Although a Nebraska’s summers can be punishing, most trees properly selected and planted can survive normal summer conditions without significant concern. However, nearly all trees deserve to be closely monitored during the summer and given a shot of supplemental water when drought conditions set in. Monitor your tree throughout the growing season so if an issue develops it can be addressed immediately if needed.
Tree health and growth depend on adequate water. When trees are unable to take up enough moisture they may begin showing signs of stress and become more susceptible to insect and disease infestation. Watch for leaf droop and drying foliage, especially at leaf edges.
Extremely hot, windy weather can cause wilting or browning of foliage, even when soil moisture is normal. If severely hot, dry weather is short lived, established healthy trees can recover on their own. For newly planted trees and during a prolonged drought for established trees, watering should be done to help reduce the effects of stress.
• To check soil moisture in the tree’s root zone, push a long screwdriver or similar object into the soil. If soil moisture is adequate, it should be fairly easy to push the screwdriver into the ground 6 to 8 inches. If the ground is dry and in need of watering it is typically very difficult to push the screwdriver in beyond a couple of inches.
• Deep, thorough watering will provide the most benefit to trees. Excessive watering, especially in heavy soils, may force air from the soil and cause roots to suffocate. Soil should be kept moist but not soggy.
• Infrequent deep watering, equivalent to 1 (or approximately 25 gallons of water) or 2 inches of rain for newly planted trees, is most beneficial for trees because it promotes healthier root systems, which are better able to sustain trees during times of drought. Frequent shallow watering will only favor grass growth.
• One of the best methods for deep, slow watering is to set a hose on the ground somewhere under the outermost edge of the tree’s canopy. This area is known as the drip line. A tree’s root system typically spreads beyond the width of its canopy. If trees are watered only around the trunk, their root system may not fully develop. Watering in the drip line will promote healthy root system development.
Run a trickle of water low enough to allow the water to sink into the soil and let it run for a couple of hours, periodically moving the hose around the drip line.
Keep in mind that residential irrigation systems and lawn sprinklers favor turf and should not be used to water trees. Also, excessive watering, particularly in heavy soils, may force air from the soil and cause roots to suffocate.
|Above are examples of drip irrigation bags which slowly releases water to the root zone. These watering aids allows you to know how much water your tree has received. Check your local nursery for these watering aids.|
Mulch helps conserve soil moisture and moderates soil temperature, so applying a 2- to 4-inch layer of wood chips or bark, will benefit your trees during hot summer months.
Spread mulch evenly around your tree and be sure the mulch does not pile against the tree’s trunk, as this can lead to disease problems. Don’t mulch with rock or use plastic sheeting under the wood chip mulch. Mulching also helps with separation between turf and trees. Increasing the distance between the tree trunk and turf will help prevent damage from mowers and weed trimmers.
|Mulch near (not against) the trunk should be approximately 1 inch deep, while mulch can be up to 4 inches deep toward the edge of the mulch ring. Don't allow mulch to rest directly against the trunk of the tree as this can encourage circling roots.|
Newly planted trees can benefit from staking, which can help trees that are tall and leggy or those that are planted in high-wind areas establish healthy root systems. Smaller trees or trees planted in protected areas may not need to be staked. Trees are staked to anchor the root ball, not to eliminate movement of the stem or canopy.
|A properly staked tree does not eliminate movement of the stem or canopy.|
A common misconception is that trees need to be fed. Trees make their own food through photosynthesis. Fertilization provides nutrients, not food to plants. In fact, fertilizing your tree can do more harm than good. Overfertilization of nitrogen in particular promotes aphid and spider mite populations and can stress trees so that they become more susceptible to canker diseases and insect borers. Unless your soil has a known nutrient deficiency that has been identified by a soil test, do not fertilize your trees. Typical fertilizer applications to the lawn generally meet the nitrogen requirements of landscape trees without the need for additional fertilizer.
Micronutrients such as iron and manganese are sometimes deficient in soils, but more often are tied up by poor soil conditions. Organic mulches such as wood chips improve soil fertility by adding nutrients to the soil and improving conditions for nutrient uptake by tree roots.
Keep in mind that root damage, soil compaction, wilt diseases and insect infestations can cause symptoms similar to those of heat and water stress. If the tree does not respond to watering it may be an indication that something else is wrong. For more information on cultural issues visit, and click on Abiotic Problems of Trees or contact a certified arborist to help identify and manage the problem.
For more information about how to make your next planting a success, see the NFS publication Avoiding the Top 10 Mistakes of Tree Planting.