Rain and Wind Dynamics
Wind forces act upon trees in unique ways depending on the distribution of foliage throughout the entire tree crown as well as along individual branches. Thinning cuts as well as reduction cuts help reduce the drag (wind resistance) on the tree canopy and lower the height of the pressure center to larger diameter wood. To prepare your trees for summer winds, a combination of both types of pruning is needed but especially reduction pruning. Research has shown that reduction pruning to alleviate end weight is the best type of pruning to decrease risk of tree and branch failure.
A big mistake is to over-thin trees with the idea that this makes them safer. There is an unacceptable pruning technique called Lion’s Tailing that removes an excessive number of smaller branches from a tree’s interior at the neglect of the outer third of the crown. You’ve probably seen these sorry, stripped-out specimens on your street. The wind blows through their lower crown but is concentrated now in the lion tails of heavy foliage that flag in the wind and often break. Properly thinned branches have an even distribution of foliage along the entire length of the branch. Consequently the force of the wind is now evenly distributed along the length of the branch, transferring that force to the base of the branch where the diameter is greater and it can better support the branch movement.
Tips to prepare your trees for summer storms:
- Plant trees in groups. They buffer the wind from their neighbor trees.
- Turn off your water! Excessive irrigation prior to a wind event can lead to entire tree failure. So turn off your watering system when a major monsoon storm is coming.
- Don’t Lion Tail your trees.
- Concentrate pruning in the outer third of the canopy using primarily reduction pruning techniques. Proper reduction pruning requires special skill to avoid making heading or stub cuts. If your trees are large or have excessive end weight, consider hiring a Certified Arborist to help out.
If you prune your own trees, consider attending one of my upcoming pruning classes. I will be teaching a class at the Desert Botanical Garden on June 22nd. Click here for more information or to register.
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Staking and Guying
After you have selected a great tree, it may be necessary to stake it temporarily until it gets established. Here are some tips on tree staking and guying to help prepare your trees for that first summer wind storm.
After planting, only stake or guy your tree if necessary. The goal is to train the tree to be on its own, not to prevent it from moving. A staking system should serve only as a failsafe.
If the tree needs to be staked, suspend it between the stakes firmly enough to prevent it from falling over but loose enough to allow it to move slightly in the wind.
Use a soft material such as nylon webbing to tie the tree to the stakes.
If the tree has a stake tied directly to the trunk, it should be removed at the time of planting. This “travel stake” is only intended to get the tree to its final destination and can cause damage to the trunk if not removed.
Finally, be sure to monitor the stakes regularly and remove them as soon as the tree roots are anchored in the surrounding native soil, usually within the first year after planting.
Next up: Prepare Your Tree for Summer Part 3 - Irrigation
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Tree Selection and Planting
Trees are one of our most valuable assets. They provide shade, energy savings, wildlife habitat, aesthetic beauty and increased property value to our homes, businesses and communities. Here are some tips on tree selection and planting to help prepare your trees for summer.
- Start by buying good quality plant stock, preferably trees with low growth along the main trunk. These trees are less susceptible to sunburn. They are also more stable due to better trunk taper. They may not even need staking or guying. Avoid lollipop trees like the two trees in the foreground of the photo. The trees behind them would be a better purchase.
- Consider buying native or desert-adapted trees when possible. They normally have a lower profile in the landscape and are less susceptible to wind damage. They also are better adapted to our local soil conditions, native pests and pathogens and other stresses common to the low desert.
- Plant trees in groups when possible. They buffer the sun and wind from their neighbor trees.
- Minimize pruning after planting. New trees need as much foliage as possible to create the energy reserves for healthy future growth.Avoid removing watersprouts. These are the small shoots growing along the lower trunk and main branches. Watersprouts help their parent branches develop taper needed to support increasing end weight as trees mature. They also shade interior branches and prevent sunburn.
Next up: Prepare Your Tree for Summer Part 2 – Staking and Guying
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Pruning out dead leaves and branches at the right time and in the right way is critical to plan t health. Here are some guidelines for getting your frost-damaged plants back on track.
When to remove frost-damaged foliage
The best time to remove frost-damaged foliage is after February 15th, the average last day of frost in the Phoenix area. That date can vary slightly for other cities. As February 15th approaches, watch the weather forecast for late freeze warnings. If the forecast is too cold, wait until temperatures rise. Try to finish pruning no later than mid-March so juvenile growth can get established before hot temperatures arrive.
How to remove frost-damaged foliage
When you are ready to prune, start by doing a scratch test with a small knife or your fingernail on the smallest twigs and branches to determine the extent of the frost damage. The cambium just below the bark should reveal a bright green color on healthy wood. If the scratch test reveals brown or black tissue, the wood is dead. Continue your scratch test on larger wood until you find the
transition zone where green wood starts. You can prune just below that point.
If you wait until new growth emerges to find out the extent of frost damage, it is harder to remove the dead foliage without damaging the new juvenile growth. It is especially difficult to extricate hard dead branches on trees like citrus that have especially tender, weakly attached new shoots. By removing dead branches earlier, full sunlight can reach the plant interior and new foliage will emerge without interference. Earlier pruning also gives new foliage maximum time to get established and harden off before hot temperatures arrive.
Plant response and restorative pruning
All trees and shrubs respond differently to frost damage. Some are frost-hardy and don’t suffer damage. Others have minor tip die-back. Some lose small branches, some major limbs. Some die right to the ground but their root systems are still alive.
Regardless of how much damage occurs above ground, undamaged root systems can remain healthy and are ready to produce new foliage. To equalize the normal root to shoot ratio, a riot of new growth emerges. Clumps of vigorous, upright and disorganized shoots grow from cut branch ends as well as along stems and even trunk wood. These random and unattractive branches lack normal density and can be a challenge to prune. But these clumps of foliage help protect plants from too much sun and are a key to survival. They replace essential photosynthetic leaf surface needed for production of sugars and starches, the energy resources plants need for growth, reproduction and defense.
So the goal at first is plant recovery. Restoration of plant growth habit is important but should wait until foliage is full and plant energy reserves are restored. For the first few months, the best practice is to allow plants to go wild. For the first six months to a year, limit pruning to minor shaping of exterior branches. After that, begin to thin out the crowded branches that emerged from cut branch ends. When restoring these clusters, leave branches with the strongest attachment to their host stem and that grow in a favorable direction.
It may take more than one season but with patience, restoration pruning can return plants to their beautiful pre-frost condition.
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