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The idea of pruning houseplants is always a daunting prospect, especially for the less experienced indoor gardener. The fear of doing permanent damage is sometimes enough to put you off getting the secateurs out in the first place. Nevertheless, some plants really benefit from occasional pruning and this guide will help you get it right.
What is pruning?
It may seem obvious what pruning is. However, it’s not uncommon for people to think they are pruning when in fact they are not. For example, if you are randomly removing branches or parts of branches, this is not pruning. Pruning involves the selective removal of plant parts, meaning each plant part is removed for a specific reason.
Pruning is different from leaf trimming and removal as well as deadheading. These are all sound horticultural practices but they are different. This is important to know because many principles of pruning do not apply to these types of plant care.
Sometimes people think they need to prune a plant just for the sake of pruning it. However, before you prune a plant, you should have a clear understanding of why you are pruning the plant in the first place.
Why prune your houseplants?
The main reasons for pruning indoor plants are:
- To improve plant appearance by controlling plant height or spread, and to keep plants well-proportioned, nicely shaped and with dense foliage.
- To promote plant health by removing dead, dying, diseased, damaged or pest infested plant parts or to remove branches that rub together. You might also wish to thin branches to allow more light penetration into the canopy or to reduce crowding.
If you are not pruning for one of these reasons, the plant probably does not need to be pruned. The reason you are pruning the plant will also impact the way you prune a plant.
For houseplants, the most useful tools for pruning are a pair of good secateurs (pruners) with bypass blades, sharp scissors and a penknife. For plants with thick stems (more than 2cm), such as yuccas or dracaenas, a small pruning saw might also be useful. It is very important to make sure that your tools are sharp (otherwise they can bruise and damage plant tissue), and that they are clean (to prevent diseases from spreading from plant to plant.
Pruning to improve appearance
Pruning is all about making the right cut. The key is to know where to make that cut on a plant. There are certain places on the plant where you can make good pruning cuts, and other places on the plant that are not good, which will result in damage or a poor appearance. Finding these spots will help you make a proper cut.
When pruning a plant, large or small, it’s important to make a cut back on the plant to an acceptable point, so that the plant won’t die back from that point. If the plant dies back from where it was cut, then the cut was made in the wrong place.
Whenever pruning any size plant, always cut back to one of three acceptable pruning points. Those three locations include cutting back to:
- A node (a swollen area on a stem, usually where a leaf of branch attaches or once attached to the stem)
- Another stem. This is usually cutting back to another larger branch or the main stem of the plant
- The base of the plant (several plants only have one growing point at the base of the plant such as Spathiphyllum and other plants with a similar growth structure)
It’s important to look at the structures of the plant when determining where to make the cut.
Whenever pruning any type of plant, regardless of whether it is a tall tree or a small houseplant, there are only two types of pruning cuts.
Heading back cuts
When cutting back to a node (leaving part of the original shoot), the pruning cut is referred to as a heading back cut. Heading back cuts are used to remove leggy, straggly or spindly growth and to encourage new stems to grow to make the plant more bushy and compact. When trimming vining or trailing plants (e.g. Epipremnum aureum or Philodendron scandens), you should also use heading back cuts
The pruning cut made here on an Aglaonema (above) is a heading back cut because it is cut back to a node and left part of the original shoot (stem) in place.
This picture (left) also shows a heading back cut. Since heading back cuts require cutting back to a node, you can only make a heading back cut on plants that have nodes.
Thinning out cuts
The other type of pruning cut is a thinning out cut. With thinning out cuts, the cut is made at the origin of the shoot (stem), and its purpose is to remove excess growth or remove shoots and stems that are rubbing or crossing over.
All shoots have an origin. In some cases, the origin of the shoot may be a larger branch. In other species, the only origin of shoots is the base of the plant (e.g. Spathiphyllum). Either way, you can make a thinning out cut on all plant types (although palms and succulents need special attention, which I will cover lower down).
On plants that branch, such as this Crassula, you can cut a shoot back to a larger branch. This is a thinning out cut where you cut the shoot back to a point of origin, such as another larger branch.
When cutting back to another branch, you almost always want to cut back to a branch that is larger than the one you are removing.
In this case, the plant had a very thick canopy with too many crowded branches in the interior of the canopy, so it needed thinning out. Here, an entire branch was cut back to another larger branch.
Thinning out cuts on plants without nodes
Quite a few houseplants have no branches or nodes to cut back to. For these plants, a pruning cut must go to the base of the plant (where the red circle is).
This is a thinning out cut since none of the original shoot remains.
For plants without nodes, the only types of pruning cuts you can make are thinning out cuts.
Plants that you cannot prune easily
There are some plants that are very difficult to prune, or have characteristics that have some safety risks that need to be considered.
Palms with trunks
Cacti and succulents
Small cacti and succulents that form clumps of growth cannot be pruned easily. If the clumps of growth get to congested, they can be separated at the base by cutting with a very sharp knife (and you may be able to grow new plants from the cut section), but slicing the stem to encourage branching is likely to cause the plant to dehydrate and die before any dormant buds have a chance to sprout.
There is a group of succulents in the Euphorbia genus that resemble cacti (and are sometimes given names such as “Pencil cactus”) that must not be pruned without taking precautions. They can be thinned and headed back to create the shape you need, but you must wear eye protection and gloves. This is because the sap, which is often under high pressure, is extremely irritating and can cause severe and permanent eye damage or skin irritation.
by: Kenneth Freeman