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Monday, January 12, 2015

Care and Pruning of Pyracantha and Honeysuckle

Q. I am writing and enclosing photos of my pyracantha and honeysuckle. I cannot find info on the issue/treatment. A friend suggested I email you after reading the LVRJ column.

A. Thanks for the pictures but they were not very helpful without more information. Let me tell you what I know about these plants and maybe that can help.

Both of these plants grow well in our climate in a mixed, non-desert landscape. They are not desert adapted or desert plants so they will not perform well with rock mulch.

Over time, they will perform better using wood mulch on the surface of the soil.

They should be irrigated at the same time as other non-desert plants. They should be on an irrigation valve that provides water as frequently as other nondesert trees and shrubs.

Most landscape plants require at least one fertilizer application each year in the spring or late winter. You can apply these spring fertilizers into March. Any general landscape, tree and shrub fertilizer will be good.

Pyracantha occasionally develops yellowing due to iron chlorosis so an application of EDDHA iron chelate to the soil at the same time as the fertilizer would be advised. Apply both within a
foot of drip emitters on top of the soil. The iron chelate needs to be covered with mulch.

Pyracantha has a history of borer problems, particularly if it is planted in a southern or westerly exposure in rock mulch with lots of heat and intense sunlight. Borers can be active in the plants and the plant can still appear healthy for one or two seasons.

After a season or two of borer attacks branches turn brown and begin to die back. They normally die back to where the borer damage while the rest of the undamaged plant below this remains green. Prune these dead branches out and let the plant regrow from these areas.

Pictures from reader
Because of the dead branches, the interior wood and trunk will receive intense sunlight. This intense sunlight increases the chance of sunburn to larger limbs and the trunk. This sunburn damage attracts boring insects (borers) to those locations.
Borer damage in purple leaf plum

For this reason, shade from the canopy on the interior wood of the plant is extremely important. Many woody plants in the rose family, which includes Pyracantha, are subject to damage from intense sunlight due to their thin outer bark.

Most of our fruit trees are also in the rose family and are subject to sun damage and borer
problems. Pruning should be pruned to maintain a moderately dense canopy. A canopy which is not so open provides filtered sunlight to the interior of the plant and reduces sun damage. You don't want it pitch black inside the canopy but you do want filtered light, not intense sunlight, for any length of time.

Honeysuckle is a good vine to use here. However, it tends to get woody at the bottom as it gets older. This woodiness at the base can be managed by pruning it correctly. Woodiness at the base is promoted when the vine is pruned only at the top. Several years of pruning the top results in an unattractive plant that is mostly wood without much foliage.

When pruning this plant this winter, instead focus pruning efforts on the area close to the soil surface. Find large stems originating from this area and remove one third of this older wood close to the ground. This removes a lot of plant material from the vine but promotes new growth from the pruned stems.

Limb dieback of peach due to borers

These types of pruning cuts encourage new growth from the base of the plant. Next winter remove one third more at the same location and you should be back on track and reversing the aging of this plant, making it more juvenile. Focus your pruning efforts closer to the ground.

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