Should you seal a wound?

Pruning paste or paint on a fresh cut isn't usually necessary, and I prefer not to do it.

The best way to avoid wound infections is to prune with clean tools in dry-hot or drycold conditions.

However, it can be worth sealing a wound if you have to prune in less-than-ideal conditions, such as during high sap flow, on a warm, moist day, or when lemon borer beetles are active.

Creating a seal over a cut stops disease and pests from entering through the fresh wood, but it won't stop sap flowing.

A sealant is most effective if applied immediately – within seconds – of cutting.

A paste that contains a fungicide ingredient is twice as effective as acrylic paint. An organic option based on trichoderma (a parasitic fungus that destroys ‘bad' fungal spores) is another good option.

If you're pruning in good conditions, using clean tools on a dry-hot or dry-cold day, a tree will send compounds to the area to protect itself, so sealing it isn't necessary. Studies have shown that pruning paste and paint don't improve on the plant's natural response to an open wound in most cases.