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

Hydrangeas are failing to bloom

QUESTION: “I have two hydrangea plants that grow every year in a sunny location, with large bright green leaves. The plants never make flowers, however, even though the woman who gave them to me years ago took the small plants from her garden where she had many flowering specimens.

“At the end of the summer, I have those long spikes which I carefully protect through the frosty winter, but by spring they are dried up and appear dead. As the new leaves start to grow, I lose hope and cut the pale spikes down. Most of the time, the deer eat the tops anyway. Any hope? Should I transplant them?” – Faith Gitlow

ANSWER: Hydrangeas can be tricky. According to the experts at www.hydrangeashydrangeas.com (my favorite hydrangea care site) there are three main reasons why hydrangeas fail to bloom:

1. A late spring freeze arrives and ruins the developing bloom buds.
   
2. Improper pruning.
   
3. Planted in wrong zone. If you have had the bad luck to plant a hydrangea that has not bloomed after the first year you planted it, you may finally have to concede that this particular variety is not cold hardy in your area.
   

If you go to their Web site you can find more information about all kinds of hydrangea problems.

QUESTION: “I have a problem with my blossoming Kwanzan cherry tree. The leaves are turning brown and falling off. Is it dying? I live in the California sierra foothills (elev. 1500ft.). It can get very hot during the summer months. The tree is planted in the middle of my lawn on an island of top soil with 2" of wood mulch on top. The island is about a foot and a half high and less as it spreads out.

“I water about every other day for 20 minutes at 4am. There are plants and flowers around it but not any closer than 2 ft. It also has new growth coming in. I just don't get it! Do you have any ideas?” – Dan Buchholz

ANSWER: Over the past four years or so, flowering cherry (and other varieties including birches) trees have been going dormant earlier and earlier each year where we live here in Tennessee which is zone 7. For the most part, it is attributed to the lack of rainfall (actual drought some of the years).

Around early to mid August, they begin to lose their leaves. Their coloring doesn’t fade to a lovely fall color, just brown. As long as there are no other issues with the tree, I would say it is the same problem. Cheryl and I have been receiving many emails this summer concerning trees doing this.

QUESTION: “For the past three seasons my pin oak trees have lost their leaves in August. The leaves turn translucent first before falling from the tree. I have used an insect treatment that you add to water and pour at the base of the tree for the past three years and it doesn’t seem to help. In the spring and during the summer the trees are full of leaves but in August they turn white and fall off the tree. The trees are 30 to 40 feet tall (I have two of them on the west side of my home).” – Susie Brown

ANSWER: Here is a link to the University of California at Davis Extension site with an article on diagnosing oak tree diseases.
http://ceventura.ucdavis.edu/newsletterfiles/Landscape_Notes11016.pdf
This article will give you a detailed listing to work with, but the most common reasons for early leaf loss with oaks is lack of water or cool wet spring/summer weather which typically causes fungus.

If you can’t figure it out with the article, contact your local agricultural extension agent for their opinion and how to proceed. To find the Extension Service nearest to you, visit this Web site: http://www.csrees.usda.gov/Extension/ or go to my Web site www.landsteward.org find this column and click on a direct link. Good luck!

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

Deer-resistant plants mean less landscape damage

I think we’d all agree that deer are hungry critters. However much you enjoy wildlife, you can be disheartened, or even outraged, to find your prized shrubs chewed down to the stumps with tell-tale hoof prints in the surrounding soil.

In the previous Plant Man column, I described ways to determine if deer are the real culprits, and I took a look at some deer repellent products, both commercial and home-made. If you missed that column, you can find it at my Web site www.landsteward.org

Today, we’ll take a look at some deer resistant plants. As far as I know, there are no “deer-repellent” plants; the kind that would send deer scurrying away in panic. No such luck. So your best bet, if deer are a potential problem, is to select plants that hold the least possible attraction to deer. Unfortunately, in times of scarcity, deer will eat almost anything green, but you can put the odds in your favor so they will ignore your landscape in search of greener – and tastier – pastures.

Do a little homework and you’ll quickly discover which plants attract deer and which plants they find less desirable. A good place to start is http://njaes.rutgers.edu/deerresistence/ a Web site hosted by Rutgers University.

That Web site consists of a long chart of alphabetically-listed plant names, color-coded to indicate which are rarely damaged, seldom severely damaged, occasionally severely damaged or frequently severely damaged.

Using the Rutgers chart, you can determine if a plant on your wish list might be better replaced with a less deer-yummy one. Although it’s a long list, I can think of other plants that you could select when deer are a potential problem. Here are some to consider:

Boxwood Wintergreen (Buxus microphylla)
I’ve found that deer don’t particularly care for the taste or aroma of boxwoods under normal circumstances. This popular low growing evergreen shrub is commonly seen as a low hedge or border defining the edges of formal and informal gardens. The Wintergreen Boxwood offers dark green lustrous leaves and creates a striking hedge with year round color, holding its green color all winter long. Suitable for USDA zones 5 – 9.

Black Eyed Susan (Rudbeckia Goldsturm)
Black Eyed Susans are true perennials, returning larger each year. They are great for mass plantings and provide wonderful contrasting colors when paired with ornamental grasses, Shasta daisies, Russian sage or dianthus. Black Eyed Susan should be deadheaded regularly for continued blooms. They are a native North American wildflower as well as being deer and rabbit resistant yet attracting butterflies. Zones 4 – 9.

Barberry Rose Glow (Berberis thunbergii)
This is an eye catching form of Japanese Barberry, emerging with early foliage that is a rosy glowing pink color that turns a crimson burgundy as it matures. Full sun produces the best foliage, looking good as foundation, border or mass planting. Barberry Rose Glow needs a well drained area and can tolerate some drought in zones 4 through 7.

American Holly (Ilex opaca)
You probably wouldn’t relish eating holly and, as a rule, neither do deer. Left untrimmed, American Holly can reach a height of 30 feet or more with a spread of 18 to 30 feet. Bear in mind you will need at least one of each sex to produce berries that will attract birds and butterflies but not deer. Hardy in zones 5 to 9.

Bamboo Sunset Glow (Fargesia rufa)
A favorite of the Giant Panda but not that attractive to deer. This is a clumping (non-running) variety. Growing to 8 feet in height, the orange-red sheaths and deep green leaves will provide a nice hedge or screen at maturity when planted in groups. USDA zones 6 – 9.

Sage, Thyme and Chives
Deer don’t particularly care for these herbs but humans do, so they’re not a bad choice as attractive groundcover and as a great, fresh addition to many home-cooked dishes.

Again, no plant is 100% deer-resistant. But when you select plants that are less attractive to deer and employ some of the deterrents we discussed in the previous column, you should find that deer will generally look elsewhere for their salad buffet.

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

Dense evergreens make perfect living fence

Fences make good neighbors, according to the old saying. This can be particularly true for homeowners living on relatively small lots in urban or suburban neighborhoods or in so-called “cluster home” developments.

“Living fences” of fairly dense shrubs and evergreen trees can disguise existing wood or chain-link fences or even replace them altogether. Cheryl and I planted a stand of Thuja Cedar Green Giants several years ago and they are growing by leaps and bounds, robust and healthy, creating a natural perimeter between our lawn and an expanse of wilder woodland.

Cedar Green Giants can be pruned annually to keep them at a manageable height, but left to their own devices, Cedar Green Giants can reach heights of 30 to 50 feet, growing three to five feet a year. Another benefit is that Cedar Green Giants are without serious pest or disease problems, giving them an advantage over Hemlocks and the disease-prone Leyland Cypress. Plant Cedar Green Giants three to five feet apart and you’ll soon have a natural screen for added privacy and as a sound barrier if traffic noise is an issue.

Another fine choice would be the arborvitae “Emerald Green” with its dense foliage and pyramidal shape. Arborvitae Emerald Green has a very bright green color and appears to have a tinge of gold to it if the sun hits it just right. Arborvitae Emerald Green grows to a height of 10 - 15 feet, with a spread of 3 - 4 feet. Emerald Green displays its bright lustrous green color all year and does not discolor in winter, adding a feeling of life to what might be an otherwise barren landscape. Its very compact and tight growth pattern make it an excellent choice for a screen when spaced 2 - 3 feet apart in the row.

Here’s a reader looking for some guidance with her arborvitae.

QUESTION: “We have a row of emerald green arborvitae across the back of our yard. We use it as a screen between our yard and the neighbors’ yard behind us.

“Starting last year six evergreens in a row started to get all brown, mostly on our side, which faces SE. We have a maple tree shading them some that has really started to grow in the last few years.

“We don't know if it's the shade or nutrients or what, but if they can't grow there, do you have a suggestion as to what would thrive there, and not look so out of place because of being something different in the row?” – Elaine

ANSWER: There are a number of reasons why this could happen to your arborvitae. Here are some of the most common:

• Dogs urinating on the plants
  
• Spider mites
  
• Not mulching enough
  
• Wind burn
  
• Over fertilizing
  
• Not hardening off before winter
  

As for the last two potential reasons, bear in mind that you should fertilize only one time during the year (with something such as Hollytone) and spring would be the best time to do it.

Do not water regularly after fall frost. Watering should begin to gradually taper off in late summer (such as late August to September depending on your location) so that the plant can harden off for winter. Arborvitae are not drought tolerant so when tapering off, simply stretch the number of days between watering. Should there be no regular rainfall during that period, supplemental watering will be necessary, just less frequently.

From the photographs you e-mailed to me, most of your plants look fine, just the ones on the inside look somewhat stressed. Take a look at the possible list of causes, above, and taking into account your local weather conditions, you should be able to narrow it down.

If you identify and rectify the problem, there should be no need to replace your arborvitae.

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

Never too early to plan fall planting

Fall planting? But it’s only just summer! It’s way too early to be thinking about fall planting, isn’t it?

Nope.

This is an excellent time to be thinking ahead to the cooler days of fall and what you can plant to enhance your landscape. What makes “right now” so special?

Right now your landscape is probably at its high point. The foliage on shrubs and trees is full and lush. Many of your late spring and early summer plants are in bloom. Take a look around your landscape. Walk around and see it as if with fresh eyes. This is the best time of year to see where the gaps are. Later in the year, and of course in winter, this is less obvious as deciduous trees have shed their leaves and even evergreens are more dormant.

What do I mean by “gaps” in your landscape? I don’t mean to suggest you should necessarily fill every square foot of soil with plants. But when you look at your landscape, as if for the first time, you’ll see areas that don’t look complete, somehow.

Perhaps there’s an awkward space between plants that looks empty, like a smile with a missing tooth. Maybe a dead plant had been removed and never replaced. Or perhaps an older plant has outgrown its usefulness, dwarfing smaller plants around it and preventing sunlight and rainwater from reaching them.

Not only that, but at this time of year you can look at your landscape and see some of your favorite plants at their best and decide if it would be a good idea to invest in one or two more. At our nursery, it is not unusual for Cheryl and me to hear from customers who bought shrubs from us one or two seasons ago and want to buy more of the same, once they’ve seen how well those plants enhance their particular garden plan.

As a general rule, it makes sense to place low-growing plants at the front of the beds with medium sized plants behind them and the taller shrubs in back. Now is the time to look at your beds and determine if there are some plants that are “out of whack” in your landscape. Instead of waiting until fall or next spring, decide now if any plants need to be retired and replaced, and which ones you’d like to see more of next summer.

Need some idea starters? Here are some plants you can research right now and probably pre-order for fall planting. Let’s start with the low-growers…

Ajuga Black Scallop PW http://www.greenwoodnursery.com/page.cfm/87441
A neat little fast-growing ground cover with deep, dark burgundy leaves and blue blossoms in spring, lingering into summer. I prefer this one to regular Ajuga bronze due to its larger leaves and deeper color.

Creeping Red Thyme http://www.greenwoodnursery.com/page.cfm/13373
(Thymus praecox subsp. Arcticus) This is a fast-growing evergreen ground cover with wonderfully aromatic foliage. If you’d planted it last season, right now you could be enjoying a profusion of lovely red flowers. Easy to grow and good between pavers, too.

Moving back to some medium-height plants…

Heuchera Lime Ricky PPAF http://www.greenwoodnursery.com/page.cfm/87490
This would be superb choice to plant behind the Ajuga Black Scallop (or adjacent to any dark foliage plant such as Black Elephant Ears or Black Mondo grass) because the scalloped leaves are a glowing chartreuse in spring turning lemon-lime in summer, emphasizing the contrast with black Ajuga foliage. Mature height: around 2 feet.

Heuchera villosa Tiramisu PPAF
Imagine these splashes of brick red color spattered around your garden, lightening to chartreuse in summer with a light silver overlay.

And now some taller plants…

Carolina Allspice http://www.greenwoodnursery.com/page.cfm/11681
(Calycanthus floridus) A dense, deciduous shrub that can grow to 5 or 6 feet (or more) at maturity, Carolina Allspice has lustrous dark green foliage and very fragrant, brown to reddish-brown flowers.

Buddleia Bi-Color http://www.greenwoodnursery.com/page.cfm/47058
Easy to grow and extremely fragrant, this variety sports two different colors on the same bloom stalk: rich lavender and butterscotch yellow. It will bloom all summer and attract swarms of colorful butterflies to your garden. Mature height: 5 to 6 feet.

Survey your landscape, plan for improvements and pre-order plants now for fall planting. Let me know if you need some more suggestions.

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

White spots on leaves could be powdery mildew fungus

QUESTION: “I just planted some salvia in my garden and noticed some white spots on the leaves. Any suggestions?” – Mazzocco

ANSWER: The white spots could be from mineral deposits from watering, fertilizer residue or a fungus known as powdery mildew.

You will need to determine what is causing them before you can take any action. Fortunately, the first two wouldn’t require any action, but if they are caused by a fungus, you might want to apply a fungicide.

Powdery mildew is one of the most common landscape fungus problems. The first sign is often curled and twisted leaves before the white or grey powder is apparent. When the mildew appears, you might see the grey patches gradually enlarge and spread until they cover large areas on one or both sides of the leaf. If you are seeing that, then you have powdery mildew.

Severe infection can result in yellow or dry brown leaves and disfigured shoots. Although powdery mildew is not usually fatal, it can bring on early defoliation and unsightly plants.

Powdery mildew fungi are most likely to produce airborne spores and infect plants when temperatures are moderate and will not be present during hot summer days. When plants are overcrowded and shaded, creating a cool, humid environment, they are at greatest risk for powdery mildew infection.

Pick up any fallen infected leaves and pick off any severely damaged or dead leaves and destroy them, preferably by burning. If it’s any consolation, powdery mildew generally won’t adversely affect a plant’s overall health, so if it appears to be quite mild, or if you can live with unsightly plants, you could probably ignore it, other than destroying the infected leaves.

However, you can use a fungicide to treat the problem. For best results, begin to spray the plants as soon as the mildew is detected. Repeat the spraying as needed, which is usually during the cooler weather seasons. Not all fungicides are suitable for all plants, so be sure to check on the recommended usage before you spray. Read the package directions!

Here are two very useful sites with photos to help you identify powdery mildew and helpful instructions on how to treat the problem and create an environment that will discourage the fungus from returning. One article is posted by Cornell University’s Plant Disease Diagnostic Clinic and the other is from Ohio State University’s Extension Service.

http://plantclinic.cornell.edu/FactSheets/powdery/powdery.htm

http://ohioline.osu.edu/hyg-fact/3000/3047.html

You can click on direct links to those sites when you find this column at my Web site, www.landsteward.org

QUESTION: “I have a very steep slope in my back yard leading from a patio down to our lake front. There is a retaining wall at the top and a retaining wall at the bottom. I would guess that the incline is about 45 degrees in some areas. There are trees on one side leaving part of the slope in deep shade, part is dappled shade and a few areas get a
good bit of sun, but the bulk of the area is pretty shady.

“Since it is so steep, we have concerns about erosion control. It's steep enough to be difficult to get out there and weed or do any other normal garden "tending", so it has to be very self sufficient. Can you give any advice on types of plants to use?” – Margaret Wilson

ANSWER: Anything you try to plant will most likely take several years to fill in at best. Vinca, pachysandra, purple wintercreeper and liriope will grow well on sloped shaded areas. Ivy might grow well, too, but may be a bit too invasive for your landscape.

If there is a problem with erosion now, I would recommend putting down erosion netting first and then planting. You can plant right through the netting, just cut an X out where you want to insert each plant. Erosion netting decomposes over 5 or so years allowing the ground cover time to take hold and spread. In the meantime, it does a good job at keeping weeds at bay. I hope this gives you some ideas to build on.

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