Tree Tips

Summer Solstice was June 21 — the longest day of the year and the height of the growing season. A great time to cut back and/or defoliate those trees that are healthy and can handle it. I’m cutting back all my healthy oaks as we speak. 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 September 30th show. Select several that have good potential. Starting now gives you the time to plan your work strategy.

Improving your trees

Use every opportunity to improve the 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 with your trees. Ask knowledgeable members of the club for help if you can’t get your trees past a certain point. This will get you to the point where you will want to show them, and give you great satisfaction with the progress you have made.

Turn your trees regularly to keep growth even. If all of your bonsai look like windswept style trees its probably because you haven’t turned them. Foliage grows toward the sun. You can defoliate or leaf-prune (cutting leaves off but leaving leaf stems on) deciduous trees except beech. Usually pulling half the leaves is sufficient to kick in a new crop. This will kick in a new set of leaves. This can be accomplished by cutting off the big leaves, every other leaf, the outside leaves or a select area of leaves of 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 this weaker area. Remember: pinching and defoliating, while helping to ramify, 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 it 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 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 on hardened shoots. 

Black Pines

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

Cut all your candles at the base and leave 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.

Pest Control

Spider mites, aphids, 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 on to it. If you get a red smear: guess what? Spider mites most likely. Try spraying them off with a hose and/or nuke ‘em! Try Sultan or Florimite for 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, a few drops of dishwashing detergent, to make it stick to the trunk and branches and foliage.

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

Fertilization

Keep feeding your trees as we outlined last month. Remember black pines need more than most other trees. Add more fertilizer in tea bags, or rapeseed cakes or cottonseed meal balls until next month. Or continue the water-soluble fertilizer as you have been doing. Osmocote is a slow release fertilizer that many of us use.

Watering

Check your trees a couple of times a day. Water only those trees that need it. When you do water, make sure that the water penetrates completely through the soil. If a crust has formed the water may just be flowing 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 to penetrate the surface soil area. Don’t water the leaves 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 tends to also cool down the soil when it could benefit from steady warmth.

Heat

High winds and bouts of heat will both dry and stress our trees, so be watchful. Day to day temperatures in the nineties points out how stressful it is for your trees. Allowing your trees to go slightly limp may be recoverable but it damages the tree’s ability to grow vigorously. It takes energy and time to recover: time lost to training the branches as you want them and makes them more susceptible to weakness in the future. So, don’t let your trees dry out. I had a number of trees get sunburn or windburn recently so I have felt the pain.

You might consider overhead shade cloth (30%-50%) to protect your trees. Also, 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 the direct sun. I have also put some sphagnum moss on the surface of the pot to keep moisture available to those surface roots we try so hard to nurture. 

If your deciduous leaves dry up on an extremely hot day, don't panic. The safety system of the tree 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 moist, but don't over water 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 indeed. 🌳