Did you know trees can get sunburned? Just like for humans, there’s sunscreen for that! Only, tree sunscreen is better. The organic materials we apply to our trees are more like if your sunscreen protected you from getting burned and gave you your daily calcium.
This is what sunburned bark looks like. It cracks like this and leaves the tree vulnerable to diseases that attack inner layers of bark.
Knowing when our trees might need sunscreen depends on a few factors. For our recently grafted apricot trees, we know that with their newly growing branches, there won’t be enough leafage to shade the trunk come summertime. For our cherry trees, it’s a bit different. We know they need a certain number of “chill hours” (or hours where temperatures are between 32 and 45 degrees) to produce a good crop. If we’re worried that we might not get enough chill hours over the winter, we’ll spray some sunscreen to help reflect heat and keep the tree cool.
It’s not exactly “sunscreen” that we’re using, though. For the apricot trees, we spray a natural clay: small particles of Kaolin clay, to be exact, which is also the material used in manufacturing fine porcelain and china. This organic, non-toxic material not only protects the trees against sunburn and heat stress, it also helps ward off pests and disease. The tree enjoys these benefits while still being a safe environment for our honeybees, other beneficial insects, and ultimately the fruit that we’ll harvest in May.
Pablo spraying Kaolin clay on apricot trees
Cherry trees prefer Microna limestone as a sunscreen, which is limestone that is ground ultra finely and mixed with water. It does what chill hours do: it reflects heat and keeps the trees cool. Cherry trees need the most chill hours out of all our stone fruit trees. Every season we’re hoping for more tha 800 hours! They could benefit from more than 900, but we haven’t seen that kind of prolonged cold for more than 10 years out here in Brentwood. With the increasing pressures of climate change, farmers are making difficult choices about whether to keep their cherry trees or not given warming patterns year to year. Microna limestone is a safe, organic way we can prep the trees for dealing with warmer conditions, while still producing lots of tasty, healthy fruit. The Microna limestone is also nutritious with calcium. So we don’t worry about applying it liberally on and below the trees, because the calcium also benefits the ground. Calcium improves soil structure, creating more aeration for higher oxygen levels in soil. More oxygen means more life, more nutrient exchange, more growth and better health of all living systems. Calcium also improves and strengthens cell structure for resistance to disease and fruit firmness.
The good news is, about a month after we sprayed sunscreen on our cherry trees, we did hit that golden number: 800 chill hours! We’re hoping for a beautifully abundant cherry crop this year.
Cherry trees after limestone application have lighter bark