Perennial division in August

Last night I was looking through my book on propagation and read about division of perennials in July and August, and thought it worthwhile repeating some of it here.

The gist was that the activity of the roots determines the time at which perennials can be successively divided. Herbaceous perennials of deciduous woodlands tend to have a quiet time in midsummer, but in July and August the roots start an annual cycle of development, producing strong anchor roots which they use for storing starch and other reserves over the winter. And although some of them will be in full leaf and even flowering now, it is a good time for dividing certain plants.

The book then lists :- Achillea, Aegopodium, Ajuga, Anphalis, Anenome, Anthriscus, Aster, Astrantia, Bellis, Bergenia, Brunnera, Campanula, Centaurea, Chelone, Chrysanthemum, Coreopsis, Dicentra, Dornicum, Echinops, Epimedium, Erigeron, Filiprndula, Fragaria, Gaillardia, Geranium, Herpatica, Heuchera, Inula, Liatris, Ligularia, Omphalodes, Origanum, Pachysandra, Peonia, Physostegia, Primula, Pulmonaria, Pyrethrum, Rudbeckia, Saxifrage, Symphytum, Tellima, Tradescantia, Trollius, Valeriana and Viola.

The book suggests the plants be dug up, divided, the foliage cut back (to prevent loss of water), well watered, and shaded for a while from the full sun. It says that they will develop roots quickly and make good plants before the winter arrives.

My own experience is that it is sometimes possible to divide a plant in situ with a spade and then just lift and remove one part, which can be further subdivided if wanted. The part left in situ will not have been set back by the process, so doesn't need to be cut back and will recover faster than the part that has been totally lifted. The lifted bit, of course, must be cut back and treated as above.

 

As I have been investigating propagation by division I would like to thank you for this post, and ask something further. Campanula and verbascum-root or basal cuttings? Which is the most successful? I have already taken basal cuttings(mini division really)of some(as where I am it can be prone to cold damp conditions early in Autumn so I have to do it late Summer really)and have some which I intend to try root cuttings with. Any experience of this on the forum?

 

Hi Lolipop. This book on propagation lists methods for most plants. But there are so many different methods that its difficult to grasp the principles, and you can't remember them all individually. Thats why I liked the explanation that woodland type plants can be divided now. I think many people, like me, like division because it is so simple and uncomplicated.

I can only quote from the book.
....Campanula: basal cuttings in April/May and division in March or July/August.
....Verbascum: semi-mature cuttings in June/July and root cuttings in Feb/March. not division.

I have no personal experience with either of these. I tend to divide everything that has more than one stem and doesn't have a tap root.

 

PeterS

Great info - I want to divide my geraniums but they are still flowering - do I have to do it now and what does it mean by cutting back? Must I cut all the leaves off?


P.S No idea when I am going to do all this mind I already have a list as long as my arm of gardening tasks!

 

Ellie - I also want to divide my Geraniums. This book is saying that you can do it now, even though they are still flowering, which I found interesting. But the book also says you can do it in April. Cutting back means cutting (say) half the leaves off. The reason is the when you lift a plant you damage its roots and so it has a reduced ability to draw up water from the soil. So you must also reduce the water loss by reducing the amount of leaf.

But you must leave half the leaves on as these create the food that it needs to regrow the broken roots, as well as building up a store in its roots to see it over the winter. Its like a bear before hibernation. Bears eat as much food as they can, and store it as fat, because once winter starts they go into hibernation and they won't get any more food. Their food store has to see them through the winter. The plant is trying to do the same thing, but in this case it stores sugars and starches in its roots to see it through the winter.

 

Brilliant answer Peter, thank you very much!

If I have time I'll do it now otherwise it will have to be April!

Thanks x