Before we know it, it will be time to start thinking about pruning our trees, gardens and hedges. We spoke to Farmlands Technical Advisor Laurence Frost for some expert advice on how to get the pruning process right.

Words Niko Kloeten

Pruning can be a lot of work, so why do we need to do it? Farmlands Technical Advisor Laurence Frost says there are five main reasons why we should regularly prune our plants:

1. Death – removing dead wood can help the remaining tree to thrive. It is also important for safety reasons, as dead branches are more likely to fall off during a storm causing injury or property damage.
2. Disease – trimming diseased branches can help to prevent disease spreading.
3. Crosses – Crossing branches can be problematic as this is where bugs such as wood lice live, meaning the branch will eventually snap or become unproductive.
4. Production – whether in a commercial orchard or just your backyard fruit tree, pruning opens the plant up for sunlight and pollination, boosting fruit growth.
5. Shape – trimming the tree to the right shape can not only assist with production, but make it look more attractive and prevent it from overwhelming nearby plants.

 

Pruning for plant type

Before you start lopping off branches, it’s important to understand the pruning needs of each individual tree. Laurence says one crucial thing to know is whether your plant fruits on this year’s new growth – such as grapes and feijoas; or last year’s like boysenberries and blackberries. ‘Apples fruit on spurs, so they fruit on wood that grew last year. You have a nice new growth, it puts out a little spur, the flower comes off the spur, and then comes the fruit.’

For plants that fruit on new wood like feijoas, prune off the older growth where necessary, back to its frame. ‘Grapes are a classic example. You’ve got this old trunk that’s 30 years old and it can be pruned back to just two little buds. Those two buds will then grow into the vine we see in peak production.’

If your plant fruits on new growth, you need to focus on thinning it, removing branches to open it up for sunlight and pollination, Laurence says. ‘You want a blackbird to be able to fly through. Birds can be great pollinators and pest controllers, so we take out a few branches to make our tree more open, and that way you have a desirable plant shape.

‘With citrus you just need to trim them back, but not so hard that you produce water shoots. Water shoots are the vertical growth that are generally not fruit bearers; it’s their laterals that then set flowers and ultimately fruit.’

With grafted plants you need to watch for rootstock or understock dominance. This rootstock needs to be removed as soon as practicable, and in some plants, you’ll need to watch for reversion. ‘Variated plants invariably want to go back to green, which is the most productive colour to be,’ Laurence says. ‘Before you know it your beautiful, variegated plant has become this green undesirable plant and not what you originally purchased, so you really need to cut out the reversion and still keep the shape.’

 

Picking your tools

Laurence, a self-described ‘secateur snob’, says whatever tool you choose for your pruning, it needs to be sharp. ‘If it’s not sharp, you have the possibility of an injury to wrists, arms and elbows when trying to cut through branches.’

With cutting tools, gardeners need to be aware of the difference between bypass – like for example scissors – and anvil pruners. Anvil pruners have a blade that cuts toward the flat surface that is the anvil. ‘The neat thing is an anvil takes about 40 per cent less energy to operate, which is great for older people as it takes less power. The advantage of a bypass is the blade is the closest thing to the cut. And as they say with shaving, nothing cuts as close as a blade.’

Laurence’s other piece of advice on tools is to make sure the one you are using is big enough for the branch you are trying to cut. ‘Use the right tool for the job at hand. If your secateurs are too small for the branch you wish to prune then use a lopper or pruning saw.’

When to prune

So, when should you break out the pruning equipment and start grooming your plants? Laurence says early winter is your best bet for most plants. ‘You need to be pruning during that dormant period. Citrus is never dormant, they just slow down, so when they’ve slowed down in June, that’s a good time to prune. Don’t sacrifice the fruit though, you can always prune after you have harvested.’

The job is not over once you have finished pruning. Laurence says to look after the tree you should use pruning paint on pruning wounds, especially those bigger than 1 cm. ‘Then use spraying oil, copper, lime sulfur, and Yield. The copper will take care of most fungi; the oil takes care of most insects, and then you have the lime sulfur or Yield for moss and lichen control.’

Laurence has one final message for gardeners doing their yearly pruning: make sure you get rid of the garden waste once you are done, especially diseased waste ‘as it could not only reinfect your plants but also those in the neighbourhood’. 

 

Laurence Frost is a Technical Advisor for Farmlands. As a formally qualified horticulturist, he is an enthusiastic propagator with a passion for nurturing knowledge in others and helping growers achieve their productivity goals, no matter how diverse their crop production. farmlands.co.nz