RHS Hampton Court Picks for 8 Pollinator-Friendly Perennials

Late flowers carry the lean weeks

Most pollinator borders are full of movement in June, then thin out by August. The count worth watching comes in September, when bumblebee queens are provisioning and forage has become scarce. Sedum spectabile, now reclassified as Hylotelephium, is one of the plants that keeps traffic moving. Its flat flower heads sit at 40 to 50 cm, and hoverflies and honeybees work over them in steady rotation through early October.

Aster x frikartii Monch covers the same difficult period from another angle. It begins in late July and carries on past the first light frosts, with far cleaner foliage than many Michaelmas daisies, which often lose their leaves to mildew by September. Monch reaches about 70 cm and usually stands without staking, a practical difference from taller Novae-angliae asters that can lean across paths late in the season.

Both plants need full sun and free drainage. Sedum in particular loses its shape in rich, damp soil, opening out at the centre as the flowers develop. A low mound, or a patch of poorer ground, keeps the stems firmer. If there is space for only two plants from this selection, Sedum and Monch are the pair that carry the gap when many borders have already slowed.

Echinacea in autumn

Echinacea purpurea brings bees to the July flowers, then goldfinches to the seed heads in autumn, so the spent stems earn their place standing through the later season. The named cultivar Magnus holds its petals more horizontally than the species, giving visiting insects a flatter landing platform.

Long-running flowers on open stems

Verbena bonariensis behaves like a piece of border structure that happens to bloom. It sends wiry stems up to 1.8 m, each topped with small clusters of purple florets, and it keeps flowering from June until hard weather kills it in November.

The insect traffic on Verbena leans toward butterflies and long-tongued bees. The tube of each floret rewards a proboscis, which gives it a different visitor profile from the flatter flowers in the same planting. It self-seeds freely. In a gravel garden that can look generous; in a tidy border it can become a recurring job.

Move seedlings early if they are growing in the wrong place. Once the taproot extends past about 10 cm, young Verbena plants transplant badly, and lifting them often leaves a weakened plant behind. Small seedlings shift cleanly, larger ones are usually best left where they have rooted.

Knautia macedonica has one of the longest flowering windows in this group. It produces dark crimson pincushion heads on branching 60 to 80 cm stems from late May into October. Individual plants are often short-lived, commonly lasting three or four years, yet they seed enough to keep a planting going if bare soil is available.

Its flower structure is useful for insects that cannot work Verbena. The domed head is made from many tiny florets, so shorter-tongued solitary bees and hoverflies can feed without needing to reach deep into a tube. That is why Knautia can look busy even on days when butterflies are elsewhere.

Geranium Rozanne earns its place at ground level. As a sterile hybrid, it does not set seed, so its growth goes into flowers from June to the first frost without a pause for seed production. The violet-blue blooms carry a white centre that acts as a nectar guide, and one plant can spread across a metre of soil while suppressing weeds. Trailing stems root readily where they touch the ground, which helps it fill space without leaving many gaps for annual weeds.

Nepeta Six Hills Giant adds a second pulse if treated hard after the first flush. Cut it back in June and it reflowers within three weeks, giving two clear visitation peaks in the same season. Bumblebees dominate the count on Nepeta, and the aromatic foliage that deters deer and rabbits seems to leave them unaffected.

Raised beds, root depth, and mulch

The drainage profile of a raised bed suits much of this planting because the elevated soil column warms earlier and dries faster than a ground-level border. Of the eight selections, Sedum, Aster Monch, Verbena, Knautia, Nepeta and Echinacea are the six that most clearly fit that faster-draining setup. Geranium Rozanne is more tolerant of moisture, while shaded beds change the growing conditions enough to weaken the whole idea.

Depth matters. A bed with 30 cm of fill gives enough root run for these perennials, except Verbena bonariensis, whose taproot benefits from closer to 40 cm if the tall stems are to hold firm in wind. In shallower soil, Verbena can rock loose and may need a single cane to keep it upright.

The fill should have mineral soil in it. A rough mix of two parts topsoil to one part compost gives better long-term structure than pure compost, which slumps and holds excess water through winter. Sedum and Knautia are especially vulnerable when wet conditions sit around their crowns.

Mulch helps, provided it is placed with the crown in mind. A 5 to 7 cm layer of composted bark or leaf mould should go onto soil that is already moist in spring, with a clear gap of a couple of centimetres around the stem base. Piling mulch against the crown traps moisture against tissue that prefers to stay dry, and crown rot losses in Sedum and Aster often follow that mistake. Kept clear of the crown, the same mulch suppresses weed germination, holds soil moisture through July, and breaks down into the bed by the following season.

Beside the tomato bed

A pollinator border can earn space near vegetables when the flowering window runs long enough. A strip of Nepeta or Knautia within a few metres of tomatoes draws in hoverflies whose larvae eat aphids, as well as bumblebees that buzz-pollinate tomato flowers more efficiently than wind alone. Basil and French marigold still do the close-quarters work between tomato plants, but the perennial flowers nearby keep beneficial insects resident in the area instead of passing through only when a pest colony is already obvious.

Aphid predators breeding around a vegetable plot need adult forage. If the plot offers only aphids, predator numbers rise late and fade early. Geranium Rozanne and Knautia together can keep nectar available from May to October, which supports a standing population that reacts to early aphids before colonies build. Growers who run a single mixed perennial border beside tomatoes report fewer aphid sprays across the season than growers who isolate the vegetable plot. The crossover matters: insects working the perennial flowers also move into the crop rows.

Edges this planting does not cover

Deep shade remains outside the range of these plants. A north-facing wall, or the dry strip under a mature tree, will leave them thin, leafy, and reluctant to flower, no matter how well the soil is prepared. That empty strip remains a separate planting problem.