What flower seeds to sow in April: 8 things to plant now, before it's too late

The gardening experts reveal the best flower seeds to sow in April for a gorgeous summer garden

composite image of flower seeds to sow in April
(Image credit: (From left to right) Kerstin Waurick / Getty Images | Jacky Parker Photography / Getty Images |SERGIVANOVITCH / Getty Images)

There are all sorts of fabulous flower seeds to sow in April, to prep for a stunning summer display. With the steadily climbing temperatures, many varieties can now be planted outdoors where they are to bloom, while others can be started on a sunny windowsill.

True, you could opt to buy pot-grown plants as they arrive in garden centres over the upcoming months. But, growing annual flowers from seed is generally cheaper and has quick results, making it super rewarding.

Whether you're tending to a container garden or trying out some new garden trends in your flowerbeds, the following eight options will be sure to bring your space to life. Plus, there's plenty of practical advice from gardening experts, for successful results.

8 fantastic flower seeds to sow in April

While planting seeds is easy, there are a few key gardening tips to bear in mind. 

Whether sowing indoors or out, aim to keep the soil moist, especially until the seeds germinate. Once seedlings appear, you may need to transplant them into larger pots if growing indoors, or thin them out if planted in the ground, to give them space to grow. Remember, also, to get rid of weeds before planting outdoors, to encourage strong growth.

It's always worth checking the back of your seed packet, too, for planting depths and other helpful info for specific flower varieties.

1. Cosmos

pink cosmos flowers growing

Cosmos can provide a long-lasting display

(Image credit: klagyivik / iStock / Getty Images Plus / Getty Images)

Dreamy cosmos flowers suit cottage garden schemes and contemporary plots alike. April is ideal for sowing the seeds indoors, to get a head start and encourage a long blooming period.

Annelise Brilli, a gardening expert from Suttons, particularly recommends cosmos "Apricotta" (available to buy from Suttons). It introduces a stunning new palette into the cosmos family, with its soft apricot petals overlaid with pink flushes, she says. "It makes a wonderful feature for the back of the border.

"Cosmos germinates readily and can be sown straight into small modules, rather than seed trays, which avoids the need for pricking out," she continues. "Although it seems brutal, it is essential to pinch out the tips of young plants – this will result in shorter but bushier plants with more flowers."

You can plant your cosmos into their final planting position once all risks of frosts have passed. Nigel Lawton, plant buyer at Dobbies, recommends a sunny, south-facing spot that's well-draining. "Make sure to water your seedlings and young plants regularly for the first stages of growth, especially if the weather is warm, because they can dry out very quickly," he adds.

It's also possible to sow cosmos seeds directly outdoors, but it's generally best to wait a little longer – until May or June – to give the soil more of a chance to warm up. 

headshot of Annelise Brilli from Thompson & Morgan
Annelise Brilli

Annelise Brilli is the horticultural copywriter for Suttons. Annelise caught the gardening bug from her mother, whose tiny backyard was crammed with a huge collection of plants. As an adult, she had a career change into horticulture, gaining a training apprenticeship with the National Trust at Powis Castle Garden in Welshpool. She went on to work in a range of private and public gardens, later running a garden design and maintenance business. She is passionate about sustainable gardening and has developed her own wildlife-friendly garden which she has opened as part of Macmillan Coastal Garden Trail.

headshot of Nigel Lawton from Dobbies
Nigel Lawton

Nigel Lawton is a passionate gardener. His interest sparked as he left high school, going on to spend three years in horticultural college. He has worked in garden centres for over 25 years and has spent over six of those years with Dobbies. Nigel is very knowledgeable about a variety of plants and spends his time as Dobbies’ plant buyer focusing on shrubs, perennials, trees and soft fruits.

2. Poppies

poppy flowers

Poppies can be sown outdoors

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Dr Emily Lambert, co-founder of Seedball, recommends sowing poppies this month for a radiant display in the summer. They're a top pick if you're looking to recreate the wildflower garden border trend.

Sow them directly where they are to bloom. Emily says, "Poppies do best in bright and sunny spots, so make sure to factor this in when looking for a place to scatter seeds." 

Annelise says, "Poppy seed is like dust and requires good soil preparation. Remove any stones and use the back of your rake to break down lumps of soil into a fine tilth. Sprinkle the seed thinly over the surface – there is no need to cover it, just water in gently afterwards."

Annelise recommends "Laurens Grape", available at Suttons. "I love the sumptuous colour of its deep plum petals and the seed heads continue to have a presence in the border long after the flowers have faded."

headshot of Dr. Emily Lambert from Seedball
Dr Emily Lambert

Dr Emily Lambert is a conservation scientist, and alongside Dr Ana Atlee, founded Seedball, a multiple-award-winning, not-for-profit organisation. Seedball’s mission is to help increase the abundance of British wildflowers and wildlife that depend upon them by encouraging people to maximise the outdoor space available to them and scattering seed balls of native flowers.

3. Sunflowers

tall sunflowers growing next to a fence

Sunflowers grow quickly, creating a tall screen of blooms

(Image credit: Jacky Parker Photography / Moment / Getty Images)

Nigel says, "Sunflowers are popular seeds to sow and can be extremely rewarding, especially if growing with children. Some plants can reach heights of up to four metres and the bright yellow flower heads can be up to 30cm in width."

You can sow the seeds directly into the ground once frosts have passed – usually in late April. Nigel recommends planting them somewhere sunny, in fertile and moist but well-draining soil. Alternatively, start them off indoors on a windowsill until they germinate, then transfer them outdoors when they're big enough to handle, he says.

"Sunflower ‘Choco Sun’ is a quick-growing dwarf variety which produces multiple flower heads and lots of seeds, making it an excellent border plant," he adds. 

We also like "Velvet Queen" sunflowers from Thompson & Morgan – one of the best plants for deep red and rust-toned blooms. 

4. Bunny's tail grass

bunny's tail grass

This annual grass makes a pretty addition to bouquets

(Image credit: Kerstin Waurick / iStock / Getty Images Plus / Getty Images)

Garden designer Melanie Hick recommends sowing Lagurus ovatus, or bunny’s tail grass in April – a wonderful native plant aptly named due to the fluffy-looking flower heads.

"These pretty little plants subtly change colour throughout the year, from pale green to buff and cream later on," she says. "These act as fantastic ground coverage, as they don’t tend to grow much past 50cm, so are an excellent option for adding interest at different levels in a flowerbed. And they’re lots of fun, too!"

You can sow these beauties directly this month and next, somewhere with plenty of sunshine and well-draining soil. Bunny's tail grass seeds are available to buy from Sarah Raven, and the plants make the perfect accompaniment to the quiet luxury garden trend.

headshot of garden designer Melanie Hick
Melanie Hick

Melanie Hick is a Melbourne-born, London-based bespoke garden designer specialising in creating beautiful spaces with sustainability and climate consideration built into every layer of their creation. As a lifelong gardener and lover of the great outdoors, Melanie passionately believes in helping people to get the most out of their gardens, using them to connect deeply with nature and each other.

5. Marigolds

calendula flowers

Marigolds are a cheery choice and so easy to grow

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Nigel says, "Calendula officinalis, also known as the common marigold, is a great, fast-growing annual with vibrant orange flowers that look like daisies."

They can be sown in April, take only a few days to germinate, and flower in around eight weeks, he continues. "Best grown outdoors, marigolds enjoy a light, free-draining soil in full sun or partial shade.

"These plants benefit from regular deadheading to keep them looking healthy and prolong flowering," he adds.

Try them at the front of flowerbeds, or in containers to add a boost of colour to your outdoor living room ideas. Suttons have organic marigold seeds available to buy.

6. Large-flowered mallow wort

pink flower of large-flowered mallow wort

Add a pop of vibrant pink to your garden

(Image credit: SERGIVANOVITCH / iStock / Getty Images Plus / Getty Images)

If you're looking for slightly more unusual flower seeds to sow in April, consider the large-flowered mallow wort – specifically Malope trifida "Vulcan" (available from Suttons). 

This alluring plant is recommended by Annelise. "When I opened my garden for Macmillan Coastal Garden Trail, this old favourite attracted a lot of queries," she says. "The big, silky pink petals contrast beautifully with the star of green sepals that can be seen between them.

"This fast-growing hardy annual can be grown directly outside into well-prepared soil that has been raked into a fine tilth," she says. "It is best to sow in rows, so you can identify where the seedlings are and distinguish them from weed seedlings."

7. Cornflowers

blue cornflowers

Cornflowers are well-favoured for their bright blue hue

(Image credit: schnuddel / E+ / Getty Images)

Emily recommends sowing cornflowers from March to May, which will reward you with gorgeous blue hues from June to September. And as they're a great plant for pollinators, they'll attract plenty of butterflies and bees to your garden, too.

They can be sown straight into the ground, Emily says. For an easy approach, scatter the cornflower seed balls from Seedball at Crocus into your garden beds.

"Very little care and attention is needed for these lovely blue beauties to thrive, just keep them well-watered and don’t let the soil dry out," Emily continues. Once flowers have finished, they can be deadheaded to encourage more blooms, she adds.

8. Sweet peas

close-up of sweet pea flower

The scent of sweet peas is hard to beat

(Image credit: Jacky Parker Photography / Moment / Getty Images)

Sweet peas may have been on your list of what to plant in February indoors, to give them an early start. But if you haven't planted them yet, or you want to sow another batch, you can now plant these seeds directly in your garden into fertile soil.

Anchor a support in place first – you can make a wigwam by tying bamboo canes together. Then, sow your seeds evenly around the base, around five inches apart, and water them in well. Just like when sowing sweet peas indoors, be sure to pinch out the tops of the seedlings to encourage bushier growth and more blooms. 

We love the vibrant shades of the "Brilliant Buckets" sweet pea collection from Sarah Raven.


Can you plant lilies in April?

Gardening expert Sarah Raven says, “You can plant lily bulbs straight into the ground in April, pointy end up, and don’t worry if the bulbs have sprouted. Allow them plenty of room, and add grit for drainage in the planting hole if you’re using heavy soil.

“I find that lilies prefer to have their feet in the shade and their heads in the sun, and they will flower better and live longer if the soil is not cold and clammy," she adds.

headshot of garden expert Sarah Raven holding flowers
Sarah Raven

Since the publication of her first book, The Cutting Garden, Sarah has led the way in introducing a new kind of productive gardening. Her aim is to create intense colour and beauty, combined with a practical and easy-to-achieve approach. Her popular gardening podcast Grow, Cook, Eat, Arrange has achieved 4.1 million downloads. She’s published 15 books and runs Sarahraven.com, which services over 600,000 customers.

What vegetables can you sow in April?

As well as there being lots of flower seeds to sow in April, there are plenty of veggies to plant now, too, if you're keen on growing a vegetable garden this year. Consider sowing peas, broad beans, carrots, and radishes directly in the ground. Indoors, you can start tomatoes, chillies, and courgettes if you haven't already.

Alongside planting blooms ready for a summer show, now's the perfect time to sort your garden out and get it looking its best, whether that's cleaning your patio or doing the first mow of the year.

Holly Crossley
Garden writer

The garden was always a big part of Holly's life growing up, as was the surrounding New Forest where she lived. Her appreciation for the great outdoors has only grown since then; she's been an allotment keeper, a professional gardener, and a botanical illustrator. Over three years ago, Holly started writing about plants and outdoor living full-time, first for Gardeningetc.com and now for popular lifestyle titles such as Homes & Gardens.