Alexandra Campbell is putting in new plants and dividing perennials

Putting in new plants and dividing perennials is best done at this time of year, Alexandra Campbell says.

AS the summer ends, it’s a good time to think about planting new plants and dividing perennials that have been in the ground for too long.

These used to be spring or autumn jobs, and you could choose whichever suited you best, but an increasing number of head gardeners are now doing their main planting and division in autumn.

That’s because over the past decade we seem to have been getting some very dry springs.

This year I remember having to water the garden in April, which seemed extraordinary. We did then get a very cold, wet May, but that didn’t help.

Even if we don’t have a dry spring, doing your planting and dividing in autumn gives plants an opportunity to get established, ready to deal with whatever the weather throws at them next year.

While they will be more or less dormant for most of the winter, they’ll still have a little more time to get settled in and will also start growing as soon as the weather wakes up.

Dividing perennials is a job I dread. I have never succeeded in separating plants using two forks back to back. Neither have many of my most experienced gardener friends.

If you don’t divide your plants, many – such as asters or symphyotrichum – will get leggy and woody, or you’ll get that bald patch in the middle of a clump, with healthy plant growing in a circle around it.

Some people suggest dividing asters every year. Although I haven’t done it, I suspect it is sound advice.

My asters were wonderful in the first year, but have since been leggy and floppy.

I thought I wasn’t supporting them properly, but now I’ve researched their care, I realise I’ve left them in the ground without

dividing them for too long.

Of course, asters and symphyotrichum are at their flowering best at the moment, so don’t divide them until the flowers are over. After that, I’m definitely going to divide mine.

Another plant to divide later on in the autumn is the Japanese anemone, because it can be very invasive and spread all over the border, crowding out other plants.

Some plants have little plantlets or bulbils that can be teased away from the main plant and replanted. These include heuchera.

Other perennials, such as day lilies, hellebores, hostas or Siberian irises, emerge from the ground in a big, determined clump, so there is no point in trying to tease them apart or treating them delicately with two back to back forks.

In that case, take a deep breath and hack or cut the plants apart. Discard any root that looks withered or old and replant immediately, adding some fertiliser or compost and watering well.

I find that sometimes the plants look a bit sad immediately after this treatment, but so far they have all bounced back.

Plants are extraordinarily resilient and want to live.

Some perennials, such as penstemons, are short lived or don’t survive winters well. In that case, it’s better to take cuttings now rather than dividing them.

Take up to six inches off new growth, which will be woody at one end and soft at the other. Don’t cut a stem with a flower on it. Cut just below the leaf node and strip off all but around two leaves.

Poke into potting compost, with or without hormone-rooting powder, and keep in a dry, frost-free place over winter.

You can also propagate fuchsias now, along with salvias and hebes, too. ■