what fruit tree rootstocks can grow in very shallow soil?

Question

I own some property close to Owen Sound, Ontario, in Canada plant hardiness Zone 5b.

The land is mostly a hardwood forest with rocky soil and maple, paper birch and some other hardwood trees grow there.

There is a cleared section in the middle that I would like to grow some fruit trees if possible, but unfortunately, in many places there is no soil (rock is exposed) and the deepest I could dig anywhere was about 1 foot.

are there any fruit trees I can grow in such a shallow soil? If I decide to make a say, 24 inches raised bed over the stone, will any fruit tree grow there?

In local climate the temperature can drop to -30 - -40 deg Celcius.

Thanks

EDIT: as promised I am giving a couple more pictures of the hard bedrock exposed. I went there digging with a pickaxe but I could not dig more than 12 inches before hitting bedrock anywhere.

My next plan of attack would be to go the raised bed route.

Answer 1

Theory do not give you much chances, but nature works differently.

As you wrote, there are some trees nearby, so it seems that soil is enough to support trees. I just assume that your place is not a extremely shallow soil compared to just nearby places, which is not a good assumption, rock bed is usually not flat.

Birches (in Europe) likes wet soil, so it seems that water is not a problem (which is usually a problem on rocky soil). If the trees are also taller that you future fruit tree, the weather should also not be a problem (wind, snow, etc. often requires the plants to have deeper roots).

So I think you could plant fruit trees. Cherries like humid soil, but in nature they grow on rocky soil. The problem: cherries are tall trees, which make me worries about shallow soil.

Apples, pears, peach (possibly to cold), plums, etc. in my opinion can grow on such soil (considering the boundary conditions). I would ask for a root stock ideal for your region, and with slow growth. The advantage: the soil will reduce your need to prune the plants. Just because the soil is rocky and possibly with a lot of water, probably you should fertilize yearly (or more frequently).

Bushes are also valid alternative (plants for berries).

Many Mediterranean plant will low such shallow soil, but your climate will not allow them. Grape vines growth well, but your temperatures are also bad.

A stone wall, or a fence (wood, or just a bush) could help making the micro-climate less severe. Or just the fig of Graham Chiu and covering roots and trunk in winter.

Answer 2

Root dept does not depend on size of tree nor are all trees the same. Some fruit trees have large tap roots and are not suitable for this type of soil. Sugar maple roots are fibrous and do not go further than 90 cm, hence why maples do so well on your property. Look for shallow rooted fruit trees that like acidic soils (I assume acidic based on the ignious bedrock as you are in the shield). Blue berries might do well.

Answer 3

Fig trees can be grown in rocky soils. They have very invasive roots so are normally confined by pots or to edges of gardens.

https://permaculturenews.org/2016/09/30/dig-fig-essential-guide-need-know-figs-ficus-carica/

Olive trees can also be grown in rocky soils. You'll need hardy varieties of both of these.

Otherwise fruit trees are going to be constrained by the rocks. And if you want specific fruit trees you can try growing them in raised beds if that means less work in excavating the rocks and replacing with a suitable amount of soil.

If you want to plant some dwarf fruit trees, then 2 foot of soil is about as much as a container and they will grow but of course you're limited to the size of the dwarf species.

Answer 4

I would guess that a very cold hardy mulberry could potentially grow there with that extra two feet of soil in a raised bed. You can grow many mulberries in containers; so, they may be able to grow in that amount of soil, as long as it's wide enough and gets enough water. Mulberries are known for having strong roots that break up sidewalks and such. So, they might be able to handle those rocks reasonably.

Of interest may be the Montreal mulberry (if you can find it in stock), and the Taylor mulberry, which are both for zone 3 (and both sold by Canadian vendors).

To keep a tree in place if the roots don't support it very well in that soil depth, I wonder if just putting something to weight the roots down on top of the soil all around the tree might help at all.

Answer 5

I am planting my orchard next spring in the Bruce Peninsula, and our soil and nearby vegetation is nearly the same. We picked that spot for the orchard because it was mainly clear, and came to realize that there were no trees because the soil depth was so different than 100 feet away. We were going to plant this year, but once we discovered the soil depth, we decided to wait. Our plan is to take rocks from the property and build 6ft wide circles (one for each tree), about 10" tall, than mound soil that we will truck in upwards, to get an additional few inches. The trees will be planted in the middle (apples, pear, peach, plum, cherry, hazelnut), with some companion/pest control plants around the edges (comfrey, garlic, chives, onion, lavender). We will than be topping the exposed soil with a hefty amount of mulch. I have done a bunch of online reading, and it appears that this will work, and I hope so, because it is not a cheap en-devour. I hope my idea inspires you, or if you have already done something that has worked, I hope you can share. Take care and good luck!