Bot Rot: Sweet Viburnum’s Achilles Heel

Bot Rot: Sweet Viburnum’s Achilles Heel

Sweet Viburnum (Viburnum odoratissimum) is thought of as being an ironclad landscape shrub, generally a rapid, healthy grower free of insects and disease.  However, this spring, many Sweet Viburnum specimens across the Panhandle have experienced varying degrees of dieback, from individual shoots to entire sections of shrubs, caused by the fungal pathogen Botryosphaeria – commonly known as Bot Rot.

Typical symptom of Bot Rot on Sweet Viburnum. Photo courtesy of Daniel Leonard.

Bot Rot almost always appears after some kind of major stress event that impacts susceptible plants – drought, pruning wounds, nutritional deficiencies, or another environmental stress.  We haven’t been afflicted lately with any serious drought conditions and the disease occurrences are too widespread to have been a result of isolated pruning or poor plant nutrition.  However, the Panhandle did experience a major environmental event around Christmas 2022 that was plenty stressful for landscape plants, a weeklong Arctic blast of extreme cold.  This abrupt hard freeze event in an otherwise mild winter is my best guess for what brought about the increased incidence of Botryosphaeria we have experienced this spring.

The Botryosphaeria fungus enters plants via wounds – in this case one probably caused by cold – and begins destroying the plant’s vascular system in the area.  As the pathogen progresses, it eventually causes sunken cankers to appear, girdles the affected branch, and cuts off “circulation” in that stem.  The first symptom of Bot Rot that gardeners notice is shoots rapidly wilting and exhibiting a blighted appearance, with brown, dead leaves holding onto affected limbs.  Unfortunately, dieback isn’t always limited to individual shoots and can spread back into plants to eventually encompass whole branches.  Entire plants dying from Bot Rot infection is not uncommon.   

While there aren’t any fungicides that are effective in controlling or preventing Bot Rot, gardeners can arrest its spread by pruning out infected branches.  To completely rid the plant of the fungus, make sure to prune 4” or so below the last infected plant tissue (symptomatic tissue will appear dark and discolored; healthy tissue will appear light and greenish).  After pruning each affected plant, it is important to sanitize pruning equipment with either a 10% bleach solution or 70%+ isopropyl alcohol to prevent spreading pathogens to other healthy plants!  Plants that have been irreparably disfigured by Bot Rot or outright killed may be pulled and discarded offsite. 

While this year’s Bot Rot infestation has been extremely frustrating and similar future freeze events can’t be ruled out, gardeners should not give up on Sweet Viburnum, an excellent specimen or screening shrub.  Keeping plants healthy with proper pruning, good fertility, and adequate irrigation is the best defense to ward off future infection when we experience harsh environmental conditions!  For more information on Bot Rot, Sweet Viburnum, or any other horticultural topic, contact your local UF/IFAS County Extension Office!  Happy Gardening.

No Mow March: 3 Pollinator-Friendly Shrubs for the Rest of the Year

No Mow March: 3 Pollinator-Friendly Shrubs for the Rest of the Year

No Mow March was an awesome success this year!  Together, by leaving some unmown areas of our lawns and landscapes, we helped create acres of additional valuable pollinator habitat in a critical time of the year.  However, we can’t forget that there are still nine months remaining in which we can provide low-maintenance food and shelter for pollinators and other wildlife in our landscapes this year!  The following are three of my favorite ultra-low maintenance pollinator friendly shrubs for Panhandle landscapes for summer and fall.

Chaste Tree (Vitex agnus-castus)

Chaste tree or vitex, an outstanding Florida-Friendly Landscape shrub/small tree, provides many aesthetic and wildlife landscape benefits throughout the growing season.  Vitex features attractive grayish-green foliage and grows into a nice, rounded shape (10-15’ tall).  However, the primary draw is its summer/fall flower show.  Sporting striking masses of purplish-blue flowers for months on end until frost, Vitex is a pollinator magnet.  Bees, butterflies, hummingbirds, and all manner of other pollinators visit vitex when in bloom and birds frequent the shrub in the fall to feed on its seeds.  Simply select a site with full sun and well-drained soil and Vitex will reward gardeners and pollinators for years to come.

Firebush (Hamelia patens)

Firebush is a showstopper for both passers-by and pollinators.  This sorta native shrub (Florida native but does not occur naturally in the Panhandle), is a prolific producer of tubular, bright-red flowers from late spring-through frost.  These flowers are a preferred nectar source for many species of butterflies, Zebra longwing and Gulf Fritillary included, and a favorite of hummingbirds.  Like vitex, birds also enjoy feeding on the berries that follow firebush flowers.  In the Panhandle, firebush tops out at around 6’ tall and about as wide and is often killed back to the ground by frost, regrowing rapidly each spring.  Firebush has no real insect or disease issues in landscapes and prefers the same sites as Vitex and will appreciate as much sun as you can give it and well-drained soil. 

Bright orange-red blooms on a firebush. Photo courtesy UF/IFAS.

American Beautyberry (Callicarpa americana)

American beautyberry, or just Beautyberry as it is commonly referred to, is a lovely little deciduous shrub native to all parts of Florida and provides benefits to all manner of landscape wildlife.  Though primarily known for its bird-attracting, vibrant purple berry clusters that appear late summer through fall, Beautyberry is a host plant for several butterfly/moth species and its dainty, pink flowers are an early summer favorite of many bees!  Beautyberry grows 5-7’ in height and is extremely adaptable in landscapes as well, thriving in sun or light shade and many different soil conditions. 

American Beautyberry Photo by: UF/IFAS

It’s important to remember that providing pollinator/bird food and habitat in lawns and landscapes is not a one month event, but a year round commitment.  Reducing mowing frequency, reducing pesticide use, planting native trees, including host and nectar annuals/perennials in landscape beds, and yes, planting native fauna friendly shrubs like vitex, firebush, and American beautyberry are all part of maintaining a pollinator-friendly yard!  Plant one (or several) today! For more information on creating pollinator habitat in landscapes or any other horticultural topic, contact your local UF/IFAS County Extension Office.

Be a Better Gardener with Raised Beds

Be a Better Gardener with Raised Beds

With the arrival of spring weather in the Panhandle, many people have begun planning a vegetable garden.  However, many gardeners that I talk to tell me more of their gardening frustrations than successes.  I surmise the main reason for their frustration is simply doing what gardeners have done across centuries and all over the world, planting in the ground.  That’s a great strategy in many places; unfortunately, in the Panhandle, we are not often blessed with great soil.  We can overcome our poor soil conditions and be more successful by going above ground with raised beds! 

Gardening in raised beds has three primary benefits for area gardeners: the ability to control soil conditions, reduce disease problems, and be space efficient.  The first raised bed benefit is the most critical.  Soil in and around much of the Panhandle is sandy in nature with little rich organic matter.  To make matters worse, much of our native soil is either too well-drained and dries out rapidly or is the opposite and frequently stands in water – neither is conducive to garden success.  We can alleviate all the above issues by creating our own perfectly draining, nutrient-rich soil environment inside a raised bed.  One can either make their own soil concoction by experimenting with different ratios of compost, aged pine bark, peat moss, perlite, etc. or simply purchase bagged garden soil.  I use either 100% mushroom compost or a 1:1 mix of mushroom compost & aged pine bark, but many soil component combinations work well.  

Cabbage grown in a 4’x8′ raised bed. The soil media is mostly mushroom compost. Photo courtesy of Daniel Leonard.

Gardening in raised beds can also dramatically reduce the incidence of disease.  Many of the most serious vegetable garden diseases like Bacterial Wilt and Late Blight in tomato are soilborne, surviving for years in the ground and only needing a splash of rainwater to transfer them onto your vegetable plants.  Growing in beds with curated soil mostly alleviates this issue.  Our sandy soils also tend to have damaging levels of difficult to control nematodes (microscopic round worms that feed on plant roots).  Because nematodes prefer porous sandy ground, switching to raised beds with rich organic soils also removes that concern. 

Finally, growing in raised bed gardens allows for a very efficient use of space.  A typical raised bed is 4’x8’ in diameter, meaning you can site one nearly anywhere, regardless of how big or small your yard is.  You don’t even need a yard space in some cases!  If you have only a sunny porch or driveway, you can certainly mimic raised bed conditions with large containers.  Most people are surprised by the amount of produce that you can pack into one or several 32 square foot raised garden beds, especially when you pay attention to plant mature size and group accordingly.  The square foot gardening method is a great way to maximize raised bed produce yield. 

If you have struggled in past years to produce a fruitful, high-yielding, mostly disease-free garden, your problem might be below your feet in the soil.  As you plan your vegetable gardening activities this year, try gardening in raised beds and get ready for your best gardening season yet!  For more information about vegetable gardening, raised bed construction, or any other horticultural topic, contact your local UF/IFAS County Extension office.  Happy Gardening!

Getting Your Plants Through a Freeze

Getting Your Plants Through a Freeze

We gardeners in the Panhandle have been spoiled by several very mild winters recently.  However, it appears that this pattern will change, at least for a few days, beginning Thursday night.  While forecasts vary depending upon your preferred media outlet, all agree that Calhoun County is going to experience several freezing nights (temperatures in the low 20’s to high teens for hours at a time).  That’s plenty cold to kill many cold-sensitive plants, so here are a few tips to keep your treasured plants alive until warmer conditions arrive next week.

Covering plants to protect from frost, cold snap, blanketing, potted plants, horticulture. UF/IFAS Photo: Sally Lanigan.
  • Bring cold-sensitive potted plants inside.  You can’t dig up your citrus trees and bring them in the living room but bringing cold-sensitive potted plants inside for a couple of nights is a fail-proof freeze protection method.
  • Water outside plants the day before extreme cold hits.  It’s natural, even good, for many tender plants (perennials, bulbs, etc.) to “die” back in cold weather.  This encourages dormancy and reduces pest/disease populations.  However, this week could get cold enough to kill “tops” of sensitive plants AND freeze root systems.  To help prevent this, water the day before a freeze as moist soil loses heat less rapidly than dry. A few degrees can make all the difference!
  • Apply mulch around the base of plants.  Mulch helps insulate the soil and reduces radiant heat losses.  For plants with a graft – like most citrus, pile mulch up around the grafted area.  If the top of the plant dies back, at least it will be able to recover from above the graft (the desirable part of a grafted plant). 
  • Cover citrus and other plants that recover slowly from cold damage.  Draping a non-plastic cloth or blanket mostly helps keep frost off and freezing wind off plants but can also insulate from freezing temperatures if it covers the entire plant to the ground.  It’s better than nothing.
  • Build a “greenhouse” around plants.   You can create a simple greenhouse structure of wooden stakes, pipe, or posts and cover with plastic (making sure the plastic doesn’t touch leaf or stem tissue).  Be sure to get this structure up while the sun is still shining before the freeze event to capture as much solar heat as possible.  For even better results, install a lightbulb, non-LED Christmas lights, or some other heat source inside the plastic structure.
  • Last ditch method – turn on the sprinkler.   Continuouslyrunning a sprinkler over sensitive plants can help protect them.  By running water, you “insulate” the plant to the water’s temperature (above 32 F).  This method requires that the sprinkler begin running before the thermometer drops below 32 degrees and must continue uninterrupted until after the freeze event is over.  If you stop before the freeze is over, the water left on the plant will freeze to whatever temperature the air is, injuring or killing the plant.

We don’t have many freeze events so take a little time this week to bring sensitive plants indoors and implement one or more of the above precautionary measures in your landscape!  Don’t let a few hours of very cold weather set your plants back years!  For more information about cold protection in the lawn and garden, contact your local UF/IFAS County Extension Office.  Stay warm and Merry Christmas!

Satsuma Fruit Puffiness in North Florida

Satsuma Fruit Puffiness in North Florida

By Dr. Muhammid Shahid

What is puffiness?

Taste and size of citrus fruits are important attributes that determine profit. Since, consumers prefer firm citrus fruit, packing houses only accept fruits of specific size without softness. Therefore, fruit that grow too large and don’t fill out properly are unmarketable and growers discard all these types of fruits. This condition is called puffiness. As fruit diameter becomes ever larger, fruit pith (the area between flesh and the peel of fruits) becomes thick and causes the fruit to shrink inward and lose its normal spherical shape. So far, this problem has been observed in both backyard and commercial Satsuma groves in North Florida, South Georgia, and Southeast Alabama. Citrus puffiness is a threat for all growers from an economic and overall yield point of view, because puffed fruits are unmarketable resulting reduced profit margins.

With increasing puffiness, the pith of the citrus fruit increases that makes it soft and fruits lose its usual round appearance.

Possible causes

A few scientific reports suggest that low fruit loads on citrus trees can cause puffiness, but the actual mechanism of puffiness still need to be explored. Based on observations, the team from our lab (Fruit Physiology lab, NFREC, Quincy) and collaborators lead by Dr. Muhammad Shahid has concluded that there are three possible causes of puffiness in citrus i.e., genetic, environmental, or nutritional. In our next phase of research, we will dig deep into this issue and try to determine what is the actual cause of puffiness. Fruit puffiness is observed more in young (4-6 years) satsuma groves than in mature groves. Puffiness on old trees could be due to fruit setting on late blooms during hot conditions. Overall, fruit puffiness is less of a concern in sweet oranges, limes and lemons as compared to satsumas.

Puffiness study by Fruit Physiology Lab, NFREC, Quincy

In our preliminary study, we divided puffiness into five different grades based on fruit size. Grade one is marketable fruits (firm without puffiness). Fruit diameter and puffiness increase gradually in grades 2, 3, 4, and 5, respectively. We have collected fruits from different groves in north Florida and the common denominator among these fruit was decreased Brix value (a common measure of sweetness) with increased puffiness. Average fruit diameter with maximum puffiness was around 40cm and these puffy fruit weighed around 475g. With increasing puffiness, peel weight was increased while juice contents were reduced – not great!

Most satsuma groves in North Florida have some degree of puffiness. However, amount and grade of puffiness varies by grove. In our observations, citrus groves in South Georgia also have puffy fruit, which clearly indicates that puffiness is not geographically specific and can develop in any citrus growing region. After visiting a number of farms in North Florida, we concluded that puffiness is mostly an issue with the Satsuma cultivar ‘Owari’ regardless of different rootstocks. Having said this, we can’t say with confidence that puffiness couldn’t appear on other varieties of citrus without further study. We are carefully monitoring all our variety evaluation trials at the UF/IFAS North Florida Research and Education Center (NFREC), Quincy, in collaboration with citrus breeding and postharvest experts from Citrus Research and Education Center (CREC) and Indian River Research and Education Center (IRREC). We are working on different aspects of citrus production including nutrition, crop load, and pruning to identify the actual cause of puffiness and how to effectively mitigate it in Satsuma groves in north Florida.