Horticulture Guy

Q. My neighbor has a lovely red Norway maple. The city inspector wants to cut it down saying it has wilt infestation. To me it looks very healthy. It is about six or seven years old. How does the inspector determine this kind of disease and how can get evidence? I do not want the tree cut if it has a chance to survive. Isabella Kates - Ontario, Canada

A. They have probably diagnosed Verticillium Wilt.  Usually you see outward signs of stress first, like reduced leaf size or wilting of leaves when there is no drought.  The strongest indicator is then looking in at the wood, which usually becomes discolored from the infection.  Your own University of Guelph has a very nice document http://www.uoguelph.ca/pdc/Factsheets/PDFs/007VerticilliumMaple.pdf  on the disease which should help you solve this yourself.  At least you will be able to converse with the city inspector and have some knowledge of what he is talking about. 

-- HG

Q. I have a 6-foot laurel hedge, which is about 35 years old. Over the past year, the leaves in various areas of the hedge have suffered from a fungal/mildew problem. On advice from a local gardening specialist, I sprayed the leaves with something they recommended. This temporarily alleviated the problem but over the weekend when I was clearing out the plants around the hedge, I noticed that there were a lot of leaves lying under and along the base of the hedge.  When these were all cleared out, it became apparent that some of the branches at the bottom were rotten through. They didn’t even need to be cut, they just snapped, despite being very thick. It now seems that the stems with this problem are the ones which have all the diseased leaves - hence the randomness of the leaf problem. All growth for about 2 foot from the bottom has now been cleared and the worst of the rotten wood removed. The majority of the hedge is healthy but it now has some gaps! Will the whole hedge die? Given that it is November and the onset of winter, it wasn’t a good time to prune it, but I thought it would be better than leaving it. The base is now clear and air can circulate. I live on a very busy, noisy road so can’t be without my hedge as it provides a vital sound and privacy barrier. Should I take it all out and replace it with the largest replacements I can buy or should I leave it and see if it survives and grows back? Your help/advice would be much appreciated as, due to the time of year, time is of the essence! Charmaine - United Kingdom Many thanks.

A. Although English Laurel (I assume it is English since you are from the UK and probably don’t call it English Laurel there) is quite disease resistant wet conditions can create conditions ripe for bacterial and fungal infections.  In this case it was probably one of the rotting pathogens like Fusarium, Rhizoctonia, or Pythium.  These can attack both roots and stems.  Your instincts were good, as cleaning diseased wood should be done as soon as you find it.  The key is to cut back into clean disease free wood if possible and clean your pruning equipment between each cut to prevent spreading the disease.  These Shrubs are very resilient but you will need to address the air circulation and also determine if the soil stays overly wet which will exacerbate the situation.  I would see how it fares over the winter.  You may see new growth from the root system.  In the future in addition to normal hedging (which concentrates the growth decreasing air circulation) you may also want to do some modest thinning. Let me know how things progress.

-- HG

Q. Hello I’ve just moved into a new home with amazing cedar hedging but I have never taken care of this type of tree before could you give me some tips on maintaining them I’ve been told they can take over can I trim them in September or will I shock them? Please help, thank you Charlotte - Abbotsford BC

A.  Cedar hedges can be pruned two times during the year.  The main pruning should take place in late spring/ early summer as soon as the new growth stops and begins to harden.  If you need additional pruning to keep it in check you can do it in late summer / early fall so September pruning is fine.  Cedars do not respond well to drastic pruning and will not look good if they are.

-- HG

Q. How do i keep crows out of my cherry trees? I heard an owl decoy might work ..Help? Scott Landon - Surrey, B.C.

A. I am sorry to say that the “Natural Enemy Scarecrow” sold to control “birds” is also the owl decoy (like the great horned owl decoys) used to attract crows for hunters – thus the term decoy. Where the great horned owl decoys may frighten smaller songbirds they instead incite mobbing behavior. Hunters use this to their advantage by setting up an own decoy and maybe a few fake crows on the ground nearby and then make an audible crow distress call. Crows are arguably the most intelligent birds rivaling and some claiming exceeding the intelligence of parrots. So if the crows are coming by to feed on your cherries (which they will remember to come back this year) they will find a predator and likely proceed to mob it. Especially if it is near their nesting sites. Once they take out your scarecrow they will be free to feast. Reflective scare tape may provide short-term control but crows may habituate to that as well if used for too long a period of time. There is also motion-sensing water propelling scarecrow sprinkler that can be set up to protect the trees. But the most effective method would be to exclude them from the tree using bird netting. There are large sizes (28’x28’) made specifically for protecting fruit trees. Put them up at least a week before you think they will ripen since the crows (just like the raccoons) are willing to eat fruit a little on the sour side and could still beat you to your fruit.

-- HG

Q.  We have a long low laurel hedge that is set about 10 feet too far into the property and we’d very much like to move it further out. I know laurels are pretty forgiving of pruning, but can they survive being moved?   At what time of the year would be best, and how would we best go about it? How much of the root structure is needed? Does one prune it right after? Does it need fertilizer etc.  Thanks so much! Virginia Keyton - West Vancouver, BC

A.  This all depends on how long the hedges have been in place and how big they have become.  When I moved into my house I had a 30-foot tall 15-foot wide hedge along a property line leading up to the side of the house that made the house look Lilliputian.  My goal was to remove them so I cut them down with a chain saw and tried to remove them with a maul.  I quickly found out just how hard their wood is.  I wore down a few blades and had to enlist the help of a backhoe to remove them.  A friend wanted to try and salvage the large root systems I wrenched from the ground and planted them on their property without success.  This of course is an extreme case and my intentions were removal and not saving the shrubs.  I think if they are not that large you will be able to move them without incindent.  Since they are evergreen I would suggest moving them in the fall just before the rainy season kicks in.  I know this doesn’t help for this fall but root-pruning a year in advance would also help their transition.  The more root system you can maintain during the transplanting process the better the chances are for the tree’s survival.  At some point you will have to determine if it is worth the work since you could plant a new hedge and they would grow in quite quickly. 

-- HG

Q. I had mildew on my peonies for the first time this year. The phlox have it every year but never the peonies. What would cause it? Thanks Marilyn Dowson - Canada

A. I bet you are wondering if the disease spread from your phlox to your peonies.  It is doubtful.  The mildew you are referring to is powdery mildew to which most phlox are highly susceptible.  Powdery Mildew is a common name used to refer to many different pathogenic fungi that attack ornamental and crop plants and appear as a white cast on the surface of leaves.  In the case of phlox the species is Erysiphe cichoracearum .  As a general rule different species of Powdery Mildew have very specific hosts and a few have a larger host range. Although Erysiphe cichoracearum has a relatively large host range the hosts are considered limited to plants in the Aster Family (Asteraceae/Compositae) (e.g. chrysanthemum, dahlias, phlox, sunflowers and zinnia).  A probable scenario is that your peonies have another fungal disease called botrytis (Botrytis cinerea) or grey mold.  If you find infection of the flowers then this is a good indication of a botrytis infection.  Both fungal diseases are exacerbated by lack of air circulation and humid conditions.  The fungal spores need some moisture present on the surface of the plant to germinate and grow.  It could be from overhead watering or even from dew that forms overnight and doesn’t evaporate due to poor air circulation.  So anything you can due to change the environmental conditions will help.  Sanitation (removal) of infected leaves is also helpful since you reduce the spores available next season.   Both diseases can be controlled with copper based fungicides.

-- HG

Q. How do you propagate Dizygotheca elegantissima and will it branch if the tip is snipped? Nancy Bandusena - Kota Kinabalu, Malaysia

A. Well I am sure where you live you can grow the False Aralia (D. elegantissima) as an outdoor landscape plant since you are in a tropical climate but here in the Pacific Northwest we know it as a house or sunroom plant. The False Aralia had a heyday during the Victorian era as a conservatory plant. It has since been used occasionally in indoor landscaping and as a houseplant. Despite being having beautiful light and airy foliage with coppery cast this plant is finicky when it comes to warmth and humidity. Lack of warmth and humidity will cause the lower leaves to drop. This detracts from their inherent beauty. The False Aralia is reluctant to branch even when cut back so it is difficult to force new foliage below. They can be propagated by seeds (if your plant produces any) cuttings, and air layering. So if a plant is getting leggy you could air layer the plants (making a cut part way through the stem, putting rooting powder, wrapping inside the wound and outside with moist sphagnum moss and then wrap with plastic) to shorten up the plant. Once roots have formed you can cut below the layer and replant all the cuttings. Or Take cuttings using BONTONE ROOTING POWDER..

-- HG