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Lawns, Rhodos and Other Questions

What to use to cover grass seed lawn patches; Rhododendrons not flowering; orchids that don’t really have any problem; still another question about lawn moss; pruning of a smoke tree; powdery mildew on crimson maples; and is Funginex still available?
by Art Drysdale
by Art Drysdale


Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at

May 7, 2006

Above, typical foliage damage on a Rhododendron caused by Black vine root weevil which usually means the larvae have also damaged the roots, probably causing the slightly wilted foliage. Below, the small plastic bottle of concentrated Funginex should still be available this year. Author photos.

This week it is back to questions of which there is no shortage at this time of year. The first one comes from one of my oldest (i.e., known the longest time!) friends—Carol Hallam with whom I was in the same class at East York Collegiate for a number of years. We won’t say when that was! Carol says: “I have a question for you--if one wants to repair patches on the lawn by using grass seed and some sort of soil, what should that soil be--triple mix or topsoil?”

That is a not-uncommon question and one that indicates a common error made by ever so many homeowners. While it is a good idea to cover grass seed (lightly) put onto bare spots in the lawn (otherwise almost all of your grass seed may simply become bird feed), it is NOT a good idea to use either of the two she has suggested. The reason is that both will contain heavy numbers of weed seeds that may not only come up in the bare spots, but also spread to other areas of the lawn. Residents of Toronto and other areas where weed-spraying is banned should particularly be aware of making this mistake. The alternatives for covering grass seed are either sterilized seed-starting mixes or sand/soil which you sterilize yourself in, for example, a microwave oven. Another route is to buy one of the premixed grass seed and mulch materials which protect the grass seed from birds. The only problem with the latter is that they generally come with an unnamed grass seed, whereas if you know what type of lawn grass you have, you can likely buy the same seed for patching. The important point is to cover with something that isn’t going come with hitchhiking weed seeds!

Stacey Paterson wrote on April 12, with a question that is difficult to answer, having not seen her plants. I think she lives on Vancouver Island. Here is the question: “My rhododendrons are budding but not blooming. They are also very spindly and do not look very healthy. If you have any information that would help I would greatly appreciate hearing from you. Thank you.”

First I should deal with the fact the plants are not as robust as she would like. That probably indicates that they need some nutrition, and immediately they are finished blooming is the time to apply some Rhododendron and Azalea food, and perhaps also some Epsom salts (Magnesium sulphate). Another cause of poor growth could be damage to the roots by Black vine root weevil. The tell-tale signs of this are half-circle holes on the outer edges of the leaves.

As regards their lack of bloom, that could also be caused by the plants being incorrectly pruned in previous years. If Rhododendron plants are pruned (as they should be) immediately after blooming, and it is not done carefully, often most or all of the flower buds for the following year can be cut off with the pruning of the old flower heads from the year of the pruning.

To offer more advice, I really need to see a photo or the plants themselves.

Faye Bourgeois, from somewhere within the AM740 listening area, wrote on April 16th: “I listened to your program on Saturday on AM740. Heard your email address and said yea. Hope you can help me. I have noticed that quite often the stem of my orchid in between the flowers gets a bit sticky. I clean it (when I see it) with a mild solution of soap and water. Could you tell me what may be causing it? Thank you.”

The first and obvious answer is that there are some predator insects such as aphids, white fly, scale or mealy bugs present, but my orchid-growing friends tell me that it is more likely to be just a natural secretion of a type of honey dew the plant produces when it is happy! So, no need to do anything. Isn’t that great?

Mike Hall, also from Vancouver Island, wrote about the ever controversial moss in lawns here: “I'm new to Vancouver Island, having bought a place just north of Nanaimo. I have a lawn that's full of moss and was wondering how I can combat this problem. The lawn is quite wet and difficult to cut. I used some moss killer that was in the garden shed but then it's rained every day since and it did not seem to work. I would appreciate any advice you can offer. Thanks.”

Since I have answered this question on several occasions, I think I shall just refer Mike to my article (on this site) of February 4. He might also be interested in further comments I made in my articles (again, here on on both March 5th and 26th. The side note about moss in space in the January 8th article might also prove of interest, although it contains no practical advice!

Still a way back on April 15th, Ina McLeish wrote about pruning: “Good morning. We have a smoke tree in the garden, it gets full sun. Could you please advise if we should prune this tree in the spring? The tree is approximately 4 - 5 years old. Thank you for your time. We enjoy your Saturday morning show and find it full of very helpful hints and tips.”

The simple answer to that question is that they should prune the smoke tree only if they feel it needs it for some reason; for example, it is overgrowing another plant or plants, or a sidewalk or driveway. These large shrubs are easily pruned at almost any time of year, but if done in early spring, you will not prevent the development of the fruiting bodies, we know as the “smoke”.

A week later, Ron Robertson of Brantford wrote: “Tried to get on your program today, but unfortunately, missed the phone number to call. Anyhow, here is my problem. We have two Crimson Sentry maples which have been in about 11 years. They are healthy, growing well and are now in full bud. In about a month, the beautiful crimson leaves will be covered with a white mildew substance that resists any fungicide we have used. If you wet the leaves, the mildew goes almost transparent, but as soon as it dries, it re-appears. It does not seem to hurt the tree at all, but it is very unsightly. The trees get lots of sun and good air circulation. We do not mulch the leaves, but pick them up with the lawnmower. They are well watered and we have been fertilizing them with a Ross root feeder. What can you recommend to eliminate this unsightly mildew like substance? Thank you so much.”

The problem of powdery mildew disease (Uncinula circinata and Phyllactinia corylea) is not uncommon on many maples, particularly (for unknown reason) those with purple foliage. The disease does literally no harm; it is primarily an aesthetic thing, as Ron has said. One treatment he could try would be to spray a good application of Funginex on the tree’s leaves when they are first fully unfurled. Though it is not mentioned on the label, Funginex (still available this year—see next question!) does have a certain preventative capacity if applied before any sign of the disease is seen. And, once mildew is spotted, the old reliable wettable sulfur applied to the leaves should help curb it, but do not apply sulfur if temperatures are over about 21o C, and definitely not if it is over 26o C. Funginex should also have an effect then. Sorry I cannot offer other ideas; but you seem to be doing everything right!

Elizabeth, writing from Coles Bay, near Victoria International Airport, had a question that might be on many other gardeners’ minds within the next few weeks: “I have about 135 roses, some of them very old, so they get black spot. I have used Funginex and Benomyl for years, but I can’t seem to buy Funginex anymore. The stores tell me they are no longer carrying it. I still have a little Benomyl left, but what products are out now that are as effective as those? I no longer know what to buy. Can you help me?”

You and thousands of others I regret to say. However, Funginex should still be available this year. If you are told it is not, then try the big box stores, or Canadian Tire—just keep looking, and then stock up. Benomyl is definitely gone from the market, but if you still have some of the powder, it will still be good. It was not removed from the market, rather, the manufacturer decided not to continue the product following a major manufacturing error that lead to a number of lawsuits from commercial growers.

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