Southern Arizona will be experiencing its first hard freeze of the year this week, which means it is time to cover your citrus trees. The National Weather Service predicts temperatures in the mid-20’s, which translates to low 20’s or below 20 in the Green Valley area and possibly colder in low-lying areas such as near washes and drainages.
To protect citrus from permanent damage, trees must be covered with either old sheets or blankets, extending the covers all the way to the ground. This is because the intent is to capture the warmth radiating from the soil, not necessarily protecting the leaves with the cover. Special frost blankets, available in various stores around Tucson, are limited in their protection range. Check the label-some are only good to around 22.
If you think a cover is enough to protect your citrus fruit, unfortunately that is not correct. To keep trees warm enough you will need to either dec out the tree with old Christmas lights, the kind that get warm, or place one or two drop lights with a 75 incandescent light bulb inside the foliage. Be careful not to place lightbulbs too close to the bark to prevent scorching.