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Black Knot Disease

April 30, 2019 | Orchard | 4 Comments

black knot disease in an infected chokecherry branch.

We have a lot of chokecherries here on our acreage, which means we have a lot of Black Knot Disease. It looks an awful lot like a big chunk of dried up dog poop wrapped around the tree branches – pretty gross! Black knot is a fungal infection (Apiosporina morbosa ) that is endemic in prairie Canada, and it is particularly common in my region.

a branch with black knot disease, which looks like dog poop wrapped around the branch

The Government of Alberta has published an article with a handy list of affected trees – black knot targets trees and bushes in the Prunus species. Besides chokecherries, the list includes Nanking cherries, apricots, sour cherries, and plums. While some cultivars of fruit trees are bred for black knot resistance, it is best to remove it any time you see it anywhere on your property.

There are not a lot of ways to deal with black knot, except for pruning. You will need to prune well back from the infected lump – at least 6 inches, though more is better. Dispose of the infected branches by burning them or removing them from the property immediately – the fungus can continue to grow and spread spores for months, even on dead branches. Once you are done, disinfect your pruning shears with a solution of 10% bleach in water, to prevent spreading the disease to other trees the next time you do any pruning.

Now is a great time to tackle pruning out black knot in your affected trees, since the affected trees and branches are much easier to see before the trees leaf out; the recommendation is to do it as early in the spring as possible, which, for us, is whenever the snow melts enough for us to be able to get to the affected trees. We have acres of scrubby chokecherry and caragana brush, so obviously we’re never going to get rid of all of it here, but I like to cut back affected trees that are close to our current orchard areas, since black knot can affect so many of the types of fruit we have planted here.

a close up photo of a black knot infection

While it may be possible to save a tree that has become infected with black knot, it hits me as a losing battle. If you have infected trees, there is obviously a source sonewhere nearby, and it is likely that your susceptible tree will get re-infected at some point. Better to save on heartache, cut down the infected tree, and plant something that isn’t susceptible.

Of course, with our place being surrounded by scrubby brush full of infested chokecherries, I expect we’ll be battling black knot disease, but we try to keep our prunus fruit trees away from the most infected areas, and we remove black knot wherever we see it in the wild chokecherries. So far, it hasn’t been a huge issue, but it certainly has the potential to become a problem for us. Hopefully, we’ll be able to keep it out of our plums and cherries!

a chokecherry tree branch with a black knot fungal infection

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By Jess

Ordering Bare Root Fruit Trees in Canada

March 1, 2019 | Orchard | No Comments

a row of young fruit trees in a grassy area

Just a couple of days ago, it was -35 at our place…and it’s almost March! While the newest zone map insists we are zone 3a, polar vortexes beg to differ, and drop us down into the -40 (and colder) range, which is pretty solidly zone 2. Locals say that these temperatures are actually closer to ‘normal’ than the 6 or so winters before; however, the extended (month-long) cold snaps are an anomaly. Climate change is clearly messing with weather patterns, and extended cold snaps may well be part of our new normal.

I suspect that long stretches of cold are not as hard on fruit trees as the melt-and-freeze cycle of chinooks that we used to get in Alberta, but we lost several of our young trees last winter, when we experienced similar long stretches of deep freeze. We plant several fruit trees and bushes every year, in the hopes of having a lush orchard at some point. This year, there were a couple of things I really wanted, so I ordered them very early, as they had sold out the year before. However, with all this cold, I am looking at ordering a few more trees to fill in the gaps I expect we’ll see in the orchard, come spring.

There are actually a pretty good selection of fruit trees that are rated zone 2 and 3 – the main trees that grow here are apples, pears, and plums, and there is a reasonable assortment of varieties from each type. However, there are not many tree nurseries that are actually within reasonable driving distance, which means we’re often ordering bare root fruit trees from far away.

We normally order bare-root trees. Bare-root trees are trees that have been grown in fields (rather than in pots), then dug up, washed off, and shipped by mail. We’ve had excellent success with bare-root trees; we’ve only had a few that did not start leafing out within a few weeks of planting, which is a pretty good success rate, when you consider how many trees we’ve planted. Our trees don’t always make it through the winters, though, which is mostly our own fault – we tend to ‘push’ zones a bit, and try out varieties that may not be fully hardy in our area.

A newly planted bare root fruit tree that has not leafed out yet

Because we’re often ordering from far away, we’ve found there are a couple of things we really have to pay attention to.

A lot of the Canadian fruit tree nurseries that will ship trees (the majority, really) are in southern Ontario and Quebec. Most of them are at least zone 5, and a couple are as warm as zone 7. Nurseries generally strive to be accurate in their zone assessments, but a zone 5 or 6 nursery is not going to be able to conclusively say that any given tree will ‘make it’ in zone 2 or 3. Sometimes things are not quite as hardy as advertised, so there is an element of risk when you are ordering from a nursery several zones warmer than you.

The odd nursery really stretches credibility with their zone ratings, so if something seems too good to be true, like a peach or a sweet cherry that is rated hardy to zone 3…well, I recommend you put your wallet down and save your money, or maybe go buy a lottery ticket, instead.

The other issue that we occasionally come across is a perfectly hardy cultivar that is grafted on a rootstock that won’t take real prairie winter. We’ve found we really have to watch this with pears, as some of them are grafted on OhxF rootstocks, which are only supposed to be zone 4 hardy, or Quince A, which simply won’t take our winters at all.

We prefer full-sized Antonovka rootstock for our apple trees, as it seems to do well with both cold and drought, which are our big challenges. We’ve also got several apples on B118 rootstock that have survived at least a couple of winters, and seem to be thriving.

Our plums and apricots are generally grafted on Mustang rootstock, which handles prairie winter just fine. Last year, we ordered a couple of plums on Myrobalan, which is supposed to be fairly hardy, though I’ve never seen a zone rating; this winter will be a good test for them, as it has been very cold.

I do recommend ordering bare-root trees, overall. If you pay close attention to the rootstocks, and cross-reference zone ratings (especially for things that seem too good to be true), you can get access to a much wider variety of cultivars, and it is often considerably cheaper to order bare-root trees than to buy potted trees at the local big-box store.

I’ve created a big list of reputable Canadian bare-root fruit tree nurseries – check it out!

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By Jess

Protecting Fruit Trees From Deer and Rabbits

February 24, 2019 | Orchard | No Comments

A young fruit tree that has been damaged by deer browsing and rabbits chewing the bark

Our first year here at the acreage, we planted over a dozen fruit trees – apples, plums, pears, and some smaller fruit bushes like currants and hazelnuts. We were pretty excited to get going with this whole homesteading thing!

Winter that year was fairly mild, and we didn’t run into any issues with the new trees. The next winter, however, was long and cold, with tons of snow and huge drifts. The wildlife really suffered in the cold weather, and they came right up close to the house to chew on our poor little fruit trees. The rabbits stripped the bark off the trunks, and the deer just bit the branches right off!

The wildlife damaged the trees so badly that a couple of them died, and several more were seriously set back, which was a sad and expensive lesson for us. We needed to figure out how to keep the critters from decimating our orchard.

Young fruit tree damaged by rabbits chewing the bark off

Coincidentally, that spring, we were doing some fencing, to create a pen for our buck goats. Goats are real escape artists, so the fences needed to be particularly tight. We had purchased rolls of tall wire mesh fencing, and, as they unrolled, we got the idea to fence the wildlife out of the trees, using the leftover bits of goat fence.

Basically, we just used roll ends to create circles of fence around each individual tree. Each fall before it snows, we bring out the ‘tree cages’, and set them up around vulnerable trees in the orchard. If they are tippy, we peg them to the ground using tent pegs, or use step-in electric fencing posts to hold up the fence, which adds a lot of stability; we don’t want the wire falling on the tender trees and bending or breaking them. Once it has snowed a couple of times, the snow does a good job of keeping the cages firmly in place.

A fruit tree surrounded by fencing to protect it from deer and rabbit damage

The fencing we use has very small mesh – 2×4 inches – and keeps the rabbits out. It is also quite tall – 5 feet – so it protects the trees from hungry deer, as well. Rabbits are terrible for chewing through the bark all the way around young trees – this is called girdling, and can kill the tree. We sometimes have problems with mice gnawing the tree trunks, as well, so we also put spiral plastic trunk guards on the youngest trees, to keep them from being girdled by smaller rodents.

In a few years, once the trees are well established and taller than deer can kill by browsing, we don’t bother with the cages anymore, though we do still put the spiral guards on the trees with thinner trunks.

In the spring, we remove the fencing, and store it away in a shed.

We haven’t lost a tree to wildlife since we started this, though our yard does look a little funny in the winter!

A winter scene showing caged trees and a small red barn.

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By Jess