Mulch Volcanos or How Not to Plant Trees

It seems a lot of people and/or landscapers are under the misapprehension that when it comes to soil, more is better. This is not always the case.

In my neighbourhood

In my neighbourhood.

This volcano of soil is doing a couple of bad things to this poor rhodo. Firstly, stems and trunks should never be buried like this. DSCN2343You’ll see more of this in the next few pics. You should always see the root flare at the junction between the stem/trunk and the soil. You’ll see “bell bottom trousers”.

Here’s a beautiful Blue Spruce in excellent condition

Blue Spruce in the neighbourhood.

LOVE this tree: Blue Spruce in the neighbourhood. You can just about see the root flare if you click on the image to enlarge it then click again.

Secondly, rhodo roots are even more shallow than other woody plants, so adding ANY soil on top of the planting area is going to make your rhodo suffer–from too much moisture and too little oxygen.

Very sad little rhodo in a brand new planting bed--the duplex was just finished in the Fall.

Very sad little rhodo in a brand new planting bed–this duplex was just finished in the Fall.

You can and should still mulch rhodos, just several inches away the the trunk, and only about 2″ of nice light mulch (wood chips or well composted compost), not soil.

The Problem:

Also my neighbourhood.

Also my neighbourhood.

Exactly the same thing above–soil (or in this case bark mulch) mounded up around the trunks of these Thuja (arborvitae).  This causes a number of problems: Too much moisture against the trunk will invite disease and bark splitting. It also promotes root girdling, which is when roots start following a circular path around the trunk instead of heading out perpendicular to the trunk. As those roots grow and fatten they will often pinch the channels that draw water, oxygen, and nutrition up the tree. Root girdling is a very bad thing for your tree.

DSCN2374DSCN2375Two views of the same tree. Here the planter put a rodent guard around the base of the tree, which will also also help reduce moisture against the bark. But the roots will still opt to grow up into the volcano soil causing the root girdling again. And then to hide the look of the mounded soil, they planted creeping raspberry (Rubus pentalobus). In other circumstances I’d say this was a good plant for under the tree, but it will hold the soil there (eroding away would be a better thing) and act like living mulch, which will just exacerbate the moisture problem. (It’s a pretty vigorous plant in coastal BC and will begin to take over the lawn area–not a bad thing maybe.)

I plan to write discreet polite letters to the owners of these trees and shrubs offering to help remediate their plantings. Hopefully they won’t be too offended at the local busybody who thinks she knows everything!

Love to get your comments and questions.

Top 5 Plants

I’m supposed to be posting about 5 Great Container Gardens, but I just found this website: Mike’s Garden Top 5 Plants. It’s an absolute Treasure Trove of information and advice about choosing plants for garden or container. Oh, and BC specific!

Have a look–you won’t be disappointed!

Tips For Designing With Trees

I’ve been driving through Richmond BC lately and have been struck by how many disastrously pruned trees there are. Most of them are pruned the way they are because they are interfering with utility lines/poles in some way.

So this post is a primer on how NOT to design with trees.

My Neighbourhood

This tree was already badly pruned away from the utility lines, when they came last Fall and chopped away mercilessly

This tree was already badly pruned away from the utility lines, when they came last Fall and chopped away mercilessly

You can see, right to the trunk!

You can see, right to the trunk!

This is “my” tree–ie, on my property. But BC Hydro doesn’t really care whose tree it is, if they think it’s interfering with their lines (why don’t we have underground lines??), they chop chop chop. And the “arborists” who did the work… arggghhh!

Let’s look at some more: this one is around the corner,

A maple, probably a sugar maple.

A maple, probably a sugar maple. You can gauge the size of it by looking at the car toward the back, just outside the tree’s shadow. And yes, that is the same tree growing way above the top of the building.

Next we have a whole street of cherry trees, about 3-4 blocks of them:

Cherry trees

Cherry trees–two blocks over from my street.

Here's a double whammy--

Here’s a double whammy– same block as previous picture.

This one doesn't have much life left in it.

This one doesn’t have much life left in it. Click on it for a larger view.

Bottom Line

So my point with all these disasters? CHOOSE YOUR SPOT. Big trees will grow big, and the utility lines don’t, so make sure your tree at maturity will be safe from the utility company.

How long before this spruce succumbs to the chain saw?

How long before this spruce (or is it a fir?) succumbs to the chain saw?

Moving on to spacing:

Sugar maples again

Sugar maples again

These maples–I think they’re sugar maples–are planted about 12 feet away from one another. Now sugar maples reach 20-35 m tall and almost as wide. So if they even only get to 15 m across but there’s only 12 ft between them, none are going to be very happy. (Interestingly, around the corner the same townhouse complex has ornamental plums spaced much further apart– more like 20′ apart.)

Now about how close they are to the sidewalk (about 4′):

Maple trees have large vigorous roots that don't do well near sidewalks.

Maple trees have large vigorous roots that don’t do well near sidewalks. This is a stock photo, not my neighbourhood.

So again, big trees need big space. Before buying your tree, read the label, determine if there’s room in your garden for the mature size of this tree, and if not, please buy something else.

More about Spacing

Still in my neighbourhood.

Still in my neighbourhood. Admirably trying to hide the … whatever it is.

These lovely Thujas (or Arborvitae) are all planted about 16″ apart. The mature size of even the smallest, narrowest Thujas is about 3′ (which I found out by Googling “mature size of Thuja”– remember, Google is your friend!) This is going to result in not only a lot of pruning, but quite a lot of dieback, as new growth keeps getting cut off. Even shrubs that tolerate a lot of pruning, like Boxwood, should still be planted with their natural mature size in mind.

Also Thuja

Also Thuja

Now I confess, this is not my preferred pruning style for Thuja, but look how healthy they are, spaced widely enough that they all get lots of light and air.


Trees are a wonderful investment, and a significant one as well, being not inexpensive. Do the best for your tree and your investment, make sure you’ve read the label, talked with the garden centre, and looked around to see a mature specimen of your chosen species before you buy. There are so many beautiful trees out there, certainly one perfectly suited to your unique environment.

Have you got a tree in the wrong place, are you having to prune, prune, prune, or is your walkway or driveway buckling with the vigour of tree roots? Leave a comment or question, and I think WordPress will also support leaving pictures (?)