Great Late-Summer Color!

Just because it's late summer doesn't mean you can't have fresh plants. We continue to receive regular deliveries of fresh perennials and shrubs for late summer and fall--check out some of the great color available now!

Beware Downy Mildew on Impatiens

I hate to even have to report this, but it appears that an ugly disease that has spent the last couple of years spreading westward across the country has reached the Pacific Northwest. It's called impatiens downy mildew, and it's quickly becoming the worst enemy of gardeners who love to grow impatiens. If you've struggled with growing impatiens this summer--or just want to be aware of what to watch for--here's the scoop on impatiens downy mildew.

First off, the symptoms (courtesy Michelle Grabowski, UMN Extension Educator). Typical symptoms that impatiens display may include the following:

Advanced symptoms of downy mildew.
Courtesy M.A. Hansen

• Leaves first appear light yellow or stippled yellow & green.
• Leaf edges curl downward; leaves appear wilted.
• Fluffy white growth occurs on the lower surface of leaves.
• Blossoms drop first. Next leaves fall off leaving bare green stems. Finally stems collapse and lay flat on the ground.
• Plants infected young are stunted and have small leaves.
• In very wet conditions, infected plant tissue becomes water soaked, soft and mushy.

Now, how does it spread? Downy mildew can spread any number of ways. It may come in on your new plants at the time of purchase. (At Vander Giessen's, we were very proactive this year, inspecting our impatiens 3-4 times per week for any symptoms of the disease. Thankfully, we never saw any symptoms.) It may also spread by spore-like structures through watering or via air currents.

Arguably, the worst aspect of impatiens downy mildew problem is its longevity. Because it's a relatively new disease to the U.S., little is known about how long the disease can last in infected soil. However, a very similar strain of the disease has been shown to last up to 10 years in contaminated soil, so impatiens downy mildew may have similar impacts.

As for treatment, unfortunately at this point there are no products that can cure the disease and little that gardeners can do to prevent it. If you discover downy mildew in your impatiens, remove the diseased plants and any fallen leaves or flowers, seal them in a plastic bag and dispose of them in your garbage. Don't risk spreading the disease by throwing your plants in a compost pile.

To avoid problems in your garden, be as proactive as possible! Impatiens downy mildew tends to be most active in wet, humid conditions, so to prevent making conditions right for the disease to thrive, water impatiens early in the morning and avoid getting the foliage wet if possible. Regularly check your plants for any symptoms of the disease and take quick action to dispose any suspect plants. 

New Guinea impatiens are a great disease-resistant
alternative for shade gardens.

All traditional varieties of impatiens (impatiens walleriana) are susceptible to downy mildew; however, New Guinea impatiens (impatiens hawkeri) have shown themselves to be highly resistant to the disease, so if you're a diehard impatiens lover, consider upgrading to the showier, larger-flowered cousin of this garden favorite. You can also consider other shade-loving and downy mildew-resistant plants like coleus or begonias for your flowerbeds.

Unfortunately, impatiens downy mildew is becoming a reality for gardeners now nationwide. While scientists work to develop a solution to the deadly disease, you can arm yourself with the knowledge of what you may be up against and the steps you can take to deal with it should it strike your garden.

Hydrangeas: When to Prune and How to Change Their Color

Macrophylla hydrangea--the most common type!

It's late summer, and despite all the other fun activities you’re trying to squeeze in before fall, now is the time to prune many varieties of hydrangeas around your yard. If you’ve ever struggled with getting your hydrangeas to bloom right—or even if you want to change the color of your blooms—here are some basic tips that can make your bushes look their best.

Hydrangeas come in many shapes, sizes and varieties, but for the most part, you’ll find four different types in garden centers and around your neighborhood—and knowing which type you have will determine when and how to prune.

First, macrophylla hydrangeas are the most common types. Whether you have the standard mophead (large, round flowers) or lacecap (very small blossoms surrounded by a ring of larger blooms on each flower head), prune them now! Macrophylla hydrangeas typically only bloom on old wood, meaning if you wait until next spring to prune your shrubs back, all the new growth they put out after their haircut will be nothing but leaves. Traditional mopheads and lacecaps should be pruned just as the blooms fade in summer so they have time yet before fall to develop flower buds for next year.

Paniculata hydrangea

The second most common hydrangea species is the paniculata family. You might know some of the common varieties like ‘Limelight,’ ‘Pee Gee’ or the newer ‘Bombshell,’ all of which are easily distinguishable by their cone-shaped flowers. Unlike macrophylla types, paniculatas can be pruned anytime between late summer and mid-spring, and may not even need regular pruning at all.

 A third common hydrangea species for our area is the arborescens type.  The most common of these varieties is ‘Annabelle,’ a white variety with large blooms, although others like ‘Invincibelle Spirit’—a  pink variety—are common, too. Like paniculatas, these hydrangeas can be pruned at any time other than late spring or summer.

The last main variety of hydrangea you’re likely to grow is quercifolia, more commonly known as oakleaf hydrangeas. They have cone-shaped flowers similar to paniculata types, but their leaf shape mimics that of an oak tree. Like macrophylla types, oakleaf hydrangeas should be pruned in late summer in order for them to bloom reliably the following year.

Now that you know the basic types of hydrangeas and when to prune each, let me offer this caveat: many of the new introductions in the last several years can be pruned just about any time of year, regardless of which species they are. So, if you’re in the market for a new hydrangea and want to keep things simple, ask at a garden center for some of the newer varieties! 

Finally, how can you change the color of your hydrangeas? In the Pacific Northwest, the acidity of our soil naturally turns macrophylla types blue over time. If you want to turn a hydrangea pink—or keep one that way—treat it with Bailey’s Color Me Pink™, a soil additive available at Vander Giessen's. Likewise, if you wish to intensify the shade of blue in your hydrangea, use Bailey’s Color Me Blue™.  Depending on your conditions and desired color, multiple applications of either product may be needed. For better or worse, the color of white varieties cannot be changed.

Hydrangeas are beautiful shrubs and easy to grow. With a little attention to what type you have in your yard, you can enjoy loads of flowers each year while also maintaining the size of your plants. And with a little extra care, you can even change the color of your blooms to suit your taste!  

A Highly Underrated Perennial

Here in the Pacific Northwest, we're blessed to live in a mild climate--our winters are anything but harsh and our summers are rarely what most of the rest of the country would call "hot." Because of our mild weather, we can grow just about anything our green thumbs would desire; in the glut of plants we have at our disposal, however, we often forget about one of the most forgiving, adaptable and beautiful perennials we could plant: the daylily.

'Mighty Chestnut' daylily

In both the cold winters of the midwest and the hot, dry summers of central California, you'll find daylilies thriving. In fact, two growers I know of come to mind: Walters Gardens, one of our main perennial suppliers for the nursery, grows a beautiful selection of daylilies in the harsh conditions of western Michigan. On the other end of the climate spectrum, the Amador Flower Farm in the arid Sierra foothills of California grows nearly 1000 varieties of the perennial in hot, dry summers.

If you're picky about what colors of flowers you plant in your garden, you have no excuse with daylilies--with literally hundreds of varieties available, there's a color or texture for every taste. One of my favorites this year is a new variety called 'Mighty Chestnut.' Just released last year, this variety boasts huge, deep orange flowers set above the vibrant green foliage.

Of course, the longest-blooming and most popular variety of daylily is 'Stella D'Oro,' a classic yellow variety that blooms repeatedly all summer long. But if you're looking for something that blooms with a different color yet still has the great characteristics of 'Stella,' try 'Purple D'Oro.' With rich purple flowers, it's a great compliment to its golden cousin.

Daylilies are truly an underrated plant--they'll adapt to just about any soil type and once established, need little moisture. They bloom prolifically and only need to be divided--free plants!--every few years. If you have a sunny spot in your garden that could use an extra burst of summer color, consider planting a daylily. You'll love how easy it is to grow and soon understand why in other parts of the country it's so admired.

Perennials on Sale!

In Search of The Perfect Plant

Heuchera 'Marmalade'

There’s something I call “The Perfect Plant.” It has colorful evergreen leaves—maybe variegated—blooms for an extended period of time, needs very little maintenance, only grows to be knee-high and does equally well in sun or shade. Unfortunately, “The Perfect Plant” isn’t quite a reality. Helping gardeners choose plants for their yards, I’m often approached with those criteria, and while there isn’t an exact match to fit the bill, there is a plant that comes close: heuchera. 

First, let me help you with pronunciation. I hate nothing more than going into a store and not being able to intelligently articulate what I’m looking for. While there are plenty of pronunciations that can be considered acceptable, you’ll sound smartest pronouncing the name “HEW-ker-a” or “HOO-ker-a.” Or, if you really feel uncomfortable, just call it by its common name: ‘coral bells.’

Now, if you’re unfamiliar with heuchera, you’ve probably seen it around and just didn’t know what it was. The leaves of the plant emerge directly from the crown—the top of the root mass—like leaves do on a hosta. Although there are a wide variety of leaf textures among heucheras, all types have a leaf shaped similarly to that of a common maple tree. 

So, how do heucheras come close to fitting the description of “The Perfect Plant?” First, heucheras come in nearly every color of the rainbow. Just five to ten years ago, you’d be lucky if you could walk into a nursery and find both green- and purple-leafed varieties. And even the purple could look washed-out. But recent breeding breakthroughs have produced an abundance of vividly-colored varieties like ‘Peach Flambé,’ an iridescent peachy-orange with hues of pink. ‘Obsidian’ grabs your eye with deep plum-purple leaves and ‘Marmalade’ will make you do a double-take when you see its tan-colored foliage with a near-purple underside. 

From oranges and purples to lime-green and two-tone variegated coloring, heucheras can fit any color palette you may have in your landscape. As for flowers, heucheras do bloom, but you likely won’t buy them for the flower. Heucheras are prized mostly for their foliage, and while varieties like ‘Paris’ have rich pink flowers all summer long, most varieties’ flowers are a pale cream or white.

Regarding maintenance, heucheras are about as easy-going as you could expect of a plant. Their foliage is evergreen, so you can enjoy the colorful leaves year-round. To keep the plants in my yard looking fresh, I prune the previous year’s leaves off after the worst chance of a deep freeze is past and I can see new buds developing—typically early March. 

If you’ve tried growing heucheras before and have found them to be hard to grow, it’s possible you planted them too deep. Heucheras need the crown of the plant to be free from any standing water, and especially if you have poorly-draining soil, they should be planted at least an inch above the existing grade of your flowerbed. 

Heuchera 'Lime Marmalade'

Finally, heucheras are incredibly versatile in the landscape—most varieties do well in sun or shade. Lighter-hued types like ‘Lime Marmalade’ can adapt to full sun but will do best with at least partial shade; similarly, those with purple leaves will have the best color in full sun. However, I’ve found heuchera to grow well in any amount of sun or shade around my yard. 

If you’ve never discovered the beauty that heucheras can bring to your landscape—or if it’s been several years since you tried to grow one—now is a great time to check out the incredible variety of colorful, vigorous plants that are available at Vander Giessen's. With so many sought-after characteristics, heuchera is hard to ignore—and it just might be what you’d call “The Perfect Plant.”

Three Reasons to Mulch Your Beds

Mulching does more than add curb appeal!

Spreading bark mulch or compost on the flower beds around your house can really add to your curb appeal.
The uniform appearance of bark around your landscaping does well to set off the treasures you've planted, pruned and watered. But bark or compost does far more than just look pretty. If your flowerbeds are currently bare dirt or it's been several years since you last applied a fresh layer of mulch, here are three great reasons to grab your gloves and a wheelbarrow and get to work.

First, bark is great for regulating soil temperature. Bare dirt heats up quickly on sunny days and freezes quickly on cold winter days. By adding a layer of mulch to your beds, you can help insulate the ground from the dramatic temperature swings that might stress or damage your plants.

Second, mulch helps to retain moisture in your flowerbeds, meaning you'll have less watering to do. When exposed to the sun, bare dirt tends to dry out quickly. With a good layer of mulch to protect it, however, it retains moisture much better on warm days when it counts.

Third--and maybe of most value to you--bark mulch greatly controls weeds. Bare dirt is just an invitation for weeds (and lots of work to follow), but bark will keep most of those weeds from germinating--and stifle many weed seeds already present in the soil. This is where compost has to play second fiddle, though; compost certainly can help with weed control, but because it's nutrient-rich, weed seeds that blow in will be more likely to germinate in it than bark. 

With warm, dry weather coming, now is a great time to spread bark or compost in your flowerbeds to keep your plants' roots cooler and the soil more moist. But how much to spread? If you don't currently have any mulch in your beds, plan to build up a base layer of three inches this go-around. In future years, you can spread an inch or two to freshen things up, but you'll achieve the best results with a deeper initial layer.

One of the most common questions we get at Vander Giessen's is, "How much bark do I need?" As a good rule of thumb, plan to spread one cubic yard over 100 square feet at three inches deep. Or, if you just need to freshen things up, a yard covers 300 square feet at an inch deep. At Vander Giessen's, we sell bark and compost in bags and by the cubic yard--and we deliver, too, if you'd rather leave that part of the job to us.

It's summer time, the season when we like to kick back and enjoy a break from the busy pace of the rest of the year. If your flowerbeds could use some fresh mulch, you'll eliminate a lot of work and stress on your plants for the rest of the year with a little time invested now. This weekend, enlist your family members to help spread some bark or compost in your beds. With less needed watering and fewer weeds for the rest of the year, you'll be glad you did!