Japanese Lilac Tree flowering problem and curled leaves

Question: We purchased a Japanese Lilac Tree from a large local garden company fall 2021. Last year 2022 we had no flowers and some of the leaves looked a little curled. I noticed that small gnats liked to fly around the tree, and some branch tips died off. I sprayed with Garden Tech Sevin Insect Killer, and it appeared to help the gnat problem. I wrapped the very bottom of tree for the winter, and this year the tree looked good as spring began. Unfortunately some more branch tips appeared bare, the gnats came back, more leaves curled up as the season progressed, and we only had one blossom bloom this year. This part of Hennepin County has a lot of sand, so I have kept the tree watered well (especially during this current drought period), but have not fertilized, nor have I sprayed for gnats this year. The tree is planted in a garden area, which has a bark mulch cover with many shrubs and Hostas, which are all doing very well. The photos show the tree with a lone blossom, some of the branch tips which have withered, and a sample of some of the curled leaves.  Any thoughts or suggestions?

responder: Evelyn Locke, MN Master Gardener, Tree Care Advisor, Volunteer    Replied June 25, 2023, 9:57 AM EDT
response: I highly recommend purchasing an inexpensive water meter. These are sold at garden nurseries and on amazon. Because the twig die off is at the top of the tree my thought is it actually needs more water on the very hot days. It could also be recovering from transplantation and hasn't had time to develop a deep root system for droughty weather. Temps over 90 are brutal for plants, the wide swings from week to week also are very stressful. Trees don't have enough time to adapt to very hot temps before it is cool again halting the adaptation to drought.  I recommend a water meter because over watering will cause leaf curl just as under watering will. On very hot days your tree may need water twice but doing so may make overwatering more likely. Lack of a lot of flowers also suggests it putting its energy into developing a root system. I would not expect many flowers for 3-5 years. You were wise not to fertilize and are wise  to pay attention to its water needs. It is a handsome tree and your bed is very attractive. Full sun is also necessary for flowering, because the hostas look so good is the trees location part shade? Part shade will impact flowering.

responder: The Question Asker Replied June 26, 2023, 3:10 PM EDT
response: Evelyn: Thanks for the quick response. It sounds like I'm pretty much doing what I should be doing. I'll purchase a water meter to help monitor the watering needs. The tree is in full sunlight, so that's not a problem. The Hostas were planted with the thought that the tree would eventually offer some shade. So far, the Hostas are thriving without much shade help, We have a lot of Hostas in various areas of our yard, full sun, partial sun, full shade. They grow everywhere! My original thought was that the gnats were a problem with the leaves. If that's not an issue, I'll just leave them alone. I'll be a little more patient with my desire for more flower blossoms. Thanks again,Dwain  On Sun, 25 Jun, 2023 at 8:57 AM, Ask Extension <<personal data hidden>> wrote: To: dwain erickson

responder: Evelyn Locke, MN Master Gardener, Tree Care Advisor, Volunteer    Replied June 26, 2023, 8:30 PM EDT
response: I don’t think gnats are a problem for lilacs. Gnats that are outside are midges and bite mammals. https://extension.entm.purdue.edu/publichealth/insects/bitingmidge.html So your lilac is safe from them. Enjoy the cooler weather.