Hawthorn pruning and growths - Ask Extension
This Hawthorn came from the arborday foundation and has been doing quite nicely.
The ones in familiar with have a nice tree canopy, but this one has ...
Knowledgebase
Hawthorn pruning and growths #876935
Asked July 12, 2024, 9:23 AM EDT
This Hawthorn came from the arborday foundation and has been doing quite nicely.
The ones in familiar with have a nice tree canopy, but this one has quite a lot of lower branches making it look more shrub like.
1.) How should I prune it for the health of the tree and should I remove the lower branches to train it into the tree it should be - or should I leave it to be more of a shrub?
2.) You'll notice in the photos these orange growths that could be natural to the tree, and I'm not familiar with it, or it had some sort of disease. Could you advise as to which it is and how to proceed?
Thank you as always! Happy Friday! Yay for rain!
Jon
Harford County Maryland
Expert Response
Hello Jon,
Based on its current state, the Hawthorn may need lots of pruning work to develop a more standard-looking and healthier (in terms of dealing with any over-crowded or crossing branches) canopy. The process make take a few years, since pruning should not remove more than about a quarter of a tree's growth any given year. Many small-maturing tree species can indeed look pretty shrubby when young, or blur the lines between a shrub and small tree when mature, so by itself, this rangy growth is not necessarily a problem as long as basic canopy maintenance is performed to keep branches in good condition. Still, Hawthorn is a diverse genus (Crataegus), with many species, some of which will mature more tree-like than others. Do you know the species of the plant they delivered? We can then ascertain what its typical mature size and shape would be -- more shrubby or more tree-like.
Presuming for the moment we need to aim for a tree-like shape, over time, suckers arising from the trunk base or roots can be removed unless you want any to mature into additional trunks. Otherwise, branches attached low on the trunk should not be removed too quickly, as they help young trees increase their caliper (trunk diameter) faster than if they are removed. This aids in trunk stability, as does being allowed to sway in the wind a bit, so if the stake pictured nearby is intended to tie the tree up, either bypass it entirely or make sure the tie used is loose enough to allow the trunks to sway several inches in the wind any direction. (Also make sure any tie used does not abrade or cut into the bark.)
Crossing branches should be dealt with as they are discovered, though winter is the best time to prune so the structure of the canopy branching can be more clearly seen. Branches attached to the trunk at a wider angle (closer to 90 degrees) will have a sturdier attachment point then one attached at a narrower angle (say, 45 degrees), so when given the choice between two branches that are too close to each other, generally you'd remove the one that has a narrower "crotch" angle. That said, to some degree, the predisposition of branch attachment angles to the trunk is genetic and inherent to tree type. (Elm trees, for example, tend to naturally develop narrow crotch angles.)
UMD Extension doesn't have a single guide to young tree pruning, but we can link to a few other Extension and reputable resources you can explore to get an idea of what issues to address (there will be lots of overlap between them). Some may focus more on canopy trees than smaller flowering trees, or setting like street tree care, but otherwise general principles still apply.
Rust infections can be very common and can affect Hawthorns and their relatives like Serviceberry, Apple, Crabapple, Quince, and Pear. These fungi are unusual in that they require two unrelated plants to move between at different times of the year to complete their life cycle. The other host, which is a juniper, is not practical to either treat or remove from the landscape (especially how abundant and widespread our native junipers are), so infection risk cannot be eliminated, though plant disease spread and severity can be impacted by weather patterns any given year.
While fungicide treatments might suppress infection before it starts, if used preventatively starting in early to mid-spring and applications continue for an 8-10 week window when airborne spores are moving from infected junipers onto Hawthorn and other hosts, their use is generally not recommended. There are several reasons for this, including that they would probably need to be applied during bloom, which may harm pollinators, and because they don't always work, and wet weather can interrupt a spray schedule and give spores a chance to cause infection. Fungicides are not curative, so will not have any impact on existing disease.
For now, since the orange spores are not re-infecting the Hawthorn but are being disseminated on the wind to junipers, and because twig infections will eventually kill those twigs beyond the point of where the spores are emanating, prune off the affected twigs showing symptoms of rust disease.
Today's rain is indeed welcome, if woefully insufficient to catch us up much during this ongoing drought. Make sure any new plantings (plus any species not very drought-tolerant) are being regularly monitored for watering needs. We noticed a wilting branch on the Rhododendron in the background of the photo, which is collapsing due to branch dieback and not drought alone, and infections like Botryosphaeria fungal canker can cause such damage after a plant has first been stressed by drought or other environmental conditions.
Miri
Based on its current state, the Hawthorn may need lots of pruning work to develop a more standard-looking and healthier (in terms of dealing with any over-crowded or crossing branches) canopy. The process make take a few years, since pruning should not remove more than about a quarter of a tree's growth any given year. Many small-maturing tree species can indeed look pretty shrubby when young, or blur the lines between a shrub and small tree when mature, so by itself, this rangy growth is not necessarily a problem as long as basic canopy maintenance is performed to keep branches in good condition. Still, Hawthorn is a diverse genus (Crataegus), with many species, some of which will mature more tree-like than others. Do you know the species of the plant they delivered? We can then ascertain what its typical mature size and shape would be -- more shrubby or more tree-like.
Presuming for the moment we need to aim for a tree-like shape, over time, suckers arising from the trunk base or roots can be removed unless you want any to mature into additional trunks. Otherwise, branches attached low on the trunk should not be removed too quickly, as they help young trees increase their caliper (trunk diameter) faster than if they are removed. This aids in trunk stability, as does being allowed to sway in the wind a bit, so if the stake pictured nearby is intended to tie the tree up, either bypass it entirely or make sure the tie used is loose enough to allow the trunks to sway several inches in the wind any direction. (Also make sure any tie used does not abrade or cut into the bark.)
Crossing branches should be dealt with as they are discovered, though winter is the best time to prune so the structure of the canopy branching can be more clearly seen. Branches attached to the trunk at a wider angle (closer to 90 degrees) will have a sturdier attachment point then one attached at a narrower angle (say, 45 degrees), so when given the choice between two branches that are too close to each other, generally you'd remove the one that has a narrower "crotch" angle. That said, to some degree, the predisposition of branch attachment angles to the trunk is genetic and inherent to tree type. (Elm trees, for example, tend to naturally develop narrow crotch angles.)
UMD Extension doesn't have a single guide to young tree pruning, but we can link to a few other Extension and reputable resources you can explore to get an idea of what issues to address (there will be lots of overlap between them). Some may focus more on canopy trees than smaller flowering trees, or setting like street tree care, but otherwise general principles still apply.
- Developing a Preventative Pruning Program: Young Trees - University of Florida Extension
- Pruning Young Trees - International Society of Arboriculture (the organization that certifies arborists)
- How Do I Care For My Tree? -- Texas A&M Forest Service
- Pruning Young Trees -- Iowa State Extension
Rust infections can be very common and can affect Hawthorns and their relatives like Serviceberry, Apple, Crabapple, Quince, and Pear. These fungi are unusual in that they require two unrelated plants to move between at different times of the year to complete their life cycle. The other host, which is a juniper, is not practical to either treat or remove from the landscape (especially how abundant and widespread our native junipers are), so infection risk cannot be eliminated, though plant disease spread and severity can be impacted by weather patterns any given year.
While fungicide treatments might suppress infection before it starts, if used preventatively starting in early to mid-spring and applications continue for an 8-10 week window when airborne spores are moving from infected junipers onto Hawthorn and other hosts, their use is generally not recommended. There are several reasons for this, including that they would probably need to be applied during bloom, which may harm pollinators, and because they don't always work, and wet weather can interrupt a spray schedule and give spores a chance to cause infection. Fungicides are not curative, so will not have any impact on existing disease.
For now, since the orange spores are not re-infecting the Hawthorn but are being disseminated on the wind to junipers, and because twig infections will eventually kill those twigs beyond the point of where the spores are emanating, prune off the affected twigs showing symptoms of rust disease.
Today's rain is indeed welcome, if woefully insufficient to catch us up much during this ongoing drought. Make sure any new plantings (plus any species not very drought-tolerant) are being regularly monitored for watering needs. We noticed a wilting branch on the Rhododendron in the background of the photo, which is collapsing due to branch dieback and not drought alone, and infections like Botryosphaeria fungal canker can cause such damage after a plant has first been stressed by drought or other environmental conditions.
Miri
