Why late flowers matter more than ever

By the middle of September, most of the garden has quietly given up. The lavender is grey and woody, the hardy geraniums have stopped, and the last of the cosmos is looking thin. The bees, however, have not given up at all. This is their busiest season. Bumblebee colonies are at their peak, raising new queens and males before the nest winds down, and honeybees are working flat out to lay down stores for winter. Solitary bees are still provisiong nests, and hoverflies, butterflies and moths are topping up before hibernation.

Then comes the gap. From late September into November, nectar and pollen become genuinely scarce in most British gardens — exactly when demand is highest. Filling that gap takes surprisingly little space, and a handful of well-chosen plants will do more for wildlife than a whole summer of bedding.

Asters: the backbone of the autumn border

Michaelmas daisies are the classic answer, and they still earn their place. Most of what we called Aster is now Symphyotrichum, but the garden value is unchanged. 'Little Carlow' is hard to beat: a froth of violet-blue daisies with open, honey-coloured centres, flowering from September into October on stems that need little staking. New England asters such as 'Andenken an Alma Pötschke' are taller and later, wonderful at the back of a border, and their flowers are properly single, so the pollen is right there on show.

They do have one weakness: powdery mildew. Give them a spot in full sun with decent air movement, water them in dry spells, and lift and divide clumps every second or third year. Crowded, dry roots are what bring on the grey dusting, and a divided clump flowers better the following autumn anyway.

Sedum: the pollinator magnet

Still sold as Sedum, now correctly Hylotelephium, and utterly reliable. The flat heads of tiny pink flowers open in late August and hold for six or eight weeks, and because each head is a shallow platform, bees can walk across it feeding without hovering. On a warm afternoon in September, one clump of 'Herbstfreude' (sold as Autumn Joy) can carry half a dozen bumblebees, plus hoverflies and the odd comma butterfly.

'Matrona' has purple-flushed stems and grey-green leaves and looks good even before it flowers; 'Brilliant' is a clear, bright pink. All of them want full sun and sharp drainage, and they resent being fussed over. Leave the faded heads standing through winter — they hold their shape under frost, shelter overwintering insects in the hollow stems, and the seedheads feed goldfinches in January.

Dahlias: choose single, skip the pom-poms

Dahlias have a poor reputation with bee gardeners, and it is only half deserved. The problem is the doubles. Single and semi-double varieties have an open ring of petals around a visible, pollen-covered disc, and bees work them happily right up to the first hard frost — often into November, long after everything else has gone.

• 'Bishop of Llandaff' — semi-double scarlet on dramatic dark foliage, flowers until cut down.
• 'Honka' and other single, star-flowered types — yellow, scented, and completely open.
• Happy Single series — bred specifically for open centres and long flowering.
• Dark Butterfly and similar single-flowered dark-leaved forms — good contrast, generous nectar.

Plant tubers out after the last frost in full sun, keep them watered, and deadhead relentlessly; the more you cut, the more they produce. In mild, well-drained spots a thick mulch over the crowns will see them through winter. Elsewhere, lift the tubers once the foliage blackens and store them somewhere frost-free and dry.

The single-flower rule

There is one principle worth remembering for every plant you buy, not just the autumn ones. In a double flower, the extra petals are modified stamens — the pollen-bearing parts — and breeding for show has turned them into more petal. The result is a bloom with little or no pollen, where the dense layers of petal also block the route to the nectary underneath.

So the test is simple: if you can see the middle, a bee can reach it. Get close and look for a ring of stamens around a central disc, then stand still for ten seconds and watch. If nothing lands, the plant is decoration, not forage. Pom-pom and cactus dahlias, fully double asters, and many modern double-flowered varieties fall into that category — lovely, but no use to a hungry queen.

Putting it together in a real garden

• Plant in full sun, out of the wind. Bees work far more efficiently when they are warm, and a sheltered south-facing border will be busy when a windswept one is empty.
• Group in threes and fives. A single aster is a pit stop; a clump is a reliable foraging patch worth returning to.
• Plan for succession. Early asters and sedum from August, main asters through September, dahlias until frost, and ivy flowering in October and November as the final course.
• Hold back on the autumn tidy-up. Leave seedheads, hollow stems and leaf litter over winter. Cutting everything to the ground in October evicts the very insects you have been feeding.
• Never spray open flowers. Even products described as harmless to bees are risky when applied to a plant in bloom; deal with problems in the evening, or not at all.
• Water new plantings deeply through their first autumn, so they establish before winter rather than sitting in dry soil and sulking until spring.

Do all that, and by mid-October your garden will still be humming when the neighbours' has gone quiet. It is a small change, made once, that pays out every single year.