You have worked hard to plant your citrus trees and other frost-tender plants. Perhaps you have given them protection during the winter by keeping them in a greenhouse or by building a frost protection frame covered with plastic, but as spring approaches and your plants begin to send out new growth, you might think they are safe from a late frost. But Mother Nature is full of surprises, and Jack Frost can still nick your plants after the final projected date for frost in your area. You can do several things to help them remain healthy and frost free.
Check the weather forecasts regularly during early spring. If temperatures are predicted to drop below 40 degrees F, take steps to provide protection for your tender plants such as citrus, cymbidium orchids and young vegetables you have already put in the ground.
Place a "cloche," or bell jar, over small plants the night before the frost is predicted. Remove it in the morning after the temperature rises. Cloches are available at garden supply stores and online.
Build a floating row cover made of plastic or a spun polyester material called Reemay. A simple method of installing this is to cut ½-inch PVC pipe with your hack saw into 4- to 5-foot lengths and then bend them over your planting area, pressing the ends into the soil on either side. Cover the structure with the plastic or Reemay. You can leave this cover over your plants until you are certain no further frosts will occur.
Spray an antitranspirant, sometimes called an antidesiccant, onto larger plants that you cannot cover. Antitranspirants reduce transpiration to help them from becoming too dry, which is the effect that frost has on them. Some antitranspirants are designed to be drenched into the soil.
Run sprinklers in the area where plants reside. Be sure that the water reaches the entire plant, and leave them running during the entire time that the temperature is low. Running water cannot freeze unless the temperature is very low; late spring frosts are generally not hard frosts.