Even though we may not usually think of drought when it comes to the Portland area very often, the recent dry spell Oregon has suffered through has made the lack of rainfall a serious concern for the landscapes of homeowners. While the NW section of the state hasn’t suffered the kind of extreme drought that the southern half of the state is currently experiencing, homeowners should still stay on the lookout for the potential signs of drought stress on trees located on their property.
Signs of Drought Stress
Symptoms of drought stress can develop suddenly or take years to eventually manifest. Drought injury symptoms to tree can include wilting, yellowing, and curling at the edges of leafs.
Deciduous leaves may develop brown, scorched looking edges or browning between veins, while evergreen trees may have their needles turn purple, red, or yellow. Needles may also turn brown at the tips and browning may continue to develop through the needle towards the twig.
In persistent drought, leaves may become smaller than normal, drop early, or remain attached to the branch even though they have turned brown in color.
In most cases, drought stress won’t be enough to outright kill a tree, but it can make a tree more susceptible to other serious issues, such as disease and insect infestations, in subsequent years.
Where to Water Your Tree
- We recommend deep watering to 12 inches below the soil surface.
- Soak the soil surrounding the tree within the “dripline” – i.e. the outer edges below the tree’s branches – to disperse enough water down towards the roots.
- Make sure to slowly water the tree, dispersing the water flow so you get deep water penetration to the roots. Watering for briefs period of time only encourages shallow rooting, which may lead to increased drought damage.
- Refrain from digging holes around the tree to allow for deeper water penetration. This actually dries roots out even more quickly. If the soil surrounding the tree isn’t too compact, consider attaching a soil needle to the hose and insert it into the ground.
- Spraying overhead is an inefficient waste of water and should be avoided during drought conditions. Water at ground level to achieve maximum soil penetration.
How Much to Water
During times of drought, the top watering priority should be tree over your lawn. A dead lawn can be replaced over several months, while a dead 15 year-old tree will take 15 years to replace.
How much water you should use really depends on the tree. A general rule of thumb states using roughly 10 gallons of water per inch of trunk diameter for each time watering. Make sure to measure a tree’s trunk diameter at knee height to get the proper measurement.