Horticulture Guy"Live Long and Garden" – Peter Punzi

Q. In one of your answers: Shinseiki Asian pear is “considered nearly completely self pollinated” Does it mean there is no need another pollinator? Lisa- from New York

A.  A little background – most fruit trees have a built in mechanism to prevent self fertilization – presumably because self fertilization similar to inbreeding reduces the vigor of future offspring and limits their gene pool.  This mechanism is not completely on or off but varies. So for example one tree may self pollinate 80% of the time and would be considered “nearly completely self pollinating”.  Another may only self pollinate 20% of the time and would be listed as requiring a suitable pollinator.  You may improve the “nearly completely” pollination with a suitable plant (usually shown on a pollination chart) and presumably get close to the additional 20% pollination.  The pollination chart takes into account the time of bloom (since bees don’t as a general rule pollinate with long term storage pollen) and how closely related the plants are.  Usually if trees share parents the self fertilization prevention mechanism can reduce pollination.  To answer your question – yes you do not require an additional tree for pollination – although pollination could be improved.  If you find that you need to thin fruit each year anyway I would say you do not need an additional pollinator tree.

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. 

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.

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.

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.