False Hope for Cold Damaged Citrus Trees

False Hope for Cold Damaged Citrus Trees

The widespread multiple night hard freeze that occurred in North Florida near the end of December 2022 resulted in numerous citrus trees becoming severely damaged. The above ground portion of many of these trees died as a result of the extreme cold.

I talked with numerous homeowners who were concerned about their citrus trees following that weather event. Many of these homeowners earnestly and hopefully watched for any sign of new growth on their cold injured citrus trees the following spring. When new growth appeared from the lower portion of the trunk and from the roots, the homeowner became excited with a false sense of hope that their citrus tree had survived and would again produce an abundance of desirable fruit.

Regrowth of cold injured citrus tree from rootstock

Cold injured citrus tree with new growth coming from rootstock. Credit: Larry Williams

Now in the spring of 2024, many of these citrus trees have somewhat regrown from those root shoots, not from the completely dead tops. In most cases, the freeze damaged, dead tops of the once large trees have now been pruned away to allow the multitude of small diameter vigorous green shoots to grow.

Most purchased citrus trees are grafted. So, what survived and is now regrowing is coming from the rootstock, not from the original, desirable, edible fruit producing top. That desirable top was completely killed.

To better understand this scenario, perhaps a basic definition of grafting will help. This definition was taken from a University of Missouri Extension publication on grafting. “Grafting is the act of joining two plants together. The upper part of the graft (the scion) becomes the top of the plant, the lower portion (the understock) becomes the root system or part of the trunk.” Understock is also known as rootstock.

Grafting involves joining two different individuals. These individuals have to be closely related. For example, citrus can be grafted to other types of citrus and peaches can be grafted to other types of peaches. But citrus cannot be grafted to peaches.

The rootstock was selected because of some beneficial trait(s): resistant to a root pest, superior cold hardiness, imparts a dwarf growth habit to the top, etc. But the same rootstock produces undesirable fruit: bitter, hard, extremely seedy, etc. The top (scion) was selected because of a superior fruit: sweeter, bigger, more disease resistant, etc. But the same scion produces an inferior/weak root system. So, grafting the two together allows for the “best of both worlds.”

When all that is left is originating at or below the graft union or rootstock, the eventual resulting fruit will usually be undesirable, sometimes not edible.

So unfortunately, the best option in this scenario is to start over with another healthy grafted tree that is well suited for the potential cold weather of extreme North Florida.

Funny Looking Growth on Azalea and Camellia Leaves

Funny Looking Growth on Azalea and Camellia Leaves

Q. Some of the leaves on my azalea and/or camellia are swollen and light green. What caused this?

A. This is caused by a fungus that has been relatively common this spring.

The fungus Exobasidium vaccinii causes leaves and flowers to become swollen or thickened, curled and waxy in appearance. This fungus causes leaves, and in some cases flower petals, to enlarge abnormally and is commonly referred to as azalea or camellia leaf and flower gall.

Swollen leaves on sasanqua camellia as a result of Exobasidium fungus

Exobasidium leaf gall on camellia. Credit: Larry Williams

Symptoms vary somewhat based on the host plant. In addition to azalea and sasanqua camellia, it can occur on blueberry, as well. Infected blueberry leaves turn an unusual bright red in spring with almost no swelling of tissue. With azaleas and camellias, leaves become large and distorted and eventually a white powder covers the galls. The white growth consists of spores, which is how the fungus reproduces. Galls ultimately turn brown and harden. Not every leaf will be infected. It’s more common for the plant’s lower leaves to be the most heavily infected but under humid conditions and in shaded locations galls may form on leaves throughout the plant canopy.

The disease relies on airborne spores produced in the whitish mold on the surface of galls in late spring to early summer to reproduce. The galls then form the following spring. It’s important to remove and dispose of infected leaves before they turn white with spores.

Once you see evidence of infected leaves, it’s too late for chemical control. Besides, there currently is no effective or practical fungicide to control this disease in the home landscape. But you can reduce the amount of infection on your plants the following year by pruning infected leaves and throwing them away before spores are produced. After removing infected leaves with galls, never leave them on the ground around the plants.

It’s best to bury, burn or place the infected leaves in a plastic bag and throw them away. This disease is more severe during a cool, wet spring. It’s advisable to not add to the problem by artificially providing the “wet weather” the spores need by frequently using an overhead sprinkler and keeping the foliage wet in the spring during disease development. This is exactly what this and many other plant diseases need – wet conditions. Yet another reason to water during early morning and on an as needed basis, versus allowing an irrigation system to frequently run when there is already adequate moisture from rain.

In the home landscape, the fungus does not cause any long-term problems for the plant. It just makes the plant’s leaves look ugly. The infected leaves will usually fall prematurely.

Neighborhood Lawn Guru Kills Lawns, Leaves Town

Neighborhood Lawn Guru Kills Lawns, Leaves Town

I remember going into a neighborhood to diagnose a lawn problem in Crestview during spring a number of years ago. The centipedegrass lawn was in a state of decline. This was the front yard of the original model home for the neighborhood. The original owner sold the house and moved. The new owner, not familiar with North Florida lawns, was dissatisfied with the condition of his front yard.

All of the residents in this neighborhood were new to Florida.

At the time of my visit, the neighborhood was approximately ten-years-old. The original owner of the home was new to Florida, as well. He had only lived in the home for about two years before selling the house and moving to another state.

The original homeowner purchased the model home when the neighborhood was new and became the neighborhood lawn guru.

Imagine this situation… the entire neighborhood was new, everyone living in the neighborhood was new to Florida, not having a clue how to correctly maintain their new centipedegrass lawns.

Centipedegrass decline. Credit: Larry Williams

A sure way to kill a centipedegrass lawn is to be a little heavy handed with nitrogen. The natural color of a healthy centipedegrass lawn is light green, almost a crabapple green. The original homeowner was fertilizing his lawn as if it were a bermudagrass or fescuegrass lawn. Centipedegrass will not put up with this. As a result of “overdosing” his lawn with nitrogen, the lawn took on an unnatural dark green color. Short-term (two to three years), centipedegrass will appear to respond nicely to too much nitrogen. But after several years, irregular areas within a centipedegrass lawn will turn bright yellow in spring, followed by turning brown and dying back to bare ground as a result of too much nitrogen. The condition is called centipedegrass decline.

Healthy centipedegrass lawn with correct light green color. Credit: Dr. Bryan Unruh

I heard a minister ask the question, “Does the person you’re following know where he is going?” This was in reference to a parable found in the Bible in Matthew 15:14 where Jesus stated, “If the blind lead the blind, both will fall into a ditch.” This expression has many implications but basically is a caution about the dangers of following a leader who is clueless.

Unfortunately, this self-appointed lawn guru was clueless as to how to correctly manage a centipedegrass lawn. A few years following his overdoing it with fertilizer and then moving, his former lawn began to die in patches, progressively followed by other neighborhood lawns doing the same, almost like a domino effect. Who you choose to follow is important.

Reliable lawn care advice is available from the UF/IFAS Extension Office in your county or online at: https://hort.ifas.ufl.edu/yourfloridalawn.

Rollercoaster Temperatures in NW Florida

Rollercoaster Temperatures in NW Florida

Fall, winter and even early spring can be a rollercoaster ride of temperatures here in Northwest Florida. One week it dips to freezing for a short time and the next week it rises to spring-like temperatures. We need to hold on for this ride of up and down temperatures and not overreact too soon.

Following the sudden ride down to the lower temperatures, we may think winter is over. But we don’t see the next drop in temperatures that’s coming, as we are experiencing the ride upwards in temperatures.

On average, it’s not until we reach mid-March that we expect our last killing frost. A killing frost is heavy enough to kill tender plant growth. And, we can have light frosts well into the latter part of March and into early April. This is particularly true in the more northern portions of our Panhandle Counties.

The main point is to not get spring fever too early and encourage new plant growth by pruning or fertilizing too soon.

Cold injured pinecone ginger plant

When landscape plants freeze, the first impulse may be to get out the pruning shears and cut away dead and dying leaves and branches. But this isn’t a good idea. Pruning can force new tender growth that is more likely to be injured by the next freeze. And, you can’t tell how much damage has been done until plants start new growth in spring. If you prune immediately after a freeze, you may cut away live wood that doesn’t have to be lost. Also, leaves and branches, which have been killed, can help protect the rest of a plant against further cold injury.

Some people want to “jump start” their lawns before our weather will allow our grasses to grow. Waiting allows for more efficient use of the lawn fertilizer. You will not injure your lawn by waiting but you can certainly injure your lawn by fertilizing too early.

So, have patience, allow your lawn to green up on its own and then fertilize, even if it’s not until April or May.

Finally, be a little philosophical. If you do lose one or two of your tender ornamentals, so what? Worse things could happen. And now you have a chance to add something new, perhaps some species native to our area that is not as subject to cold damage.

Even with this winter/spring rollercoaster ride, with thousands of plants to choose from and a generally mild climate, who can complain?

Muscadine Grapes, a Southern Treat

Muscadine Grapes, a Southern Treat

I grew up with muscadine grapes. I liked them as a kid and still enjoy them today. In my opinion, they are a southern late summer and fall treat.

Not everyone shares in my fondness for this native fruit of the Southeastern United States. If you did not grow up here, muscadines may be an acquired taste. They are different than the bunch type grapes that most are accustomed to eating. As a matter of fact, most first timers require some instructions in how to eat a muscadine. Nowadays you can search “how to eat a muscadine” on the internet and find written instructions and even short videos on how to eat this grape.

Fruit clusters on a muscadine grape
Muscadine grapes (Vitus rotundifolia) on the vine. Credit: David Nance, USDA Agricultural Research Service, Bugwood.com

Muscadines have thick skins (hulls) and contain fairly large seeds. Some muscadine purist may pop the entire fruit in their mouth, bite down and eat hull, pulp, juice and seeds. The few people that eat hull, seeds and all may do it for health benefits. The skin and seeds are full of antioxidants and nutrients. But most people do not like the thick and sometimes bitter hull or seeds. So, one technique is to place the grape with the stem scar facing upward in your mouth and squeeze or bite the grape. The sweet juice and pulp will burst into your mouth. The thick skin is then removed and discarded. The seeds are contained in the pulp. It can take some practice removing the seeds from the pulp while in the mouth. Some people enjoy the juice and spit out the pulp with seeds. Others use their teeth and tongue to remove the seeds and then eat the pulp. Some swallow pulp with seeds.

Apparently, muscadines were a pleasant find by the early European explorers to our area. Many names have been used to denote this native grape in the wild including Bullace, Bullis and Muscadine. ‘Scuppernong’ was the first named variety of the bronze muscadine discovered growing in the wild in North Carolina in the mid-1700s. Even though there are now numerous named varieties of the bronze muscadine such as ‘Carlos’, ‘Fry’ and ‘Summit’, many southerners still refer to all bronze types as Scuppernong. Purple or black varieties are commonly called muscadines.

Muscadines range from bronze to dark purple to black in color when ripe. There are more than one hundred improved varieties from which to choose.

Winter, December through February, is the time to plant bare-root vines. Check with local nurseries on availability. More information on selection, planting and care of muscadines is available at https://edis.ifas.ufl.edu/publication/HS100 or from the UF/IFAS Extension Office in your County.