7 fast-growing seeds to sow directly outdoors in May for a garden bursting with flowers by summer

Filling garden borders and containers with flowers and plants bought from the garden centre can be pricey, and while growing your own from seed is much cheaper, it takes time and requires lots of space when starting young seedlings. The good news is that there are plenty of fast-growing flowers that can be direct sown from seed now that will bloom in time for summer, saving time, effort, space and money.

‘As the soil warms and the risk of frost passes, May is the perfect time to sow seeds directly into the ground to guarantee a blooming display throughout summer,’ says Shelley Davis, plant expert at Flying Flowers. ‘By the time May arrives, the ground has typically retained enough warmth to support sowing most seeds directly into the soil.'

‘The secret to success lies in mindful placement, ensuring you are matching each variety’s specific needs for either dappled shade or full sunlight,’ adds Shelley. ‘By buying seeds and getting them in the earth now, you are effectively guaranteeing a garden overflowing with vibrant colour in just about eight weeks.’

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1. Sunflowers

‘Nothing beats the sight of a towering sunflower brightening your garden, and when it comes to when is the best time to plant sunflowers, now is the ideal time to get your seeds in the ground,’ says Shelley. I've bought these Sunflower 'Gummy Bear' seeds, £2.99 from Suttons, with huge lemon-yellow fluffy heads to add a little extra interest.

‘As their name suggests, sunflowers love to be planted in areas of full sun, so choose a spot with as much light as possible, and sow your seeds about 12mm deep and 10cm apart. As they develop, thin the seedlings to a final spacing of 45cm, prioritising the strongest and tallest plants to ensure they have the room they need to thrive.’

‘To protect your golden investment, try placing a headless plastic bottle over new shoots or surround with crushed egg shells, to create a simple barrier against slugs and snails, who find young sunflower shoots irresistible.’

Where to buy sunflower seeds:

• Suttons: With huge lemon-yellow fluffy heads, try these Sunflower 'Gummy Bear' seeds, £2.99.
• Mr Fothergills: Or go for these striking dark red-coloured flowers, Sunflower Evening Sun seeds, £3.19.

2. Cosmos

‘May is the perfect time to plant half-hardy annuals like cosmos, as they require the frost-free warmth of late spring to truly thrive,’ says Shelley. ‘For how to grow cosmos, get started by sowing your seeds roughly 5-8cm apart and keep the soil well-watered. Once the seedlings emerge, pinch out the growing tips to encourage a bushier shape and more prolific bloom.’

‘Beyond their aesthetic appeal, cosmos are a powerhouse for local biodiversity too. Their nectar-rich petals act as a vital filling station for bees, butterflies, and hummingbirds, with bumblebees and honeybees being especially frequent visitors to these garden favourites, and they reward you with continuous blooms throughout the summer.’ The multicoloured blooms of Cosmos bipinnatus 'Sonata Series Mixed' seeds, £1.69 from Thompson & Morgan, are my top pick.

Where to buy cosmos seeds:

• Thompson & Morgan: Try the multicoloured blooms of these Cosmos bipinnatus 'Sonata Series Mixed' seeds, £1.69.
• Sarah Raven: Or try these all-white Cosmos bipinnatus 'Purity' seeds, £7.16 for three.

3. Nasturtiums

‘May is also the ideal window for planting nasturtiums, as these vibrant, easy-to-grow annuals thrive once the soil has warmed,’ suggests Shelley. ‘Simply tuck the large seeds about 2cm deep and 25cm apart in a sunny spot with poorer soil, which encourages more of their iconic trumpet-shaped flowers rather than just lush green foliage.’

‘These fast-growing flowers are a multi-purpose marvel for any gardener, serving as a “trap crop” that lures pests away from vegetables while simultaneously acting as a magnet for pollinators. Their bright, edible blooms provide an accessible feast for long-tongued bees, making them as functional for the local ecosystem as they are beautiful in the garden.’ This Nasturtium Trailblazer variety, £1.99 from Amazon is my top pick as they will add a fiery orange blaze of colour.

Where to buy nasturtium seeds:

• Amazon: Enjoy a blaze of fiery orange colour with these Nasturtium Trailblazer Seeds, £1.99.
• Dobies: Or go for these pretty multi-pink and purple Nasturtium 'Purple Emperor' seeds. £1.29.

4. Zinnias

‘Perfect for a beginning gardener, zinnias are very low maintenance and can grow nearly everywhere thanks to their weather tolerance,’ suggests Shelley. ‘When it comes to how to grow zinnias, these vibrant annuals don’t like root disturbance, so make sure, when direct sowing, that you are certain with their placement.' These colourful Zinnia elegans 'Giant Double Mixed', 89p from Thompson & Morgan, will create maximum impact.

'Zinnias are also perfect when they are ready to be cut, as they have a long vase life, typically lasting for 7 to 10 days if cared for correctly, meaning your garden and home can be filled with their bright blooms.’

Where to buy zinnia seeds:

• Thompson & Morgan: Add wow to your garden borders with these colourful Zinnia elegans 'Giant Double Mixed', 89p.
• Crocus: Or make a statement with this striking pale pink Zinnia elegans 'Zinderella Lilac' seeds. £4.99.

5. California poppies

California poppies are another easy-to-grow flower that can be direct sown from seed in garden flower beds and borders. Adding swathes of vibrant colour, in shades of orange, coral, pink and red, they are a great filler flower if you have gaps and are also a self-seeding flower, so once planted will come back year after year. The Californian Poppy Seeds 'XL Jelly Beans', £2.99 from Marshalls Garden, will pop up in shades of pink, rose, gold and orange for plenty of colour.

California poppies thrive in hot, dry spots where the soil is poor. They are best sown directly where they are to flower, as they do not like having their roots disturbed. Sow in straight drills, with rows about 15cm apart. Take pinches of seed, scattering them thinly along the drill and covering lightly with soil.

Where to buy California poppy seeds:

• Marshalls Garden: In shades of bright gold, rose, pink and orange, try these Californian Poppy Seeds 'XL Jelly Beans', £2.99.
• Amazon: Or keep it simple with these sunny orange Californian Poppy Eschscholzia californica Orange King seeds, £2.99.

6. Cornflowers

For a rustic, mini meadow style planting scheme, cornflowers are another lovely, easy-to-grow option that are great for beds and borders or can also be grown in containers too. With ruffled, thistle-like blooms and thin, wiry stems, they can reach between 30cm and 120cm tall (depending on the variety) with a vibrant blue colouring that is loved by pollinators.

Grow cornflowers in a sunny spot in well-drained, weed-free ground. Sow the seeds directly onto the soil, lightly rake over, and they should flower within around 8-10 weeks. Little aftercare is needed, apart from deadheading faded flowers to encourage more blooms.

Where to buy cornflower seeds:

• Gardeners Dream: Create rustic meadow-style beds and borders with these Cornflower 'Double Blue' seeds. £2.80.
• Dobies: Mix it up with these blue, pink and red blooms - Cornflower 'Tall Double Mixed', £1.19.

7. Night-scented stock

For fragrance after dusk, then night-scented stock is a must. Easy to grow in both borders and containers, stock also works well as a cut flower in indoor arrangements with its elegant, blowy blooms and foliage that helps add texture and structure to displays. These Stocks 'Night Scented' - Start-A-Garden™ Seeds, £1.29 from Thompson & Morgan are an easy-growing variety.

To grow night-scented stock, choose a spot that gets plenty of sun and has moist, well-drained soil. Stock works best in informal flower borders or cottage garden planting schemes. Simply scatter the seeds directly where you want them to grow, such as along the edges of patios, garden paths, or around seating areas, so that the perfume can be enjoyed up close.

Where to buy night-scented stock seeds:

• B&Q: Enjoy the fragrant evening aroma of these Verve Night Scented Stock seeds, £2.80.
• Thompson & Morgan: Or try these easy-growing Stocks 'Night Scented' - Start-A-Garden™ Seeds, £1.29.

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Are your beds and borders lacking colour? Will you be direct sowing your own seeds? Let us know.