Q • I’ve noticed some orchards look like they have their trees painted white, and I was curious as to why that was. I have a few apple trees around my house and thought maybe this was something I should be doing.
A • Whitewashing tree trunks is a tried-and-true technique to prevent injury to trees from sunscald and frost cracking during the colder months. These injuries typically occur on the southwestern side of trees during sunny winter days, which can raise bark temperatures to 80 to 90 degrees before rapidly cooling at night. The high temperatures lower cold hardiness, opening them up to frost damage. The temperature drop at night can cause the bark to quickly contract, causing cracking.
Young, thin barked species such as maples, apples and sycamore are particularly susceptible to these types of injuries and appreciate extra protection to prevent damage.
Be sure to keep trees hydrated until the ground freezes. Having properly watered trees is the most important step you can take to prevent them from sustaining winter injury. To beef up your tree’s defense further, you can either use a tree guard or apply whitewash, as is done in orchards. Tree guards are best for trees less than 2 years old, and sturdier models can provide additional protection from animals like rabbits over the winter. Loose-fitting, light-colored guards with ventilation are your best choice. Any snug wraps need to be removed in spring when the tree starts growing.
Whitewashes are popular for use in orchards and larger trees as they are easy to apply and are a great economic option if you have a lot of trees. Mix white interior latex paint with equal parts water and apply it to the trunk while temperatures are above 50 degrees. For more details: tinyurl.com/3jwff6ak
Write to the Missouri Botanical Garden's Center for Home Gardening at firstname.lastname@example.org or the Horticulture Answer Service, 4344 Shaw Blvd., St. Louis, MO 63110.0 comments