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deathbypunches · 9 days ago

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Fig 1: A boxelder

How to Guerilla Trees (in CALGARY)

In my region of Southern Alberta, there are a few trees worth planting in order to enhance the urban forest. Granted, these trees are partially or completely removed from their ecological context half the time, but they still provide some services- shade, carbon storage, habitat for birds or certain insects. The list goes on.

The species I'd recommend here are Acer negundo, Fraxinus pennsylvannica, Populus balsamifera, Populus deltoides occidentalis, and Salix sp. for their ease of cultivation... In some cases I think Prunus sp. can be a decent choice... I'll use common names from here on... boxelder/Manitoba maple, ash, cottonwood / poplar, willow. Maybe cherry, maybe "moutain ash" or Rowan (sorbus sp).

What is a microhabitat?

This tree here is a boxelder on the third summer of it's little life. It is in a small depression in the soil that collects slightly more water than the surrounding. It is protected by stones, a ribbon, and stakes. This tree is watered every week or two in the heat of summer, if it hasn't rained. I believe it has a good future ahead of it.

You might notice that small trees sprout quite often along the shade of fences, or between a fence and a shed, etc. These places are sheltered from trampling and mowing, and the soil stays more moist and cool in the heat of the summer.

You may also notice that ash and Russian elms particularily can grow in cracks on the sidewalk. Growing out of the concrete isn't as bad as it appears, because there is much less competition for the soil beneath a concrete slab, especially for a plant that can grow a large root system like a tree does. Even if the soil doesn't get rained on directly, water percolates through the soil from the surroundings.

Also, the direction of a slope can significantly affect the amount of direct sunlight the soil recieves, or the amount of water that collects there. The bottom of ravines, and north slopes are the most moist. The top of a ridge or a south facing slope is the driest.

Boxelder and Ash

Boxelder and to a lesser extend ash are very hardy trees that can hold their own in this climate without having to be watered once established. These trees grow reasonably fast and are native at least to the great plains of North America. They are well adapted to growing in sites disturbed by human activities, and can also be found as far south as Texas or Arizona along sheltered streams- so their ability to survive the changing climate seems pretty certain. I also have a hunch that before the last glaciation, the range of these species probably extended further north than it does now, along with perhaps oaks and elms. Boxelder is considered a low value tree, and maybe I'll change my mind someday, but for now, it is useful because it is so easy to grow. These trees are partially tolerant of shade when they are young - and ash seedlings in particular can be found growing underneath spruce trees.

It is easy to source seedlings of boxelder, ash, and cherry. If they are in a spot that isn't exactly a good long term site for a tree, and you can either pot them or plant them somewhere else right away. Sometimes vacant lots can have dozens of tree seedlings. You have to be careful digging up even a small tree as the taproot can be a lot longer than you would expect even for a seedling that is barely 10 cm tall. I think it is better to pot them and keep them for at least a season so that they get large enough to be conspicuous.

There are multiple reasons to prefer growing a tree to conspicuous size-

1- You can find them again. You ought to mark a tree with a stake anyway, though.

2- Once a tree is 2 feet tall, it might be safe from public mowing because it has crossed the threshold of looking like nothing or a little weed to looking like a little tree.

3- you can be sure that it didn't die from being dug up.

4- A tree that is around 2 feet tall can graduate from significant competition with weeds

I choose a microhabitat where there is a depression in the land, or at the base of a slope, or especially on a north or east facing slope. These places will dry out the least.

It is also easy to collect and sprout boxelder and ash from seed en mass - you can collect kilograms of seed in the fall and winter. The seeds probably have less than a 1 in 1000 chance of surviving their first year on barren soil, but they provide mulch for their own germination. Barren soil is good enough to get them started anywhere that isn't likely to be mowed. Ravines and north or east slopes are better, as they can have a hard time getting enough water. They probably will need some water in hot stretches from July through September to survive the first 2 summers, unless they are in a particularly good site.

It helps to mark them with stakes, to mulch them. The mulch legitimizes the planting as "intentional and human," along with helping reduce competition from weeds and maintaining soil moisture. In places with mowing risk, mark them with a ring of large stones. They aren't as prized as the poplars for their bark but they can be fodder for rodents and could benefit from some protection.

Cherry and Rowan

There are native species in both the genus Prunus and Sorbus, but neither of these native species are popular or even common within urban habitats compared to the horticultural cultivars- the native cherry is scrubby, but common in grassland habitats - it can be difficult to identify with certainty, but P. virginiana (the native variety) has shorter racemes with sparser, slightly larger flowers and fruits , and has a less tree-like shape. The native rowan are very small trees or scawny shrubs and a very minor component of cooler forests habitats.

Both of these genera are popular flowering trees and decently hardy, and they provide a lot of food for birds.

Willow and Poplar-Staking

These trees can be grown from seed, but they typically reproce vegetatively- and are easy to produce with "cuttings." You can take a branch that is about thumb-diameter, cut it into about 30-60 cm stakes, and stick them into wet soil. You'll get pretty decent survival rate as long as they stay moist and are not girdled by rodents. You can keep them in a pot for the first year, or stick them into mud near permanent sources of water. . .

This willow was not watered at all- I put a dozen stakes into the mud on a seep along a south-facing slope.

Poplar

There are four species in the bow-river valley and 3 of them are in the "cottonwood" subgenera (if that's valid) that appear to have a more recent ancestor with each other than with the aspens (which is the 4th species). The cottonwoods are easier to grow because they can be started from stakes like willow. Trees in this genus tree NEED full sun, and will create a quite open canopy forest with a very rich understory.

Poplar is the best tree in the bow river valley, as they are a keystone species that supports pretty much the entire ecosystem. Forests of cottonwoods create an extremely diverse patchwork of sub-habitats for a variety of shrubs and wildflowers, and they are food for a huge number of insects. They also have the handy habit of growing extremely quickly and volunteering in turfgrass. The easiest tree to grow is a volunteer poplar- I put a stake on either side of the sucker when it is around 1m tall, surround the base with a 1m ring of softball sized stones, and weed everything within that ring, and place mulch within that ring. The tree should be safe from mowing, but nothing is guaranteed. They can easily become taller than a person by their second complete growing season, and from then on, you don't have to care for them, really.

The deep rooting system and the support of their parent tree (which they are connected to underground) means a volunteer poplar doesn't have to be watered.

The bark can be food for rodents and the leaves are a favorite of aphids, so they might benefit from some protection- a cage of chicken wire, or a wrap around the trunk to protect the bark. I don't do anything about aphids personally, as they are the "base of the food chain," but if I was to do something to control them, maybe wiping them off of the leaves would help reduce the damage.

Aspen

Although aspen is ecologically important, it takes extra effort to grow. You can try to protect a sucker in the same way, but they do not grow quite as quickly (less than 1m per year). Aspen cannot grow roots from a branch cutting easily (but allegedly can be done), allegedly they can be grown from a root cutting, or suckers can be dug up. The seeds can be started from the cottony fluff in late spring if the soil is kept perpetually moist and not too HOT. The seedlings are a little bit fragile and a favorite food of rabbits and rodents, so they have to be protected until they are probably about a meter high, and even then the bark is vulnerable to gnawing until they are probably thicker than a thumb.

As of this writing, my only aspen have been eaten by rodents. Some of them roasted in the late summer sun. These trees need some care when they are young.

Conifers

I've tried digging up and transplanting tiny saplings of spruce, sowing spruce, and marking and protecting small spruce saplings. They grow quite slowly and can have a hard time getting established without shade. These trees are later successional and really benefit from a forested environment- at least in the Calgary metropolitan area, they don't do extremely well without care - besides, the most common spruce in city limits is the non-native Colorado blue spruce. The Alberta white spruce (p. glauca) definitely needs to keep it's feet in the shade- north facing slopes and ravines only- but it does well growing behind fences, in the shade of other trees, between houses, etc.

Pines are not native to the Calgary area, or at least are very rare in natural environments. The lodgepole pine benefits from a slightly cooler climate. The Ponderosa pine is the second closest to being a native species and it may be a decent choice here in the future, but they seem to come from places with much milder winters.

Birch

Birch is sensitive to heat and drought. The seeds can be collected en mass and sown on moist barren soil. I haven't grown birch. I think the paper birch is at its limit for heat tolerance as the climate changes beyond the 21st century in Calgary', and it probably will not compete well with boxelder or ash or the elms in the future. I'm sure it could be grown if it has shaded soil- the north side of a house, behind a fence, etc. The scrubby Betula occidentalis is a common large shrub in the communities of plants along natural water bodies. Collecting and sowing seeds seems easy enough if there is disturbed soil along the margins of a creek. They need constant supply of moisture. I have not cared for a sapling of birch.

Elm

Elms are not native to Alberta, but they are found to the East and the South. They are river valley trees. The American elm is a lovely tree but it doesn't reproduce easily naturally in Calgary, probably because it isn't a great climate for the sensitive seedlings. The russian elm is hardier and can be found naturalized in Montana. It probably will become more common in the future. I do not plant elms. I do not plant oaks either. There is a species of oak native to places East of here. It is possible that in the distant past, Alberta was home to elms and oaks.

Happy sprouting. Wear an orange vest so people know you are doing important work, and I don't recommend digging with a full sized shovel within the city because of underground wires, and because it's super illegal.

#guerilla gardening #unlicensed forestry #deciduous trees

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