Pruning is an essential practice for any gardener. Most types of plants benefit from pruning, but many gardeners shy away from the task. Knowing how a plant will positively respond to pruning takes a lot of guesswork and trepidation out of gardening. Every plant responds differently to pruning, and that’s what this article will cover.

What is pruning?

Pruning is the activity of removing stems or branches from a tree or plant to generate a series of beneficial effects. Pruning can be used to improve the health of plants by removing dead or diseased limbs. This can help many plants to enjoy extra spurts of immediate growth, while a hard pruning of certain plants in winter can set them up well for the following spring. Pruning is also used for shaping plants or increasing crop yields.

Effects of Pruning

There are five main benefits of pruning, and we’ll examine each of these in more detail below.

Structural training

Pruning can be used to train plants to have strong, robust structures, especially trees. This helps the plant to survive inclement conditions such as snowfall or strong winds, resulting in a longer, healthier life. The best way to train a plant depends on its individual characteristics. For example, some trees like cedars use a central leader system (one central branch) to support the whole tree. To train one of these trees effectively, any competing thicker branches must be pruned to keep the central leader strong and healthy.

Maintaining plant health

Pruning also helps keep plants healthy. All year round, gardeners can remove dead or infected stems to redirect the plant’s resources into healthier branches, providing a boost to current growth. Thinning out the middle of a plant also increases air circulation, helps to mitigate disease, and lets more sunlight reach the inner branches.

Controlling plant size

As plants grow, they can cause problems because they might encroach on the space of other specimens or interfere with buildings or power lines. Pruning is commonly used to control the size of plants to avoid these problems. When choosing which plants to use in different spaces, consider what the mature height and width are likely to be. This allows for better use of space and reduces pruning requirements.

Nurturing fruits and flowers

Pruning can also provide a growth boost to fruits and flowers. Pruning a flowering shrub at the correct time of year can set the plant up for a more productive subsequent growing season. Deadheading is a type of pruning that can generate multiple rounds of blooms during spring and summer by removing any wilting flowerheads. This redirects the plant’s energy into newer buds.

Rejuvenating stagnant plants

Over time, plants can lose a bit of momentum if they’ve been growing in the same spot. Strategic pruning can be deployed to give these plants a new lease of life. This is known as rejuvenation. If the plant shows signs of dieback, a lower quantity of flowers or fruit, and smaller foliage, then it likely needs some rejuvenation.

General vs local

The pruning response of plants can be categorised as either general or local. The general response refers to the effect on the plant as a whole, which has been reduced in overall size. But it’s the local effects that gardeners have in mind when pruning. This refers to the new local growth that bursts forth from the buds left behind after a pruning cut. These buds now receive more energy instead of competing with the pruned growth.

Healing process

As beneficial as it might be, even light pruning causes harm to a plant. Plants don’t heal like animals do and cannot regenerate damaged tissue. Instead, plants effectively seal their wounds using specialised tissues to guard against decay, diseases, and pests. The plant then releases specific cells that create a biological barrier between the wounded area and the rest of the plant, keeping the damage from spreading further. This is called compartmentalisation.

Types of cutting

There are three main types of pruning cuts used by most gardeners – pinching, heading, and thinning.

Pinching

Pinching has the lowest impact of any pruning method. In essence, it involves “pinching” the bud at the tip of a stem between your fingers and removing it. This releases the hormone auxin into the stem, encouraging buds that were dominated by the tip bud to experience more growth. This can be used on fruit crops such as tomatoes to stop the plant from growing outwards and instead concentrating on raising ripe fruit. It can also create more lateral branching earlier in the season, potentially increasing the number of fruits produced by the plant.

Heading

Heading is a versatile way to generate more immediate growth. Deadheading is the most common example and involves pruning a wilting flower and a section of the stem beneath it. This prevents the plant from wasting energy on spent blooms and redirects resources to younger buds that can still flower. Heading can also create multiple extra branches or increase the strength and durability of a plant.

Thinning

Thinning involves removing entire branches or stems and is usually done when a plant has finished flowering and gone dormant. Thinning can involve removing a few old stems in the centre of a plant to bring in more air and sunlight. Thinning is also used to drastically cut back buddleias, roses, and other shrubs in late winter to invigorate them for the new growing season by pruning away old or diseased growth.

Making pruning cuts correctly

Pruning always damages plants, but the damage can be minimised if gardeners follow the correct techniques. A good pruning cut should reduce the amount of healing required by a plant. Cuts should always be clean and smooth and angled in the direction that the gardener wants the new growth to follow. Don’t overdo it straight away. Focus on removing dead, decaying, or diseased branches first before stepping back and assessing the plant. When removing diseased branches, always clean and sterilise tools to avoid spreading pathogens to healthier plants. Once the necessary parts have been removed, the gardener can then decide if more pruning is needed. Incorrect pruning kills more plants than diseases or pests, but gardeners can take several steps to ensure correct pruning practice. Situating a plant in the best possible location, somewhere consistent with the plant’s needs and the expected mature size, can reduce the need for pruning. Learning when to prune a plant is just as important as knowing how to prune it. Different types of plants need to be pruned at varying times of the year. For shrubs, this can involve deadheading during the growing season before a harsher pruning in the winter. Learning this information about a plant helps to eliminate the risk of pruning it incorrectly.

Covering pruning wounds

The previously accepted wisdom among horticulturalists was to seal pruning wounds using pruning paint or other products. In reality, this practice can cause more harm by impeding the plant’s natural healing process. Many pruning paints use petrol-based ingredients to repel water, but these are also ineffective at stopping disease or decay from entering the plant. Avoid using these products and instead focus on correct pruning practices to help plants to heal faster.