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Do you have a potted plant that’s outgrown its pot? Perhaps you have a plant that’s underperforming all round. It might be time to consider root pruning.
When carefully done root pruning can reinvigorate tired plants and allow you to keep that plant in that favourite pot for much longer.
Here is a guide on root pruning plants. Let us know if you have any questions. We'd be happy to assist.
Why root prune?
A good root system is crucial for the survival and performance of your plants, but often we concentrate on foliage, not giving much thought to what’s happening beneath the soil or potting mix.
In many respects root pruning is no different to pruning leaves and branches – it stimulates new growth and can be used to keep the size of a plant contained.
Root pruning is one of the essential steps in the creation and maintenance of bonsai plants. Most of us, though, do it when a plant has become totally root-bound and we want to replant it in the same pot.
Understanding root structure
Different plant species can have very different root structures, just as they can have very different branch structures above ground. Generally speaking, however, most of our potted plants have some common traits. These include:
- A tap root or central root. This is the main root that others branch from. It is the first root to form from the original seed, so it’s not present in plants grown from cuttings. It generally grows straight downwards and can be thought of as the anchor root.
- Side roots or secondary roots. These branch off from the central root and will run more or less horizontally. These roots stabilise the plant in the soil or potting mix. They are the main roots in plants grown from cuttings.
- Fine roots. These are often called feeder roots as their main purpose is taking up nutrients and water. These roots branch off from the side roots and can form a very dense web. They are easily spotted as they tend to be lighter coloured and white tipped.
- Some plants are described as “surface rooting”, which generally refers to these fine roots being close to the surface. This can be a natural characteristic of the plant or it may be induced through poor watering practices. Too little water encourages roots to rise up seeking moisture.
When to root prune
As with pruning above ground it’s important to root prune at the times that will give you the best results and avoid harming your plants. Below are some things to take note of:
- Avoid root pruning during extreme heat or cold, or when such conditions are expected within a few weeks.
- The best time for root pruning is when the plant is kicking into its new growth season after winter. The exact timing will vary with location, but it’s generally late winter or early spring.
- The second-best time is late summer through early autumn, when the plant is still actively growing but the heat isn’t too severe.
Tips for root pruning
The process of root pruning is quite simple. It’s all about taking care and the time to do the job well in a way that minimises shock to the plant.
Make sure you wear gloves while de-potting and handling potting mix and consider a dust mask too, especially if you have any respiratory issues.
Here are some other tips:
- Your tools, such as a pruner or secateurs, a garden knife and a pruning saw, must be clean and very sharp.
- Clean the blades of your tools with methylated spirits between plants to avoid transferring any pests or diseases.
- Make sure you have a premium-quality potting mix to suit your plants.
- Make sure you have any new pots you may need as well.
- Set yourself up in a warm spot out of direct sun.
- Use great care when de-potting your plant. Do not attempt to pull it out by the trunk or stem. Running a garden knife around the inside of the pot may help loosen the plant.
- If your plant is in a plain plastic pot and is resisting your efforts to remove it consider cutting the pot off.
- Once the plant is free from its pot use your gloved hands to gently massage and tease out the root ball. Aim to open it up and remove most of the potting mix.
- Make clean cuts and don’t split or crush roots while cutting them. You’ll get the best cuts by keeping the blade of your pruners facing towards the plant.
- Start by removing any roots that are clearly dead or damaged.
- Work your way inwards and remove some of the finer roots.
- Reduce in size any large roots that have started to spiral around the pot. If left these will start to constrict the plant. Cut them back to the point where they start heading into a curve.
- Allow the plant to sit for at least an hour or two, out of direct sunlight, before repotting. This allows cuts to seal.
How to look after plants after pruning their roots
Looking after your plants after you’ve repotted them is just as important as the root pruning process itself. Here are some things you can do:
- Reduce your plant’s foliage a little. The main cause of “transplant shock” in a root-pruned plant is water loss caused by the leaves losing more moisture than the roots can take up.
- Do not overwater or underwater your plant. It’s best to avoid saucers under pots.
- Apply a product that will stimulate new root development and reduce transplant shock such as Osmocote Plant Starter.
- Water weekly with a suitably diluted solution of Seasol.
- If your plant seems to be struggling an application of a broad-spectrum fungicide, such as Yates Anti Rot, may help.
Plants you shouldn’t root prune
You may be surprised at how many plants respond well to root pruning. There are, however, a few that need to be approached with caution. These include:
- Plants that have sensitive roots, such as avocadoes or Daphne. The labels on such plants will often contain such notes as “Avoid root disturbance” or “Avoid disturbing root ball when planting.”
- Grafted plants. They can respond poorly because the pruning may stimulate shoots from the rootstock which can then appear as suckers popping up through the potting mix, or as shoots from the trunk or stem below the graft. If not controlled these shoots will start to dominate, weakening and ultimately killing the grafted-on plant.
Don’t be afraid to try root pruning of some of your potted treasures. Just take the time and due care and you should find it’s an easy and effective way to bring new life back to tired plants and keep your most-loved plants where you want them for longer.
More advice on growing and pruning plants
The Bunnings Workshop community has shared several other resources on pruning and repotting different types of plants and maintaining a healthy garden. These include:
- How to pot a plant
- How to know when to repot your plants
- How to prune roses
- How to prune citrus trees.
More inspiration for your garden
Bunnings Workshop members have shared many impressive and inspiring gardening projects. Check out our Top 10 most popular garden makeovers and Top 10 most popular landscaping projects.
Our collection of Top 10 most popular raised garden beds and Top 10 most popular planter box projects should also spark some creative ideas for your garden.
Need more help with your garden?
The Bunnings Workshop community is here to help if you need a hand with your garden projects. Feel free to Start a new discussion and let us know what you need.
