English oaks: why so rare in America?

It’s a beautiful tree but not the best choice for landscapes in many parts of the USA. However, there are good alternatives to the English oak.

QUESTION: “We have about 5, very beautiful, English oaks where I work. They
look like they're related to the White Oaks, and appear to be doing very
well here in Philly...why aren't English Oaks more numerous?” – Scott

ANSWER: English oaks are beautiful trees that, despite their name, are not strictly English as they are also native to much of Europe and also northern Africa and western Asia.

The foliage of an English oak is similar to that of the more familiar White oak but lacks the eye-catching reddish leaf color in fall. You can sometimes spot English oaks in urban landscapes, reaching a height of around 50 feet with a 50 foot spread.

Botanists have been using the English oak as genetic stock to generate hybrids with other members of the White Oak group as they can be very useful landscape shade trees.

Although it is not an American native, English oak adapts to the sometimes challenging conditions of the eastern and midwestern United States. It is at its best in zones 5 and 6 and doesn’t thrive in the hot dry summers of the South. It seems to do okay in moderately dry, poor quality soil, but prefers moist, well-drained, moderately rich soils of variable pH.

Problems? The main potential problem is powdery mildew, something it shares with its cousin White Swamp oak. Powdery mildew can form on its foliage around mid-summer, but is considered a ‘cosmetic’ disease that does not adversely affect the overall health of the tree.

I believe that English oaks are not too numerous due to the simple law of supply and demand. Nurseries grow and sell what people are buying in the greatest quantities. Low demand means fewer English oaks are being grown at the nursery level.

There are a number of hardy and attractive oaks that are fast-growing and fairly easy to care for. I’ll devote a column quite soon to some of these varieties such as Water Oak, Sawtooth Oak, Cherrybark Oak and the ever-popular Trailing Periwinkle need? Is it easy maintenance? If planted on a slope, would I need to plant them high and let them trail down or low and high and let them fill in? I am in Huntsville, AL. How will they do in whatever zone that might be?” – Alex Haynes

ANSWER: The Huntsville, AL area borders zones 7 and 8. Vinca will grow in that region and is recommended for USDA zones 3 through 8. You’ll be pleased to know that, as with most groundcovers, Vinca minor (Trailing Periwinkle) requires minimal maintenance.

After fall planting, average watering will run every 3 to 5 days for the first 6 or so weeks depending on local rainfall, soil type and the planting location. Since you are planting on a hillside or slope, it will vary even more. You will need to check the soil and adjust the water schedule accordingly.

For a slope, I recommend setting up a sprinkler attachment to a hose for a soft spray to moisten the soil. Otherwise, most quick waterings and rainfall typically runs off without soaking into the soil.

Until the plants securely root in, you may need to place a light layer of straw over the area during periods of heavy rainfall to prevent the plants from being washed downhill.
Vinca grows and roots wherever the new growth touches the soil. Spacing can vary from 6 inches to 18 inches apart over the entire area. The closer the plants are spaced, the quicker the area will fill in.

Vinca minor is an excellent evergreen ground cover for full sun, shaded and semi-shaded areas. It has dark green oval-shaped foliage and conspicuous blue flowers in early spring.

The Plant Man is here to help. Send your questions about trees, shrubs and landscaping to steve@landsteward.org and for resources and additional information, including archived columns, visit www.landsteward.org

Native plants lessen invasive concerns

Selecting plants that are right for your landscape takes more than sticking a pin in a catalog or clicking a picture on the Internet. It’s important to consider what impact that plant could have on the rest of your landscape.

In a recent Plant man column, I addressed the frustration many people feel when they find that their prized plants have been chewed to the ground by deer. I also referred readers to a Web site that listed plants that are “deer resistant.” Although deer will eat almost any plant when they are hungry enough, they find some plants somewhat unpalatable and some plants downright unpleasant.

A few days later, I received an e-mail from reader Ethan Kaiser, referring to one of the plants mentioned in the column. Ethan wrote, “Japanese barberries and their cultivars are actually exotic invasive species in the U.S. and are known to take over woodland areas and forest edges, especially in Wisconsin and the Midwest as a whole. They outcompete many native plants that the deer would munch on instead of landscaped plants.”

Ethan makes a good point. Japanese barberries are indeed deer-resistant but, left to their own devices, can become invasive. In fact, Japanese barberries are prohibited in the state of Massachusetts. As you may know, this column is published in newspapers in 30+ states, and can be read world-wide on the Internet. As such, unless we are answering a specific question regarding a particular geographic location, some of the information has to be somewhat generalized.

As visitors to our Web site www.landsteward.org know, Cheryl and I are strong advocates of selecting native plants when ever possible, but we do understand that in quite a few cases, it isn’t practical or feasible.

We strongly encourage everyone to do a few minutes homework and check out the pros and cons of any tree, shrub or groundcover before introducing it into your landscape. So what can you do?

• For a start, what works well in New Mexico might be a dud in New Hampshire. Is this plant recommended for planting in your USDA zone? If you’re not sure of your zone, go to http://www.usna.usda.gov/Hardzone/
  
• You can also find a comprehensive state-by-state list of plants that are found where you live at http://plants.usda.gov/ but note that these lists do include plants that are considered to be invasive.
  
• At that same Web site, you can click on a link to a list of noxious and invasive plants that you can sort by state, common name or scientific name. If you want to steer clear of possibly invasive plants, this is a good reference.
  
• Adamant about using native U.S. plants in your landscape? Take a look at a collection of articles and links on a Web site hosted by the Environmental Protection Agency titled “Landscaping with Native Plants” located at http://www.epa.gov/greenacres/
  
• Aptly titled “Native Gardening and Invasive Plants Guide,” http://www.enature.com/native_invasive/invasives.asp provides easy to follow information on using native plants while avoiding invasive plants. Highly recommended if you’re looking for a guide written for the home gardener rather than the horticulturist!
  
• The U.S. Fish & Wildlife Service is a good resource for a lot of current information on invasive plants.
  
• Go to http://www.fws.gov/invasives/ where you can click on a lot of links, including one titled “What You Can Do.” A note at that site points out: “In addition to the many invasive species from outside the U.S., there are many species from within the U.S. that are invasive in other parts of the country.” What is just fine somewhere else might be considered invasive in your location.
  

Again, before you plant, I strongly recommend taking the time to find which plants will thrive where you live and meet your requirements, both esthetic and environmental. It’s an investment that will pay dividends for you and the landscape.

The Plant Man is here to help. Send your questions about trees, shrubs and landscaping to steve@landsteward.org and for resources and additional information, including archived columns, visit www.landsteward.org

American chestnut trees: on their way back

If you had given up hope of ever again gazing up at the vast leafy canopy of an American chestnut tree, take heart! The majestic tree was almost completely wiped out several decades ago by a disease and it seemed that the American chestnut had gone the way of the passenger pigeon and the dodo.

However, plant scientists are working diligently to bring back the American chestnut in a stronger, disease-resistant form.

The magnificent tree had been a familiar sight on the American landscape. Its timber was used for building homes and barns. The chestnuts provided food for livestock and wildlife. Its canopy provided shade for both humans and animals.

But all that was about to come to a rapid end. Asian chestnut trees were imported into the United States and those trees carried with them a fungus that quickly transferred to the American chestnuts. Over centuries, the Asian trees had learned to resist the fungus but their American cousins had no such immunity.

In 1904, botanists at the Bronx Zoo in New York were the first to notice that the chestnut trees there were infected with a fatal fungus. The disease swept quickly across the continent and by the early 1950s the American chestnut had all but disappeared. As many as four billion trees were wiped out.

Botanists have undertaken a long-term project to revive the American chestnut. They have planted 1,200 chestnut tree saplings in national forests in North Carolina, Tennessee and Virginia, and are watching over them as closely as a mother hen with her chicks.

In a November, 2009, story reported by USA TODAY, Ron Sederoff, professor of forestry at North Carolina State University said that the American chestnut was one of the most important trees in the ecology of the Apalachian Mountains. “There were communities that depended on it. There was wildlife that depended on it,” he said. “When the blight came through, all of those things were lost.”

According to the USA TODAY story, those 1,200 saplings survived their first year under the care of the Foundation, the U.S. Forestry Service and the University of Tennessee.

But the scientists have taken steps to help their new trees survive the deadly fungus. Although the saplings are 94 percent American chestnut, they have been crossbred with Chinese chestnut trees that are resistant to the blight.

This is by no means a quick fix. It will be at least 15 to 20 years before botanists can determine if the trees are able to fend off the blight and continue to grow well enough to compete with other trees.

So let’s wish Good Luck to those little saplings and to the scientists who are nurturing them. Hopefully, the American chestnut tree will again be reaching 100 feet into the sky. With today’s focus on climate issues, the American chestnut would be a very welcome addition to the landscape as it stores carbon dioxide on a massive scale and, as such, will be an ideal – and all-natural – tool to fight climate change.

Meanwhile, if you can’t wait 20 years but would like to grace your landscape with some spectacular trees, consider these:

Black Walnut (Jugans nigra)

A majestic tree with a moderate growth rate, the Black Walnut Tree is prized for its wood veneer at maturity used in fine cabinets, gunstocks, and furniture. The Black Walnut Tree makes a wonderful shade tree, and when planted for a wood plantation, is a long-term investment. Zones 4 to 8.

Oak Gobbler Sawtooth (Quercus acutissima)

Gobbler is the same as the Sawtooth Oak but produces a smaller acorn that is desirable as a food source for wild turkeys. Oak Gobbler Sawtooth is the first choice tree to plant for wild turkey and wild game enthusiasts. Oak Gobbler Sawtooth will begin to provide acorns in 4 - 6 yrs. Zones 5 to 9.

Pin Oak (Quercus palustris)

Probably the most widely used native oak for landscaping, Pin Oak is one of the faster growing oaks, 12 to 15' over a 5 to 7 year period, reaching 75 feet at maturity and can also be used in a wetland environment. Zones 4 to 9.

The Plant Man is here to help. Send your questions about trees, shrubs and landscaping to steve@landsteward.org and for resources and additional information, including archived columns, visit www.landsteward.org

Stinky ginkgoes offend delicate noses

What rhymes with ginkgo? For people in many American cities, the word is STINKO.

The ginkgo tree has a long history, dating back to the Permian era which lasted from 290 to 248 million years ago. As you might guess from that statistic, the ginkgo is recognized for its remarkable hardiness, able to overcome extraordinary adversity. Legend has it that ginkgo trees survived the atomic bombing of Hiroshima.

That hardiness is an asset prized both by private landowners and civic planners. What could be better than a row of trees with attractive foliage that are also exceptionally hardy?

Ah, well…

There is one major drawback, at least in the eyes (and noses) of many people. The ginkgo is one of those trees that is gender specific: they are either male or female. Mature female ginkgoes produce ovules which when fertilized by pollen from the male tree grow into bunches of seeds that look like fuzzy green cherries.

Now here’s the problem, at least from a human point of view. The fleshy coating around the seeds contains butyric acid, the same stuff that gives that distinctive smell to rancid butter. In addition to the rancid butter smell, many people complain that the odor reminds them of vomit, rotten eggs or even doggy-doo.

Not everybody finds the odor offensive. Depending on your olfactory sensibility, you might feel that the smell is really awful or not too bad or just one of those “nature smells.”

But the seasonal smell isn’t the only potential problem. The slimy seed pods can make sidewalks slippery and some municipalities are concerned about the possibility of lawsuits resulting from injuries caused by slipping and falling on pods dropped from city-owned ginkgoes.

As a result, many cities are deciding to plant only male ginkgo trees and/or removing and destroying existing female ginkgoes. Cities as widespread as Lexington, KY, Bloomington, MN and Easton, PA have taken action to limit or remove ginkgoes.

To me, it seems a great pity to destroy trees because some people find the odor offensive for a few weeks each year. At the same time I can appreciate the problem faced by a city that wants to avoid injury to citizens and the subsequent lawsuits.

Should you plant ginkgo trees on your property? That depends! If you don’t mind the odor or if the trees are a fair distance from your house, the smell issue (and probably the slippery sidewalk issue) shouldn’t be a major problem. Alternatively, you can plant only male ginkgo trees. Ginkgoes are very hardy, long-lived and attractive so there definitely are benefits.

But what if you really want trees and shrubs that are pleasantly fragrant? What could you look for? Here are some you can consider:

• Mock Orange Philadelphus Innocence x. lemoinei
  
  This is perhaps the most fragrant of the Mock Oranges. Cheryl and I love to inhale the sumptuously intoxicating orange sweetness given up by Mock Orange Philadelphus Innocence's, pure white blossoms. This variety grows to 5 – 8 feet at maturity in USDA zones 5 to 8.
  
• Old Fashion Lilac, Syringa vulgaris
  
  Old Fashion Lilac is perhaps the most popular of all lilacs due to its rich color ranging from purplish red to lilac and purple. Old Fashion Lilac has extremely fragrant with a broad, rounded habit. It is a moderate growing shrub with attractive dark green foliage. It is great for hedges, or screens, and can also be planted as a specimen plant, growing to maybe 20 feet in zones 3 to 7.
  
• Carolina Jessamine Gelsemium sempervirens
  
  A fragrant, early-blooming perennial, the yellow Carolina Jessamine is an attractive semi-evergreen vine that tends to remain bushy and compact when grown in bright sun. When shaded, Jessamine Carolina can climb up and over adjacent shrubs and trees to heights of more than 20 feet. Carolina Jessamine will rapidly cover arbors, tree trunks, trellises, etc. in a season or two. Zones 8 – 10.
  

And of course there’s honeysuckle and fragrant, low-growing plants such as lavender and rosemary that produce delightful aromas.

So go for ginkoes if you can shrug off the stinko, or select more fragrant plants that bring a smile to your nose.

The Plant Man is here to help. Send your questions about trees, shrubs and landscaping to steve@landsteward.org and for resources and additional information, including archived columns, visit www.landsteward.org