Your backyard tree questions, answered

Master arborist Gerard Fournier joined Alberta at Noon to share his best practices on tree care in Alberta.

Master arborist Gerard Fournier shares his tips and tricks to keep your trees thriving

A sparrow perches in a crabapple tree in southwest Calgary in spring 2021. Spring is when 'trees are revealing their true identities,' says arborist Gerard Fournier. (Submitted by Nyckie Rea)

It's that particular time of year in Alberta where trees across the province showcase spring flowers and green buds, and a master arborist from Didsbury has tips and tricks to keep those trees thriving.

Gerard Fournier joined Alberta at Noon with host Judy Aldous on Friday to address wide-ranging gardening questions when it comes to trees.

He says now is the time of year that "trees are revealing their true identities."

  • Have a photo to share of your pretty spring trees in bloom?  Email, or tag @CBCCalgary on Instagram, and we might feature your work on CBC Television, online, or CBC's social platforms.

"It's such a relief to see all those new leaves, all those new flowers, all the great fragrances. And it's like coming out of lockdown and unmasking."

Fournier, who is also president of For Trees in Didsbury and an instructor at Olds College, recommends that you "just get out there and get personal with the trees."

He shared his advice on caring for backyard trees, in particular.

You can get a machine that grinds down pesky stumps, says Gerard Fournier, and then use that for mulch in your garden. (Getty Images/EyeEm)

What to do with a backyard stump?

"[You can] grind it up, dig it up or let it rot," says Fournier.

"A little bit of high nitrogen fertilizer and 10 or 20 years will usually do the trick and it will completely rot away on its own."

Letting nature take its course does run the risk of the stump regrowing into a tree, he cautions.

You can also go the route of stump removal through excavation, but that can lead to a wrecked lawn and enormous root ball.

Fournier says many people opt for the use of a stump grinder, a machine that chisels down the stump.

"You're left with a big pile of mulch instead of a stump."

How do you get rid of spider mites?

Before you do anything, he says, make sure the problem is actually spider mites.

"I am a little bit leery of a diagnosis of spider mite. They really don't seem to be as much of a problem as people think," he said.

The best trick to get rid of them is waiting for warm days (15 C at night and between 20 C and 25 C during the day) and using water.

"A strong blast of water to the underside of the foliage of the tree, every tree. Three days for about two to three weeks."

He recommends avoiding insecticides, as that can also kill the mites' natural predators and actually make the problem worse.

How do you boost tree growth?

Fournier recommends a good pruning.

"In the first 25 years, four or five good prunings from a certified arborist to address those structural issues," he said.

Adding four or five inches of mulch around the tree (while being careful not to pile the dirt against the trunk or touch the trunk) is also beneficial.

He says using an organic fertilizer in holes around the drip line of the tree works, too.

Should you cut the dead branches off a pine tree?

Yes, you can.

Fournier says in nature, these would normally just shed but there's no harm in removing some "dead weight."

"Basically, it cuts down on the surface area that can accrete ice in ice storms and prevents storm damage," he said.

What type of fertilizer should be used on a tree?

"There is no magic bullet when it comes to fertilizers," says Fournier.

"But basically any kind of fertilizer would be better than nothing at all."

He says arborists, like himself, come up with their own formulations. Researching the type of soil you have in your area and what might complement it, is also a good route to go.

  • LISTEN to all the tree questions here:

With files from Alberta at Noon


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