10 summer-flowering plants to plant by the end of May

Anyone who puts a little time into the soil in February, March, April or even May will be rewarded in high summer with colour, fragrance and abundant flowers. The key is to choose perennial summer-flowering plants grown from bulbs, tubers or rhizomes, which can return year after year rather than putting on a brief display like traditional seasonal bedding plants.

Why planting now transforms the whole summer

When people think of flower bulbs, tulips and daffodils planted in autumn usually spring to mind first. However, a dramatic summer display comes from entirely different contenders: amaryllis, dahlias, cannas, lilies and more go into the ground in spring before rapidly getting going within a few weeks.

Planting in spring gives you a complete fireworks display of flowers in the very same year – and, depending on the species, for several seasons to come.

These bulbous and tuberous plants have an advantage: those sold commercially have generally already been cold-stored. Their required cold period has therefore been completed, so all you need to do is wait for a frost-free moment. Planting from February to the end of May will usually have them ready for the height of summer.

There is just one important rule: avoid waterlogging. Soil must be loose, free-draining and not continually wet, as bulbs rot quickly in soggy conditions. In containers, use a drainage layer of expanded clay pellets or gravel.

How to plant spring bulbs correctly

Whether they are called bulbs, tubers, rhizomes or corms, the planting method is much the same:

• Dig a hole around two to three times as deep as the bulb is tall.
• Place the bulb in the hole with its pointed end facing upwards.
• Backfill with fine soil and firm it gently.
• Water it in so that the soil and bulb make good contact.

For pots, start with the drainage layer and then add a layer of good-quality potting compost. Plant tubers fairly close together to give window boxes and containers a particularly lush look later on.

The 10 best summer-flowering plants to plant by the end of May

These ten reliable performers provide the foundation for a summer that looks far more impressive than the usual geranium-filled planters.

1. Amaryllis (Hippeastrum) – an exotic star for warm spots

The amaryllis known as a houseplant can also be grown outdoors. It thrives in sun, warmth and well-drained soil. Its large, trumpet-shaped blooms look especially elegant on a patio or in a sheltered border.

Growing the bulb in a container makes protection easier: bring it indoors dry in autumn, store it somewhere cool but frost-free, and place it outside again in spring.

2. Anemones – floating clouds of flowers

Anemones create something like a carpet of blooms in borders or containers. Their delicate, usually single flowers hover above fine foliage, making them ideal for the front of a planting scheme and for filling gaps.

Soak the small tubers in lukewarm water for several hours beforehand to help them shoot more reliably. A partially sunny position is entirely sufficient.

3. Tuberous begonias – vivid colour in shade

For dark corners, north-facing balconies or spaces beneath trees, tuberous begonias are almost unbeatable. They cope with little direct sun while still flowering for months.

Plant the tubers shallowly in spring, with the hollow side facing upwards. Lift them in autumn, store them dry, and start again the following year.

4. Caladium – a foliage plant with wow factor

Caladiums stand out less for flowers than for their leaves: heart-shaped, speckled, pink, white and green, often appearing as if they have been painted. They are perfect for partially shaded patios or shady balconies.

The tubers need warmth. Do not plant until nights are consistently mild. Keep them indoors, dry and frost-free over winter.

5. Canna – tropical flair in the border

Cannas resemble banana plants in appearance, with large, dramatic leaves and colourful flower spikes rising above them. They enjoy full sun, plenty of water and regular nutrients.

Many gardeners plant the rhizomes directly into the border. In colder areas, it is worth lifting them in autumn and keeping them in frost-free winter storage.

6. Crocosmia – fiery splashes of colour

With their slender, arching sprays of orange or red flowers, crocosmias bring movement to perennial borders. They work particularly well with grasses or in front of dark hedges.

In mild areas, the corms can remain in the ground, with a layer of mulch providing protection from severe frost.

7. Dahlias – classics for full borders

For many amateur gardeners, dahlias are essential. Their forms range from simple, bee-friendly varieties to enormous pompons. They bloom throughout summer if faded flowers are removed regularly.

Do not plant the tubers until night frosts are no longer expected. Lift them in late autumn, store them dry and replant them the next year – saving the cost of buying new ones annually.

8. Gladioli – ideal cut flowers

Gladioli produce tall, elegant flower stems that are superb for bouquets. In borders, they create crisp, graphic vertical lines.

Planting fresh corms every two weeks noticeably extends the flowering period: the spikes will then open in succession well into late summer.

9. Lilies (Lilium) – fragrance and elegance

Lilies are dependable garden residents. Once established properly, their bulbs can stay in the ground for many years. Numerous varieties have an intense scent, making them ideal near patios or seating areas.

They prefer sunny to partially shaded positions, with cool roots and sunny tops, so plant them among lower-growing perennials.

10. Tuberoses – evening fragrance for the patio

Tuberoses are still genuine hidden gems in the UK. Their slender flower stems may look understated, but their evening fragrance is powerful.

Place the tubers in warm, sheltered locations, such as containers beside a seating area. Lift them again in autumn and store them frost-free.

Which bulb suits which position?

Choosing the right location will help you get much more from these plants. As a broad guide, plan as follows:

Position	Suitable plants	Particular advantage
Full sun in a border	Canna, dahlias, crocosmia, gladioli, lilies, tuberoses	Tall, colourful backdrop, good for insects
Sunny balcony / patio	Dahlias, gladioli, amaryllis, canna	Lush containers, plenty of cut flowers
Partial shade / shade	Tuberous begonias, caladium, anemones	Brighten up dark corners

How to overwinter your summer bulbs safely

Many of the species listed originate from warmer regions and can only tolerate UK winters to a limited extent. To keep them, follow a systematic approach in autumn:

• Cut back above-ground growth after the first frost.
• Carefully lift the tubers and shake off excess soil.
• Leave them to dry for several days in an airy place.
• Store them in boxes with some newspaper or dry soil.
• Keep them frost-free, dark and fairly cool.

Lilies and, depending on the region, crocosmias can stay in the ground if the site is not too wet. A mulch layer of leaves or bark compost offers additional protection.

Practical tips for reluctant waterers and balcony gardeners

If you have little time, choose large pots. The greater the volume of compost, the less often you need to water. Combining different bulbs in one container creates varied heights and flowering times – for example, anemones at the bottom, dahlias in the middle and gladioli at the back.

Liquid feed added to the watering can every two weeks, or a controlled-release fertiliser applied at planting time, is usually quite enough. Without nutrients, flowering and growth will be noticeably weaker.

What many people underestimate about flower bulbs

Summer bulbs are often considered “complicated” because they are meant to be lifted again in autumn. In reality, this small effort pays off: many tubers become larger over the years, can be divided and will therefore provide almost free new plants.

If you have children, planting together can become a small seasonal ritual. The visible change from a bare border to a wall of flowers is far more striking when you have done the work yourself – and that is precisely the hidden appeal of this spring activity.