by Julie McConnell | Apr 16, 2018
I’m hard pressed to tell you my favorite song, movie, or place to eat, but when we start talking plants I can come up with whole categories of favorites. I won’t commit to just one species, but when it comes to woody shrubs I am a huge fan of viburnums. We have small ones, tall ones, evergreen, deciduous, smooth leaves, textured leaves, berry producers and sterile types. There are so many different types there must be one for every gardener.
Buds and flowers of Viburnum luzonicum. Photo: J_McConnell, UF/IFAS
I thought I knew a lot of viburnums after spending ten years in the nursery industry, but had not seen Luzon Viburnum, Viburnum luzonicum, until Dr. Gary Knox gave one to me in the fall of 2014. The plant was little more than a couple of stems and light green leaves, but he assured me it would get large and would perform well in the Florida panhandle.
That scrap of a plant went into a large, non-irrigated, full-sun bed in my yard and was hand-watered through the first summer, but after that has been left to fend for itself. My Luzon viburnum is currently over 6 feet tall by 4 feet wide and covered in flowers. It gets no TLC in my landscape, but has yet to be plagued by any pests. The foliage emerges with a slightly pink tone then settles into a light green usually starting in February or March. By late March clusters of small white flowers cover the shrub. It is reported to have the potential to produce berries that transition from red to black, but I have not yet observed that in my garden.
This is not a plant you are likely to stumble across in most garden centers, but is worth keeping a lookout for in case you see it. It is on display with many other wonderful plants in the Gardens of the Big Bend at the UF/IFAS North Florida Research and Education Center (NFREC) in Quincy and in the past has been available at Gardening Friends of the Big Bend plant sales.
For more information about this plant see Missouri Botanical Garden webpage.
by Julie McConnell | Mar 13, 2018
Shore juniper forms a thick groundcover and tolerates hot, dry sites. Photo: J_McConnell, UF/IFAS
We all know that when you have bare ground in Florida, eventually something unwanted moves in or the soil moves out. To avoid either of these negative outcomes, a good practice is to grow robust vegetative groundcovers, especially if the soil slopes and is at high risk of eroding. Turfgrass is one option, but what if you don’t enjoy caring for a lawn or the site is difficult to maintain or even unsafe to mow? An often overlooked option in our area is Shore Juniper Juniperus conferta.
Although some people find this plant less than exciting, its easy to explain why it can be a good option in certain situations.
- Easy to find at nurseries
- Inexpensive
- Low water requirements once established (you’ll need to turn the irrigation off on these!)
- Salt tolerant
- Evergreen
- Cold tolerant
- Low, spreading growth habit (won’t block view)
- Do not require pruning (junipers cannot tolerate heavy pruning!)
A common cultivar of shore juniper is Blue Pacific Juniper which grows to be about one foot tall but spreads two to three feet wide. The new foliage has a blue cast that gives it the common name. It creeps along the ground and will provide good ground cover to sloping sites. This plant should be planted on 3 foot centers so they have room to expand without crowding. Plant in well-drained soil and apply two inches of mulch on bare soil between plants to reduce weeds while the plants are filling in. Only water until established, then stop automated irrigation and only water as needed. Read more at Establishing Shrubs Florida Landscapes.
by Sheila Dunning | Dec 14, 2017
Photo by Sydney Park Brown UF/IFAS
Holly has been considered sacred in some cultures because it remained green and strong with brightly colored red berries no matter how harsh the winter, even when most other plants would wilt and die. According to Druid lore, hanging the plant in homes would bring good luck and protection.
Later, Christians adopted the holly tradition from Druid practices and developed symbolism to reflect Christian beliefs. Today, the red berries are said to represent the blood that Jesus shed on the cross when he was crucified. Additionally, the pointed leaves of the holly symbolize the crown of thorns Jesus wore on his head.
Several holly species are native to Florida. Many more are cultivated varieties commonly used as landscape plants. Hollies (Ilex spp.) are generally low maintenance plants that come in a diversity of sizes, forms and textures, ranging from large trees to dwarf shrubs.
The berries provide a valuable winter food source for migratory birds; however, the berries only form on female plants. Hollies are dioecious plants, with male and female flowers on separate plants. Both male and female hollies produce small white blooms in the spring. Bees are the primary pollinators, carrying pollen from the male hollies 1.5 to 2 miles, so it is not necessary to have a male plant in the same landscape.
Several male hollies are grown for their compact formal shape and interesting new foliage color. Dwarf Yaupon Hollies (Ilex vomitoria ‘Shillings’ and ‘Bordeaux’) form symmetrical spheres without extensive pruning. ‘Bordeaux’ Yaupon has maroon-colored new growth. Neither cultivar has berries.
Hollies prefer to grow in partial shade but will do well in full sun if provided adequate irrigation. Most species prefer well-drained, slightly acidic soils. However, Dahoon holly (Ilex cassine) and Gallberry (Ilex glabra) naturally occur in wetland areas and can be planted on wetter sites.
For a more comprehensive list of holly varieties and their individual growth habits refer to ENH42 Hollies at a Glance: http://edis.ifas.ufl.edu/mg021
by Beth Bolles | Dec 1, 2017
There are plants that gardeners may know and love from other regions that just do not perform well in the heat, humidity, and soils of our area. One example is the Japanese pieris, an attractive evergreen shrub with showy white blooms in spring. This shrub has a few specific environmental requirements that make it unsuitable for most gardens along the Panhandle, including the need for rich organic soil that holds some moisture but is well drained.
Late winter/early spring flowers on the Mountain Snow. New foliage also emerges reddish. Photo by Beth Bolles, UF IFAS Extension Escambia County.
For those of you who thought that a garden with Japanese pieris is only a dream, the nursery industry has now made your dream a reality. Part of the Southern Living plant collection is a more heat tolerant Japanese pieris called Mountain Snow™ that is showing promise. Site selection is still very important. Mountain Snow™ will grow best with summer shade and in beds that are amended with organic material. Water must be applied when rainfall is lacking and soil must be well drained.
Shrubs will grow about 4 feet by 3 feet. Flower buds cover this established plant. Photo by Beth Bolles, UF IFAS Extension Escambia County.
Although those requirements can not be met in all landscapes, there are gardens like the Escambia County Demonstration Garden where a Mountain Snow™ plant will grow well. Our shrub is planted in an irrigated ornamental bed with organic mulch on top and receives summer shade from a deciduous tree. At two years old, it appears to be doing well in our area. If you have a garden spot with the conditions appropriate, consider trying this shrub for early season interest.
by Gary Knox | Nov 6, 2017
Crown gall symptoms on roses caused by the bacterium Agrobacterium tumefaciens (Rhizobium radiobacter) – Photo credits: Kamil Duman
A plant with a mature gall that is potentially releasing the crown gall bacterium into the potting media. Photo credits: Susannah Wright
For gardeners, rose enthusiasts and rosarians, each of the many rose diseases is as important as the others. But we can say for sure Crown Gall is one of the most unsightly of the many rose diseases that can been seen currently.
The disease got this name from the large tumor-like swellings (galls) that typically occur at the crown of the plant, just above the soil level. The cause of crown gall disease is a bacterium that resides in the soil, Agrobacterium tumefaciens (updated scientific name Rhizobium radiobacter).
SYMPTOMS
Galls or overgrowth (1/4 inch to several inches in diameter) of host plant tissue typically form at the soil line but also can form on branches or roots. Galls are initially white, spherical, and soft but darken with age as outer cells die. It can either be almost entirely on the surface of the plant and easily detached or can be almost indistinguishable from normal plant tissue except for its greatly enlarged appearance.
The bacterium that causes Crown Gall disease survives and persists in the soil for up to 3 years. It can invade recent wounds on the branches or roots. Swelling can be seen as early as 14 days following entry of the bacterium into the plant. The tissue near the gall can be crushed due to rapid cell enlargement. If vascular tissue is crushed, wilting can result from the restricted water movement.
Early stage symptom of Crown Gall on roses can be noticed as the small white galls. Photo credits: Susannah Wright
The galls can enlarge to a quarter size in a short period of time from the initial small galls. Photo credits: Mathews Paret
ABOUT THE BACTERIUM
Agrobacterium uses its genes as a weapon to attack plants. It enters the plant mostly from the soil through wounds on the roots or lower stem or from the branches during plant pruning. Symptoms are caused by the insertion of a small segment of DNA (known as the T-DNA), from a plasmid, into the host plant cell, which is incorporated into the plant genome. When the plasmid links up with the plants own DNA, the altered plant cells start dividing rapidly and uncontrollably, and the root or stem develops a tumor-like swelling.
Galls can range from pea size to softball size. Tiny cracks from freezing temperatures or wound sites can be the site of gall formation. Once the wound compounds are generated, the bacteria detach from the xylem cell walls and are carried upward with water during evapotranspiration to the wound site where they initiate galls. One of the common ways of the spread of the disease is by pruning infected plants and moving the bacterium accidentally while pruning nearby healthy plants.
The crown gall bacterium is a soil pathogen, which means main inoculum source is soil. The bacterium can overwinter in infested soils, where it can live as a saprophyte for several years. The bacterium can easily during field preparation, pruning and irrigation. Insects, nematodes and grafting materials, can also transfer the bacterium.
The galls will turn dark in color as they age. Photo credits: Kamil Duman
HOW CAN YOU MANAGE ROSE CROWN GALL DISEASE
- Plant only disease-free roses. Check very carefully before you buy plants for any kind of galls in the crown or branches. Use good sanitation practices in handling roses.
- Plant in clean soil. Avoid areas with a history of crown gall infestation.
- Avoid fields with heavy infestations of root-attacking insects and nematodes.
- Select well-drained soil and irrigate from clean water sources.
- Keep grafts and buds well above the soil line.
- Destroy diseased plants as soon as you notice them to avoid cross-contaminating other plants, or pruning equipment. Also, do not keep infected plants with healthy plants, as the likelihood of accidental transmission through pruning is high.
- Avoid mechanical injury to plants from tillage and hoeing. Provide winter protection so that the bark does not crack.
- Disinfect pruning tools between plants. disinfect budding/grafting tools before and after use. Bleach (10%; equivalent to 0.6% sodium hypochlorite), or quaternary ammonium-based sanitizer are effective as disinfectants. Make sure to prepare fresh stock routinely.
- If crown gall plants are noted, please let your local county extension agent know about it and they will be able to contact us for additional site-specific management plans if needed.
Gall formation at pruning sites indicating contamination of the plant during pruning. Photo credits: Kamil Duman
Authors: Kamil Duman, Susannah Wright, Fanny Iriarte, Barron Riddle, Gary Knox and Mathews Paret, University of Florida – NFREC, Quincy, FL
by Matt Lollar | Oct 2, 2017
Over the last month or so, home gardeners and commercial growers alike have noticed what look to be large dust particles floating through the air. It’s probably not uncommon to have inhaled a few or even a few hundred of these mysterious particles. Most likely, these “particles” aren’t dust at all but whiteflies instead. Whiteflies are small (less than a tenth of an inch long), white, soft-bodied insects. They aren’t flies but are considered ‘true bugs’ by entomologists. The most common whitefly species in Northwest Florida is the silverleaf whitefly, also known as the sweetpotato whitefly. Whitefly numbers have exploded exponentially this year because of last years’ mild winter. These irksome insects feed on a variety of annuals, shrubs, vegetables and trees.
Magnified whitefly adults and eggs. Photo Credit: James Castner, University of Florida/IFAS.
Whiteflies typically feed on the underside of leaves. Initially, disturbed leaves will become pale in color, then a sticky substance may develop on the surface of the leaves. This sticky substance is called honeydew. Honeydew is actually a sugary substance excreted by the whiteflies as part of their elimination process, similar to what aphids and scale insects produce. After honeydew is deposited, sooty mold develops to feed on this readily available sugar source. Sooty mold is a fungus that forms a gray to black colored coating on plant leaves. It normally grows on leaves that were previously covered with honeydew. Sooty mold hinders the ability of leaves to absorb light and ultimately limits photosynthesis.
Pale squash leaves due to feeding from whiteflies. Photo Credit: University of Florida/IFAS.
So what should be done to control whiteflies? It depends on what is being grown. If whiteflies are present, the role of beneficial insects should be taken into consideration. Plenty of predatory insects such as lady bugs and green lacewings are around to feed on whiteflies. In fact, leaving the whiteflies alone on your trees and shrubs will attract more predatory insects. Below are some whitefly control methods that produce minimal damage to beneficial insect populations.
Whitefly Control in Vegetables
- Sticky Traps – Yellow sticky traps are a good way to monitor whitefly populations and can help determine when insecticide application is appropriate.
- Insecticidal Soaps – Insecticidal soaps are usually applied as a 1 to 2 percent solution (2½ to 5 tablespoons per gallon of water). It is important to follow the application directions on the label. Insecticidal soap should be applied in the evening, when the sun is low in the sky and the temperature is below 85°F. Some insecticidal soaps available at local lawn and garden centers include: Bonide Insecticidal Soap, Bonide Insecticidal Soap, and Bayer Advanced Natria Insecticidal Soap.
- Horticultural Oils – Horticultural oils should be handled like insecticidal soaps. Like the soaps, they should be applied in the evening. Some horticultural oils available at local lawn and garden centers include: Bonide All Seasons Spray Oil, Southern Ag Parafine Oil, and Garden Safe Neem Oil.
- Other Insecticides – Harsher chemicals are not recommended for the home gardener, because whiteflies have become resistant to most products on the market. Use of broad spectrum insecticides may also contribute to an increase in whitefly populations because they kill beneficial predatory insects.
Hopefully winter will be cooler this year and the profuse whitefly population will be knocked back. Until then, we wish all home gardeners the best of luck with fall gardening!
Photo by Sydney Park Brown UF/IFAS
