by Daniel J. Leonard | Jul 26, 2016
The Live Oak (Quercus virginiana) is one of the most iconic figures of the Deep South. Mentioning the words Live Oak invokes all sorts of romantic nostalgia of yesteryear and the reputation is not unearned. In fact, many Live Oaks still stand that were growing on American soil when the first English settlers set foot on Plymouth Rock. They are long-lived, picturesque trees that also happen to be nearly bulletproof in the landscape. Given these factors, it is not surprising that Live Oak is far and away the most common tree included in both residential and commercial landscapes in the Coastal South. However, even the venerable Live Oak is not without its problems; this article will discuss a few of the more common issues seen with this grand species.
The Angel Oak near Charleston, SC
Few conditions afflict live oak but when they do, improper planting or cultural practices are usually at play. Observing the following best management practices will go a long way toward ensuring the long-term health of a planted Live Oak:
- Remember to always plant trees a little higher than the surrounding soil to prevent water standing around the trunk or soil piling up around it, both of these issues frequently cause rot to occur at the base of the tree.
- If planting a containerized tree, remember to score the rootball to prevent circling roots that will eventually girdle the tree. If planting a B&B (Balled and Burlap) specimen, remember to remove the strapping material from the top of the wire basket, failure to do this can also result in the tree being girdled.
Live Oak has few insect pests but there are some that prove bothersome to homeowners. The following are two of the most common pests of Live Oaks and how to manage them:
Typical galling on Live Oak
Galls are cancerous looking growths that appear on the leaves and twigs of Live Oak from time to time and are caused by gall wasps that visit the tree and lay their eggs inside the leaf or stem of the plant. The larvae hatch and emerge from the galls the following spring to continue the cycle. These galls are rarely more than aesthetically displeasing, however it is good practice to remove and destroy gall infected stems/leaves from younger trees as gall formation may cause some branch dieback or defoliation. Chemical control is rarely needed or practical (due to the very specific time the wasps are outside the tree and active) in a home landscape situation.
- Black Twig Borers can also be problematic. These little insects seldom kill a tree but their damage (reduction of growth and aesthetic harm) can be substantial. Infestations begin in the spring in Northwest Florida, with the female twig borer drilling a pen-head sized hole in a large twig or small branch and then laying her eggs in the ensuing cavity. She then transmits an ambrosia fungus that grows in the egg-cavity, providing food for the borer, other borer adults, and her offspring that take up residence and over-winter in the twig. The activity of the insects in the twig has an effect similar to girdling; the infected twig will rapidly brown and die, making removal and destruction of the infected branches a key component
In conclusion, though there are a few problems that can potentially arise with Live Oak, its premier status and continued widespread use in the landscape is warranted and encouraged. It should be remembered that, relative to most other candidates for shade trees in the landscape, Live Oak is extremely durable, long-lived, and one of most pest and disease free trees available. Happy growing!
by Carrie Stevenson | Jul 26, 2016
Summer is full of simple pleasures—afternoon rainstorms, living in flip flops, and cooling off in a backyard pool. Among these, one of my favorites is walking out my door and picking handfuls of figs right from the tree. Before we planted our tree, my only prior experience with the fruit was a Fig Newton—I’d never eaten an actual fig, much less one picked fresh. Now, they are my favorite fruit.
When ripe, figs are a deep shade of pink to purple. Larger green figs will ripen over the course of a few days. Photo credit: Carrie Stevenson
Native to Asia Minor and the Mediterranean, figs were introduced to Florida in the 1500’s by Spanish explorers. Spanish missionaries introduced these relatives of the mulberry to California a couple hundred years later. Figs are best suited to dry, Mediterranean-type climates, but do quite well in the southeast. Due to our humidity, southern-growing figs are typically fleshier and can split when heavy rains come through. The biggest threats to the health of the trees are insects, disease (also due to our more humid climate) and root-knot nematodes.
Fig trees can grow quite large and produce hundreds of fruit each year. Photo credit: Carrie Stevenson
Our tree started out just a couple of feet tall, but 12 years ago we replanted it along a fence in our back yard. It has grown so large (easily 25 feet tall and equally wide) that it hangs over our driveway, making it handy to grab a few as I hop in the car to run errands. The tree is in full sun at the bottom of a slope, and seems to be a satisfied recipient of all the runoff from our backyard. This position has resulted in a thick layer of soil and mulch in which it thrives.
We usually see small green fruit start to appear in early May, becoming fat and ripe by the second half of June. The tree produces steadily through early August, when the tree’s leaves turn crispy from the summer heat and there’s no more fruit to bear. The common fig doesn’t require a pollinator, so only one tree is necessary for production. The fiber-rich fig is also full of calcium, potassium, and vitamins A, E, and K. As it turns out, the “fruit” is actually a hollow peduncle (stem) that grows fleshy, forming a structure called a synconium. The synconium is full of unfertilized ovaries, making a fig a container that holds both tiny flowers and fruit in one.
The insides of a fig show the small flowering structures that form the larger fruit. Photo credit: Carrie Stevenson
With the hundreds of figs we’ve picked, my family has made fig preserves, fig ice cream, baked figs and of course eaten them raw. We typically beg friends and neighbors to come help themselves—and bring a ladder—because we can’t keep up with the productivity. Often you can tell you’re near our tree from around the block, as the aroma of fermenting fruit baking on the driveway is far-reaching.
No matter what you do with them, I encourage planting these trees in your own yard to take full advantage of their sweet, healthy fruit and sprawling shade. As Bill Finch of the Mobile (AL) botanical gardens has written, “fresh…figs are fully enjoyed only by the family that grows them, and the very best figs are inevitably consumed by the person who picks them.”
by Beth Bolles | Jul 7, 2016
Many of the plants in our gardens have been developed and discovered that offer interesting characteristics. These may include leaves with variegations, dwarf growth habits, or even contorted stems. We enjoy these plant differences and many of these plants are big business in the nursery trade. In nature, it is likely these interesting plant mutations would not survive as they are less likely to be able to reproduce successfully. Horticulture professionals keep these plants available most often by propagation through cuttings and tissue culture.
Sometimes in the landscape, nature prevails and we see one of our favorite plant varieties revert back to its original or “wild” form. You may see a stem on a variegated plant that has larger leaves that are all green.
‘Butterfly’ Japanese maple has beautiful variegated foliage. One stem has reverted to an original form with large green leaves. Prune out this stem. Photo by Beth Bolles
These stems often grow more vigorously and can use nutrients and energy that the remainder of the plant needs. As soon as you see these different stems, prune them back to a connection with another stem that exhibits the plant characteristics you want.
by Mark Tancig | Jul 5, 2016
When you don’t know what’s ailing your plant, ask an expert.
Many gardeners get stumped when a favorite plant of theirs comes down with a strange “something”. Many of these gardeners know about UF/IFAS Extension and call their local horticulture and agriculture agents for assistance in figuring out what’s going on. However, even these experts are often stumped by what they see. Fortunately, the agents have another layer of experts to fall back on. In addition to the resources in Gainesville, we have the Plant Disease Diagnostic Clinic, located at the North Florida Research Center in Quincy. Plant pathologists here can help determine what fungus, bacteria, virus, or viroid may be the problem.
Plant pathologists are basically plant doctors. They use all sorts of sophisticated techniques to determine what is the cause of a particular plant problem, from growing out fungal spores to examining DNA. Not only do these plant doctors tell us what the ailment is, they also provide recommended cures, or control options. They are also doing research to prevent different diseases from taking hold in our area and reduce the impact on our local growers.
Plant pathologist at work!
At a recent workshop in Quincy, we learned that plant pathology researchers are working on a fungus that affects watermelons, virus and bacteria that can wipe out a farmer’s tomato crop, and a virus that could impact our local roses. Working as a team of scientists, they study these pathogens in the lab and conduct controlled field experiments to figure out which techniques are most effective. Some of this research is leading to different methods and/or products that can help growers and gardeners alike keep their fields and landscapes healthy.
So, if your plants have problems, please contact your local Extension Office. If they don’t know the answer, then the network of scientists, including plant pathologists, in the UF/IFAS Extension family can be called on for backup to provide you with the best possible answer.
by Sheila Dunning | Jun 22, 2016
The showy chaste tree makes an attractive specimen as the centerpiece of your landscape bed or in a large container on the deck. Easy-to-grow, drought resistant, and attractive to butterflies and bees, Vitex agnus-castus is a multi-stemmed small tree with fragrant, upwardly-pointing lavender blooms and gray-green foliage. The chaste tree’s palmately divided leaves resemble those of the marijuana (Cannabis sativa) plant; its flowers can be mistaken for butterfly bush (Buddleia sp.); and the dry, darkened drupes can be used for seasoning, similar to black pepper, making it a conversation piece for those unfamiliar with the tree.
Vitex, with its sage-scented leaves that were once believed to have a sedative effect, has the common name “Chastetree” since Athenian women used the leaves in their beds to keep themselves chaste during the feasts of Ceres, a Roman festival held on April 12. In modern times, the tree is more often planted where beekeepers visit in order to promote excellent honey production or simply included in the landscape for the enjoyment of its showy, summer display of violet panicles.
Chaste tree is native to woodlands and dry areas of southern Europe and western Asia. It will thrive in almost any soil that has good drainage, prefers full sun or light shade, and can even tolerate moderate salt air. Vitex is a sprawling plant that grows 10-20 feet high and wide, that looks best unpruned. If pruning is desired to control the size, it should be done in the winter, since it is a deciduous tree and the blooms form on new wood. The chaste tree can take care of itself, but can be pushed to faster growth with light applications of fertilizer in spring and early summer and by mulching around the plant. There are no pests of major concern associated with this species, but, root rot can cause decline in soils that are kept too moist.
by Daniel J. Leonard | Jun 22, 2016
Gardeners in Northwest Florida were blessed this spring with conditions conducive to great gardening, mild weather and plenty of rain. However, with those pleasant conditions has come an unusually high occurrence of Fireblight. Cases of Fireblight have been brought into our office almost daily this spring/early summer!
Mature ‘Bradford’ Pear infected with Fireblight
Fireblight is a difficult to control, rapidly-spreading disease caused by a bacterium (Erwinia amylovora) that affects many fruit trees, especially apple and pear but is also seen on quince, crabapple, hawthorn, loquat and photinia. Fireblight is generally noticed in late winter and early spring during periods of frequent rainfall as the plant begins to bloom and leaf out. The bacterium enters the plant through the opening flowers causing them to blacken and die. The disease then makes its way down the infected stem, destroying newly developing twigs along the way. Most homeowners notice the problem at this point in the progression; the new shoots have died, turned black and hold on the plant, giving it the tell-tale “burned” look. Homeowners also generally notice sunken lesions, or cankers, that form on the infected stems.
So, with a problem as unpredictable and destructive as Fireblight, what can one do to prevent it or combat its spread? There is no one method that can prevent or cure a Fireblight infection but there are several precautions homeowners can make to mitigate its effects.
- Plant resistant species and/or resistant cultivars of susceptible species, such as pear and apple. Under conditions like we’ve had this year, no pear or apple is immune but these cultivars have some proven resistance:
- Edible Pear: ‘Keiffer’, ‘Moonglow’, ‘Orient’
- Apple: ‘Anna’, ‘Dorsett Golden’
- Ornamental Pear: ‘Bradford’, ‘Cleveland Select’
- Remove infected and dead wood when the tree is dormant. Make a clean cut at least 12” below the last sign of infected wood and dispose of it. It is always a good practice to sanitize your pruners between cuts on a diseased tree. Also, there is little evidence to suggest that pruning out diseased wood on actively growing plants has much effect on further disease spread as long as conditions are still suitable for Fireblight formation.
- If you have noticed Fireblight on your trees in the previous year, it is good practice to make a preventative spray of a copper fungicide prior to the plant breaking dormancy.
- During bloom, streptomycin may be applied every three or four days for the duration of the bloom cycle to prevent infection. Consult the label for required days between spraying and consumption.
Fireblight is bad news in a fruit orchard but homeowners can take heart in the fact that the condition is not always fatal, especially if the preventative measures outlined above (proper cultural practices, proper pesticide use, and planting of resistant cultivars) are taken!
