Tag Archives: dividing perennials

A postscript – or maybe an update –  to my last two posts on digging ‘n dividing and bluebells.

I photographed this patch of asters trimmed to the ground because I thought it was a good example of when not to let sleeping asters lie. Digital photography is very handy for dating things and I see it is only three years since these were last dug and divided. It had become a seamless carpet of aster in the time since. Both Zach and I noted that it did not look as good as it should have last summer. They weren’t helped by getting hit by mildew which has not happened before, but there was no mass flowering.

It should have looked like this last summer, but it didn’t. This is from summer 2024.

Time for a dig and divide, which Zach did this week. A perennial that has to be lifted and split every two to three years is on the high maintenance side and we don’t have many in that category. My friend, Sue, who leads the team of volunteers at the pretty Te Henui cemetery, told me she is culling plants that are too high in maintenance for their labour resources and this aster might fit that category. I must ask her for her latest list of culls. Fortunately I have Zach to carry out such tasks or I might be casting around for a less demanding plant option.

Enter the rabbits. After a quiet few months on the rabbit front, they are back and there is nothing they like more than an area of soft, freshly dug garden and mulch to dig. I sent Zach a text yesterday telling him that the rabbits were undoing his work. He was equally unimpressed but at least the photo shows you the size of division he split off from the previous carpet to replant.

I have just replanted the casualties, filled in the holes and spread blood and bone. The rabbits don’t like blood and bone and will stay away from that area but it does need to be replenished after rain and we have had plenty of that this week.

A whole lot of bluebell bulbs, just from the Iolanthe garden. There were more. I have already disposed of some.

The war on bluebells continues and I am at an advanced stage of boredom. I took this photograph as proof that I am not exaggerating. This is by no means all of the bulbs I have dug out of just the Iolanthe garden. Most were never planted there but I will have spread a few when I planted that area in 2019. Some have already been disposed of and still there are more to be dug.

They did not dehydrate in the summer sun. They grew instead.

Bluebells have no place in the cultivated garden. I found a couple of photos from last year, recording our attempts to deal with some culled from the Avenue Gardens. I worried about how many we were dumping on our wild margins and they don’t rot down in the compost. I had the idea that if we spread them thinly on weedmat, they would dehydrate and die in the summer sun. They didn’t. They kept growing. I then thought they might compost in plastic bags in the sun, as wandering tradescantia does. Some did over the summer months but others in those bags were still firm and viable. Responsible disposal is quite a big problem.

Nor did they rot down in the plastic bags, as I hoped.

We have a lot of bluebells in the park and the Wild North Garden and they can stay there. To get rid of them, we would have to go for repeated use of some heavy-duty sprays and we try and avoid that. Besides, they are very pretty in spring. Ours are all Spanish bluebells or hybrids; the more desirable English bluebells are extremely scarce in this country. I don’t think I have ever seen them.

“If they stank like onion weed, they would be seen as a weed,” said Mark. “They are a weed,” I replied.

If we had our time over again, we would think twice about introducing them to our property. Mark put a bit of work into building up numbers in the first place. A decade or so on, I am putting a great deal more work into digging them out from some areas, all but sifting the soil to get the baby bulbs. You have been warned.

From happier bluebell days

Gardening 101: Dividing perennials

0011) Clumping perennials can get overcrowded and start to deteriorate over time. Some will stop holding their flowers up well, some can die out from the middle while others just look tired and messy. Some need digging and dividing relatively frequently to stay looking their best. This clump of pulmonaria (unromantically known as lungwort) probably started as a single crown two years ago but grows rapidly.
0022) Dig out the clump, shaking off the soil. If you are not sure what you are doing, hosing off the dirt can make it easier to see the structure of the root system which varies between different plants.
0033) Part the leaves to find the separate sections growing from the centre or crown of the plant. Some plants just pull apart. An old carving knife is helpful and a meat cleaver is good for larger clumps with tough crowns. You can use a spade but it is hard to get accurate cuts. The pulmonaria yielded at least 15 divisions, all of which would grow as separate plants if I wanted that many.
0044) Replant the strongest divisions into soil which is well dug and friable. If you are only lifting and dividing every 10 years or longer, this can be a major task as soils compact over time. If you are doing it more often, it is easy as the soil stays looser. Spread the roots evenly and cover to the same level it was earlier. We like to add compost mulch and then water thoroughly but gently. Removing some leaves reduces the stress on the plant.
0055) These three perennials also benefit from lifting and dividing every few years. From left to right: an aster which just pulls apart into separate sections, mondo grass (ophiopogon) which also pulls apart but sometimes needs the runners snipped, and polyanthus which usually needs to be cut through the crown to ensure that each piece has roots attached.
0066) This patch of stachys (lambs’ ears) was dug and divided three weeks ago and has already recovered well because it is in full growth. Timing is not critical in our mild climate but done in midsummer, care needs to be taken to avoid the roots drying out and plants will need thorough watering for the first week.

First published in the Waikato Times and reprinted here with their permission.

“A good soil, like good food, must not be either too fat, or heavy, or cold, or wet, or dry, or greasy, or hard, or gritty, or raw; it ought to be like bread, like gingerbread, like a cake, like leavened dough; it should crumble, but not break into lumps; under the spade it ought to crack, but not to squelch; it must not make slabs, or blocks, or honeycombs, or dumplings; but, when you turn it over with a full spade, it ought to breathe with pleasure and fall into a fine and puffy tilth. That is a tasty and edible soil, cultured and noble, deep and moist, permeable, breathing and soft – in short, a good soil is like good people, and as is well known there is nothing better in this vale of tears.”

Karel Capek, The Gardener’s Year (1929)

Garden lore

“If gardening isn’t a pleasure for you, chances are the work will merely give you a rotten disposition. If you’d rather be golfing or fishing, get a bumper sticker that says so, and forget gardening.”

Elsa Bakalar A Garden of One’s Own (1994)

014
Dividing plants

If you have been buying perennials recently, you can often divide these immediately and plant double the number. This is Hosta June which showed more than one growing point. I cut it down the middle, making sure that each side had both leaves (which means growing tips) and roots. I find a meat cleaver is easiest for this operation although a carving knife will do. Some people use a sharp spade but it is harder to get the cut in exactly the right place because you have less control over the spade.

Plants which are in full growth, as most perennials are in spring, will recover more quickly. Just make sure you plant them into ground which you have prepared well by digging it over thoroughly and preferably adding compost or humus. Water the plants in and keep the moisture levels up for the next few weeks. You need to give them a good start because you will have shocked the plant by cutting it in half.

Commercially, these plants are generally divided in winter with much more precision and controlled conditions (which will generate many more plants) but for the home gardener, dividing it in full growth can give good results and it is easy to see what you are doing.

First published in the Waikato Times and reprinted here with their permission.

In the garden: March 12, 2010

  • With temperatures cooling, particularly at night, conditions are good for gardening. Leave planting or shifting of woody trees and shrubs until later in autumn but you can turn your attention to clumping plants and perennials. Lifting overcrowded plants and splitting them up at this time of the year means that the plants can recover and re-establish before winter. This can avoid bare patches in the garden in spring which is particularly important for those who open their gardens. Always dig the ground over to loosen up the soil and add some compost or other soil conditioner along with a dressing of fertiliser. To reduce the shock to the plants, cut back the top foliage by about half and water the plants in well. Keep watering for a few days if we don’t get rain.
  • While working with your perennials, you may want to try taking some cuttings from types which only grow from a few stems rather than forming a clump of many shoots. We demonstrated this in an earlier Outdoor Classroom but the rule of thumb is to use firm new season’s growth and to take off any flower buds or stems. We are about to do some gypsophila cuttings.
  • Flaxes, astelias and grasses will respond very well to being divided at this time of the year but they need their tops cut back. The Mohican hair cut is not a good look but done now, the clumps will spring into fresh growth and cover that. Done later, you will have the ugly cut leaves until late spring.
  • A sharp spade makes digging and cutting hugely easier. We sharpen our spades by securing them in a bench-top vice and using a file. Remember to only sharpen the side which faces outwards when you use it. Once you have used a sharp spade, you will appreciate just what a big difference it makes.
  • In the vegetable garden, you are really too late now for Brussels sprout, leeks, carrots and parsnips but you can still plant Florence fennel, winter spinach, peas, winter lettuce and all the obliging brassica family.
  • Gardeners in colder, inland areas should be thinking about starting the autumn hedge trimming round. The trick to timing is to allow the hedge to make a light flush of fresh growth only and have time to harden it slightly before the onset of winter stops all growth. Get a man in, was the suggestion of friends over dinner at the weekend. We own up to having just such a treasure here (and he is not Mark) who is a perfectionist when trimming sharp hedges, even using a string line to keep the levels straight.