Identifying root rot
Hello, I'm trying to figure out if we might have a problem with root rot fungus affecting a chaste tree. We have two of these trees, on either side of a driveway, both planted about 4 years ago and healthy since. Last year they both had full growths of large leaves, but this year one seems sickly. Leaves are only appearing at the tops of branches and they are small. You can see the overall difference in the first pic. I also noticed, when taking these, what might be cankers? The concerning part is that where the sickly tree is we also have a whole bunch of hyssop and other plants, and about a month ago a patch of hyssop just suddenly wilted and died. I mean sudden--like within a day. Other hyssop and plants around there still seem fine, but the chaste tree is within a few feet of the hyssop that died. The area is on the upside of a slight slope, not particularly wet, but there is a downspout pipe that empties into the space. That led us to wonder if the sudden death of the hyssop might be root rot, and now worried that it could be affecting the tree (or migrated from the tree to the hyssop). So I'm wondering if we can adequately diagnose/treat this ourselves, or should get an expert. My research has shown some methods to assess the tree or the roots, and say that it's possible to treat the fungus if it can be identified. We'd hate to lose the chaste tree that has been doing well! Or the whole idea could be wrong and this is just normal variation. What do you think? Thank you!
Montgomery County Maryland
Our suspicion is that there is too much water in the area because of the downspout pipe. As you know, we have had a large amount of rain lately. So it is true that this is a root problem but not in the sense of what you are thinking. This is not a treatable issue. This tree may always struggle or even die because of the site. So the other plants including the hyssop were subject to the same amount of water and therefore died. Due to the water discharge in this area, it probably is not feasible to treat both sides of the driveway equally as far as choosing plants. A thought is to choose plants that would do well in a rain garden. They can take handle wet to dry conditions. Look at page 39 of the following publication for some ideas, http://extension.umd.edu/sites/extension.umd.edu/files/_docs/articles/Rain_Gardens_Across_MD.pdf
Thank you for the quick reply! If the problem is simply too much water we can extend the downspout outlet to bypass the area with the tree. But I may have overstated the situation. Even as it is, the water is not trapped in that area, it's simply that a lot of water might come through the area during a big storm. We do have areas that are low and very wet, and have been adjusting the plants to accommodate (including a "rain garden" type of installation in another part of the yard). In this case, though, I'm suspicious of something more nasty because the tree has done so well in that spot for almost four years. Plus, other hyssop, butterfly weed, lavender, lamb's ear, etc. are all still doing well around the tree (see attached photos). You don't think the pix indicate any health problem with the tree other than too much water? I hope you're right!
Chaste trees like a well-drained soil in full sun. Is it getting that?
(See here: http://www.mortonarb.org/trees-plants/tree-plant-descriptions/chaste-tree) We would definitely let the drain by-pass that area.
In your third photo it looks like the woody branches have had damage, and in some areas it has tried to heal over, but was unable to completely. Do you know what caused that? Breakage? Pruning? That could cause stress, or internal rot if water can enter those old wounds. Is there something that is scratching or knawing on the bark? We can't tell from your photos.
Often these plants are grown as shrubs and can come back from the ground if the roots are healthy enough. In the north, they do this every year.
Hello again, Yes, I would say that the sun situation is fine (in fact its companion on the other side of the driveway is partly shaded by larger trees and is doing well). The location is at the top of a shallow slope but, as you know, the soil around here is mainly clay so I guess that might inhibit the best drainage. As for damage, I've only ever seen squirrels climbing (not scratching), and we have done some pruning. Trying to follow recommended practice but new at this. At different times two of the largest side limbs seemed to be drooping badly, especially with heavy snow, and I was afraid they would break so I supported them with large pieces of insulated wire. They now seem pretty solid but the tree tended to produce a lot of growth out at the ends of the limbs so it gets heavy. For what it's worth, this is a Vitex Agnus "Shoal's Creek" variety, intended for 7-8ft tall, put in with a 1.5" caliper trunk in Fall of 2014. The first year it shot up tons of suckers and weird verticals which we didn't trim initially because we were unsure. Since then we've tried to shape it better. Since it has done well for 3+ years I wouldn't even have thought to be concerned except that the leaf growth is poorer than it's companion. Last summer it was great. As I recall, leading into this Spring it was super dry, then we finally got a ton of rain. Could just heavy rain really cause this much reaction, without some disease involved?
The common Vitex (negundo) is hardy to zone 6 (i.e. the roots survive but it may die back to the ground in harsh winters.) Vitex agnus is less hardy. It's possible that your vitex has some winter damage.
Also, Vitex is a vase-shaped multi-trunked small tree/shrub. Pruning it to a single trunk is going to stress it.
We also see what appears to be significant problems with the bark at the base of the trunk. The cracking suggests rot or infection underneath.
We cannot say with certainty exactly what is affecting your tree. Nothing is obvious. If there is infection in the root or trunk, it's very unlikely anything can save the tree. You could have a certified arborist from a tree service company look at it (usually no charge except for work done), but it would probably be more efficient to replace the vitex. You can find certified arborists by following the prompts on the International Society of Arboriculture website: www.treesaregood.org