Tree Care

Summertime is Here

How to Help Your Trees Survive a Texas Summer

With temperatures soaring into the high 90's, lack of rainfall, and drying winds the daily question the Texas Trees Foundation receives is "How much do I need to water my new and existing trees?". As most residents here in the Metroplex know, we are faced with unique challenges not seen elsewhere in the state. Variations of soil types, weather conditions, terrain, and soil density all impact the way we plan our landscape.

The theme for the past three years is to water wisely and efficiently. Seventy percent of all water usage is in the landscape and much of that is lost to watering incorrectly with sprinkler systems.

The first two years after a tree is planted are crucial to the long term viability of all trees. How much water do your trees really need? How often should they be watered? Where should it be applied? The answers to these questions depend upon several important factors:

• Weather
• Plant Maturity and Type
• Root Depth
• Soil Type

Learning to water efficiently is easy. The Texas Trees Foundation has some basic guidelines to ensure the survival of newly planted and existing mature trees.

Watering Newly Planted Trees

Irrigate newly planted trees at the base, making sure to wet the entire root ball area. Water as needed, perhaps as often as twice a week during the first growing season. Young trees (up to two years after planting) should continue to be watered at the base, but the diameter of the zone of wetted soil should expand outward as the tree grows. Check the soil periodically to see if it is dry; allow the soil to dry out moderately between watering.

Watering Established Trees

Established trees should not be watered at the trunk. Instead, irrigate from the dripline (the edge of the tree's leaves) outward. The distance will depend upon the size of the tree and the nature of the tree's root system. As a basic rule of thumb, apply water in a circular band that's at least half as wide as the distance from the trunk to the dripline.

How Water Should Be Applied

The method used to water trees is as important and when the water is applied. Trees prefer to be watered slowly and deeply. Spray irrigation (sprinklers) is great for lawns but not for watering trees. Instead, use a bubbler, multiple drip emitters, or a hand-held hose to deliver water to the tree's root zone. Water the soil to one to two feet deep each time you water, and let the surface dry between waterings. The simplest method of watering is to turn your garden hose on a slow trickle and leave it in different zones within the dripline until each is soaked. Another simple method is to spiral a soaker hose out from the trunk. Maintain a 2-foot spacing between each successive coil, and be sure to extend the spiral out to the tips of the branches. Monitor how quickly the water soaks in, using a rod method - stick a thin metal rod into the ground soon after you irrigate. If you can penetrate 6-12 inches, you've probably provided adequate water. Remember, deep watering encourages deep rooting - and deep roots are the best way for a tree to survive a drought. Irrigate established trees once every two weeks during the growing season.

When Should I Water?

The best time to water is at night from 10 p.m. to 8 a.m. Watering at night allows effective use of applied water and less loss from evaporation, assuring more water moves into the soil and tree. Nighttime application hours, when dew is already present, does not expand the foliage-wetting period and consequently this watering cycle minimizes pest problems.

Irrigating Trees in Drought

During times of drought, a lack of moisture can cause trees to suffer from drought stress. One early sign of drought stress is wilted leaves. Another sign is leaf scorching; when the edges of leaves or the space between a leaf's veins turns brown. When a tree begins to exhibit signs of drought stress, irrigation must begin immediately to avoid long-term damage to the tree. Drought and high temperatures deliver a one-two punch to trees. Trees exhale moisture from their leaves in a process called transpiration. As temperatures climb, transpiration kicks into overdrive. During a drought, there isn't enough water in the soil to replenish the water lost. When this happens, trees adopt survival strategies that can stress and weaken them.

In times of drought and water restrictions, trees should be given priority over other landscape plants, including lawns. Why? It takes 20 years of growth for a newly planted tree to reach the size of an existing 20 year old tree. A turfgrass lawn left unwatered will naturally go dormant for the season and turn brown, but may turn green again after a rainfall or when irrigation is reintroduced. Even if reseeding or resodding is necessary, a lawn can often be re-established in a single season - a large tree cannot.

Remember: During a drought, the goal of irrigation should be sustaining the tree, not watering for maximum growth.

Other Considerations

Many plants, including turf grass, can compete within the soil root zone for available water. This water competition can be severe. Remove grass and excess plant competition from around any tree to decrease water stress. Use mulch to conserve water and prevent week competition. Mulch is any tree's best friend. Besides minimizing evaporation of soil moisture and limiting rainwater runoff, mulch also protects the tree from mower and weed trimmer damage. Wood chips, shredded bark, grass clippings can all be used for mulch. Cover the area with mulch about 3 to 4 inches deep, taking care to avoid the area next to the tree's trunk.

Proper Planting Techniques

How to Plant a Tree So It Lives

The level of care makes a difference in how trees will grow and develop. The goal of tree planting is to have a vigorous, healthy tree that lives to the limits of its natural longevity. Achieving this goal begins with careful tree selection. Next, the tree must be handled carefully until it is safely installed in its new home.

These two cardinal rules will help keep trees alive until they can be planted.

1) Carry trees carefully. When transporting, load and unload gently, being careful not to break branches.  Always provide support beneath balled or potted plants.

2) Keep roots moist! Techniques to prevent drying vary, depending on the trees and how long you must store them before planting. Balled and burlapped or potted trees should be checked for dryness by finger-length probing into the soil. Sprinkle or water as necessary. Then store them in a cool garage or shaded area out of the wind.

Planting Containerized Trees

Recommendations for planting have evolved in recent years as more is learned about the nature of roots and urban soils. Local conditions make generalizations difficult, but here are some guidelines that reflect the latest opinions of tree experts.

The Planting Hole

Proper preparation will encourage root growth rather than adding to the difficulties already challenging the young tree.  Most roots spread through the top 12" of soil in a wide periphery around the tree.  Therefore, slope the side of the hole and dig or deeply rototill an area around the hole at least twice the diameter of the container.

How Deep Should You Plant?

Under normal conditions, planting even with the surrounding terrain best encourages root growth.  When wet conditions or heavy soil are problems, raising several inches of the root ball above ground will aid the spread of lateral roots. In arid climates, a basin can be used to collect precious water.

Filling the Hole

Backfill with native soil unless it is clay from basement excavation or other undesirable fill material. In that case, blend together one part washed sandy loam, or bring in as much good topsoil as possible. Tamp gently and ad water to fill large air spaces and to give the tree its first good drink in its new home. Do not use excessive tamping around tree base: compacted soil may inhibit the spread of roots. Rake a ridge of soil two to four inches high around the margin of the hole.

Following Up After Planting

Watering

Watering is the key to tree survival. It should be used when filling the planting hole to eliminate large air cavities, firm the soil around fine roots, and provide nourishment for the new tree. During planting, bare-root trees can be dipped in water-absorbing polymers. This amazing chemical comes under a variety of brand names and is available from nurseries. Its function is to attract water when abundant and hold it longer than the soil when conditions get dry. It can also be used with balled and burlapped trees, being mixed with the backfill. The effects last for about two years. With or without the aid of polymers, water deeply around your tree once a week during warm, dry spells.

Pruning

Unless directions specify otherwise, it is better not to prune after planting if the tree will be watered regularly. Leaves manufacture the food needed for root growth, so the young tree needs as much of its crown as possible. Exceptions to this rule include trees that will be exposed to strong winds or drought conditions, in which cases rarely pruning will reduce the demand for water from its roots. Always prune dead or broken branches. The best time to prune oaks are in winter and midsummer.

Fertilizing

Avoid fertilizing shade trees until late spring of the second year following planting. Fertilizers can “burn” roots or stimulate crown growth faster than the roots can supply water.

Staking

Stakes and guy wires should be used only if support is necessary. When using, avoid common problems by following these guidelines. If the main stem droops, find the best place for support ties by moving your hand up the trunk to locate the point above which the top can stand up on its own. Place the support ties about 6” above the point. Ties can be made many ways, but a loosely-fitted figure 8 tie made of polyethylene, cloth, or webbed strap is easy to install, provides good support and cushions the tree from rubbing against the stake. Using two ties will also minimize the chance of bark damage from rubbing. Regardless of the tie used, allow slack for sway.

Mulch

Mulch is a young tree’s best friend. It holds down competing weeds or grass, retains soil moisture, prevents soil cracking that can damage new roots, protects the trunk from lawnmower damage, and helps prevent soil compaction. Organic mulches such as wood chips or pine needles also contribute to better soil structure and aeration as they decompose. Avoid limestone rock and allow no mulch to touch the tree’s trunk or be piled higher than 2 to 3 inches.

To give your tree a long, healthy life:

• Handle carefully
• Dig hole 2x the width and same depth as the root ball
• Remove tree from container
• Prune spiraling roots
• Put tree in center of hole so root ball is level with surrounding soil
• Fill in hole using existing soil, not potting mix or soil additives
• Use surplus soil to form “saucer” around tree base
• Remove air pockets by soaking planting hole
• Add 2” of mulch
• No root stimulant or fertilizer for 12 months
• Stake only if necessary