http://www.gainesville.com/article/20100320/ARTICLES/100319346/1004

Caring for cold-damaged citrus

By David Holmes
Columnist

Published: Saturday, March 20, 2010 at 6:01 a.m.
Last Modified: Friday, March 19, 2010 at 11:47 p.m.

A couple years ago, when climatically speaking, everything went right, I picked citrus off trees in my backyard from late November through late August.

As the Extension Service actively promotes consumption of fruit and vegetables to enhance health and longevity, and because no fruit or vegetable can be fresher than that which you produce yourself, I found this source of fruit to be particularly satisfying. Following the prolonged cold snap north central Florida experienced this year from early to mid-January, several people who know I have citrus — and, OK, I admit it — a few palms I shouldn't have, inquired whether I had lost any trees. My response has been the same — not so far, but for many things, we won't know until mid to late April the extent of this cold damage.

About two weeks after the January cold snap, I was delighted to see my citrus trees drop all their leaves. This is a good sign, for it indicates new buds are emerging and are pushing the old leaves off the tree. Close examination revealed small green buds on many — not all, but many — of the branches. The thought also occurred to me that the intense cold the region experienced had to be hard on the pysllid insect population that is responsible for the spread of Citrus Greening, a disease that is presently a major threat to both the commercial and dooryard citrus industry across the state.

It doesn't make me feel a bit grieved to think these pests suffered during the cold and, hopefully, their populations have been burnt back severely. One thing for sure, there won't be many citrus leaves for them to consume this spring.

If you have citrus trees, there are several items that should be addressed now to help trees recover and to prevent headaches as the summer progresses.

First, if your trees have dropped leaves, these should be raked and removed from the property. Old leaves are a harbinger for diseases and heavy spring rains can spread disease spores from the leaves up into the canopy. While you won't be able to remove every leaf, get as many as possible, bag them and send them to the landfill.

Next, trees should be starting to leaf out. You'll probably notice that some, maybe several, branches have been killed outright by the cold weather and won't have any evidence of new leaves emerging. In many cases, the end of a forked branch may have dead wood, while the other half of the fork is alive. Now, while leaves are small, is a good time to prune out limbs that are obviously dead.

Removal of these branches is important to prevent melanose, a disease that spreads from dead wood. Again, do not submit these branches to your compost, but remove them from the site.

Prior to the first flush of growth —which generally occurs at the end of February — is the time to make the first fertilizer application of the year. If you have not done so already, make an application of 6-6-6 fertilizer (select an organic form if available) at a rate of 6 pounds of fertilizer for trees that are of bearing age.

In late May, and again in early September, make a similar application. Remember, it is important to place fertilizer where roots can actively uptake the material; as a rule of thumb, fertilize an area twice the diameter of the tree canopy.

Following two seasons of cold weather, even mature citrus trees are stressed, so it is important to do what we can to return trees to health. Generally, rains have been fairly well spaced as we have begun 2010, but windy March conditions quickly dry out topsoil where many roots are located.

One expects dry conditions in May, and combined with hot temperatures, this can be very stressful for trees. Over the next couple months, dooryard fruit producers should monitor rainfall, wind and temperatures carefully and should supplement irrigation on citrus as needed.

The University of Florida has an excellent publication for dooryard citrus producers, “Your Florida Dooryard Citrus Guide,” SP-178. It may be obtained online at www.ifasbooks.com or at 800-226-1764.

David Holmes is Marion County extension director. Contact him at david.holmes@marioncountyfl.org.

I fertilized my satsuma grove late this afternoon. I missed the recommended fertilizer analysis by 2 points. I was able to get some 8-8-8 with micro nutrients and I applied about 3 pounds per tree of this mix. I plan on coming back later in April with a second application and some epsom salts. My satsumas survived the global warming winter and I even have a Croxton Pink Grapefruit that is loading up with flower buds. Thanks for the post!

Stan, the University of Florida's book shown in the above post, “Your Florida Dooryard Citrus Guide", states you can use either 6-6-6 or 8-8-8. Further the book states that when the trees are 4 years old or older, then a 10-10-10 can be used. By the way I am going to be in Charleston in a couple weeks, and would like to stop by your place and see your grove. I will let you know soon what day I will have free to visit, perhaps with Lazz. Hopefully, the day will be free for all of us. - Millet (1,030-)
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Hey Millet, Thats great news! I will look forward to your visit.. Just let me know as soon as your plans are firmed up so I can make myself a note to be around the farm that day! The satsumas should be blooming in a couple of weeks!

[quote="Millet"]Stan, the University of Florida's book shown in the above post, “Your Florida Dooryard Citrus Guide", states you can use either 6-6-6 or 8-8-8. Further the book states that when the trees are 4 years old or older, then a 10-10-10 can be used.

Millet help me out I always used 10-10-10 until this year I saw the 5-1-3- ratio recommended for citrus so I found 16-4-8. 6-6-6 8-8-8 and 10-10-10-are the same if you use less of the higher Analiese. Where am I wrong and getting confused.

Citrus trees absorb nutrients in the ratio of 5-1-3, therefore 5-1-3 is the optimum ratio for the replacment of nutrients that have been taken up by the tree. A 5-1-3 ratio fertilizer is important for container citrus, as it helps to avoid build ups of unused nutrients, and salts, in the container, leading to many problems. For trees planted in the ground, this nutrient replacement ratio is not as critical, because any possible nutrient excess, or buildup, is continually leached out of the root zone. (Giovanni Dugo and Angelo Di Giacomo authors of the text book "Citrus, The Genus Citrus" would not agree, and would still recommend a 5-1-3 ratio for in ground fertilization). In containers, ratios such as 9-45-15, the excess elements continue to build up in the medium, unless the growers has an ongoing program of flushing out the container with clear water, even then it would be difficult to leach out phosphorous. Using a fertilizer with a over supply of potassium, discourages magnesium absorption, and delays acid decreasing and maturing ratio in fruit. . There are many fertilizer formulas. They should be chosen according to the replacing of minerals lost, and their ratio. 5-1-3 is the ratio of the main elements lost from the medium, through root absorption of citrus trees. Fertilization must respect this ratio when the mineral content in the leaves is satisfactory. Obviously, in cases of over dosage or deficiency of one or more elements this ratio must be changed to a more appropriate one, until the ratio balance is corrected. - Millet (1,029-)[/u]

Citrus trees absorb nutrients in the ratio of 5-1-3, therefore 5-1-3 is the optimum ratio for the replacment of nutrients that have been taken up by the tree. A 5-1-3 ratio fertilizer is important for container citrus, as it helps to avoid build ups of unused nutrients, and salts, in the container, leading to many problems. For trees planted in the ground, this nutrient replacement ratio is not as critical, because any possible nutrient excess, or buildup, is continually leached out of the root zone. (Giovanni Dugo and Angelo Di Giacomo authors of the text book "Citrus, The Genus Citrus" would not agree, and would still recommend a 5-1-3 ratio for in ground fertilization). In containers, ratios such as 9-45-15, the excess elements continue to build up in the medium, unless the growers has an ongoing program of flushing out the container with clear water, even then it would be difficult to leach out phosphorous. Using a fertilizer with a over supply of potassium, discourages magnesium absorption, and delays acid decreasing and maturing ratio in fruit. . There are many fertilizer formulas. They should be chosen according to the replacing of minerals lost, and their ratio. 5-1-3 is the ratio of the main elements lost from the medium, through root absorption of citrus trees. Fertilization must respect this ratio when the mineral content in the leaves is satisfactory. Obviously, in cases of over dosage or deficiency of one or more elements this ratio must be changed to a more appropriate one, until the ratio balance is corrected. - Millet (1,029-)