December 2010

FROST SEASON -December 2010


The National Weather Service is predicting temperature lows in the 23-24 range this Thursday, December 30th, and Friday, December 31st.  Rain is also predicted for Wednesday December 29th, and should this occur, it will lessen the freeze possibilities.  However, if we only receive minimal amounts of rainfall, then precautions should still be taken for your citrus trees. Due to their size,  mature citrus trees are more tolerant than younger, or recently transplanted citrus. Older tree will have established roots and a larger canopy which helps against the cold. Young citrus are more susceptible to freezing,  and sometimes can freeze lower than the bud union.  This is the area on the trunk where your desired variety has been budded on the rootstock.  If the top portion of the plant freezes out, new growth may appear from below the bud union area down to the ground level. Subsequently your tree will grow back, but not with the desired variety.  To protect the plant and the bud union portion of your citrus tree during a freeze,  you can place several layers of newspaper, or wrap burlap around this area. Also keep your tree covered if possible with a blanket or sheet. In addition, added protection can be possible by slowly running water in the well all night long, or at least filling the well with tap water just about midnight. Artificial heat can also be supplied by adding a 60 watt bulb under the tree canopy. Use caution with electrical lights if water is present.   Agricultural Frost forecasts normally run from November 15 through March 15 here in the Salt River Valley of Arizona. Check you local weather station for updated conditions.   




Recently planted citrus, especially those younger than five years old, may be a little more frost sensitive, because the citrus root system has not established itself, and the intake of moisture is reduced. Plus the branches are smaller and they freeze easier than established wood.  Therefore, play it safe and provide the necessary protection for the first  frost season.  Established plants are more resistant to a hard freeze in January if they are given ample time to "harden over" or get accustomed to the cooler temperatures. An early season freeze will be more damaging than a late season freeze of the same temperature. Unfortunately our late season warm temperatures haven't allowed sufficient hardening off time, so a minimal freeze can result in more damage to young plants. Cover, Water, and Artificial Heat, are most important for protection.




1.The first line of defense when trying to protect your newly planted citrus, is to water the basin area.  Fill the basin area, or well, with water from your garden hose, and then you can also fill a 5 gallon bucket of water from your bathtub faucet, and apply this “warm” water to the basin.  This warm water will keep the roots warm and moist, keeping the “drying” freeze temperatures from hurting the tree.

2. Second, you can cover the tree canopy with a light cloth, like an old bed sheet, laying this cloth on the top of the canopy. Do not use any plastic material to cover the tree’s canopy.  You can secure the cloth with clothespins or tie the corners of the cover to the branches of the tree.  You don’t need to envelope the canopy of the tree.  You are just trying to protect the outside tips of the branches.

3. Christmas lights in the tree?  Putting lights in the tree will not protect the plant unless using high wattage bulbs. Watering is the easiest way  to help against freezing in addition to a cover.  So, use your energy and resources for the best protection.


 Remember, the fruit on the tree, (if the citrus tree is an established size), will freeze at temperatures below 32 degrees F for > 4 hours, and the tree will freeze at temperatures below 27 degrees F for > 4 hours.  Generally, our freeze episodes are very early in the morning, just before sunrise.  If the forecast predicts the temperatures will be dropping before midnight, then your citrus worries are justified, but be on the safe side and take the necessary precautions.  If your citrus tree does experience some frost damage, the outside leaves will turn a grayish, white color.  Don’t worry, and don’t trim off this dead protective layer until after March 15th. This “freeze burnt” area will add some protection should we received more frost weather before March 15th.  Greenfield Citrus Nursery sells small frost cloth covers, and large 6’ x 6’ burlap sheets for larger citrus trees.  Again, established citrus trees are generally “safe” for our quick frost episodes.  If you have questions about freezing, we’re always happy to help you here at the nursery.  Call us, email us, or stop by to get your trees’ covers.