When cold weather comes to Houston, your first thought might be what temperature do plants freeze, in other words, how cold is too cold? There is no easy answer to this. Different plants freeze and die at different temperatures. That is why they are given a hardiness rating. Some plants produce special hormones that keep them from freezing, and these plants have a lower hardiness rating (meaning they can survive colder weather) than plants who produce less of this hormone. That being said, there are also different definitions of survival. A plant may lose all its foliage during a freeze, and some can regrow from the stems or even the roots. So, while the leaves cannot survive a certain temperature, other parts of the plant can.
The best thing to do is bring your plants indoors during a freeze. However I know for some, this might be an issue due to the sheer amount of containers they might have or the pots are simply too heavy to move. We have listed ways you can help protect your plants before a freeze hits.
Coverings to use:
Bed sheets
Drop cloths
Old blankets
Pillow cases
Burlap
Plastic sheets (use stakes to keep material, especially plastic, from touching foliage)
Bubble wrap
For your outdoor pots, wrap the containers in one of the recommended coverings above. What is most important to cover is the pot itself as it is the roots that need shielding. These protective coverings will help trap in heat and keep it at the root zone. Also, when covering, avoid damaging the top part of the plants. Injury sets up the plant for cold and pest damage. Another way to help insulate your container is placing your pot into a larger pot for added protection. This will work best if the larger pot has thick walls for added insulation.
For a short cold period, remove the coverings when temperatures rise the next day. For a long cold period, group several pots together on soil and close to the house or wall. Place the cold-hardiest plants on the outskirts of the grouping with the less hardy plants in the center. Putting them together increases the mass and volume of insulation and protects them from cold, harsh winds that cause desiccation and freezing. Then make sure to wrap the outside of the pots with a recommended covering.
