It has been a hard summer climate wise and as we go into fall it is nice to start getting some relief from the heat. As the heat tones down, we are still facing a drought, which is not as severe as areas to our west but is still significant across much of the Panhandle. In our tree cover, the stress from the harsh summer this year is starting to show. You can see it in trees around the area, and it particularly seems to affect certain trees and conditions more than others. Where you are starting to see it most is in our ever-present pines, which make up the majority of our forest and tree cover in our region. If you keep a look out you may notice some pines in the areas with yellowing or brown needles or that are losing their needles. Those are clear signs of a possible bark beetle attack, which is a common issue when pines are stressed or damaged. Trees planted in the last year that are not yet fully established often show stress in a hot dry summer like this year. Even older and well-established trees in areas are showing some signs of stress from the hot dry conditions we have had this summer. Some trees are less adapted to dryer areas and when planted off site can experience more stress in dry conditions. If you look around across the Panhandle right now you can see clear signs of stress in some trees. It becomes more evident in late summer and early fall as the accumulated stressors of summer push trees into physiological conditions that cause stress responses. The big question is what to do if you notice a landscape tree that is exhibiting signs of stress, particularly drought stress.
Pine damaged by construction equipment. Barking injuries like this can encourage bark beetle attacks. Photo Credit: Ian Stone
For pines the issue is likely to be bark beetles, of which there are several types. All pine bark beetles are native to our area and the degree of damage they do varies by species and conditions. The issue with stressed trees is that most bark beetles attack those trees. When a hot dry summer occurs bark beetle activity increases as the stressed trees become less able to fend off attacks by these beetles. Unfortunately, when bark beetles attack a pine in an area the best answer is prompt removal and disposal of the infected tree material. To protect high value trees in an area where bark beetles are active there are some injection pesticides that can prevent infestation, but once a tree has been infested and begun to show symptoms little can be done to bring it back. When bark beetles attack a stressed pine, most are effectively finishing off a tree that may have died regardless. The key is to prevent them from spreading to other pines in the area or attracting them to a stressed tree in an area. With trees already stressed in our area the big prevention option is not to damage or stress any pines already on the landscape. Most pine bark beetles are attracted to trees by chemicals in pitch and resin given off by wounds or damage. Often the stress from new landscaping projects or construction around pines can cause several to succumb to bark beetles. Your best prevention is to keep equipment well away from the tree and avoid damaging or injuring the tree, especially scraping areas of bark off. Larger and older trees can be vulnerable, as well as overcrowded trees that are too dense or overtopped by others. As the cooler weather approaches bark beetle activity should decrease along with the risk of losing a pine to these pests.
Recently constructed sidewalk. Construction activities extended well into the root zone of the tree, which can cause stress and damage. Photo Credit; Ian Stone
For other trees there are additional precautions that can be taken to lessen the potential that a tree will succumb to drought and other stress. Newly planted trees or those established in the last several years are particularly at risk and should be watered regularly during this dry period. Until rains return, a good method of slowly applying water deeply to the root zone is best. Properly applied mulch can help keep the soil cooler and moist around a newly planted tree. Drip irrigation, soaker hoses, and similar methods are best, and a method that specifically applies water slowly to the tree’s root zone gives the best results. Watering your lawn does not supply sufficient water to landscape trees, especially in drought conditions. Lawn irrigation is designed to apply irrigation needed to the top portion of the soil that is available to the grass. Trees have completely different requirements and need different watering methods and amounts. If you don’t have dedicated irrigation available and you have a tree that needs water, you can use irrigation donuts or bags. These are often a good solution for a tree that needs watering temporarily. Once a tree is well established it usually can withstand even severe drought, but during the establishment phase paying attention to water needs is critical in a summer drought like we have had.
Large established trees are also not immune from the heat and dry conditions that have plagued the Panhandle this summer. Usually when conditions change these trees recover but may abort some branches or exhibit some leaf drop while stressed. Leaf drop is a phenomenon that can occur when deciduous trees are stressed. It is a method of conserving water needs by reducing the leaf demand. Usually, the tree will recover and leaf out again fine next year. A tree may abort some branches or have some branch tips die back to make it through a rough period. Trees that are overcrowded, overtopped, or have other issues are the most at risk from environmental stress. This is why good tree selection along with proper tree care and maintenance is essential. When a hot dry summer like we have had comes along well cared for and maintained trees do best. Trees that prefer more moisture like bald cypress, red maple, sycamore, and some oaks can be planted in dryer sites, but when a severe drought comes along they often don’t have the ability to handle the moisture stress that trees adapted to dryer sites can. This is why site selection is so important, it is when we have extreme conditions that off site plantings typically suffer the worst and those can be larger more established trees.
With the cool weather hopefully we will get a reprieve and some rain soon. Given that fall is one of our dryer periods it may be likely that drought conditions could persist until early winter. Good care and tree maintenance is essential to getting your trees through stressful periods like this summer. For younger trees watering and care is essential while they get established. For older established trees avoid doing any construction or other disturbing activities around them until conditions improve. If you have trees that are exhibiting signs of decline or pest attacks call your local extension office or Florida Forest Service County Forester office. With any luck, colder weather with winter rains will be here soon and trees in our area will recover over the dormant period.
Sometimes we just need a little privacy. This is especially true if you live on a busy road or just have annoying neighbors. There are a few things to consider when selecting a screen tree: 1) full-grown size; 2) speed of growth; and 3) aesthetics. With these three factors in consideration, let’s review some screen options for different situations.
Pineapple Guava (Acca sellowiana) hedge. Photo Credit: Daniel Leonard, University of Florida/IFAS Extension – Calhoun County
Pineapple Guava (Acca sellowiana)
At one time this shrub was hard to find, but it is slowly becoming more available. Pineapple guava is native to South America, but it adapts well to the Florida Panhandle. This plant can reach 10 to 15 feet in height with an equal spread and has a moderate rate of growth, so it’s a great choice when you just need a small screen. Pineapple guava is moderately salt-tolerant and does well in coastal landscapes. As a bonus, the flowers and fruit are edible. It’s hard to find a more aesthetically pleasing large shrub. Pineapple guava is evergreen with leathery green leaves that have grey undersides. This plant can be grown as a large shrub or pruned to be a small tree.
A large ‘Emily Bruner’ holly at the Santa Rosa County Extension Office. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
‘Emily Bruner’ Holly (Ilex x ‘Emily Bruner’)
‘Emily Bruner’ holly is a cross between the Chinese holly (Ilex cornuta) and the lusterleaf holly (Ilex latifolia). This evergreen shrub has glossy green leaves. It has a pyramidal growth habit and is listed as reaching 15 to 20 feet tall by 5 to 8 feet wide, however the specimen at the Santa Rosa County Extension Office is about twice that size. ‘Emily Bruner’ holly prefers moist, well-drained soil. This holly has dense, prickly leaves so it does well keeping people out of your yard in addition to buffering sound. The flowers have a sweet scent and are a favorite of honey bees.
Dahoon holly foliage and berries. Photo Credit: University of Florida/IFAS
Dahoon Holly (Ilex cassine)
Dahoon holly is native to North America, is tolerant of wet, shady sites (but can also handle full sun), and displays some salt tolerance. This evergreen, small tree is somewhat shrubby. It can grow to be 25 to 30 feet in height with an 8 to 12 foot spread. Dahoon holly has nice light green leaves that are smooth, not prickly like ‘Emily Bruner’ holly. It has a moderate growth rate.
Bracken’s Brown Beauty as an accent tree in a lawn area. Photo Credit: Beth Bolles, University of Florida/IFAS Extension – Escambia County
Southern Magnolia (Magnolia grandiflora)
It’s hard to beat a majestic southern magnolia in the landscape. Why not utilize it as a screen tree? Now, not all southern magnolias are made equal. There are a few cultivars that do well as screens as well as on their own. ‘Bracken’s Brown Beauty’, ‘Claudia Wannamaker’, and ‘D.D. Blanchard’ are three that come to mind and are readily available in the trade. Southern magnolias can reach up to 80 feet tall and 20 to 40 feet wide depending on cultivar and growing conditions. Not only do these three cultivars have beautiful dark green, leathery leaves, their leaves also have brown undersides. These versatile trees can tolerate are variety of soil conditions and they are very wind resistant. And as another bonus, they have beautiful, fragrant flowers.
Middle-aged Juniperus virginiana ‘Burkii’: Burk Eastern Redcedar. Photo Credit: Ed Gilman, University of Florida/IFAS
Eastern redcedar (Juniperus virginiana)
If your looking for softer texture in your landscape, then you can’t go wrong with a cedar tree. Unbeknownst to its name, eastern redcedar can be found growing all over the United States. This evergreen conifer prefers well-drained sites in full sun. It can grow 30 to 40 feet in height by 10 to 20 feet wide. Eastern redcedars have good salt tolerance. These trees produce beautiful, blue-green foliage. One key to growing this tree successfully is to give it space. Plant trees 12 to 24 feet apart. If using as a screen, you may consider staggering this tree to give it the space it needs.
There are lots of good options when selecting trees for a screen. It’s important you select plants that fit the site. The University of Florida has an excellent plant selection tool found at the Florida Trees for Urban and Suburban Sites webpage.
Moderate to strong El Nino conditions were predicted for this summer and I think this revelation has come true. The heat and humidity in the latter part of June were on the verge of being unbearable and the precipitation cycle is unpredictable. In the middle of the month, a series of storms with strong winds hit a number of areas in the panhandle, bringing down some large trees. University of Florida/IFAS Extension recommends removing large branches and trees that pose a threat to damaging your home and other structure before the start of each hurricane season. However, sometimes we just don’t get around to removing these trees until after they fall.
Trees laying on the corner of a house. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
Luckily only the tops of the trees in the photo above fell on the roof of the house. These are laurel oaks (Quercus laurifolia) which are fast growing but not tolerant of wind. In this situation, four trees fell together and are laying on the corner of the roof. The trees also pulled down the power, cable, and phone lines to the house.
So where do we go from here? Unfortunately the trees were uprooted and pose the potential for additional harm to the house if not removed correctly. In this situation, a tree service that owns a crane was recommended to remove the trees without administering more damage to the home and other trees and plants in the landscape and to avoid knocking down the powerlines again.
A crane used in conjunction with a boom lift to cut and lift trees off of a house. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
The tree service utilized a boom lift and a crane to safely lift the trees away from the house and utility lines. The employee on the lift connected each section of the tree to the crane before each cut. The boom was then moved to a safe location before each tree section was lifted away to the road to be cut into smaller pieces.
In this situation, the homeowner was lucky. There was no damage to the house other than a couple bent panels on the metal roof. However, this little bit a damage could have been totally avoided if these weak trees had been removed before the storm hit.
The trees featured in this article fell during a thunderstorm and possible tornado. If these trees had fallen during a weather event that was Federally declared, then a portion of the cost for their removal and cleanup might have been eligible to be considered an itemized deduction on Federal income tax forms. For more information on filing this type of loss please read the publication “Income Tax Deduction on Timber and Landscape Tree Loss from Casualty” from the USDA Forest Service.
After Hurricane Michael indiscriminately felled millions of trees in the Florida Panhandle five years ago, I’ve gotten much more selective with which trees I recommend to shade-seeking homeowners. Category 5 hurricanes don’t strike every year, or even every decade, but Michael reminded us that 150 mph+ wind events are possible, and we should choose the trees we plant accordingly. Keeping Michael’s lesson in mind, the shade tree I’ve recommended most to area homeowners lately is the ultra-wind resistant Nuttall Oak (Quercus texana) *.
While probably not native to our area (Nuttall is native to Mississippi River Valley bottomlands and nearby Gulf Coast regions), Nuttall Oak is a well-adapted deciduous oak species perfect for the Panhandle. The species is a strong, long-lived tree, yet also a quick grower (3-4’ per year in its youth, reaching 60-80’ at maturity). Unlike many rapidly growing trees, Nuttall is extremely resistant to wind breakage, disease, and other disfiguring issues. There are several Nuttall Oaks in Panhandle landscapes that survived Michael’s fury completely intact, with little more than wind-whipped leaves as evidence a storm had passed.
10 year old Nuttall Oak in a Calhoun County landscape. Photo courtesy of Daniel Leonard.
Nuttall is also an awesome landscape ornamental and a wildlife magnet in maturity. The species possesses a strong central leader and a stately, upright-rounded appearance. In summer, Nuttall leaves are large, dark green, deeply lobed, and pointed, somewhat reminiscent of our native Southern Red Oak. In fall, trees are capable of Blue Ridge quality color with fiery orange-red foliage, though the foliage show is not as consistent year to year here as farther north. The bark of Nuttall even has aesthetic appeal – dark and smooth in youth becoming ridged/furrowed with age. And it’s not just people that find Nuttall attractive, several beneficial insects use Nuttall as a host plant and various wildlife (deer, squirrel, and ducks especially) are fond of the prolific, highly nutritious acorns that mature trees produce in earnest each winter.
Finally, Nuttall is among the easiest of trees to grow and thrives in a variety of landscape conditions. Because it’s adapted to grow in poorly drained bottomlands that are either seasonally flooded or very dry, Nuttall is very tolerant of both compacted, poorly aerated soils common in urban areas and unirrigated, often droughty soils present in many Panhandle landscapes. However, like any tree, Nuttall Oak performs best with regular water and fertilizer for the first couple of years until established.
If you’ve been searching for a native-ish, hurricane-resistant, quick-growing, low-maintenance, wildlife-attracting shade tree for your property, Nuttall Oak is an excellent option and one I can fully recommend! For more information on Nuttall Oak or any other horticultural topic, please contact your local UF/IFAS County Extension Office. Happy gardening!
*Nuttall Oak was recently reclassified botanically from Quercus nuttallii to Quercus texana.
Written by: Muhammad Adnan Shahid and Shahid Iqbal.
UF/IFAS Horticultural Sciences Department, North Florida Research and Education Center, Quincy FL
Biostimulants are a type of substance or microorganism applied to plants to improve their nutrient efficiency and resistance against abiotic stress (salinity, cold, heat, UV, flooding, drought, heavy metal toxicity, nutrient deficiency), diseases, and quality traits. Due to the increase in world population, the growing pressure on crop productivity is a demanding challenge; therefore, it is necessary to reduce the use of agrochemicals with negative impacts on human health and the environment. Thus, new strategies from the bio-based industry must be found and adopted. Citrus is a highly desirable and profitable fruit crop with undesirable characteristics like excessive flowering and physiological fruit disorder that negatively affect the market value.
Biostimulant Types and Practical Application
Many crop growers have expressed an interest in biostimulants in recent years. As these products gain popularity, we have found that there’s still a lot of controversy about their efficacy. Before determining whether Extension endorses them, let’s review the various types and their practical usage.
Several types of biostimulants include humic and fulvic acid, seaweed extracts, protein hydrolysates, chitosan, beneficial bacteria, fungi and microbial inoculants, and other types of amino acids and polyamines. These products are commercially available with different formulations and ingredients and have immense potential in horticultural crop production, especially in citrus.
Plant biostimulants can be applied through foliar application, fertigation, or directly through the soil, enhancing crop growth and quality. Biostimulants could reduce plant environmental threats and minimize the negative consequences of unsystematic chemical application.
Benefits of Using Biostimulants in Citrus Crop Production
Biostimulant products improve plants’ overall health and help maximize fruit production and quality by providing complete nutrition. The benefits of using biostimulants are highlighted below.
Improve plant metabolism to induce high-yield and quality.
Enhance soil fertility by fostering complementary soil microorganisms.
Increase tolerance against abiotic stresses.
Facilitate nutrients and their movement inside the plant vessels
Boost fruit quality attributes like color, sugar content, etc.
Application of biostimulants and its effect on plant growth and quality traits.
Concluding remarks and recommendations
Biostimulants are in the frontline as a novel strategy to achieve the goal of sustainable citrus crop production, yield, and superior quality. Proper management practices are important for high-yield and quality fruit in citrus production. The use of biostimulant products can provide producers with sustainable production. Before using these products, contact a regional extension specialist or citrus expert for their proper application and trail setup. The Fruit Physiology Lab at North Florida Research and Education Centre (NFREC), Quincy, Florida has started a research project on determining the efficacy and efficiency of different microbial and non-microbial biostimulants in cold hardy citrus production, to improve yield, and fruit quality. For any further information on the use of biostimulants please contact Dr. Muhammad Shahid, Fruit Physiologist/Assistant Professor of Horticulture at mshahid@ufl.edu.
