How to Take Root Cuttings

Daisy.Days
Published on November 10th 2019
6
A row of different sized, brown root cuttings led on a wet grey slate
Getting a plant to grow is, to me, the best feeling in the world. This can get a little tricky in the low light of the winter months. But where there's a will, there's a way.
In Winter, we have more time to take cuttings from roots of dormant plants, providing us with new plant babies to nurture.
Root cuttings can be taken from a variety of plants, from herbaceous perennials that have died back to woody shrubs and trees and climbers. Hopefully, this article will give you the knowledge for you to have a go.

Timing

You can take root cuttings any time between November and January, ideally when the plant is fully dormant; after the foliage has died back and before the new buds have started to grow. Roots in dormant plants are full of stored energy and will be more successful than those who’ve already begun to grow.
I have a client who wants to take a Pasque flower with them to a new location, and we’ve been waiting for it to die back. This Autumn’s mild and wet weather has not been not helping, but time is running out, so I’ve had to propagate.
For those of you who’ve grown the Pasque flower before, you’ll probably be aware they do not take well to being dug up and moved, and they have a very long taproot. Root cuttings can be taken but at the cost of the parent plant.

Method

There are two main methods on how to take root cuttings, depending on the type of plant.
  • Herbaceous perennials have a shallow root system, so I'd recommend digging up the whole plant up to make identifying and taking ideal cutting points a lot easier.
  • Woody shrubs and trees - dig to expose roots and take cuttings directly from the ground.

Healthy plants

Whichever plant you are propagating, always choose a plant that is healthy and shows no signs of stress or disease. It is also worth checking you have a plant worth reproducing. For example, Ailanthus altissima (Tree of Heaven) has either male or female flowers. I would choose to grow the female, as the male tree produces pungent flowers and not the good kind.

Prepare

Like most gardening activities, having clean, sharp tools and supplies at the ready will speed up the process and increase the likelihood of success. You will need:
  • Secateurs/long-handled pruners/sharp knife
  • A container of lukewarm water and a scrubbing brush.
  • Clean pots/trays
  • Cutting compost (1 part grit to 1 part well-rotted leaf mould or compost)
  • Grit/Perlite
  • Labels (pre-written when your hands are clean and dry)

What to cut

The best roots to take are young, roughly the thickness of a pencil and can be cut away from the root-ball as close as possible to the crown.
  • Make horizontal cuts at the top of the root (closest to the crown) and angled cuts at the lower end, so you can orientate the cuttings when you come to plant up.
Tip: Take no more than one-third of the plant's roots and replant/cover as soon as possible. Water it thoroughly back in.
  • Ideally, you are looking for cuttings that are between 5 - 10cm (2 - 4in) long. The thinner the root, the longer the cutting needs to be to provide as much energy as possible. It is possible to get several cuttings from each length of root removed. Just remember to make horizontal cuts at the top end.
  • Throw away the thin ends and remove any fibrous side roots.
For the Pasque flower, the fatter the cutting, the more likely it is to take. However, this drastically reduces the amount of stored energy available to the parent plant. It will take a long time to recover, and it's probably not worth replanting.
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Potting up

At this point, you can use one of three different methods:
1 Perennials: These cuttings can be potted up around the edge of pots filled with a gritty compost mixture. Ideally 4cm (2in) apart from each other, you should put the horizontally cut end just below the surface of the compost. The surface should then be covered with a 1cm (3/8in) layer of fine grit or perlite.
As you can see, I haven’t followed my own advice of top-dressing my cuttings, because I hadn’t prepared and didn’t have any grit available. Fingers crossed that the free-draining nature of the cutting compost won’t block too much light, and the new growth isn’t rotted off by damp conditions.
2 Perennials: Cuttings can also be placed sideways onto trays lined with moist standard cutting compost. These can then be covered by 0.5cm (1/4in) of compost. The advantage of this method is that they can send up new shoots from several places along the length of the cutting.
3 Woody stemmed plants: can be treated the same way as perennial cuttings. Alternatively, you can loosely bundle them up and place into a prepared hole for the Winter. The hole needs to be below the frost layer and have a good 5cm (2in) layer of sand at the bottom to prevent the cuttings from rotting.
Place the bundles with the angled cut ends at the bottom and backfill. You will want to mark the spot, so you don’t accidentally plant over the top. In the Spring, these cuttings will have started to grow roots and stems. They can be dug up and planted either into containers or directly into the ground, roughly 5cm (2in) below the soil surface. They will need to be kept moist.
A labelled pot of root cuttings in a gritty compost, inside a cold frame.
Potted up cuttings need to be kept frost free but not allowed to dry out.

Aftercare

Containers can be kept in cold frames or propagators. Some slow rooting species will also benefit from bottom heat. Water sparingly to keep the compost from drying out.
Once new growth has appeared in Spring, you can gently tease the cuttings up to make sure new roots have formed. These can then be grown individually in 9cm (3in) pots with standard potting compost.
Tip: remember to label each container. In the past, I've only marked one in a group, believing I'd keep them all together so wouldn't have a problem. I learnt my lesson when a neighbours cat knocked over and mixed up two different coloured fuchsias, whose growth was too similar to tell apart.
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What to grow

I've put together a list of plants which can be easily propagated through root cuttings. Taking root cuttings from variegated plants will always result in plain green leaves, so you'll need to take different types of vegetative cuttings.

Herbaceous perennials

Woody shrubs

Climbers

Have a go and share your successes with us, and if you've too many, well there's plenty of people looking for new plants, list them on our marketplace.
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