UK

March marks the real beginning of the gardening year. As the soil begins to warm and daylight increases, more flower varieties can be sown directly outside or indoors for transplanting later. It’s the month when everything starts moving—so it’s worth making the most of the time with a focused planting plan

Hardy annuals

With milder days and fewer frosts, hardy annuals can now go straight into prepared beds. Flowers like calendula, cornflowers, larkspur, clarkia, and godetia do well when direct sown in March. Sow them thinly into raked soil and water gently. These varieties can handle unpredictable spring weather and will establish quickly.

Are half-hardy annuals best to start indoors

It’s too early to plant half-hardy annuals outside, but they can be started indoors this month. These include cosmos, zinnias, marigolds, petunias, and nicotiana. Sow them in seed trays with warmth and good light. They’ll be ready to harden off and plant out after the last frost, typically in May.
If you’re growing from seed, March is a perfect time to start long-growing perennials like echinacea, rudbeckia, lupins, and gaura. These are best sown indoors in seed trays and kept in a warm, light-filled space. They’ll flower in their second year but add lasting value to borders and beds.

Sweet peas for climbing colour

If you didn’t sow sweet peas in autumn or February, March is still a great time. Start them in root trainers or deep pots so their long roots have space to grow. Keep them cool and bright to avoid legginess. You’ll get strong plants ready to go out by April.

Summer bulbs to plant now

March is the start of bulb season for summer-flowering varieties. Plant dahlias, lilies, gladioli, and begonias in pots indoors or directly into the ground if the soil is workable. These bulbs love sun and good drainage, so choose a spot that won’t stay soggy in spring rains.

Flowers to avoid this early

It’s still too early for tender annuals like sunflowers, nasturtiums, or tithonia to go outdoors. If you want to start them now, keep them indoors in warmth and transplant after the last frost. Likewise, don’t plant bedding plants like impatiens or geraniums outside yet.

Soil and site preparation

As the ground warms, it’s a good time to improve your beds. Rake over the soil, add compost, and remove weeds before sowing. If your soil is heavy or clay-rich, dig in some grit or organic matter to help drainage. Good preparation now will give your flowers a much better chance to thrive.

List of Flowers to plant in March in the UK:

Hardy Annuals (sow outdoors or under cover):

• Calendula

• Cornflowers

• Larkspur

• Nigella (Love-in-a-Mist)

• Clarkia

• Godetia

• Eschscholzia (Californian poppy)

Half-Hardy Annuals (sow indoors with warmth):

• Cosmos

• Zinnias

• Marigolds (Tagetes & French)

• Nicotiana

• Petunias

• Salvia

• Cleome

Perennials (start from seed indoors):

• Echinacea

• Rudbeckia

• Lupins

• Delphiniums

• Gaura

• Aquilegia (Columbine)

• Verbena bonariensis

Climbing Flowers (sow indoors or under cover):

• Sweet peas (Lathyrus odoratus)

• Morning glory (Ipomoea)

Summer-Flowering Bulbs (plant indoors or outdoors):

• Dahlias

• Gladioli

• Lilies

• Begonias

• Crocosmia

• Freesias

Final thoughts

March is a high-energy month in the gardening calendar. The mix of sowing indoors and planting outdoors gives you flexibility and plenty of options. Focus on hardy varieties for now and use indoor space wisely to get a jump on the season. The effort you put in this month will set the tone for a colourful, long-lasting garden through spring and summer.