| Welcome to our tree column, “Ask your local arborist.” Each month, arborist George Reno from the Davey Tree Expert Company in Menlo Park discusses a tree-related topic from general care and planting tips to how trees can impact your property. If you have a tree-related question or an idea for a topic to discuss, email lifestyle@embarcaderopublishing.com or post in the comments section at the end of this column. |
By mid-July, it’s common to receive questions from Peninsula homeowners asking why their trees are already showing brown leaves, even though summer has only just begun. The good news is that brown foliage doesn’t always signal a tree in decline. In many cases, it’s a response to seasonal conditions that can be managed with the right care.
Brown leaves can be caused by several factors, from heat and drought to spring insect activity. The key is learning how to recognize what’s normal and when it’s time to call an arborist.
Heat stress vs. drought stress
The Bay Area’s climate brings long, dry summers, which naturally put trees under more stress. Newly planted trees are especially vulnerable, but even mature trees can struggle if they aren’t receiving adequate moisture.
One of the biggest mistakes homeowners make is relying solely on lawn sprinklers to water trees. Turfgrass and trees have very different watering needs. While lawns benefit from frequent, shallow watering, trees thrive with slow, deep watering that reaches the entire root zone.
Trees experiencing drought stress may develop brown leaf edges, curled foliage or begin dropping leaves early to conserve water.
It might not be this summer’s weather
Sometimes the damage actually started months earlier.
Trees that experienced heavy feeding from spring insects, such as native caterpillars, may still be recovering during the summer months. While healthy trees typically produce new foliage, the combination of earlier defoliation followed by hot, dry weather can make browning more noticeable later in the season.
Fortunately, most healthy trees recover well when they’re properly cared for.
When brown leaves are normal
Not every brown leaf is cause for concern.
It’s perfectly normal for some older interior leaves to yellow or drop during summer as trees naturally shed older foliage and direct energy toward new growth. This seasonal leaf drop is common and doesn’t necessarily indicate poor tree health.
The concern arises when large sections of the canopy suddenly turn brown or when an entire branch begins declining.
How to help your trees through summer
Supporting tree health during the hottest months often comes down to a few simple practices:
- Water deeply and infrequently rather than lightly every day.
- Apply 2-4 inches of mulch over the root zone, keeping it several inches away from the trunk.
- Avoid unnecessary pruning during periods of extreme heat.
- Watch for signs of insects, disease or continued canopy decline.
Healthy trees are remarkably resilient, but reducing additional stress during summer gives them the best chance to recover from both environmental conditions and earlier insect activity.
When to call an arborist
If more than half of the canopy has turned brown, large branches are dying back, or you notice mushrooms at the base of the tree, cracks in the trunk or repeated leaf loss year after year, it’s a good idea to have the tree evaluated.
Catching problems early often allows homeowners to address issues before they become more serious.
Thanks for reading our tree column, “Ask your local arborist.” Each month, arborists from The Davey Tree Expert Company in Menlo Park will discuss a tree-related topic, specific to the Palo Alto area. If you have a tree-related question or an idea of a topic to discuss, email them here. If you are interested in having an arborist come to your property to assess the trees in your landscape before listing your home, call 866-923-5658 or visit www.Davey.com/menlopark.
George Reno is a local arborist at The Davey Tree Expert Company in Menlo Park, which serves communities on the Peninsula, including Menlo Park, Atherton, Palo Alto and Redwood City. Reno can be reached at 866-923-5658.
