Cold damage on kumquat. Photo by Beth Bolles, UF IFAS Extension Escambia County.
In December, winter rolled in with extreme low temperatures that affected landscapes across Florida. Horticulture Agents have been receiving a high volume of calls asking about the long-term fate of landscape plants impacted by the cold, so the Gardening in the Panhandle team decided to offer a special episode addressing these concerns.
Gardening in the Panhandle LIVE! Special Episode Freeze Damaged Landscapes will be held on Thursday, January 12, 2023, at 12:15 p.m. CDT/1:15 p.m. EDT. We will follow our usual format where the audience can join on Zoom, Facebook, or watch a recording on YouTube. The only change is that this program will be condensed to 30-45 minutes, rather than a full hour.
Freeze warning is a terrifying phrase for gardeners. Cold damages your plants and may even kill them outright. Understanding how plants freeze will help you create mitigating strategies for their preservation. Informing yourself as to how freeze damages plant tissues will allow you to fortify your garden.
How do Plants lose Heat
Cold exposure happens in a couple of ways. Radiant heat loss occurs when one surface emits waves of heat into a colder surrounding environment. The surfaces of leaves and stems are not immune to this type of temperature transfer, nor is the soil in your garden beds. Frost may or may not form depending on moisture levels in the air, but cold damage will still be the result. The other main source of heat loss in gardens is through Advective freezes. These occur when cold air from the north moves south en masse resulting in colder temperatures and often increased winds. Mitigating this is a little tougher than radiant losses but not impossible
IFAS Photo
As with all things, planning is at the forefront. When designing your garden, cold hardiness should be considered. Certain plants naturally handle cold weather better than others. Utilizing native plants and those specified for your USDA hardiness zone will keep gardens alive in winter months. These tend to be acclimated for colder temperatures. Once the proper plants are selected and planted, ensure they are properly treated. Keeping your plants as healthy as possible is also critical in cold tolerance. Mulches and watering prior to a freeze event will reduce risk from radiant heat loss. The water absorbs warmth through the day and holds onto it more efficiently than dry soil would. Addition of a frost blanket will further reduce heat lost and ultimately the damage to your plants. A slightly more in-depth protection method comes from establishing microclimates in your yard. Use taller trees and windbreaks. Taller trees create a canopy that blocks heat loss to the atmosphere. Windbreaks keep the colder air away from your gardens and again prevent heat loss. None of these methods are fool proof but will help keep your gardens alive through the colder months. You may still experience damage from freezes. If this does happen, make sure your plants are watered to thaw any roots ensuring they function properly. Inspect stems by scraping a little tissue. Prune away any that shows black or brown tissue while keeping any which still looks green.
IFAS Photo
Summing up
Freezes can be devastating to your gardens. A little knowledge can go a long way toward mitigating loss. For more information on cold protection, see this Ask IFAS document, or contact your local extension agent for additional information on this and any topic regarding your gardens and more.
Turfgrass lawns are popular. Homes and businesses alike often have at least some portion of their landscape dedicated to turf, and while it is often maligned, turfgrass does have some benefits when used and managed responsibly.
Well-managed turfgrass, like this centipedegrass lawn, can be a sustainable and attractive option for landscapes. Photo credit: Dr. J. Bryan Unruh, UF/IFAS
Detractors of lawns may argue that lawn maintenance uses water, gasoline (for mowers), and pesticides, all while contributing little to the environment. The varieties of grass we use in the Florida panhandle are not native to the area, with the possible exception of St. Augustinegrass. Planting anything – and especially non-native plants – in a monoculture limits biodiversity and does not support native wildlife. These complaints may be valid in cases, but this does not mean there is no room for turfgrass in the landscape. Instead, it is important to design landscapes appropriately and maintain lawns sustainably. The ideal of a lush, completely weed and insect free, beautifully green all year long, neatly trimmed magazine-cover style swath of grass is unrealistic.
That being said, what are lawns useful for? What are the benefits of turfgrass?
When managed properly, turfgrass can be used for numerous beneficial reasons. Grass is a plant, which means that it has roots to stabilize soil, slow runoff, and filter water. It keeps down dust, mitigates heat, and can outcompete unwanted weeds. It is useful as a surface for recreation, and can add aesthetic value to a landscape. Turf does, in fact, support wildlife to a certain degree as well, as the insects that live in and feed on it can serve as food for birds and other animals.
Improper irrigation can cause big problems with turf and lead to wasted water, but turf can help to slow down runoff and absorb excess nutrients.
Artificial turf is sometimes considered as an alternative to grass, but the differences can serve as an example of the benefits of turf. Artificial turf can heat up in the hot Florida sun. Where it is used on athletic fields, it may need to be irrigated to both cool it and keep dust down. The water used for this has much more opportunity to run off the site, as the artificial turf has no roots to slow it down. Turfgrass is also much softer than its man-made replacements; sports fields with artificial turf have a higher incidence of injury than those planted with grass.
Lawns must be managed well, however, as has been stated before. Proper species selection (whether bahia, centipede, Bermuda, St. Augustine, or Zoysia), establishment, irrigation, fertilization, and mowing practices all contribute to making turfgrass a sustainable option. You can find information on all of these in our EDIS publications, which are linked to above, or contact your local Extension office for help. If turfgrass still seems like an unpalatable option, you can also find information on turfgrass alternatives and more on Florida Friendly Landscaping. Keep your expectations reasonable and your landscapes sustainable!
This month’s program focused on Gardening Myths and Home Remedies providing clarification of commonly held beliefs and insight into homemade gardening products. Below is a summary of the program with links references.
Panelists introduction:
Beth Bolles – Horticulture agent, Escambia County (Moderator)
Donna Arnold – Agriculture and Horticulture agent, Gadsden County
Mark Tancig – Horticulture agent, Leon County
Larry Williams – Horticulture agent, Okaloosa County
Dr. Adam Dale – Associate Professor at UF, Home Landscape Entomology
Dr. Dale was asked about use of home products for pest control:
He pointed out that products designed to eliminate pests are specific for that purpose. Those meant for use in the home such as Dr. Bronner’s soap are not designed as pesticides and have not been tested for that purpose. The Environmental Protection Agency (EPA) would tell you that it is technically illegal to use this product in that manner. There may be risks associated (to pets, humans, and plant life) with using these products as pesticides. Specifically spraying soap-based products on plant life is that soaps are designed to strip oils including protective oils from leaves potentially causing damage to your plants
Some products may have breakdown issues leading to phytotoxicity or may have cost/availability issues. Products may not be labeled specifically as pesticides, but all labels should be read and followed.
Your local extension agent is a good guide toward an appropriate solution for your specific issue.
Dr. Dale discussed natural pest control through plant selection:
To him, selecting plants which are less susceptible to pest is the key. For example, Yaupon holly (Ilex Vomitoria) or Dahoon holly (Ilex cassine) may be a better choice for Florida landscapes than Chinese holly (Ilex cornuta) or American holly (Ilex opaca). As a bonus, proper plant selection reduces management in your gardens.
Mark then dispelled myths surrounding using plants as mosquitos (Culicidae) repellant:
His quick answer was no, unless you were in a field of citronella (Cymbopogon nardus) and were to roll in the plants no research shows them to be effective in small scale plantings. Extracts from some of these plants do have some efficacy, but it is limited. Toward the back of the UF/IFAS Mosquito Control Guide outlines control strategies base on research. Primarily, eliminating standing water around your home including gutters which may accumulate organic matter and retain moisture is most effective. That is not to say a bird bath or rain barrel must be emptied. A similar product to Bt is Bti (Bacillus thuringiensis subsp. Israelensis) commercially sold as mosquito dunks. These are donuts or crumbles are designed to eliminate mosquito larvae in rain barrels or birdbaths thus breaking their life cycle.
Dr. Dale was asked a question on the efficacy of companion plantings:
He defined it as using plants which attract beneficial organisms. Beneficials are predators or parasitoids reducing or controlling pests in your landscape. This is not an all-encompassing solution but makes a big difference. The example cited was lawn landscapes with flowering plants nearby vs those that do not. The lawns with flowering plants have about 50% more predation and parasitism of caterpillar pests reducing pest stress.
Links were not shared during the broadcast, but here is some helpful information:
Larry was spoke concerning fall web worm (Hyphantria cunea):
He reemphasized Dr. Dale’s opinion that landscapes be planted with pest resistant varieties. Fall web worm is commonly found in many fruit, flowering, and nut trees and are easily identified by the cobwebs which begin to appear in the late summer/early autumn. This insect feeds on the leaves of these trees and tends to appear on deciduous species. This makes us worry more so than the plant does as the trees are shedding those leaves anyway. Pruning or spraying to eliminate this pest may be more detrimental to the plant than letting the insect run its course. As spring comes around and the tree puts on new leaves, they’ll appear blemish free. Better to think of them as extra Halloween decoration than treat something that isn’t causing significant damage.
There is some research showing corn gluten meal can be effective, but only as a preemergence and even then, only on some weeds. Application to growing weeds is ineffective. For larger issues it is better to work with extension agents to establish a management plan utilizing known products. Doing so may save the effort and money applied to ineffective weed control.
Beneficial nematodes are microscopic worms in soil which act as a parasitoid for soil borne insect pests. Essentially, they release a bacteria into the insect and use it to reproduce. The offspring feed on the bacteria until the host dies and the offspring is then released in the soil. They are an effective tool in IPM but have specific environmental needs to survive. They will most likely already be present in the soil, but there are commercial products containing them available.
Donna answered a question concerning lowering soil pH using sulfur.
It is a temporary fix and will be localized to the application site. Repeated applications will be needed and may cause damage to the plant life in that location. A more permanent fix is to plant appropriately for your soil conditions. These conditions may be determined through soil testing.
Larry was asked about snake repellants and whether moth balls are effective in this arena
Florida has 46 species of native snakes and only a handful are venomous. Snake identification is crucial as many have beneficial aspects. A lot of mythology surrounding snakes come from fear. Snake bites should be taken seriously but are rare, and often the person is ok post bite. There are deterrence products available, and some contain the same ingredients as moth balls. The problem with these lies in their susceptibility to environmental conditions. We get lots of rain and these chemicals wash away easily reducing their efficacy. A better method is to eliminate habitat around your home. Overgrown areas and log piles fall into this category. Keep in mind, you’ll need to clean up anything attracting other animals the snakes view as prey. Finally, inspect your home for any entrances snakes may use to enter your home and eliminate these.
Mark clarified concerns with biosolid based compost in the garden.
Biosolids are a byproduct of the wastewater treatment. At the end of the processing, there is a sludge remaining. Normally it is not recommended for any crop intended for human consumption. The Escambia County Utilities Authority (ECUA) composts this sludge other products such as yard waste to create a product that is safe for vegetable gardens. That said, it is best to apply these 120 days prior to harvest of leafy greens or 90 days for crops not touching the ground such as tomatoes as you should with all manures.
Dr. Dale was asked about vegetable oils as an alternative to petroleum based horticultural oils.
It is not a good idea to use oils other than those designed for horticulture on your plant life. It opens that plant to potential harm as the leaf cuticle and other tissues may be inhibited from their natural processes. There is no known pesticide use for these products and they are not labeled or tested for this use.
Mark spoke to using home made products using vinegar to control weeds.
There are vinegars designed for weed control, but these products are labeled and tested for this purpose. Using vinegar designed for use in the household will likely have undesired effects. Namely die off of desired landscaping for indeterminate periods. A more effective method of weed control is hand pulling.
Larry then addressed using Epsom salts in the garden.
This may be a practice passed from neighbor to neighbor. Epsom salt is made of magnesium sulfate. Both are micronutrients needed by plants for healthy growth. The neighbor who had this trick work may have been lucky in that their plants were deficient in these elements. A better way to approach this problem is through soil testing. These tests will show elemental deficiencies which may be used to establish a fertilizer program designed for your needs.
Donna was given the question as to use of eggshells in soils
The easy answer to this is yes, but use is conditional. The plant will have a hard time absorbing the calcium from eggshells in their whole form. Grinding the shells will help with this process. A better way may be to add them to your compost, but even with this, you’ll benefit from grinding them.
A question came in from facebook asking if coffee grounds acidify soil.
Mark spoke up and stated that most of the acid form coffee grounds winds up in the coffee itself, and that it is considered a “green” or nitrogenous product in composting. As most of the acidity is gone by the time they are applied to the garden, there is little effect on soil acidity but may aid soil microbiota. The key is moderation, coffee grounds should be thought of as amendments and used lightly.
Dr. Dale and Donna were asked about fire ant control
Grits and club soda are not effective tools for fire ant control according to Dr. Dale. Fire ants are an invasive species that has moved into the southern portion of the country. They are aggressive and may create large mounds and if disturbed they will sting (not bite). The most effective control for them is to use insecticide specifically designed for fire ants. Broadcast or spread these around the mound. The key here is around the mound, not on top. Bait placed on top of the mound will be treated as a disturbance and cause the colony to move rather than be eradicated. Many home made fire ant controls also encourage relocation and may cause damage to your plants. The key to ants is eliminating the queen, insecticides applied according to the label are designed for this purpose.
Gardening and pest control are surrounded with myths and home remedies. The best solution is always to find products specifically designed to resolve your specific problem. If you need help, your local extension agents are available and ready to help.
Homeowner accounts of white fluffy woolly masses on woody ornamentals, oak trees and Muhly grass have been on the rise. The good news is they are native insects that need a nursery for their young and will cause little harm to the host plant. The bad news is scientists know very little about the complete live cycle and role in the environment of these insects.
Within the cottony mass there are citrus flatid planthoppers, woolly oak aphids, or Muhly mealybugs. The adults have laid eggs or birthed their young on the leaves. The young nymphs have excreted large amounts of the woolly wax to protect them from predators and weather while they grow larger. Food from the plants is needed to grow, so these piercing-sucking insects are removing sugars from the host plant. But, typically it is not enough to significantly change the plant’s appearance, so most people are not alarmed until they notice “all the white stuff”.
Adult citrus flatid planthopper, Metcalfa pruinosa
(Say). Credits: Photograph by: Lyle J. Buss, University of Florida
The only one that moves quickly are the citrus flatid planthoppers. When a person reaches for the flocked branch, something small moves and seems to jump at you. Most likely the jumping direction is away from you, but it still may be startling. They are planthoppers (Metcalfa pruinosa), an insect in the order Hemiptera. As the name implies, they occur on citrus but can also be found on many woody ornamentals and other fruit trees. The adult planthopper wing arrangement is tent-like, meaning that the forewings are held over the insect abdomen in a tent configuration.
Stegophylla brevirostris Quednau colony on oak. Photograph by Susan E. Halbert
Woolly oak aphids are conspicuous pests on oak (Quercus spp.), because they are covered with large amounts of flocculent wax. Two genera of woolly oak aphids occur in Florida. One species, Stegophylla brevirostris Quednau, is common, and the other, Diphyllaphis microtrema Quednau, is rare. Florida woolly oak aphids are recognized easily by the large quantities of woolly wax that they secrete. Beneath the wax, aphid bodies are pale. Young nymphs are typically pale green, and they tend to be more mobile than adults. The majority of reports of woolly oak aphids indicate a preference for live oak (Quercus virginiana Mill.) as the host. These aphids are live-bearing females. It is not known how these aphids disperse, but possibly they are picked up and carried by birds and larger flying insects because of the sticky wax that surrounds the bodies of the aphids.
Muhly grass infested with mealybug. Photo: Beth Bolles
Muhly grass (Muhlenbergia capillaris) is a generally pest free plant in its native habitat, however, the native mealybug, Stemmatomerinx acircula, has made an appearance on plants in various landscapes. Insects feed on the leaves and are grey with white wax that may have some filaments. You may also see long ovisacs on the leaves which contain eggs and crawlers. With close inspection, you will notice they have legs and can move about.
So “what do you do?’ If the plant doesn’t appear to be suffering, let nature take its course. “This to will pass.” If someone demands perfection, use insecticidal soap to reduce the population. The soft-bodied creatures will dry up before they can become adults. To read more about these odd creatures of nature go to: https://entnemdept.ufl.edu/creatures/
Many future problems can be avoided by paying attention to tree selection, planting and maintenance in Florida’s high wind climate. We may think of tropical storms causing tree damage but our typical summer thunderstorms can produce winds in excess of 50 miles per hour with downbursts reaching over 100 mph.
There is no way to protect trees from all storm damage. Trees are not adapted to worst-case storms, such as Hurricanes Michael or Ian, only to our average wind climate.
It’s wise to take time to select and correctly plant the right trees for North Florida.
Past hurricanes have taught us that large growing trees planted too close to curbs, sidewalks or buildings blow over easily because they don’t have adequate room to develop a sound root system. It’s best to either plant these trees farther away, plant trees that may stay small, or increase the size of space allocated for tree root growth.
Research and storms have taught us that tree roots need large soil spaces for strong, stable growth. The more rooting space trees have, the less likely they are to fail. Strong root growth is essential for tree stability and health. Large maturing trees need at least 30 feet by 30 feet (900 ft. sq.) of rooting space. Many construction practices such as paving over roots, raising and lowering soil grade, and soil compaction from equipment result in root injury for existing trees, making them less durable and less stable.
Magnolia Tree in the Landscape. Photo courtesy Stephen Greer
Studies have also shown that trees growing in groups better survive high winds compared to individual trees. A group was defined as five or more trees growing within ten feet of another tree, but not in a row.
A short list of large maturing, storm resistant trees to consider include live oak, sand live oak, bald cypress, pond cypress, black gum and magnolia.
Do some homework and take a look at tree species that have done well in your area. If you don’t want or need a large tree in your yard, there are many small and medium sized wind-resistant trees from which to choose, like Crape Myrtle and Vitex. Many palms are wind resistant too, particularly the cabbage palm.
Having success with trees in the landscape involves starting with healthy, well-developed trees. Plant the right tree in the right place. Follow good planting procedures, including not planting trees too deep and providing adequate root space to allow for strong, healthy root growth. Practice correct maintenance techniques, which includes learning how to prune to produce a structurally sound tree. Finally, consider if it is time to be proactive and have large over-mature, declining trees removed and replaced before the next storm.
