Downy mildew diseases present a challenge to growers because they can be present but not obvious and they are difficult to control with fungicides once established. The pathogens are very different from powdery mildews. They attack different plants under different environmental conditions, and are controlled by different classes of fungicides. Downy mildew diseases are caused by oomycetes, a group of fungus-like organisms that also includes Pythium and Phytophthora species.
Most of the downy mildew fungi are very host specific and infect only one plant family. Pathogens include species of Peronospora, Pseudoperonospora, Bremia, Plasmopara, and Basidiophora. Downy mildews infect almost all ornamental plants as well as some indoor plants. Perennial hosts include aster, buddleia, coreopsis, geranium (not Pelargonium), geum, gerbera, lamium, delphinium, veronica and viola. Downy mildew is also caused on rose by Peronospora sparsa. All types of roses are susceptible: wild roses and all cultivated roses including shrub roses. In addition to roses, other hosts of this pathogen include caneberries (blackberries and raspberries), dewberries (Rubus spp.), and cherry laurel (Prunus laurocerasus).
Source: UMass Extension
Crunching the numbers
Departments - Viewpoint
The USDA Census of Agriculture released its 2017 report, which includes horticulture production.
Although the majority of the USDA Ag Census is comprised of farm data, there are some horticulture and floriculture-related stats. The report is based on 2017 data and includes comparisons to the 2012 census.
A few explanations:
The census definition of a farm is any place from which $1,000 or more of agricultural products were produced and sold, or normally would have been sold, during the census year. The definition has changed nine times since it was established in 1850. The current definition was first used for the 1974 Census of Agriculture and was used in each subsequent census of agriculture. This definition is consistent with the definition used for current USDA surveys.
Nursery stock crops: data includes ornamentals, shrubs, shade trees, flowering trees, evergreens, live Christmas trees, fruit and nut trees and plants, vines, palms, ornamental grasses, and bare root herbaceous perennials.
Data is also broken up into production under cover (“square feet under glass or other protection”) and outdoor production (“acres in the open”).
In 2017, the USDA reported 15,092 outdoor production nurseries in 2017, down from 19,184 in 2012.
Those nurseries represented 337,855 acres total in 2017, down from 404,382 in 2012.
In 2017 there were 4,302 under cover production nurseries representing 309 million square feet. In 2012, there were 4,883 under cover production nurseries representing 258 million square feet.
The value of sales from both outdoor production nurseries and under cover production totaled $5.8 billion in 2017, up from $5.1 billion in 2012.
The census also includes stats from individual states. The top three producers should come as no surprise.
For outdoor production, Florida leads the pack with almost 46,000 acres. The Sunshine State comes in second for under cover production with about 53 million square feet. The total value of sales of Florida’s horticulture crops equals $870 million.
Oregon is second in outdoor production with 26,676 acres and third in under cover production with 35 million square feet. Total value of horticulture sales amounts to $646 million.
California is third in outdoor production with some 26,000 acres, but first in under cover production with 67 million square feet. California’s total value of horticulture sales adds up to $1.1 billion.
Results are available in many online formats including video presentations, a new data query interface, maps, and traditional data tables. http://bit.ly/2017USDA_AgCensus
My first introduction to Lonicera crassifolia was several years ago at the Elisabeth C. Miller Botanical Garden in Shoreline, Wash. I had been invited to tour the garden by Richie Steffen, the executive director of the Miller Garden. It was a lovely day in early June, and I was introduced to a plethora of wonderful plants I’d never seen before. There was a lovely vine growing in a pot that I couldn’t name, which Richie identified as Lonicera crassifolia, or creeping honeysuckle. It was in bloom at the time, covered with beautiful yellow-orange flowers that emerge from white buds. Of course, the first thing I did was to put my nose down and take a big whiff and was a little disappointed that the plant didn’t have the same fragrance of some of its cousins of the same genera. My disappointment was brief as I simply enjoyed its fabulous trailing form and dainty flowers. Even the close-up details of the slightly ovate, dime-sized leaves are beautiful, being quite fleshy, almost leathery and covered with small dark hairs.
I have since seen L. crassifolia at several other gardens and in a few specialty nurseries around the country. One of the gardens, the Rhododendron Species Botanical Garden in Federal Way, Wash., has a large planting covering some 300 square feet. It’s fitting that it is planted here, because Steve Hootman, the executive director of the garden was the person who first collected L. crassifolia. I spoke with Steve about the plant and he told me about its discovery.
“This was the first introduction of this species into cultivation. It was September of 1995 and it was collected in south Sichuan, China, in a Karst mountain range called the Jinping Shan at 2,300 meters in a deep, bouldery ravine in deep shade near a stream. It was growing with a rich assortment of other interesting plants including Asarum cardiophyllum, Primula moupinense, lots of species of Rhododendron, Ribes davidii, numerous ferns and Berneuxi thibetica. When I first saw it, I thought I had found a Chinese version of the East Coast native Mitchella repens which was a long-time favorite of mine. It seems very adaptable in cultivation and I know folks are growing it even in Michigan, so it seems quite hardy. Probably best in light shade with some summer moisture and will even slowly climb a tree if it gets a hold on the bark.”
I agree with Steve’s assessment that this is a great plant for most regions in the U.S. It makes a great groundcover and is absolutely charming in a container or hanging basket.
Why grow Lonicera crassifolia?
It’s a beautiful evergreen groundcover, reaching a height of 3-4 inches.
It has dainty tubular flowers in late spring, showing colors of rose-pink, light orange and white.
It works well as a container plant and in hanging baskets.
It’s attractive to bees and other pollinators.
Steeped in history
Departments - Native tongue
Choose to grow and sell plants that make the garden truly alive.
Opening a native plant nursery 17 years ago in western North Carolina may not have been my best idea. I didn’t know what I was doing but was open to new opportunities. One of them came quickly when a potential new client called about cutback rhododendrons. Having no clue what he was talking about, I called my local cooperative extension agent and started asking questions. So of course, he gave me a quick lesson in what cutback rhododendrons were and introduced me to some local guys that could help, and help they did. They still are.
Native plants have been harvested in the mountains of western North Carolina for centuries. Ginseng and Galax are well known. Rhododendron maximum (rosebay) and Kalmia latifolia (mountain laurel) have been harvested and shipped up the East Coast for decades by the hundreds of thousands. Although a little dated, it was reported that in 1979, western North Carolina sold $4 million worth of these native ornamentals ($14 million in today’s dollars).
These plants have provided an important source of jobs and an economic boost to parts of western North Carolina when others disappeared. Mitchell (home of Mt. Mitchell) and Avery (Grandfather Mountain) counties became the center of cutback production when logging and mining left the men of the area jobless.
Logging and mining were essential parts of the economy of these counties. An immense logging industry that existed in these counties from the late 1880s ended by 1940. Logging had employed roughly 30,000 people in North Carolina in the 1920s. Thousands of acres had been clear cut. A massive flood in 1940 due to the environmental degradation caused by this clear cutting was the final blow. It was also during this time that the conservation efforts that lead to the preservation of Grandfather Mountain as well as the Blue Ridge Parkway were underway. The resulting tourism would become a large part of the economy of western North Carolina, too.
Prospectors first started mining mica in the Spruce Pine Mining District (Avery and Mitchell counties) in the 1850s. A mica boom in 1878 helped supply materials for an insulator in Thomas Edison’s electric motor, windows for furnaces and woodstoves, insulation in toasters, and was used in vacuum tubes. When World War II broke out, the over 700 mines in Yancey, Mitchell and Avery counties began working overtime to supply the nation with all it needed. The mica mines went full bore until solid-state electronics were developed in the 1960s, causing many mines to close.
Many of these unemployed men in the counties went to the woods and started growing, digging and selling cutbacks.
Rhododendron and kalmia cutbacks are available either as field-grown or harvested in place. Field-grown cutbacks involve removing the top of the plant and digging rootstock out of an area of younger wild plants. Rootstock is no more than 1 foot in diameter, usually smaller, healed in for a short period of time and then lined out in a field like any other field-grown nursery plant. This represents a small portion of cutback production. They are easy to dig, can be fertilized and sprayed, and are fairly uniform in appearance.
The vast majority of cutback plants are produced “in place” on the nurseryman’s land. A patch of rhododendrons or kalmias will be cut all off to the stump (burl). The first year’s growth produces the first few sets of leaves from dormant buds then the following years show 6-12 inches of growth. It usually takes three to four years before these plants reach the 2-3 feet range. This practice is a sustainable practice, too. These plants, especially the rhododendrons, come back from the roots that remain after harvest.
The tools of the digging trade are a weighted spade (20 pounds or more), ax, chainsaw, files, burlap and pinning nails. These plants can take from a couple of minutes up to 20 minutes to dig, burlap, and then have to be hauled out and loaded. If you have ever been to western North Carolina and seen how steep it can be, imagine carrying these plants out.
Rhododendron maximum and mountain laurel have been a mainstay of the nursery trade for decades. They both naturally occur throughout the eastern U.S. Generations of landscape designers and architects from western North Carolina northward have counted on these evergreen natives for their beauty, durability and supply for decades. Perspective on the economic importance and history of these native plants may make their use a little more meaningful.
Opinions expressed are those of the author and do not necessarily represent the views of GIE Media, Inc.
Bill Jones is president of Carolina Native Nursery in Burnsville, N.C., a specialty grower of native shrubs, perennials ferns, and grasses. www.carolinanativenursery.com
Standing on the shoulders of giants
Departments - Guest Voice
Many of today’s popular landscape plants were introduced more than a century ago by prolific breeders.
The year 1823 was significant in the annals of horticulture. Victor Lemoine was born in Delme, France, and a young, adventurous German physician set foot on the man-made island of Dejima, a trading post for the Dutch East India Company off the coast of Nagasaki, Japan. These two events would help usher in a Golden Age of plant breeding.
Fresh out of medical school, Phillip Franz von Siebold was looking for a bit of adventure when the Dutch East Indian Company offered him an opportunity as resident physician and scientist at Dejima, Japan. He was to be the successor to Engelbert Kaempfer and Carl Peter Thunberg, both famous plantsmen you may recognize from the specific epitaphs on a number Japanese plant species including Larix kaempferi and Berberis thunbergii.
Siebold excelled as a physician and botanist while in Japan. His unique abilities as a cataract surgeon (along with his knowledge and supply of belladonna for dilating the pupil) gave him a freedom of travel afforded to few foreigners in this isolated country. Between his personal acquisitions and the gifts paid to him in kind for his doctoring and teaching, Siebold amassed over 1,000 native Japanese plants in his backyard garden. Amongst these plants were Hydrangea paniculata (wild type) and H. paniculata ‘Grandiflora’ (aka Pee Gee hydrangea), both of which he sent to Europe and today are still common landscape plants.
Meanwhile in Nancy, France, the now 27-year-old Victor Lemoine started his nursery, which went on to introduce a treasure trove of ornamental plants. While most famous for his 214 French hybrid lilac varieties, Lemoine, along with his wife Marie Louise and son Henri, gave our industry a plethora of plant introductions in the genera Philadelphus, Deutzia, Weigela, Gladiolus, Delphinium, Potentilla, Astilbe, Heuchera, Penstemon, Diervilla, Spiraea, Chrysanthemum and still others. He developed the first double flowered perennial potentilla, tuberous begonia and geranium. He was one of the first to make wide, interspecific hybrids of Streptocarpus, Weigela, Syringa and Philadelphus. What is truly amazing is that so many of his plant introductions are on the market and being grown to this day. His contributions to horticulture were so vast that the Royal Horticulture Society in London awarded him the Victorian Medal of Horticulture, the first time it was given to a foreigner, and the Massachusetts Horticultural Society named him a George R. White Medal of Honor winner. With all of these accomplishments and innovations, the nursery industry of his day must have appreciated Victor’s work, right? I’m not so sure. I recently read an article about Lemoine that contained a quote of a contemporary complaining that Lemoine was introducing too many plants. Can’t you just hear people saying, “Victor, do we really need another lilac?”
In my 27 years as a plant hunter, I’ve met some remarkable plant breeders and have witnessed some incredible modern plant introductions. One of these was while visiting the late Jelena DeBelder in the summer of 1996. We met at Hemelrijk, her family estate near Antwerp, Belgium. As she shuttled us about the grounds in her beat-up Volkswagen Rabbit filled with pots, shovels and plants, I soon realized I was in the presence of someone special. Her every word was filled with passion. With the pride of a mother, she introduced us to her hydrangeas: ‘Pink Diamond’, ‘Unique’, ‘The Swan’, ‘Burgundy Lace’, ‘White Moth’ and her personal favorite ‘Little Lamb’.
“This is a very special plant,” she told us. “Little lambs dancing about in joy. Very special.”
Soon after, I met the renowned plantsman Pieter Zwijnenburg. At the time, Pieter and his wife Anja had a small nursery in the Boskoop area of the Netherlands. As the “Heronswood of Europe,” his nursery offered over 2,500 different varieties of trees and shrubs. In his career, Pieter has introduced over 50 different new plants. On this particular day, he showed us his newest development, a hydrangea that would soon be named ‘Limelight’. And just down the road a few miles, on another day, Rein and Mark Bulk showed me their new, early flowering hydrangea that had volunteered in his nursery. In a few years, we’d introduce this one as Quick Fire Hydrangea.
Still later and to the south, we and the world came to know Dr. Johan Van Huylenbroeck of the Flanders Research Institute for Agriculture. Johan’s outstanding Hydrangea paniculata breeding would give us Mega Mindy, Pinky Winky and Bobo. Meanwhile in France, Jean Renault was also breeding H. paniculata which would yield Vanilla Fraise, aka Vanilla Strawberry. And back in Grand Haven, Mich., while standing on the shoulders of all these giants, I helped to develop and introduce five additional H. paniculata plants.
It is simply remarkable how this once unassuming Japanese hydrangea has changed and improved. We now have cultivars with stronger stems that do not flop. We have dwarf and early blooming selections. We have green flowers and flowers that age with hues that range from green to bubblegum pink to rich pomegranate red. We have big and small flowers, full and lacey flowers.
What is most amazing to me is that Pee Gee hydrangea is still being grown 157 years since it was introduced by Dr. Phillip Franz von Siebold. With each generation and with each new breeder it has gotten better and better. Also amazing is that very little has changed since the days of Victor Lemoine. I regularly hear people exclaim, “Tim, do we really need another hydrangea?” And I answer, with a smile and in a way that I suspect Victor would approve. “Yes, of course we need another. So long as it is better, we need more ______________.” (You can fill in the blank.)
Tim Wood is a fourth-generation plantsman that travels the world hunting for new shrubs for the Proven Winners plant brand. He is also an accomplished plant breeder with over 100 plant patents to his name. An avid lecturer, photographer and writer, he writes a blog called “The Plant Hunter” and has written three books.http://plant-quest.blogspot.com