by Daniel J. Leonard | May 4, 2018
H. macrophylla ‘Bloomstruck’
Photo courtesy of Andrea Schnapp
Generally, when folks find out what I do for a living, among the first questions asked is “What is your favorite plant?” Being somewhat of a plant nerd, that can be a tough question to answer! However, I usually circle back to the same answer, “Hydrangea”. There are many reasons my fellow gardeners and I love hydrangeas. It’s undeniable that few plants conjure more fond memories of summers gone by or cause more impulse purchasing at nurseries than a hydrangea in full, billowy bloom. Additionally, few specimen shrubs give more floral firepower and ask so little of the gardener in return. My own love affair with hydrangea stems from my first propagation experience, a softwood cutting of Hydrangea macrophylla ‘Nikko Blue’ (taken with the help of someone who knew a lot more about what they were doing than I did) that, seemingly magically, sprouted roots in a makeshift greenhouse, a cypress box with an old, crusty, sliding glass door. Hydrangeas hooked me. However, even with all of those attributes to its name, Hydrangea, as a genus, remains underappreciated and underutilized in modern landscapes. Let’s shed some light on the two primary reasons for gardeners’ failure and frustration with hydrangeas in the landscape and highlight some of the best Hydrangea species and cultivars to look for at the nursery!
First, hydrangea has a reputation as being a high water user. As the name (hydrangea comes from “hydor”, which is Greek for water) might suggest, hydrangeas are indeed water sensitive. However, this does not necessarily mean they require more or less water than other plants, rather they simply betray drought quicker than most other plants. This feature makes hydrangea particularly useful in the landscape as an indicator plant. As a general rule, hydrangeas (particularly those planted in too much sun) wilt in the afternoon heat; this is totally normal. However, if the plants remain wilted the next morning, it is an indicator to the gardener that irrigation is required! If they don’t get irrigation soon after telling you they need it, the plants may begin to decline. Rather than being viewed as a drawback, think of this feature as an early warning system. Name another plant that looks out for us gardeners like that!
The second primary reason people fail with hydrandea is improper site selection. Attempting to grow hydrangea in full sun in Florida leads to less than spectacular results. All species of hydrangeas are most happy when sited to receive at least some afternoon shade, if not filtered shade throughout the entire day. Exposure to blistering afternoon sun is problematic and results in increased wilting from heat stress, increased irrigation requirements and “bleached” flower coloration. Remember, there are fewer frustrating things than growing the right plant in the wrong place!
Now that you know how not to fail with hydrangeas, it’s time to select the proper plant for your property! Three primary species perform noticeably better here than the rest of their kin and deserve the gardener’s consideration in Northwest Florida: H. macrophylla (Bigleaf Hydrangea), H. quercifolia (Oakleaf Hydrangea), and H. paniculata (Panicle Hydrangea).
H. macrophylla
H. macrophylla, the old-fashioned hydrangea everyone’s grandmother grew, is truly one of the standouts in the shady, Southern landscape and commands attention when in flower. Sporting giant “mopheads” of inflorescences in gorgeous hues of blue (or pink, depending on soil pH), H. macrophylla is an extremely low maintenance plant, requiring only periodic irrigation and infrequent fertilizer; H. macrophylla even tolerates salt spray and can be grown on the Gulf Coast! By far, the greatest percentage of questions I receive concerning H. macrophylla involve plants not flowering because of pruning at the wrong time of year. For best flowering results, time pruning of once-blooming traditional cultivars like ‘Nikko Blue’ soon after flowering is finished in late summer. These plants set flower buds on the previous season’s wood; pruning older cultivars in the fall or winter may rejuvenate the plant but will prevent flowering the next year! Fortunately, over the last twenty years, advances in Hydrangea breeding have given gardeners the option of planting remontant cultivars that bloom on current season’s wood. Commonly sold remontant cultivars like ‘Endless Summer’, ‘Penny Mac’, ‘Bloomstruck’, and ‘All Summer Beauty’ have an early summer flower display like the traditional types but then continue to flower periodically throughout the rest of the summer! Even better, they may be pruned at any time without worry of damaging the next season’s flower show!
H. quercifolia (Oakleaf Hydrangea) Photo Courtesty of Andrea Schnapp
Those looking to diversify their hydrangea collection should next look to the native Oakleaf Hydrangea (H. quercifolia). The Oakleaf Hydrangea is a Florida native, growing wild on the steep, shady ravines along the northern end of the Apalachicola River. If the plants never flowered, the Oakleaf would be worth planting; its massive leaves, oak-shaped as the name suggests, can grow up to a foot in length and provide some of the best fall foliage color available to Floridians. However, the real show, as with all hydrangea species, are the flowers. This species flaunts 8”-10” white, panicle shaped flowers that are held elegantly above the coarsely textured foliage. In addition to these features, Oakleaf Hydrangeas couldn’t be easier to grow; obtaining heights up to 10’ and asking very little of the gardener other than adequate irrigation and some shade in the heat of the day! Look for the author’s favorite cultivars: ‘Alice’, ‘Semmes Beauty’, and ‘Snowflake’. Each of these cultivars and selections of the common species H. quercifolia perform very well in Northwest Florida.
H. paniculata ‘Quickfire’
Photo courtesy of Andrea Schnapp.
Finally, the newest hydrangea species introduced to Florida gardens, H. paniculata, has made significant inroads in the landscape industry over the last decade. Primarily grown as the cultivar ‘Limelight’, H. paniculata overcomes some of the weaknesses of the two aforementioned species, namely it tolerates full-sun and persists on much less water, making it a potentially more sustainable plant for many landscapes. This plant, like the remontant H. macrophylla cultivars, blooms on new wood and even seems to enjoy a hard pruning each winter; plants pruned this way seem to be more vigorous the next season and produce larger greenish-white flower panicles than unpruned specimens. Though it is a relative newcomer, H. paniculata, particularly ‘Limelight’, is a worthy addition to any landscape.
As you can see, there is a hydrangea for every yard and no true Southern landscape is complete without a few. When perusing your local garden center this summer, look for the selections and species mentioned above, plant properly, and enjoy the ensuing annual flower show for many years into the future! Who knows, you may be hooked by hydrangeas as I once was!
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
Photo by Sydney Park Brown UF/IFAS
