Despite unusual warmth and heavy rain in some places, there is still plenty of colour in the garden. Many bedding plants should still be flowering well and rudbeckias, heleniums and helianthus, along with asters and even phlox may still be in bloom.
But September is not peak time for flowering shrubs. There may still be the odd flowers on buddleias and, of course, roses should still be in bloom, but there are not many shrubs that are at their best in late summer.
Clethra are hardy shrubs you have probably never heard of but they deserve to be planted a lot more. They are useful because they flower in late summer, with pink or white flowers that are sweetly scented. The spikes of flowers are attractive, though not large, and they flower for several weeks. They vary in habit and some are very compact but most are medium shrubs. They lose their leaves in autumn, often turning butter yellow before they drop.
They are not too fussy to please but prefer an acid or neutral soil, ideally with added organic matter and a spot in sun or part shade. Mine are in heavy soil and seem happy enough. When established they may sucker from below ground to make a large clump. Avoid soils over chalk or that are baked dry in summer.
‘Ruby Spice’ is among the best because of the pretty pink flowers. The flowers are sweetly fragrant and bees love them too. ‘Sixteen Candles’ is similar but more compact, with white flowers. Clethra fargesii is larger in habit, eventually becoming a small tree, and rather rare, with longer clusters of flowers but just as fragrant.
Heptacodium miconoides is a relatively new addition to our gardens but has rapidly become very fashionable. I had it in my last garden and it was among the first shrubs I planted in this one. Forget the mouthful of a name, this is a shrub to consider for a long season of interest. It is a large shrub, that can have the lower branches removed to form a small tree as it grows.
The leaves curve in a curious way and the bark is pale brown and peels attractively. Every shoot ends in large clusters of small white flowers that are faintly scented and attract bees and especially butterflies. The flowers are not the end of the display however and when they drop the calyx behind every bloom expands and turns brick red, often making a better show than the flowers themselves. This continues till the first hard frost of autumn. It is not ideal for tiny gardens but is not fussy about soil and will thrive in any sunny spot, providing interest all year.
If space is at a premium then the hardy hibiscus (Hibiscus syriacus) is a good choice. These deciduous shrubs always start to produce leaves rather late in spring and even after all these years I still panic when there is little sig of growth by late April. They begin to bloom in August. They love sun and warmth and can be grown against a sunny wall. Although the flowers may be white, pink or crimson, I always think that the ‘blue’ varieties are the most beautiful. Avoid the doubles which, in wet weather especially, do not open fully and they lack the beauty of the simpler kinds. The flowers are not fragrant.
While blue hibiscus are not really blue, the flowers of ceratostigma are as blue as you can imagine. Their brilliant, cobalt blue flowers are not large but they are produced for many weeks in autumn and enhanced by the foliage which turns orange and crimson as the season cools. They are small, suckering shrubs that are ideal for the front of the border in a sunny spot.
Callicarpa is one of the most desirable and amazing autumn shrubs. I know I am straying from flowers now because it is the berries that provide the colour. In summer the tiny pink flowers are pretty but not spectacular but the round berries are dazzling purple, unlike any other shrub and the leaves turn yellow and mauve as they drop, to reveal the berries. It is simple to please in most soils provided they are not too dry in summer, in sun or part shade.
Weekly Reminders
Keep watering baskets and patio pots and feed once a week to keep the flowers going
Remove the lower leaves and any yellow leaves from tomatoes. Avoid getting water on the leaves which can cause rot
Plant autumn-flowering bulbs now
Plant prepared hyacinths in pots of bowls for Christmas flowering