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Trees & Shrubs FAQs

Check out questions about Birch, Gooseberry, Cotoneaster, Rhododendrum and more.

Gooseberry Worms
Green Ash
Manchurian Ash
Mulching Rhododendron
Paper Birch

Q. We have a clump of paper birch trees that are about 20 years old. They are about 30-35 feet high. This year the top half of the tree has not grown any leaves . The smaller branches up top are dead. I haven’t cut any of the larger branches or trunks yet. Will these larger limbs come back next year or should I cut all dead branches and trunks off. The lower half of the trees appear to be growing fine.

A. Though we’ve seen significant moisture the last few years, prior to that Birch were severely affected by our drought.  It is very common for many of the older birch to have died back at the top of the tree.  Dead material should all be pruned away at this point.  Though it is getting a little late in the season to fertilize (we recommend not fertilizing past mid August) you can till a generous amount of bone meal around the base of the tree, and next season ensure you fertilize with a water soluble fertilizer such as 20-20-20 every couple of weeks during the growing season.  If you don’t have one already, a Root Feeder is a great investment; it attaches to a hose and when the prong is pushed into the soil it delivers water and fertilizer directly to the root zone.

Q. What is the best time to spray for gooseberry worms and what is the best product to use?

A. The best product to use is Fruit Plus and it is best applied just as the blooms are fading but before fruit forms.


 Q. I have this white coating on stems of my cotoneaster shrub. It seems to cover most of the stems and some of the branches or portions of whole plants are dying off. What is affecting my cotoneaster?

A. The problem with your cotoneaster is an insect called scurfy scale and this particular insect feeds by sucking sap from the plant. Scale are difficult to control because of their hard coating. One or two applications of dormant oil applied in the fall or spring (after leaf drop and before bud break respectively) should control the problem. If the problem is severe then the whole hedge can be cut down and allowed to grow again.

Q. The new growth on my Manchurian/Black ash is severely distorting and curling under. The tree has not leafed out well at all and most of the growth appears near the tips of the branches.

A. Your ash has Cottony Psyllid which is an insect related to aphids. These insects have been attacking Manchurian and Black ash in the area. They emerge from overwintering eggs early in spring (to coincide with bud break), migrate to the new leaves and start feeding. This feeding causes the leaves to curl over and eventually fall off. As the insects develop, they cause this cottony mass to form inside the leaf. Regular sprays of insecticidal soap might provide some control as would spraying with dormant oil in the fall and again in the spring. Focus the spray of dormant oil on the tips as that is where they overwinter. To find out more about the cottony psyllid click here.

Q. The leaves on my Green Ash are curling up in a cone shape. This seems to be happening all over. I notice some very small caterpillars dropping from 'threads' about early summer. What is the problem?

A. Your Ash tree is being attacked by the Ash Leaf Cone Caterpillar. These guys cause very little damage and rarely kill the tree. The damage is aesthetic. If you notice them dropping on silken threads in early summer you can attempt to spray them directly with either Malathion or Trounce. Since they are inside the rolled portion of the leaf, contact insecticides such as Malathion etc will not work. There is a beneficial wasp present that is controlling them so spraying should be avoided; just allow mother nature to take care of them for you. To see our What's Bugging information on Ash Leaf Cone Caterpillar, click here.

Q. My hardy rhododendron has not bloomed since I bought it two years ago. What can be done to encourage it to flower?

A. Make sure that your rhododendron is protected by a good layer of mulch or snow to protect the flower buds that have formed the previous season. Take care not to prune them until after they are done blooming. You can also feed it during the growing season with a fertilizer that has the numbers 15 - 30 - 15.

Q. I have purchased a new variety of rhododendron that is considered hardy to Zone 3. It was still recommended that I mulch it. When and how should it be done?

A. You should mulch your rhododendron when the daytime temperatures are consistently -5 degrees Celsius or colder. Use peat moss, straw or shredded leaves as mulching material. Mulch to ensure that the flower buds are covered. The flower buds will be located at the tips of the branches. In order to cover these, you will need to either construct a frame to enclose the mulch or use stakes and burlap to create an enclosure (this can then be filled with the mulching material). The reason the flower buds need to be mulched is because they are the most susceptible to winter damage. Keep the mulch in place until the day time temperatures remain above 0 degrees Celcius in the spring. The other important thing to remember is to water the rhododendron very well before the ground freezes solid. Make sure that the ground is consistently moist so that when the ground freezes there is a solid block of ice around the roots.

Q. I know we have had a very dry fall and I have watered all my plants in to prevent winter damage. How do I know if I have watered enough? When is the latest I can water?

A. When watering in your plants for the fall, check them once a week by poking down into the soil a few inches to check to see if the soil is moist enough. If the soil appears dry then water very slowly and deeply either by using a soaker hose or by using a Ross Root Feeder. Continue checking once a week up until the ground freezes solid. When the ground freezes solid will be the latest you can water (usually around late October, early November).

Q. Are there any trees or shrubs that should not be pruned in spring?

A. Yes there are. Birch, Maple and spring flowering trees/shrubs should not be pruned in spring. Birch and Maple tend to bleed excessively if pruned too early. Those can be pruned after the buds break and the leaves have fully formed. Prune no later than the end of June. Spring flowering trees and shrubs such as Lilac should be pruned after they are done flowering. If pruned too early the flower buds are often cut off as well.