9 Fast‑Growing Flowers to Plant in May for Colour in Just a Few Weeks – From Cosmos to Pansies

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1Cosmos beautiful cosmos flowers with background of kochia grasses. Kriangkrai Thitimakorn//Getty Images

Cosmos are easy to grow and provide quick colour, making them a great addition to any garden.

‘You can grow them from seed, they germinate quickly and they don’t need much fuss or special care,’ says Chris Bonnett, plant expert and founder of online garden centre Gardening Express.

‘Even better, bees, butterflies and other pollinators love them, so they’re a great choice if you’re looking to support local wildlife and make your garden more nature-friendly.’

2Calendulawulingyun//Getty Images

Calendula, also known as pot marigold, is an easy-to-grow hardy annual that will add colour to your borders in no time.

‘Calendula is a favourite of mine,’ says Mirela Bajic, senior garden designer at House Designer. ‘They have a bright, cheerful colour and it just gets on with growing without much intervention.’

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3Lobelia lobelia erinus Meitu//Getty Images

Looking for no-fuss groundcover? ‘Trailing varieties of lobelia are fast growing and quick to establish from plug plants,’ Chris tells us. ‘They create a full, cascading effect quickly, so they are particularly good for filling in gaps in hanging baskets and containers.’

Lobelias can be grown both as perennials and annuals, but the latter are the fastest to spread in the summer, the expert adds.

4Nasturtiums nasturtiums tumbling over the side of a raised bed in an english garden in summer Photos by R A Kearton//Getty Images

This leafy plant bears orange and yellow flowers and is a real garden hero. ‘Nasturtiums are brilliant because they’re not fussy about soil quality and will flower quickly while either trailing or climbing, depending on which variety you choose,’ Mirela says.

But that’s not all. Nasturtiums are also edible and they can be planted next to vegetables to act as sacrificial plants for slugs and caterpillars.

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5Pansies close up of smiling violas in the garden Barbara Rich//Getty Images

‘Pansies are super fast-growing and vigorous annual plants,’ says Chris. ‘They establish quickly and bloom continuously – often needing a light pruning to keep them in check.’

They thrive in a sunny spot with fertile soil and regular watering and feeding. Deadheading will keep your pansies fresh and encourage more growth throughout the summer.

6Petunias close up of bright pink petunia flowers with green foliage, creating a colorful garden display George Pachantouris//Getty Images

Petunias are another ideal choice for quick colour. ‘Many popular petunia varieties are fast-growing, particularly the “spreading” or “trailing” types,’ explains Chris. ‘These types act as groundcover, spreading many feet and covering large areas within a single growing season.’

Without regular maintenance, petunias have a habit of becoming leggy and crowding out other bedding plants, so it’s worth trimming them back every once in a while.

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7Verbena purple colored vervain flowerbed soft focus shot. MirageC//Getty Images

This pretty plant comes in different shades of purple, pink and red and adds vibrant colour and height to your plot. ‘Verbena is a very fast-growing plant with many varieties reaching their full size and flowering within a matter of weeks,’ says Chris.

‘It’s also quite low maintenance and thrives in full sun and well drained soil, making them excellent for quick colour in borders, containers and hanging baskets.’

8Geraniums closeup of vibrant purple and white flowers with lush green foliage Paolo Carnassale//Getty Images

Geraniums, a genus that includes 422 varieties, are popular bedding plants that are delightfully easy to grow.

‘Often affectionately referred to as geraniums, pelargoniums are a beloved choice for adding a burst of colour during the summer months,’ Ross, who is the resident horticultural expert for Pelargonium for Europe UK, tells us.

‘Their versatility is unmatched; they thrive in various settings, whether in pots on a balcony or in hanging baskets… Many varieties even boast aromatic leaves, which add an extra sensory element.’

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9Zinnias colourful zinnias in the garden. glennimage//Getty Images

Sun-loving zinnias, with their vibrant, wide-open flowerheads, aren’t just a sight to behold in beds and borders but also a boon to bees and butterflies.

‘May is perfect timing if you want quick impact in the garden,’ says Mirela. ‘Zinnias are my go-to choices for this. They’re reliable performers that grow quickly from seed and don’t need fussy care, which makes them ideal when you want results fast.’

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