Burkwood Viburnum looking pale and new shoots drying up

(Question)

My 5 year old shrub was growing in the spring a looked great. It has stopped growing with any new shoots now drying up and he leaves look pale. My concern is that lack of water due to our faulty drip line may be the problem. It may also be crowded with other plants growing nearby. From my description do you think it will survive? I have been watering it now that I know there has been an issue with the drip. Any suggestions? I am having a tree near it replaced and wonder if I should just remove it at the same time.

(Answer)

Thank you for contacting the Toronto Master Gardeners with your inquiry.

What a lovely shrub to have in your garden. Burkwood viburnum prefers full to partial sun and does best in moist, moderately fertile and well-drained soil that is slightly acidic. However, this shrub is regarded as a great choice for urban gardens because it can survive alkaline soil, poor or compacted soil,  heat and drought.

The most common reason that plants’ leaves turn yellow is because of moisture stress, which can be from either over watering or in your case due to your faulty dripline, under watering. If plants don’t receive enough water, they drop leaves to prevent transpiration (water loss through leaves). This defence mechanism allows the plant to conserve water. What begins as a few leaves curling and yellowing on a plant can lead to all of the foliage dying – and that means the plant is dying as well.

If your plant has begun dropping leaves as a defense mechanism from drought, increasing watering is the natural remedy to the problem. However, sometimes the problem is the way plants are watered. Instead of frequent, shallow watering, water your plants less often but deeply. This encourages roots to grow deep in the soil, where water doesn’t evaporate easily as it does from the topsoil. This type of watering is particularly important for plants like Viburnums that actively grow, blossom or fruit during spring and summer, when they need more water to support their growth.  You can also apply a layer of mulch around the base of your plant which will aid in conserving soil moisture. When adding mulch make sure to keep it a couple of inches away from the trunk of the shrub.

To determine whether the shrub or parts of the shrub  are dead or just look dead take a sharp knife, and gently scratch away a small amount of bark from the limbs that seem damaged. If they appear green and moist below the bark, then chances are the branches are alive and will recover over the next year or two. If the branches are brown and dry underneath the bark, then prune those stems back to where they connect to a main branch. If there are only a few dead branches, then the shrub should recover quickly; if the entire shrub is damaged, then you may need to consider planting something new.

Viburnums, like all plants prefer good air circulation which helps prevent the spread of fungal disease such as powdery mildew. If you decide to transplant the Viburnum it is best to do it in the fall or spring when temperatures are cooler.

Good Luck with your Viburnum.