Propagation, Rhodos, Mites & Tree Suckers

Propagation is on the minds of the readers today—both of Rhododendron shrubs and Explorer rose bushes; then a problem that I first dealt with over 40 years ago—clover mites; and difficult-to-control suckers from some flowering trees.
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

June 4, 2006

A lovely spring afternoon visit to Clayoquot Island (Stubbs) was the highlight of our weekend two weeks ago. Above, one of the beautiful borders that greets visitors on arrival and a view through to one of the ponds. Below, one of the residences on the Island with a nice paperbark maple (Acer griseum) on the right, and a delightful Meconopsis baileyii just in front of a fully-in-bloom Rhododendron. Author photos.

Barry Herman, of Sherwood Park Alberta wrote with a question that could apply to homeowners/gardeners in al-most all areas of the country: “We have in our newer home (2 years) very small reddish coloured insects that are collecting near the bottom at the sill of the basement window (bi level). The insects are almost microscopic and move slowly and stay collected in the one bottom corner of the window. What might they be and how should we treat for effective eradication?”

My response was: “I’m sure they are clover mites; the reason I asked your location was because we don’t seem to have them here, at least I haven’t seen or heard of any in four years. They are hard to control, but Doktor Doom certainly has a couple of insecticides that will. Also, there is a consensus that they get to the house by crawling on grass, and if you have a 45-60 cm border of anything but grass (i.e. annual plants, pea gravel, black plastic, or even just open soil) they will not arrive at the house.

“They leave a red stain if crushed but they are harmless to individuals or plants. I once had an infestation in my Toronto office that lasted about two months. I had to clear my desk every night, so I could wipe them away each morning. And, I as the horticulturist at Sheridan Nurseries in Toronto, only one of 12 people in the head office, was the only one to be bothered by them!

“If you cannot find a Doktor Doom product call him, he’s right near you: toll-free 1-800-452-0023.”

Likely the most widely available Doktor Doom product for this use is the House and Garden spray in the dark green labeled aerosol can.

Several weeks ago, I did a segment on my “Daily Gardener” vignette on Shaw TV here on Vancouver Island, and mentioned using the air-layering method to propagate Rhododendron shrubs. I believe I used my standard recommendation of taking an angular bite out of the stem to be propagated, just below a bud union. A variation, often used on Rhododendron shrubs is to carve a circle all the way around the stem, removing the bark, again just below a bud union. Just last Sunday, Ken Olenick, of unknown location on the Island wrote: “I watch your show on Shaw and saw the one about air layering Rhodos with plastic. What I was wondering how long does it take before they get roots, a week, a month, or more, and does the moss dry out? I tried doing some just after the show aired.

“Thanks and again I enjoy your show you have given me some interesting things to think about and try.”

The answer to Ken’s question varies with the particular Rhodo, but generally it will take a couple of weeks for the callus to form, and then another few weeks for roots to grow. But, it is easy to tell when the rooted ‘layer’ is ready to sever from the main branch because the plastic wrapping will be filled with roots. And, if the plastic wrapping is tightly enough applied, say with wire twistems, the sphagnum moss wrapping should not dry out, and thus generally does not need to have water added.

Just a day later, Mark Edwards wrote, from unknown location, with this question: “We have two large ‘Jens Monk’ [Explorer rose] bushes in our back yard and we would like to start a hedge in the front. Can these plants be di-vided like hostas? Please e-mail back and thank you very much.”

It is highly unlikely you would be able to divide most rose bushes, but there is some good news. Most Explorer rose bushes are now produced on their own roots which means that you could use one or a couple of methods to reproduce new bushes from the two you have now. For example, you could use the air-layering technique de-scribed above in this article. Or, you could try ordinary layering, which involves taking a side branch that is only about one or two year-old-wood, and bending it down and taking down into the soil, but at the same time having the growth tip still pointing above ground. You will need to hold the part in the ground down with some sort of a small stake. Make sure you have at least a couple of bud unions (the locations where there were leaves that you remove) within the soil. There are many variations of this method including putting sphagnum moss in a hole through which you loop the branch, and nicking the branch with a knife, etc. but the basic young branch through the soil will usually root within one season. Much will depend on your location, which you did not supply. Good luck!

Finally this week, Sylvia Jones, a regular listener to my AM740 programme out of Toronto wrote: “Three years ago I purchased a Double Flowering Almond Standard which is a beautiful tree that I am very happy with. This year I am bothered with the roots shooting up in many places, even in the lawn. I have been breaking off these roots but it is becoming a full time weekly job. Is this natural for this type of tree/bush? And if so, is there an easier way than breaking off the roots as they appear?

“We listen to your programme every weekend and think you are doing a great service to the gardening public – some things we can’t get out of a book. Keep up the good work.”

The flowering almond standards are generally top-grafted on another Prunus species rootstock. The suckers you refer to are from the rootstock. Unfortunately, there is little you can do about them. It is better to pull them out than to cut them off, but that doesn’t stop them growing at all. You could resort to painting them with say Wilson’s WipeOut but be sure not to get it on any adjoining plants. It should not harm the main tree.

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