Late-summer planting tips

As the days begin to shorten in late summer, we know we are on the cusp of autumn and need to consider how we can help insects like butterflies and moths get through the coming winter.

Some garden butterfly species such as Small Tortoiseshell and Peacock overwinter as adults and will need to feed up on nectar, which they store as fat inside their bodies. Like mammals such as squirrels and hedgehogs, their metabolism will slow down in winter so they use as little energy as possible until springtime. Others like Painted Lady and Red Admiral will use the nectar to fuel their migrations to Europe and Africa – it’s amazing to think that butterflies we see in our gardens in the UK may turn up in another garden hundreds of miles away!

My favourite late-summer planting style is known as Prairie planting, as many of the plants used in it are derived from the prairies of North America. Plants like Goldenrod, Monarda, Salvia, tall daisies, Phlox, Rudbeckia, Echinacea and Helenium are all available in garden centres. They produce colourful flowers on tall spikes that you can mix with wavy grasses, giving a very naturalistic appearance that only improves as the summer goes on. These are all perennial plants, and have the advantage that invertebrates can tuck themselves down at the bases of the plants to spend the winter there.

If you’ve got a smaller space, or even a windowbox or small balcony or patio with planters, it’s essential to choose plants which really give a lot of nectar so you can cram as much good into a limited area. I recommend any of the Sedums with large flat heads studded with pink flowers, such as Sedum ‘Autumn Joy’ (just a note though – these Sedums have recently had their botanical name changed to Hylotelephium, but Sedum is still widely used). It’s also hard to go wrong with lavender, Salvias and Veronica. Most garden centres also sell at least one variety of Sea Holly (Eryngium species), but I love them all! The stem leaves are soft and green at first, but as they mature the flowers and stems turn electric blue and become spikey. The flower heads hold hundreds of tiny flowers packed with nectar which are great for insects now, and the dried flower heads look stunning on a crisp winter morning when covered in frost.

Butterflies and moths will also take sugar from fallen fruit, so remember to leave fallen fruit on the ground for them, or move it all to certain spots where the fruit can break down to release those sugars. You could even make a butterfly feeding table! In my garden I see Comma butterflies drinking sugar from fallen Rowan berries every September, so I leave them on the ground for this reason.

If you’ve got a slightly more shaded area with decent soil, Japanese Anemones and Thalictrum will be reaching their peak come September, and hardy geraniums may give a second late-flowering if you’ve dead-headed them after the first flowering earlier in the summer.

We are also encouraged to prune some shrubs and trees (such as apple, pear and plum trees) in late summer, and this is sensible if it can be done without disturbing any nesting birds. If you do prune now, why not simply stack the material in a quiet corner of the garden to make a place for wildlife to shelter? Chipping or burning it will kill any caterpillars or eggs of butterflies and moths which will be there, but if you leave it in the garden it can create a whole new space for wildlife – for free!

Finally, if you have an area of long grass which you are treating as a meadow, the advice is sometimes to cut it in July or August. However, caterpillars of Meadow Brown, Ringlet and Speckled Wood butterflies all feed on grass and can remain active as long as the temperatures are warm enough - this can be well into autumn. So I recommend leaving the cut until early the following spring, or cutting only part of the meadow each year so that the invertebrates in the rest of the meadow survive.