Tree Tips

August 2025

I love this time of year. June through mid-August is one of the busiest, most productive, and impactful times for working on trees. Yes, it is a little hot and unpleasant out in the sun, but it’s the core growing time for the trees.

Pruning and Maintenance

I have been cutting back, thinning, and defoliating where needed, as well as wiring and shaping my trees, especially the deciduous and broadleaf evergreens, for the past couple of months. Now I have so many shoots that I need to pinch the new growth before it gets too long. Pinching also keeps the internodes (the distance between leaves) short and maintains the silhouette of the tree. Of course, I’m not transplanting at this point.

When working on trees that you will want to show this year (October 4th), remember that it takes a number of weeks for cutting back to produce new shoots, and a few more for the foliage to harden off. So, plan ahead for your trees to show their best.

Watering Tips

It’s not a good idea to water the foliage after dark, as a moist condition on the leaves can lead to mildew in the warm summer evenings, and it can damage later flowers and developing fruit. However, watering foliage early in the morning acts like dew. In fact, if you heavily mist your trees that are battling mites or other insects that prefer hot, dry, and cramped conditions, you can wash and blow them off without using chemical treatment. I had some spider mite problems, and this has really helped. Give the sun and wind a chance to evaporate the surface moisture on the foliage before dusk. But you can still water the soil. I’m using a hose-end filter (Aqua Crest Garden Hose Filter) that works quite well and doesn’t leave water spots or calcium deposits on my pots. I got it online.

Rotating Your Trees

Rotate your trees. Trees are heliotropic—growing toward the sun. Get them looking good from every direction. The sun will be slowly getting lower in its trajectory through the sky, and rotating your trees can really make a difference.

Anyone who has a supply of sun moss, the kind that has a silvery look to it, should save it for top dressing. If you have seen any sources for moss, please pass it on. My sources are burned out.

Wire Management

Watch your wires. The explosive growth we have had since spring is expanding the branches rapidly, and the wires may be cutting into the bark. If the wires are small, unwrap them rather than just cutting them off. If the wires are larger, cut them off so as not to knock off freshly formed buds or shoots. Also, if in removing the tight wires you cut into or expose any cambium tissue, dab it with a little tree seal so it won’t dry up and form a weak part of the branch. When you later wire that branch with a weak spot and try to bend it, it could break right there, and you’ll be wondering why it happened.

Branches that you are developing from scratch must be wired and allowed to run and thicken to develop that first critical movement out from the trunk. Let it run until January/February, when you will cut back to start your next segment of the branch next year. On your refined trees for the show, you will notice that the growth usually slows down around now with the high temperatures. If you have been pinching throughout the season, you will probably notice that trees are not quite as quick to throw out vigorous new growth at this point. Let the growth elongate a little. We will have another growth spurt at the end of the month and will cut back before the show and do some show wiring to dial the tree in.

Pest and Disease Management

Watch out for signs of fungus damage. Bi-weekly, spray a fungicide in the evening, such as Cleary’s 3336, Daconil Ultra, or Zerotol for powdery mildew.

Honeydew, a shiny and sticky substance on leaves, is a sign of sucking insects in the aphid family. They can’t digest all the sugar they get from the plant and deposit it on the foliage. Many times, ants, which love the honeydew, will cultivate the aphids, whiteflies, and scales that produce it. You might also see a dirty substance called sooty mold, which grows on the honeydew. This readily washes off, but the insects may not, so use Merit® granules or spray with Malathion®, Diazinon®, an oil like Ultra Fine®, or Neem oil, or a systemic insecticide like Orthene® to control these problem insects. Scales are resistant due to their hard shells but can be picked off easily. Apply any spray in the evening to minimize damage to your trees. Wash off any oils thoroughly!

Look for splotchy or speckled foliage that might indicate spider mites. Hold a piece of white paper under a branch and tap the foliage above it. Rub your finger over whatever is on the paper. If it smears red (Yuk!), you probably have spider mites. Zap them with a jet spray of water to knock them off—do this every three days for a week. If you still see evidence (smears), spray every third day with Safer Soap. Lastly, try spraying a miticide on the underside of the foliage once, with a second application a week later. Remember that spider mites are arachnids, not insects. The foliage will not immediately turn around and look healthy—the mites suck the chlorophyll out! New growth, however, should be the regular color for the species you are treating.

Mildew and other fungi thrive in the warm, moist crevices of the tree when we mist or overspray the foliage. Daconil® is a good broad-spectrum fungicide that can be very effective for this problem.

Sun Exposure and Shade

Trees that are growing in the ground really benefit from having full exposure to the sun. Those in nursery containers need a little shade, especially late in the day, and those in bonsai pots need considerably more shade and, especially, surface protection for the soil. I have been using a top layer of shredded sphagnum moss/green moss to keep the soil surface moist, to promote surface roots, and to insulate the root system from the sun. Also, try using shade cloth (30-40%) overhead to cut the sun. Except for Bougainvillea, crepe myrtle, black pines, olives, and peppers, which seem to thrive in the sun, a little shade will help your trees during this stressful time. This will help them stay green and show their best.🌳