Summer is the season a flower garden is made for, and it is also the season when it needs the most attention. A bed that is deadheaded regularly, watered at the roots, fed lightly and staked before it flops will flower from June until the first frosts, while a bed left to itself will bloom once, set seed, and fade by August. The work is not heavy — a few minutes with secateurs, a watering can, and a regular walk around the garden — but it needs to be regular, because flowers grow fast in summer and a week's neglect shows quickly. This guide covers deadheading, watering, feeding, staking and pest care for summer flowers, in annuals, perennials and roses alike. For local advice, check your local extension service.
Deadheading: the habit that keeps flowers coming
Deadheading — removing spent flowers — is the most useful summer flower job, because most annuals and perennials will keep flowering if they are not allowed to set seed. Once a flower sets seed, the plant's job is done, and it stops producing new flowers; remove the faded head, and the plant tries again. Snap or snip the flower off, cutting back to just above a leaf or a side bud, and do it once or twice a week, carrying secateurs on your regular walk around the garden so it becomes a habit rather than a chore.
Roses, dahlias, zinnias, marigolds, cosmos, petunias, sweet peas and geraniums all respond well to regular deadheading, and a few minutes a week will keep them flowering until autumn. Sweet peas in particular need picking or deadheading every few days, because they stop flowering quickly if pods are allowed to form. Leave some flowers to set seed if you want self-sown plants next year, or if the seed heads feed birds — sunflowers, echinacea and ornamental grasses are better left standing. For growing detail, see growing roses, growing zinnias and growing marigolds.
Watering flowers in summer
Water flowers at the base, in the morning, so the foliage stays dry and the water reaches the roots. Newly planted flowers need watering every day or two until they are established, while established perennials with deep roots often need watering only in a dry spell. Containers and hanging baskets are the exception: a pot in full sun can dry out completely in a day, and a hanging basket faster still, so check them daily and water until it runs from the drainage holes. Mulch the surface of beds and containers to hold moisture, and group pots together so they shade each other's sides.
Roses need deep watering in summer, especially when they are flowering, because a rose short of water will produce small flowers and drop its leaves. Water slowly at the base, and mulch around the plant to hold the moisture in. Dahlias, which are thirsty plants, need regular watering once they are in flower, and they will wilt quickly in a hot spell if they are allowed to dry out. The watering calculator can help you work out how much water a bed needs, and our summer watering guide covers the principles in detail.
Feeding and staking
Feed flowering plants lightly and regularly through the summer, with a liquid feed high in potash, which encourages flowers rather than leaves. Roses and dahlias are the heaviest feeders among common flowers, and both respond well to a liquid feed every two weeks through the flowering season. Container flowers need feeding more often than bed flowers, because their small volume of compost is quickly exhausted — every one to two weeks at half strength is a good rhythm. Do not feed a plant that is stressed by drought; water it first, let it recover, and feed it only when it is growing again.
Stake tall flowers before they flop, not after. Dahlias, lilies, delphiniums, sunflowers and tall cosmos all need support, and a stake or a ring put in place while the plant is still upright is far easier than trying to lift a plant that has already fallen over. Tie stems loosely with soft twine, in a figure of eight around the stake and the stem, so the stem can move a little without being strangled. Check ties through the season, loosening them as stems thicken. Our summer pruning guide covers the light pruning that goes with staking and deadheading.
Pests and diseases in the flower garden
Aphids are the main summer pest of flowers, clustering on the soft tips of roses, dahlias and sweet peas. A strong jet of water dislodges most of them, and ladybirds and other predators will do the rest if they are not sprayed away. Slugs and snails are at their worst in a wet summer, feeding on hostas, dahlias and young seedlings at night; go out after dark and remove them by hand, and keep beds clear of debris where they hide. Earwigs hide in dahlia flowers and can damage the petals, but they do little lasting harm and can be trapped in an upturned pot stuffed with straw.
Powdery mildew shows as a white coating on leaves in warm, dry weather, especially on roses, phlox and squash, and it is best prevented by watering at the roots, spacing plants for air flow, and removing the worst-affected leaves. Black spot on roses shows as dark spots on leaves that then turn yellow and fall, and it spreads in wet weather; remove affected leaves promptly, do not compost them, and avoid wetting the foliage when you water. The pest identifier helper can help you identify what you are seeing.
Keeping beds blooming until autumn
A flower bed that blooms all summer is usually a bed that has been planned for it, with a mix of plants that flower at different times, and a gardener who keeps up with deadheading, watering and feeding. Sow or plant a second round of quick annuals — cosmos, zinnias, nasturtiums and marigolds — in early summer, so they come into flower as the spring-sown plants fade. Cut back perennials that have finished flowering, such as hardy geraniums and delphiniums, and many will produce a second flush of flowers and fresh foliage.
At the end of summer, leave some seed heads standing for birds and for self-sowing, and take notes on which plants flowered well and which did not, so next year's planting is better. A flower garden is a living thing that changes every year, and the notes you take this summer are the plan for next summer's planting. For the rest of the summer routine, read our summer pruning guide and summer mulching guide, and browse the guides hub and the planting calendar for the full seasonal series.
Frequently asked questions
How often should I deadhead flowers in summer?
Once or twice a week, removing spent flower heads back to just above a leaf or a side bud. Roses, dahlias, zinnias, marigolds, cosmos, petunias and sweet peas all keep flowering if deadheaded regularly, and sweet peas need picking or deadheading every few days.
How do I water flowers in summer?
At the base, in the morning, so foliage stays dry and water reaches the roots. Newly planted flowers need watering every day or two until established; containers and hanging baskets need checking daily, because they dry out fast.
Should I feed flowers in summer?
Yes, lightly and regularly, with a liquid feed high in potash that encourages flowers rather than leaves. Roses and dahlias benefit from feeding every two weeks, and container flowers need feeding every one to two weeks at half strength.
When should I stake tall flowers?
Before they flop, while they are still upright. Put stakes or rings in place early, tie stems loosely with soft twine, and check ties through the season so they do not strangle thickening stems.
What are the white patches on my rose leaves?
Powdery mildew, common in warm, dry weather. Improve air flow, water at the roots rather than over the foliage, and remove the worst-affected leaves. Check your local extension service if the problem is severe.