Questions - Wisteria, Vinca & Sinetti

The old “My Wisteria doesn’t bloom” question and a bit about the groundcover, Vinca minor; plus what is Sinetti?!
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

April 29, 2012

Above, two Wisteria shots I have used before—the first on our old house on Nesbitt Drive in Toronto, taken in May 2001; and the second of an old friend Pierre Bourque, the horticulturist/manager of the Montreal Parks department (later a two-term Mayor of Montréal) shows a Wisteria in bloom at Le Jardin botanique de Montréal in 1993. Below, shots of Vinca minor and V. major growing under our Coastal Douglas-fir hedge and one of the newly-acquired Sinetti plants. Author photos.

Still more questions! The first one is from Cameron Ghent in London Ontario. “I enjoy your broadcast, but am usually in the car when it is on.

“First, I have had a luscious Wisteria plant at the corner of a sunroom, facing south for about ten years. I have abused it, trimmed it away back, coddled it and fed and watered it, and at times totally neglected it. It grows to the roof with long tendrils but it stubbornly refuses to bloom. What am I doing wrong?

“Second, I planted some periwinkle under a big Colorado blue spruce tree. Although periwinkle grows like a weed in other shady spots around the house, it promptly died there; I am guessing that the pine needles make the soil too acid, but am I right?”

Two good questions Cam!

Wisteria is a very aggressive vine/shrub; once the initial growth becomes woody, little if any artificial support will be needed. The vigour of the plant, however, is not to be denied! You will have to prune the plant hard twice each year once it is established. In the summer you need to remove completely (2/3) or shorten back (1/3) to about 25 cm (10”) all the young thin green growths (which some call tendrils). You can actually do this several times through the summer, and at the same time direct the growth of the main branches so the plant, more or less, grows where you want it. It’s not necessary to cut all of these young spindly new growths back to the main stem, in fact you should leave some (1/3) of them at a length of about 25 cm (10”) from the main branch.

Then in early spring, likely in mid to late March, you prune again--at that time all the woody side shoots should be cut back to about 20-25 cm (8-10”), just ahead of a large bud. At that time you will already see many growth buds, but also possibly a few that are larger and appear like small acorns on the branches. These latter will be flower buds and you definitely should not cut them off. This pruning should aid the plant in blooming.

Unless the plant you buy in the spring is actually in flower, you may have to wait several years for flowering. The Japanese type (Wisteria floribunda) produces longer slender panicles of bloom, is capable of growing to 10 metres (30’) and is usually considered slightly hardier than the Chinese cultivars (Wisteria sinensis) that have slightly ‘fatter’ and shorter bloom panicles on much taller trees/vines, to 30 metres (100’).

If you follow that regimen Cam, you’ll hopefully have blooms on your Wisteria in a year or two.

Now as to your second question, I do not think the problem with the periwinkle (Vinca minor) under your Colorado spruce tree is acidity of the soil. The reason I say that is that here in Parksville, our soils are very much more acidic than any in Ontario. In fact, at this time of year, most gardeners are busy applying lime and moss killers to their turf in order (in the case of the lime) to reduce the acidity of the soil, and thus discourage the growth of moss in the lawns.

We ourselves have extensive plantings of both Vinca minor and V. major under a “hedge” of Coastal Douglas-fir (Pseudotsuga menziesii) along the street-side of our property (about 20 metres—70 ft. in width). Believe me, no evergreen drops more needles than these firs! When we bought the house ten years ago, the Vinca was well established but somewhat ratty looking. We eventually cut some of the less healthy trees (in order to install our new fence) and began giving the area a little more TLC. Now the Vinca is spreading out from beneath the trees to an area previously covered in just weedy grass which was cut regularly. I can easily see it reaching the road shoulder in just a few more years.

So, if it is not the acid soil, what is your problem? I would try a dozen plants again now, and plant them on 30 cm centres, raking away the needles in the specific area. Fertilize the plants with a liquid fertilizer (anything, 20-20-20 for e.g.) two or three times during the growing season. Any of the food that washes through and is not picked up by the Vinca will only help the Colorado spruce. In case there happens to be a unique problem to that particular area of your garden, you might also want to try planting a dozen of another groundcover such as Japanese spurge (Pachysandra terminalis). In two growing seasons you should see which one does best, and more importantly, whether the Vinca does better the second time.

Where you get the plants could be important—try to get locally-grown plants. If you do not know a good nursery I suggest you drive to St. Thomas and visit the highly respected Canadale Nurseries Ltd. I would ask for Tom Intven (son of the founder) and ask him, or if he is not available, his sister Pauline who manages the retail garden centre.

Good luck with both problems Cam!

* * *

Well, what do you know about Sinetti®--an annual now to be found in some garden centres, at least here in British Columbia.

If you have ever bought Cineraria either as a flowering indoor plant or as a summer bedding plant outdoors, you have been close to Sinetti. They are close relatives and look similar, although Cineraria require a more tricky treatment when grown from seed, whereas Sinetti are propagated asexually.

They are generally available in reasonably-sized pots (1 gallon) and grow well in such and flower for at least three months, I am told. I bought the magenta-coloured one, although both nurseries where I saw them also had a blue bi-colour.

We will leave them in their pots and likely set them on a bench we pass many times each day. Perhaps I can re-port more on these at a later date.    

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