Below-freezing temperatures damage some semi-evergreen plants, while others may only appear that way. It’s not a bad idea to wait for spring and see what leafs out and what doesn’t.
When residents of south-central Texas experience rare deep freezes, with temperatures dropping to 19 degrees. many homeowners welcomed the cold temperatures as an incentive to cut back bougainvilleas and other tropical perennials that have become overgrown.
Hard freezes also damage a few “semi-evergreens”, plants that normally don’t drop leaves for long, or only in certain conditions like drought or extreme cold. In San Antonio, this means species like striped agaves, some citrus and especially Mexican olive (Cordia boissieri) have taken a hit.
Although we all know that Mexican olive can suffer in cold weather we rarely have a chance to see it bare in San Antonio. In extreme cold, the trunks may or may not experience damage. Trees located just south of a warm sunlit wall that protects them from north winds may get by with little damage at all.
When in doubt scrape off a sliver of bark and look for green tissue underneath. Start in the upper branches and move down toward the trunk. If you see green tissue under the bark, the branch is still alive; it may even have new leaf buds already present. If you reveal black or “slimy” tissue, mark it for later pruning. But don’t be too eager to cut Mexican olive back just yet! The roots of the tree are generally well protected against cold; it’s not a bad idea to wait for spring and see what leafs out and what doesn’t.
The Mexican olive at the front door of the Alamo always provided a good touchstone: it’s frozen and been cut back to the ground more than once, so it was always a useful local example of when to wait and when to cut. A recent investigation found it had already been cut back to the ground, though not due to the freeze. It appears it was removed for other reasons earlier last year.