Is this tree’s peculiar leaf and canopy a result of possible lawn herbicides or just late freezes

Asked June 19, 2020, 2:38 PM EDT

There’s a ~40’ high linden in my HOA’s common area in Longmont that has one side of its canopy with either no leaves, or leaves with peculiar cupping and chlorosis. The other half of the canopy looks pretty normal, but some of dark green leaves are starting to cup and its blossom calyxes aren’t normal (see photo 1). Various other large shade trees in our 90 home community were clearly affected by the various hot sunny to deep freeze events we had Oct- April here (4-5?) but most have been able to send out a second round of leaf buds and now have almost normal canopy. I suspect chemical damage to root system especially on bare side, as the only time I’ve ever seen just 1/2 or part of a tree canopy damaged like this was on an autumn purple ash tree that straddled a property line, surrounded by a shared very large rock mulch area. One property owner used a sprayed pre-emergent on the surrounding rock mulch area in very early spring, the other property owner did not. When the tree leafed out, the canopy above the treated rock mulch was almost bare of leaves. It was an otherwise very healthy tree, and over the summer the bare side recovered. Can you diagnose what’s likely going on with the linden from my photos? It’s in turf that gets a lot of water ( 3xwk for past 6 wks, perhaps too much water) and 1-2 applications of a commercial pelleted fertilizer/broadleaf, and the dry creek area may have been treated with pre-emergents (it’s been suspiciously clear of weeds for a 20 year old feature that is filled with dirt and debris under the rocks, never hand weeded). The damaged side of the tree next to the dry creek faces south; the tree was healthy last summer. Photo #1 shows side by side leaf branches—cupped & chlorotic vs “healthy (-ier), #2 is view of tree & site, #3 is closeup of lower canopy damaged leaves. Is this weather related or chemicals? What’s the prognosis? Thanks!

Boulder County Colorado

7 Responses

Thank you for the photographs. In the third photo do you seen anything unusual that is not in the first photo? I don't have the magnification to be certain if, my eye is seeing an anomaly.

Have you seen any pests or disease in this tree? Lindens are susceptible to

  • verticillium wilt - fungus, infects branches and spreads to leaves
  • cankers - open wound -allows insect/ fungi, creates swollen woody bulges
  • sooty mold - sweet sticky substance excreted by scale insects
  • powdery mildew - airborne disease - white growth on surface of leaves
  • black mold - aphids
  • leaf spot - brown - black lesions on the leaves
  • insects
    • aphids
    • fall web worms
    • japanese beetle
    • lace bug
    • ambrosia beetle
    • Linden borer
    • gypsy moth causes damage to the foliage
  • Wood decay
  • White Rot (cool and humid weather)
  • Anthracnose (winter & rainy season)
In the absence of any pest or disease suggestion would be to measure the amount of irrigation. Lindens thrive in moist but not wet soil
Above is the link to Fact Sheet 7-199. Look for paragraph "amount". This will tell you how to accurately measure the amount of
irrigation the Linden receives.
Determining chemical damage is above my pay grade! You may be referred to an expert with that specific expertise if, all other factors can be ruled out.

If, none of the suggestions fit then I would suggest that your tree is suffering from
the late April cold snap.

In the first photo, I’m showing a branch from the heathy side of the tree (bottom, green) next to a branch from the almost leafless side of the tree where the leaves are distorted, chlorotic and weak looking (top branch). Photo 3 is a closeup of the top branch that doesn’t look ok. There are many lindon trees close to this one, getting approximately the same amount of water. There are many more around this 90 home neighborhood, but none of the others looks like this, nor did any of the, suffer from the April freeze. I’m a CO Master gardener too; please kick my question up the ladder. Thanks!

Also, no pests or fungal diseases that I can see on the affected lindon. Here’s another picture showing the half and half (leaves on one half, almost no leaves on the other half) perhaps with better lighting.


The affected tree has a large maple tree directly behind it in my second photo of the whole tree. The linden is much shorter than the maple but is not shaded by it except for an hour or two very late in the afternoon.

Just to add my 2 cents here.... :-)
I noticed a crab apple tree out on my walk with 1/2 the tree looking awful and the other half doing fine. Upon closer inspection i saw the bad 1/2 had obvious oozing from the bark...bad sign of probable infection. Does your Linden tree have differences in bark on the sides as well?
I can also see how to "kick this up the chain" to the Diagnostics team.
thanks, Louise

Hi again,
Thats an interesting observation about the crab apple. I’ve seen that bark condition with really bad fire blight, which also kills branches and leaves on a lot of apples and related trees, gets to trunk if totally not treated and pruned. I’ve even seen fire blight take out whole cotoneaster shrubs, a new one for me! Hawthorns too. Cotoneaster was diagnosed by the Diagnostic team at Ext. HQ in Longmont, from actual samples of damaged branches. We get to learn so much as MG’s!
Ill check the the trunk of my problem lindon tree and thanks! I’ll get back to you tomorrow about bark.