Tree Tips

JULY 2025

This month's program will feature JT discussing and demonstrating appropriate activities for this time of year. Topics such as watering, shading, fertilizing, cutting back, pinching, defoliating, and wiring will be covered. Some audience participation will be needed, so be ready. It should be a fun evening.

Tree Care Strategies

The Summer Solstice was June 20—the longest day of the year and the height of the growing season. It’s a great time to cut back and/or defoliate those trees that are healthy and can handle it. I’m currently cutting back all my healthy oaks. I expect bud back and new growth to regenerate within a few weeks.

Now is a good time to think about which trees you want to show for our October show. Select several that have good potential. Starting now gives you the time to plan your work strategy.

Use every opportunity to improve your trees. Every time you touch or water your trees, ask yourself what you can do to make them better. A little wiring or pruning to improve the shape at the right time will work wonders. Ask knowledgeable members of the club for help if you can’t get your trees past a certain point. This will help you reach the stage where you will want to show them and give you great satisfaction with the progress you have made.

Managing Heat Stress

Like last year, we’re getting a stretch of hot weather. Many of your trees may be showing stress during this prolonged heat spell. Allowing your trees to go slightly limp may be recoverable, but it damages their ability to grow vigorously. It takes energy and time to recover, which can be time lost in training the branches as you want them, making them more susceptible to weakness in the future. So, don’t let your trees dry out. I’ve had several trees get sunburn or windburn recently, so I’ve felt the pain. Watering is a must and sometimes necessary several times a day—early, noon, and around 5 PM, if needed.

If your deciduous leaves dry up on an extremely hot day, don't panic. The tree's safety system sloughs off flowers, fruit, and leaves when it is distressed to protect the core life zone in the tree, namely the vascular system. You may lose some of the ramification in the branches, but you should be able to build your tree up again. Many times, the tree will sprout new buds as if a new season were beginning. Keep the soil moist, but don't overwater, as you may drown the roots, which have been weakened. Again, shading the soil with shade cloth or sphagnum moss covering should make this problem very rare.

Consider using overhead shade cloth (30%-50%) to protect your trees. Also, placing some shade cloth on the surface of the soil, extending out farther than the edge of the pot, can help keep the pots cooler in direct sun. I've also placed some sphagnum moss on the surface of the pot to keep moisture available to those surface roots we try so hard to nurture. Water only those trees that need it. You’ll notice that not all trees dry out uniformly. When you do water, make sure that the water penetrates completely through the soil. If a crust has formed on the surface, water may just flow off the top and down the sides without penetrating the root mass. Use a chopstick to agitate and break up the soil. Adding a little dishwashing detergent acts as a surfactant and helps the water penetrate the surface soil area. Don’t water the foliage in the evening, as mildew can form in the warm conditions at this time of year. Early morning is the best time for thorough watering. Watering in the evening can also cool down the soil when it could benefit from steady warmth.

Maintenance and Care Tips

If you haven’t done it already, de-candle your black pines. Finish decandling your standard-sized and large black pines, and start on your shohin if you have any. The longer you wait, within reason, the shorter the new candles and needles on your tree will be. Wait too long, and if we have a cold, overcast summer (not this year!), you won’t get enough growth on the new candles. It's always a balancing act. One caution: Don’t decandle trees or specific branches on trees that are weak, or on branch tips that need to be lengthened or fattened in your design.

Cut all your candles at the base, leaving more needles on the weaker branches and fewer on the strong branches to equalize the strength. Pull the fertilizer off the decandled trees until the new candles are pushing toward the middle of August.

Turn your trees regularly to keep growth even. If all of your bonsai look like windswept style trees, it's probably because you haven’t turned them. Foliage grows toward the sun. You can defoliate or leaf-prune (cutting leaves partially off deciduous trees) except for beech. Usually, pulling half the leaves is sufficient to encourage a new crop of leaves. This can be accomplished by cutting off the large leaves, every other leaf, the outside leaves, or a select area of leaves on the tree. There are many ways to do it depending on your intended outcome. Be sure they are healthy and vigorous before trying this technique. It is usually best to remove most of the leaves on the top and outside of strong branches while leaving more of the inner leaves to strengthen the weaker areas. Remember: pinching and defoliating, while helping to ramify, can weaken a strong tree. Don't do it to a weak tree, and don’t do it every year.

Keep pinching new growth on trees you are refining. When you see the growth spurts slow down, as they probably will toward the end of this month or in August, let the growth go and return energy to the tree. We can trim it back prior to the show. The trees will naturally go through another growth season in the early fall.

For those trees in development, where you need movement and length for styling or to strengthen or thicken a branch, let the shoots grow after first wiring them.

You can still air layer your trees, but please don’t defoliate them at the same time. The more foliage load on the tree, the faster the roots will develop. This is also a good time to take cuttings from hardened shoots.

Pest and Fungal Management

Spider mites, aphids, and scale suck the life out of your trees. Look for them on the tree or tap a branch over white paper, then smear whatever drops onto it. If you get a red smear, guess what? Spider mites most likely. Try spraying them off with a hose and/or using targeted treatments! Try Sultan or Florimite for the best results. For aphids and scale, apply Merit granules to the soil surface or spray soluble Merit on the foliage and branches. Spray from underneath and on top. Use a spreader, like a few drops of dishwashing detergent, to help it stick to the trunk, branches, and foliage.

The same goes for fungal issues. Fungicides like Daconil or 3336 can help with tip blight problems, or Benlate®, which can control mildew that breeds on the foliage when you have a combination of warm summer evenings and moisture (from watering too late in the day), as well as other fungal problems. Be sure to leave any oil treatment on for an hour, then wash it off completely. You don’t want to sauté your foliage in the sun. 🌳