Impatiens downy mildew stunts growth, yellows leaves and eventually kills the plant. Photo courtesy of Purdue University Plant and Pest Diagnostic Laboratory
It’s been one of those springs—cool and wet, which is just the right formula for leaf diseases.
Maples, in particular, have brown or black spots, most likely a fungus disease call anthracnose.
“This was the most common plant problem sample that was brought into our office during the past month,” said Steve Mayer, horticulture educator at Purdue Extension-Marion County.
Maple leaves have also shown up with blisters, another fungus disease, he said. “Neither of these two foliar diseases will cause any long-term detrimental effects to healthy trees. However, most trees are stressed from last year’s drought and producing a second crop of leaves to replace those that fall prematurely (from the fungus disease) may cause additional stress.”
Purdue recommends adding 2 to 3 inches of mulch around trees, making sure to keep it away from the trunk.
Trees, shrubs and other drought-stressed plants should get at least 1 inch of water each week from either irrigation or rain. “Do not fertilize any more this growing season, as this may only stress the trees and shrubs by forcing new growth,” Mayer said.
Impatiens trying patience
More gardeners have sickly or dying bedding impatiens (I. walleriana). This best-selling annual for shade gardens has been hit with impatiens downy mildew, a deadly disease that persists in the soil for at least five years. The disease also can be carried by wind.
If impatiens did not do well last year, do not plant them again this year. There’s nothing you or growers can do to prevent this disease because there are no fungicides or other pesticides to control the problem. Remove infected plants. Do not compost them, but rather discard in the trash.
The disease started showing up in Indiana last summer, but has been severe in other states and Europe. The best remedy is to use other shade-tolerant plants, such as begonia, torenia or tropical plants. New Guinea impatiens and SunPatiens are not affected by impatiens downy mildew.
Maple blister disease. Photo courtesy Purdue Plant & Pest Diagnostic Laboratory.
Maple anthracnose. Photo courtesy Purdue Plant & Pest Diagnostic Laboratory.
Golden Japanese forest grass. (C) Jo Ellen Meyers Sharp
‘Aureola’, a golden Japanese forest grass (Hakonechloa macra), is a perfect plant for softening the front edge of a border, cascading over a wall, working as a ground cover or adding a bright spot in the perennial bed. This is a great plant for a shadier location, where its golden color brightens some of the darker spots in the garden. It also can be used as a container plant for summer color and transplanted to the ground in fall, if desired. ‘Aureola’ was named the 2009 Perennial Plant of the Year.
Hakonechloa macra is native to Honshu Island, Japan. Hakon refers to the Japanese region and chloa is the Greek word for grass, according to the Perennial Plant Association (www.perennialplant.org), a not-for-profit organization made up of educators, plant breeders, growers and others. Each year members make nominations and vote on their favorite perennial. Previous popular winners include ‘Maicht’ or May Night Salvia, ‘David’ Phlox, ‘Husker Red’ Penstemon, ‘Jack Frost’ Brunnera. The fragrant, variegated Solomon’s seal (Polygonatum odoratum ‘Variegatum’) received the 2013 Plant of the Year honor.
Like other ornamental grasses, golden Japanese forest grass adds soft, graceful movement and sound to the landscape. ‘Aureola’ forms a mound of cascading layers of one-half inch wide bright yellow blades with green stripes. A mound gets 12 to 18 inches tall and up to 24 inches wide. The plant has small, delicate flowers in late summer and fall, but they are not particularly showy. In fall, the blades take on a pinkish-red hue. In cold climates like Indiana, the plant dies back in winter. In warmer zones, the plant may be evergreen.
Hardy in USDA Zones 5 through 8, golden Japanese forest grass does best with four to six hours of sun a day, or part shade. Morning sun would be ideal. If the plant will be in a west- or south-facing garden, provide dappled shade. The more shade, the less golden the color. The plant prefers soil that is moist, well drained and rich in organic matter.
Fall color of 'Aureola' golden Japanese forest grass with Crow Feather Tiarella. Photo courtesy PerennialResource.com
‘Aureola’ is one of my favorite plants. It is easy and it brightens some of the darker landscape spots. Its form and texture work extremely well with other part-sun and shade plants. The fine foliage of this grass complements the bolder leaves of hosta, coral bells (Heuchera), heucherella (Heucherella), hellebores (Helleborus), foam flower (Tiarella) and Epimedium. ‘Aureola’ also does nicely around shrubs and trees. When planted in masses, a sea of grass forms a lush ground cover.
The maintenance on this plant is pretty low. Cut back to the ground in early winter or when it starts to look bad. Divide in spring. It has few disease or insect problems and, as a bonus, the deer do not seem to favor this grass. Besides ‘Aureola,’ there are other golden cultivars on the market. ‘Bene Kaze,’ is an all-green variety.
- Japanese honeysuckle vine smells heavenly, but it has escaped landscapes and rooted in natural areas, where it smothers native plants. This aggressive habit puts it on the invasive plant lists in Indiana, other states and the federal government. Photo courtesy of Invasive.org
Some perennials are attractive, vigorous growers. And those last two words are the reasons why I would not plant them in my yard.
These are the plants your neighbors, friends and family want to share because the perennials have done so well in their yards. These also can be found in garden centers and mailorder and online retailers, frequently described as vigorous growers. Don’t bother.
Here’s a sampler:
Evening primrose (Oenothera speciosa). This native plant forms huge colonies of quarter to 50-cent size, pretty pink flowers atop 12 to 18 inch tall stems. It gets its name because the flowers open at dusk. A popular cultivar is ‘Siskiyou Pink’. Alternative: ‘Bath’s Pink’ cheddar pinks (Dianthus gratianopolitanus).
Bishop’s goat weed or snow on the mountain (Aegopodium podagraria, A. p. ‘Variegatum’). There are solid green and variegated varieties. I planted the variegated type as a ground cover when I first started gardening. After a few years, I was pulling it out by the bucketsful. This plant, with lovely Queen Anne’s lace type flowers, does not know when to stop spreading. Alternative: bishop’s cap or barrenwort (Epimedium).
Bishop’s goat weed and evening primrose could be grown in a bed bounded by sidewalks, house or other hardscape.
Japanese honeysuckle vine (Lonicera japonica). A fast growing vine with fragrant, yellow-white flowers make this an attractive plants. And just as fast at it grows in your yard, it is taking hold in natural areas throughout Indiana and elsewhere. It’s vigor has earned it a spot on the state and federal lists of invasive species. Alternatives: ‘Major Wheeler’, ‘John Clayon’ (L. sempervirens); ‘Goldflame’ (L. x heckrottii); ‘Serotina’, Peaches and Cream (L. periclymenum).
Evening primrose can be a thug in the garden, overtaking neighborhing plants. © Jo Ellen Meyers Sharp
Sweet autumn clematis (C. terniflora, C. paniculata) is another fast growing vine that self-sows like crazy. Alternatives: honeysuckles (see above); other clematis; late blooming annuals vines, such as cardinal vine (Ipomoea quamoclit).
(C) Jo Ellen Meyers Sharp
Pansies, Johnny jump-ups and violas love the cooler weather and right now, they are beautiful. But fewer than 5 feet from these spring bloomers site more than 100 annuals, perennials, roses and shrubs for their trials in my garden this year.
The dilemma is when to pitch the pansies and replant pots with the new stuff. Many gardeners have this issue even with no plants to trial. Their new plants come from trips to the garden centers.
I’ve already started filling the hanging baskets or other pots that I pulled plants from last fall. Other pots contain tropical plants, such as Crinum, rain lily (Zephyranthes) and possibly one of the new lily of the Nile (Agapanthus). These wintered over on the enclosed, but unheated porch or in the basement.
Soon, I’ll transplant the Johnny jump-ups (Viola tricolor) and viola (V. cornuta) to a spot in the yard and compost the pansies (V wittrockiana).
Rose slug and rose slug damage. Photo courtesy Missouri Botanical Garden.
Seemingly overnight, rose leaves developed what’s called a stained-glass window look. A tiny caterpillar munches just enough green tissue to give rose leaves an opaque look.
The critter is commonly called a rose slug, although it is not a slug at all. It is the larvae stage of two or three sawflies. The sawfly lays eggs on the under side of rose leaves in early spring. As the eggs hatch and the caterpillars emerge, they feed on the leaves.
The best defense is a good offense. Every few days examine your roses, especially the under sides of leaves, for eggs. Use a strong spray from the hose to wash them away. Beneficial parasitic wasps like these insects, so Mother Nature will catch up with the problem if you avoid using pesticides.
If the infestation is severe, insecticidal soap and neem oil may work. Always read and follow the label directions.
Creeping phlox. (C) Jo Ellen Meyers Sharp
I never have to look outdoors to know what’s blooming. The customers at the garden center where I work part time keep me informed.
They come in and ask for the plants they see blooming. Here’s what’s on the hit list this year.
Creeping phlox (Phlox subulata), a low-growing evergreen ground cover that has had a splendid spring. This perennial does best in full sun and well-drained soil. Once established, this North America native plant is drought tolerant. Creeping phlox retains its needle-like leaves all winter. It gets about 6 inches tall with a 24 inch spread. Plant in rock gardens, in the front of a flower bed or border, along walls and slopes or as a carpet of color under trees and shrubs. Shear off spent flowers to tidy up the plant in spring.
Cascading branches of white flowers on bridal veil spirea (Spiraea vanhouttei) spur interest in this old-fashion, easy-care shrub. This was in my yard and all over the neighborhood where I grew up. It remains a staple in older neighborhoods today, but can be hard to find, so ask your garden center to order it. Bridal veil spirea does fine in part shade to full sun. It can get up to 10 feet tall and 20 feet wide, so make sure to give it room. If this needs to be pruned, do so right after it is done blooming.
Bridal veil spirea. (C) Jo Ellen Meyers Sharp
I’m lukewarm on crabapples (Malus) until I see them bloom like they have this spring. And this is the first year that I noticed intense fragrance on this common tree. Look for crabapples that are resistant to the leaf diseases that can plague this tree and for cultivars that hold the fruit through winter for extended interest. Newer cultivars have been grafted on root stock that reduces or eliminates suckering—sprouts coming from the base of the tree, a common complaint about this and other fruit trees.
Alliums add dramatic flair to the garden. (C) Jo Ellen Meyers Sharp
Except for a few 80-degree days, it’s been a slow, low-temp spring, which has prolonged tulips, in particular. This year, the large alliums, a gift from Carol Michel at May Dreams Gardens, are beautiful and so dramatic. I’m going to have to get a lot more of these and other alliums, especially those that bloom a bit later in summer.
Native columbine (Aqueligia canadensis). (C) Jo Ellen Meyers Sharp
The lower temps have also delayed the bloom cycle of other plants. Just starting to reign supreme in the garden are the beautiful native columbine (Aquilegia canadensis), which self-sows about, but would never be considered invasive. This year, the flowers’ red-orange seems more intense.
The coral bells (Heuchera) are forming a nice mass, with so much foliage color…oh, they bloom, too. There are a few heucherella and tiarella mixed in there too, along with sweet woodruff (Galium odoratum) and Spanish bluebells (Hyacinthoides hispanica). The bluebells are always such a nice surprise because they bloom later than other spring bulbs.
My maidenhair fern (Adiantum) survived the winter, always cause for celebration. The clump was given to me by a regular customer at the garden center where I work. She over heard me telling another customer that maidenhair ferns were hard to find in the trade and brought one for me! The garden center has some really nice customers.
The ‘Bath’s Pink’ Cheddar pinks (Dianthus gratianopolitanus) grows more on my asphalt driveway than in the garden bed. I swear this plant would grow on concrete. It is so fragrant right now!
Jack-in-the-pulpit (Arisaema triphyllum). (C) Jo Ellen Meyers Sharp
The reblooming bearded iris (Iris) ‘Immortality’ is lovely and soon, the blue one will bloom, but I don’t remember its name. Reblooming iris flowers are large, fragrant and put on a nice show in spring and again in late summer.
A favorite plant—Arisaema triphyllum—has emerged amid the Epimedium (E. x versicolor ‘Sulphureum’) and I’m thinking about moving it before it gets completely swallowed up. The jack-in-the-pulpit came from the late Jim Story, the first reader who wrote me when I started writing about gardening in 1989. He was such a generous soul, as are many gardeners, but he was special.
Last fall, Longfield Gardens sent a bunch of spring-blooming bulbs. By far, among my favorites is Anemone de Caen ‘Mr. Fokker/Sylphide’ (Anemone) mix. I hope they return next year, but if not, they have been beautiful this year.
A variety of heuchera, heucherella and tiarella have rooted nicely to offer a mass of colors. (C) Jo Ellen Meyers Sharp
Dozens of trial plants have arrived for the 2013 growing season. (C) Jo Ellen Meyers Sharp
Last spring, I whacked back my 20-year-old ‘Miss Kim’ lilac (Syringa pubescens subsp. patula) and last fall, shifted her to the back yard because Carol Michel’s garden designer (Wendy Ford, Landscape Fancies) said it was too big for its space and blocked the view of my front door. I planted another one in the front, but about 5 feet from the original, which allows for a better view of the door. Both are ready to bloom.
With all of this work from Mother Nature, it’s like Christmas for me. And not just because of the plants blooming in the garden. Awaiting planting are this season’s trail plants. Before it even gets in the ground, I think I’m really going to like ‘Purrsian Blue’ catmint (Nepeta faassnii). I’ve already cut it back once and it’s not even planted in the ground yet. However, it immediately—within a week—began blooming, not something I’ve noticed with catmint. It’s not supposed to flop, either, so we’ll see how it does once its in the ground.
Bath's Pink Cheddar pinks (Dianthus gratianopolitanus). (C) Jo Ellen Meyers Sharp
Thanks to Carol at May Dreams Gardens for being the host of Garden Bloggers’ Bloom Day. Please feel free to join in. We think it’s the longest running gardening meme on the Web.
Winter hardy sunchokes are related to sunflowers and are native in to the Eastern United States. © CanStockPhoto Inc./Jochen
Questions about tulips, jet bead and Jerusalem artichokes fill the inbox.
M.S. of Indianapolis wants to know “why do some tulips in the landscape change color?”
Several things could cause this. Some tulip bulbs are bred to do change colors through the day. Other times, it could be the natural aging of the flowers, when many colors fade.
“While not common, it occasionally happens that a bulb flower’s bloom color can change through a spontaneous mutation or exposure to natural elements that cause one layer of cells to mutate to another color,” said Tim Schipper, owner of ColorBlends.com. “The bulb itself is unaffected and remains healthy, but the flower color is different.”
D.O. read about jet bead, a shrub noted for thriving in “bad soil, shade and slopes. I thought I hit the jackpot. However, after doing some research, I find that it’s a very invasive shrub. Is this true?”
Jet bead (Rhodotypos scandens) does sound like a dream plant because it survives in less than desirable growing conditions. Its over-adapatability and proliferation is why this Asian shrub is considered a pest.
“Jet bead is a serious problem in Indy Parks, and a few other natural areas in the state,” said Ellen Jacquart, director of northern stewardship at the Nature Conservancy of Indiana and a member of the Indiana Invasive Plant Committee. “This is one we’d really like to get assessed and out of trade.”
P.B. “is interested in planting Jerusalem artichoke, but am having trouble finding any bulbs. Any suggestions?”
Jerusalem artichoke (Helianthus tuberosus), frequently called sunchoke, is a perennial in central Indiana, usually planted from edible tubers. It is related to the sunflower, but not to artichoke (Cynara cardunculus var. scolymus), which can be grown from seed as an annual in cold climates. Each of these will likely have to be ordered from online retailers. Jung Seed sells both. Purdue University has more info on growing sunchokes.
Viburnums, tulips, lilacs and other plants perfume the spring air. (C) Jo Ellen Meyers Sharp
A good spring overloads the senses. Not only does the earth break out in eye-pleasing blooms, many of the flowers release delicious fragrance.
Until just a few days ago, the office, kitchen, bedroom, backyard and enclosed back porch have been perfumed by viburnums, incredibly easy-to-grow shrubs.
In a partly sunny location in the back of the yard are two Burkwood viburnums (Viburnum burkwoodii), an upright shrub that can reach 10 feet tall and 6 feet wide when grown in full sun. Mine are closer to 6 feet tall and 4 feet wide.
In their shadier location, the burkwoods have a more open growth. In full sun, the growth is much more dense. Although my burkwoods have fewer flowers in the shade than they would have in full sun, they still are loaded. This viburnum is semi-evergreen, retaining its foliage through winter, depending on the severity of the weather.
Outside the bedroom window and bordering the enclosed porch sits a Judd viburnum (V. x judii). This is a rounded, 6-foot tall and wide fragrant beauty with blue-green leaves that turn a deep red in fall and cling to the plant for several weeks of late season color. It prefers full sun, but tolerates light shade.
Like all spring bloomers, the viburnums’ flowers and fragrance can be rushed through their season with high temperatures in spring.
We all know about borrowed landscape views—the scenes created by a neighbor’s plants. Some of us also enjoy borrowed scents. A neighbor’s old fashion lilacs (Syringa vulgaris) have burst open, adding fragrant breezes to my living room.
Any day now my two ‘Miss Kim’ Manchurian lilacs (Syringa pubescens subsp. patula) will begin blooming outside the living room and the bedroom windows. These bloom a few weeks later than the old fashion lilacs. ‘Miss Kim’ also is not affected by the powdery mildew fungus disease that afflicts many traditional lilacs. It has decent fall color, too, with deep purple leaves.
And just a few days ago, the crabapples (Malus) were in full bloom at the Indianapolis Museum of Art. The blooming branches created a large arch, which held the fragrance at nose level. I’d never noticed that crabapples were so fragrant.
These scents of the season reinforce the good sense of planting fragrant bulbs, perennials, annuals, trees or shrubs where you can enjoy their elusive attributes.
Tomato, pepper and cucumber transplants are among the vegetables that don’t like cold soil. Plant these outdoors around Mother’s Day. © Jo Ellen Meyers Sharp
As we head into prime planting season, here are a few things to keep in mind.
When potting up containers, use a high quality potting mix. This is usually a soilless mix with vermiculite, finely shredded organic matter and other ingredients that promote drainage. Potting mixes also are light weight. Since the mixes are soilless, be sure to fertilize regularly, according to the product label directions.
Containers have three basic elements: thriller, filler and spiller. The thriller is the largest or most dramatic plant, frequently the centerpiece or backdrop. Fillers are moundy-roundy and help fill gaps. Spillers cascade over the edges of containers.
Vegetables and Herbs
Don’t push planting. Warm season vegetables, such as tomatoes, eggplant, cucumbers and peppers, are not happy in cold soil. Wait until May 10 (or Mother’s Day) to plant these crops and to sow seeds for green beans, corn, squash and pumpkins.
Basil (Ocimum basilicum) is extremely sensitive to cold temperatures. It’s ok to plant parsley (Petroselinum crispum), sage (Salvia officinalis), thyme (Thymus) and other perennial herbs outdoors now.
If a perennial or ornamental grass has all of its new growth around the perimeter of a dead or sparse center, that’s a signal it needs to be divided. Lift the plant and slice off the healthy growth to transplant. Discard the dead center.
If you fertilized the lawn in fall, you probably won’t have to fertilize in spring or early summer. Doing so will increase mowing duties. Try to keep the lawn at about 3 inches high.
Annuals and Tropicals
Some annuals tolerate the cool temps of spring, but others, such as impatiens (I. walleriana) and geraniums (Pelargonium) do not fare well. Wait until mid-May to plant tender annuals and tropicals.
Try Something New
Lastly, try something new, whether it’s a vegetable or herb you’ve never grown, or a new perennial or annual. Trying new things in the garden keeps us growing.