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!
Gardeners love to share plants. My yard, like many of my gardener friends, is filled with plant gifts that were started from a cutting or division of a favorite plant. These two methods of growing new plants is fairly easy once you learn the techniques and allows gardeners a way to save a little money and grow more plants for their yard, special community projects, or even some fundraising events.
In our enthusiasm over a favorite plant, gardeners must be aware that we are not allowed to propagate certain plants from cuttings or division. Many of our ornamental plants, especially newer introductions are patented plants. These are seen as ‘premium’ plants that will hopefully be in demand by the public. The plant developer or nursery invests in the patent in hopes that the plant will become the next must have ornamental. Only businesses or individuals with authorization from the patent holder are able to asexual propagate these plants since the Plant Patent Act protects these new varieties for 20 years from the date of introduction.
So if you bought a beautiful Limelight hydrangea (Hydrangea paniculata ‘Limelight’ Plant patent #12,874) for your yard, you may not take a cutting to start a new plant, even if it is only for yourself.
If you want more than one Limelight Hydrangea, you must purchase it. Photo by Beth Bolles
When you visit the nursery, look on the plant label which will often indicate if the plant is patented. You may also look online to see if plant has a patent.
Coral ardisia is also known as coral berry, spice berry, and scratchthroat. It was introduced into Florida in the early 1900’s for ornamental purposes.
Coral ardisia. Photo credit: Les Harrison.
In the ensuing years it has since escaped cultivation and become established in hardwood hammocks and other moist woods of natural areas and grazing lands. Specimens have been collected from 19 western and south-central Florida counties as of 2004.
This evergreen sub-shrub reaches a height of 1.5 to six feet and tends to grow in multi-stemmed clumps. Leaves are alternate, 8 inches long, dark green above, waxy, without hairs, and have scalloped margins and calluses in the margin notches.
Flowers are typically pink to white in stalked axillary clusters, usually drooping below the foliage. The fruit is a bright red, globose, single-seeded berry, measuring approximately 0.25 inches in diameter. White-berried populations are also known to exist.
Coral ardisia is considered invasive. Control of coral ardisia may be accomplished by two methods. A low-volume foliar application of Garlon 4 or Remedy provides suppression of this plant. Complete foliar coverage is essential to success and retreatment will be necessary for complete control.
Basal bark applications with Garlon 4 or Remedy in an oil carrier can also be utilized for suppressing this invasive weed. Do not apply more than 8 quarts of Remedy or Garlon 4 per acre and treat no more than ten percent of the total grazed area if applying greater than two quarts per acre.
Do you have azaleas or camellias with leaves that are thickened, curled and waxy in appearance? This is fairly common this year and is caused by a fungus.
Camellia leaf gall on Sasanqua Camellia. Note swollen, malformed leaves. Photo credit: Larry Williams
Exobasidium vaccinii is a fungus that causes leaves, and in some cases flower petals, to enlarge abnormally and is commonly referred to as azalea leaf and flower gall.
Infected azalea and camellia leaves become large and distorted. 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.
The disease relies on airborne spores produced in the whitish mold on the surface of galls in late spring to early summer to reproduce. Some plant pathologists believe that once the spores are released, they are blown and washed to leaf and flower buds where they cause new infections. Galls then form the following spring. Other plant pathologists think that the spores are produced the following year from the old dried, brown galls that fell to the ground around infected plants the previous year. In spring, the spores blow and splash onto new leaves and petals as they emerge causing infection. One or both lines of thought may be true. But in either case, 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 home landscapes. But you can reduce the amount of infection the following year by pruning infected leaves and throwing them away before spores develop. After removing infected leaves with galls, never leave them on the ground around the plants.
It’s best to bury, burn or place infected leaves in a plastic bag and throw them away. This disease is more severe during a cool, wet spring, which we experienced this year. 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. It’s best to water established landscape plants on an as needed basis.
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. Infected leaves will usually fall prematurely.
People are, by nature, skeptical. Humans are and have always been questioners of the world around them and that’s a good thing! For instance, when one reads a sensational article on Facebook or watches an infomercial selling a too-good-to-be-true product he/she is immediately dubious of the veracity of the claim. Given this innate sense, why do consumers take plant tags displayed on retail plants and the information listed there as infallible fact when in reality they are often full of hyperbole and misleading?
I do not mean to insinuate that nurseries and landscape professionals are intentionally leading consumers astray. They are not. However, there is much incorrect information disseminated to consumers by the green industry on plant fact sheets. Take my titular example, ‘Little Gem’ magnolia is widely advertised and sold as a “dwarf” magnolia, only growing 15’-25’ tall. If given proper care, it will grow to that height…in seven to ten years. Given enough time, ‘Little Gem’ has will grow in excess of forty feet. People plant this cultivar under the eaves of single story houses on a regular basis! I promise that cute little magnolia you were told would grow 15’ tall will look rather silly when it is four times the height of your house. Take another example, how many times have you seen or heard of ‘Acoma’ crapemyrtle being sold as a “semi-dwarf” cultivar that grows to 10’ in height for use in a tight spot of the landscape in lieu of the much larger ‘Natchez’? It will fill that tight spot and fill it rather quickly. ‘Acoma’ can easily reach 20’ in height and width at maturity, engulfing its intended area.
Typical plant tag. Notice the “Average Size” section. This is where consumers should use discretion.
So why does this happen? Why are plant tags so often mistaken? There are two primary reasons that correct mature sizes are not given. First, in the competitive world of plant breeding and introduction where there can be hundreds or thousands of cultivars of a single species, it is of utmost importance to introduce plants as quickly. Quick introduction is necessary because others are probably working to find similar traits; therefore, if one notices that a plant possesses a drastically different flower, flowering pattern, leaf shape, leaf size, or growth habit, the plant is often rushed to market. This leaves little time for complete trials of the plant to see what it would look like at maturity.
Secondly, most well-adapted or native trees/shrubs have relatively long life spans. A crapemyrtle or magnolia can easily grow and thrive in a landscape for thirty years or more before reaching maximum size. Nurseries simply do not have time to evaluate plants that long. Many nurseries, due to vagaries of economic cycles and length of career spans, don’t even exist for thirty years much less trial a single plant for that length of time!
In conclusion, nurseries are not likely to change their plant tag practices, but there are a couple of checks consumers can use to make sure they buy an appropriate plant for the scale of their site. First, it is a good rule of thumb to double the advertised plant height to arrive at a better idea of the plant’s mature size. Second, drive through established neighborhoods and observe what certain plants look like in a mature landscape. This will give one an idea of what the plant is capable of. The third and best option is to consult your local County Extension Office. They will be able to offer research-based information to help you make the right decision in your plant choices. Keep this in mind the next time you are thinking of buying the latest, greatest plant at your local nursery!
You could certainly argue that the azalea bloom is the symbol of the southeast during spring time. This time of year, yards across the panhandle explode with vibrant colors of this unmistakable flower bloom. Even though Florida’s azalea plants put on a spectacular flowery show, most of us pay very little attention to their management at this time of year. However, the kind of care azaleas receive in late spring and summer can have an effect on the bloom production for next season. There are some management measures that can be done during this time to ensure that you have a bountiful azalea bloom next spring.
Credit. Carolyn Wildes, UF/IFAS.
Chlorosis, a condition that causes leaves to produce insufficient chlorophyll, is the most common problem with azaleas this time of year. Fortunately, this is easy to recognize and correct. Chlorosis shows up as yellowing in between the veins of leaves, the veins stay dark green. It’s caused by lack of available iron in the soil.
To correct chlorosis, add aluminum sulfate to the soil. The addition of ¼ to a ½ pound per square yard of soil surface should suffice. Broadcast the aluminum sulfate over the soil surface and add a layer of mulch. It’s important to remember that you should not apply aluminum sulfate more than once a year. More applications will cause detrimental effects to the plant. Other chemicals that are useful in correcting iron chlorosis in azaleas are ordinary agricultural sulfur, ferrous sulfate and chelated iron compounds. Each of these chemicals have different application directions, so be sure to read the labels for direction of use.
Proper watering is also imperative. Generally, established plants should receive ¾ – 1 inch of water every 10 days to 2 weeks during dry periods to wet the soil to a depth of 10-12 inches. When the weather is hot and dry, azaleas need soil saturation in the root zone once a week. Azaleas have shallow feeder roots that dry out very quickly if the soil is dry. Remember, soil with a sufficient amount of organic matter holds moisture better than sandy soils, and will require less watering. Also, a mulch layer helps to reduce evaporation and keep the soil cool and moist.
Pruning your plants should be done in late spring. If you prune later in the year, there’s a good chance you may reduce or eliminate flowers for next year. Usually it’s best to prune right after flowering.
As for fertilizer applications, frequent and light applications are necessary in Florida’s sandy soils. Acid-forming fertilizers like 12-4-8, 15-0-15 or ammonium sulfate should be applied in all four seasons. Apply approximately ¼ pound to a mature plant, or ¾ to 1 ½ pounds per 100 square feet.
Following these recommendations will help secure your rich bloom season for next year.
