Monthly Archives

April 2015

Versatile Spirea japonica

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This is one of my favorite shrubs. It tolerates pollution, produces beautiful tiny flowers in corymbs (flat-topped clusters), and has attractive fall leaf color.


My research showed that Spirea produced a second bloom when cut back after flowering. The picture below shows the results of my field test. The second bloom came, it just wasn’t as profuse as the first.

When the shrub looses its leaves in fall, you can cut back the stems in winter to keep the plant from outgrowing its space.

Is Your Viburnum tinus Full of Holes?

By | Arborist Insights, Landscaping, Resources, Strata Maintenance, Tips | One Comment

Healthy Vuburnum tinus are great plants with fragrant pinkish white flowers. But sometimes your plants get attacked by the Viburnum leaf beetle ( Pyrrhalta viburni) in numbers and soon all you see is tons of holes in your leaves. The larvae attack in spring and adult beetles in late summer.

Now what?

The cheapest solution is to renovate the plants by cutting them back hard at the base and waiting for new growth to emerge. A more expensive but better long-term solution is to remove the plants and plant a more suitable substitute.

Urban Forests Save Lives

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“Urban forests save lives” (link) was the heading of an article from The Vancouver Sun (March 24, 2015). And yet, our city trees often live short, brutal lives. They fall victim to storms, bad practices, bad design, and bad or new drivers. So let’s be mindful of the great work our urban trees do and treat them well.

Tree ID Quiz

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Take a good look at the pictures below and see how many you know. Answers are below.

Show Answers!

A Liquidambar styraciflua
B Gleditsia triacanthos inermis
C Pseudotsuga menziesii
D Quercus palustris
E Paulownia tomentosa

Avoiding Tree Mulch Volcanoes

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Yes, we have all seen them and most of us have made them but they are detrimental to the tree’s health. Why? Because piling mulch against the trunks of trees and shrubs creates a dark, moist, low-oxygen environment to which above-ground tissues are not adapted.

Fungal diseases require a moist environment to grow and reproduce; piling mulch on the trunk provides exactly the right conditions for fungi to enter the plant.
Also, opportunistic pests are more likely to invade a plant whose bark is wet due to excessive mulching.

Instead of creating mulch volcanoes (see pictures), instead, taper the mulch down to nearly nothing as you approach the trunk. This donut-shaped application will protect the soil environment as well as the above-ground plant tissues.

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Now you know.

Source: Washington State University Extension Fact Sheet FS160E

Parking Lot Bioswales On Our Cities

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If you are like me, you park your car and rush to do whatever is on your to do list. Perhaps it’s a sale or a Zumba class. But stop and look at the hard-working bioswale. The plants in it remove your vehicle pollutants, capture carbon and cool the surrounding air. Paved surfaces tend to heat up and act as heat islands.

Water is captured by the plants and slowly soaks into the ground and eventually reaches local streams the way nature intended.

Note that while periodic weeding normally happens in bioswales, the one pictured below is covered with arbor-chips (free and effective) and Horsetail (Equisetum) is NOT an enemy in this setting.


Searching for Female Ginkgo biloba Trees

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Have you ever wondered why city boulevards are dominated by male Ginkgo biloba trees? My first field encounter with a female Ginkgo biloba specimen only happened last summer and I wondered why that was.
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It turns out the females produce seeds in a fleshy covering (the sarcotesta) which contains butyric acid. Once fallen on the ground the fleshy parts produce an unpleasant odour; not exactly the best thing for city boulevards. I have seen various descriptions of the smell but why not find out for yourself? If you can find a female Ginkgo.