Planting Trees

The 1001 Techniques for Planting a Tree—Part 2

Mature tree in field
Well planted trees are happy trees. Image: Gianny on Pixabay.

Last week, I presented MY tree planting technique to you in detail, while emphasizing the fact that there are probably as many planting techniques as there are people who plant trees! In reality, these different techniques all lead to the same result: a successful planting. This week, let’s take a look at these other practices.

Add a Fish to the Planting Hole

Person planting a tree with an arrow pointing from a fish to a hole
A fish in each hole, as did my grandfather. Image: Julie Boudreau with Canva.

When I started my studies in horticulture, my father shared what seemed to me a strange tale. He claimed that his own father, originally from the Chaleur Bay area in New Brunswick, used to put a fish at the bottom of the hole every time he planted a tree. I later discovered that this is a common practice among just about every coastal dweller. The reasoning behind this idea is that the rotting fish will release nitrogen and various nutrients which can then nourish the roots. And you can also assume that this practice also helps to maintain a certain amount of soil humidity. It doesn’t seem to hurt the tree and I’d say it probably really does help!

Squaring the Planting Hole

I have also run into some gardeners who solidly stick to the “square planting hole” technique.

Square planting hole for a tree
There is no scientific proof that square holes are bette for three growth. Image: Solum on Wikimedia Commons.

Here the argument is that if you dig a round hole, the roots will tend to follow the contour of the hole and start to form a never-ending spiral, eventually girdling and killing the tree. A square hole, though, would force the roots to head off into the surrounding soil instead of going around in circles.

Here, it’s important to emphasize that even if several serious sources publicize this practice, it doesn’t have much in the way of scientific support. On the contrary, the few studies devoted to this subject tend to show that the shape of the hole has no effect on tree growth. Not even star-shaped holes (yes, scientists have tried even that!) made any difference. Whether the hole is round, square, pentagonal or in the shape of an isosceles triangle, trees want to grow and will grow.

In addition, a simple mathematical calculation shows that you have to shovel 25% more soil to prepare a square hole than a round one! The term “squaring the circle” is sometimes used as a metaphor “for trying to do the impossible”. I prefer making the possible easier!

Sloping Sides

This is a practice that I have observed a lot among horticultural colleagues. Instead of digging a hole with vertical walls, they create gentle slopes. Not only does this technique work well, but studies that confirm it works, directing tree roots somewhat upward into a zone with better air circulation. Some specialists highly recommend this technique in places where droughts are likely to be frequent.

Compacted Bottom

Today, many professional horticulturists avoid loosening the soil at the bottom of the planting hole. It’s a subject the laidback gardener blog has covered several times. You can learn more about it in the article No Need to Dig a Deep Hole, for example.

Here too, the approach is more than valid. Indeed, by keeping the soil under the root ball compact, you make sure the plant is positioned at the right height from the start. And it won’t tend to sink into the ground the way it can when the soil has been loosened and enriched in compost or manure.

Ways of Upping the Water Content!

Many gardeners dig a planting hole to the proper depth and diameter, then fill it with water. Only after all the water has soaked in do they plant the tree. Here, the purpose is to moisten the soil all around the root ball so that later the roots will be able to draw water in quickly when needed. It’s a great idea!

A variation of this practice is, when you plant the tree, fill the hole with soil about halfway up and then water generously, letting it soak in. Once the water has drained into the surrounding soil, you can finish the planting.

Replace All the Soil When You Plant a Tree

This one, I just don’t get. Nor does the work of Dr. Shigo, the great American tree specialist, backup of this belief. Ideally, gardeners should reuse the existing soil as much as possible when planting. Why? Because this local soil is already full of microorganisms well adapted to the environment. Because it’s in this soil that the tree will have to grow for the next hundred years (OK, so I’m a bit of an optimist!) Because it avoids waste. After all, any soil you discard soil will have to go somewhere else. Replanting using the original soil is 100% laidback, but 100% effective.

True enough, trees whose soil is completely replaced at planting sometimes develop and grow well. Even if I’m not in total agreement with this practice, it must be recognized that it sometimes works.

Let Your Boots Do the Compaction

As I mentioned in last week’s column, I plant using my hands. Often even without gloves! So, I compact the soil around the roots with my hands as I plant. That said, I believe most gardeners compact with their feet. I’ve always found that with your hands slide more easily into the soil’s cracks and crevices and therefore that you can more easily detect the big air pockets that you want to avoid when planting. But don’t worry too much. Trees planted by you filling in with the tip of your boots grow just as well!

Donut-Free Planting

Planting a tree without leaving a “watering berm” or “watering donut” (see last week’s blog) is still the common practice among professional landscapers. They want the end result to be flawless. Therefore, they choose not to install a donut around the edge of the planting hole. That’s because if they create one, they’ll have to come back to flatten it out in a year or two… and that’s of little interest to them!

What they do instead is to apply a very generous layer of mulch at the base of all the plants. This allows the soil to retain its moisture better. And that’s great! As long as they don’t add so much, it becomes volcano mulching (see gaffe #7 in 10 Gardening Gaffes to Avoid in the New Year), that’s perfectly all right.

But the conclusion is there. With good, thorough watering at planting time (and perhaps regular watering using an irrigation system afterward), you can do without a watering donut!

So, with Part II of this article, I hope I’ve demonstrated that you can plant a tree using ALMOST any method. And yes, it will grow! So, if your only obstacle to planting a tree was not knowing the right technique, you can free yourself from worrying about having to do a perfect job of planting. Even if I’ll always invite you to use MY technique, do understand that MY technique is not THE technique. It is ONE technique among many!

Julie Boudreau is a horticulturist who trained at the Institut de technologie agroalimentaire in Saint-Hyacinthe, Québec. She’s been working with plants for more than 25 years. She has published many gardening books and hosted various radio and television shows. She now teaches horticulture at the Centre de formation horticole of Laval. A great gardening enthusiast, she’s devoted to promoting gardening, garden design, botany and ecology in every form. Born a fan of organic gardening, she’s curious and cultivates a passion for all that can be eaten. Julie Boudreau is “epicurious” and also fascinated by Latin names.

1 comment on “The 1001 Techniques for Planting a Tree—Part 2

  1. I use as much of the original soil as possible, but I often have to remove several substantial rocks while digging. Since I don’t replace those rocks in the planting hole, I use compost to make up the difference.

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