Currently, a handful of stone fruits are in-season in the Portland area. Stone fruits enjoy summer heat, but too many days of extreme temperatures can adversely affect the maturation process and health of the fruit tree. This is starting to become a potential chronic summer issue - according to Oregon Live, climate scientists have observed summer temperatures becoming hotter and drier. The issue is all-encompassing, as even night temperatures aren’t providing as much needed relief for plants. 

Unfortunately, this heat wave is something that scientists say would not have happened without human influence. If this indeed the new norm, we may need to prepare for a greater average temperature in the summer months, and consider that the highs may become more extreme. This leads to more instances of heat stress, where your trees are losing more water than they take in. In fruit trees, heat stress can show itself in the form of wilting (drooping stems and leaves), dried out leaf edges, scalding or blistering on fruit, and cupped or rolled up leaves. 

Here are a few things you can do to protect your trees when preparing for a heat wave, or when you notice these symptoms in your trees:

1. Consider leaving more leaf coverage when you’re pruning, as this will provide extra protection from the Sun. Generally, pruning is an effective and productive way to care for your plant. However, it is best to avoid it in order to protect against leaves and fruit being sunburned.

2. Hold off on planting, transplanting, applying fertilizer or chemicals! During extreme heat, these will create high-stress environments that your plant may not be able to handle.

3. Water, water, water. Trees will use a lot of it during heat waves, and this only increases if it is extra dry or windy. Plants with lots of foliage in smaller pots are especially ones to watch for drying or wilting, along with young plants with less developed roots, as they cannot seek out water as effectively. 

4. If you want to limit water usage, creating more shade and moisture are also ways to go! Shade cloth is a great way to reduce harsh sunlight while not completely eliminating it. You could also use your roof, umbrella, or other shade device, but may want to provide some period of direct sunlight if that is what the plant or tree requires. 

If you have any questions or concerns, please feel free to reach out to us at treecare@portlandfruit.org. Stay tuned for Part 2, which covers why it is so important to consider Portland’s housing development history in this summer heat!