Eye Candy for Gardeners

Rosa Morden Snowbeauty

Rosa Morden Snowbeauty

This photo seems to perfectly capture one reason gardeners have such a long-standing love affair with the rose. I can’t think of another flower as delicate and elegant when first opening as a rose. The Morden Snowbeauty rose shows just the faintest hint of pink before opening to pure white. Aren’t roses fantastic?

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Bristly Roseslug

Bristly Roseslug leaf damage

Bristly Roseslug leaf damage

It never ceases to amaze me how all it takes is one rose in a garden in order for the Bristly Roseslug to find it and attack. The roseslug is the transparent (when young) or green (when older) larval caterpillar of a sawfly (wasp), Endelomyia aethiops. The larvae are no more than one-half inch in length and, if you’re lucky, can be found  while eating leaves and promptly squished. Younger larvae skeletonize the leaves, as seen in the photo at left, while older larvae chew holes in the leaves, often along the leaf edges.

Older Bristly Roseslug curled up on a paper towel

Older Bristly Roseslug curled up on a paper towel

In addition to hand-picking, you can try spraying the plant with a strong jet of water. Once the larvae are knocked off the plant, they can’t climb back up. For protection, try a 2%-3% solution of horticultural oil in water as long as the plant isn’t in bloom. Treatments for severe infestations involve systemics, such as acephate (Orthene) or carbaryl (Sevin), which are nerve poisons. Systemics should be used with extreme caution, and only if treating for other pests where damage can be severe, such as Japanese beetle.

Roseslugs tend to emerge early in the season (late May, early June) and have only one generation per year in Zones 5-6. Careful monitoring, combined with hand-picking or water blasting, should minimize seasonal damage.

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Four-Lined Plant Bug

Four-Lined Plant Bug nymph

Four-Lined Plant Bug nymph

For the past two years I’ve had problems with Four-Lined Plant Bugs. As shown in the photo at left (click to enlarge), the nymphs are black and red, so they’re easy to spot, even though they’re only one-quarter inch in length. They have voracious appetites, and with their chewing-sucking mouthparts they can leave numerous small holes on tender leaves. The plant tissue surrounding the holes dies from the toxins injected by the bugs and appears as a series of brown, shot-hole marks or the holes can blend together into more of a blotch.

Four-Lined Plant Bug damage on Alchemilla mollis

Four-Lined Plant Bug damage on Alchemilla mollis

Four-Lined Plant Bug adult

Four-Lined Plant Bug adult

The nymphs emerge in early June, and, since damage occurs at the beginning of the growing season, they should be considered a serious pest since they reduce the amount of leaf surface for photosynthesis. Less photosynthesis means the plant  makes less of  its own food. As you can see from photos of typical leaf damage (click photos to enlarge), the nymphs and adults attack a wide range of plants. Although their favorite plants are Nepeta (Catmint) and Perovskia (Russian Sage), so far they’ve also attacked my lilies, Ligularia, Alchemilla mollis, asters, Veronica–and even the weeds! As for control strategies, my favorite approach to venting my rage at the plant bugs is to squish them in place. If you’re squeamish, try a spray of 2%-3% horticultural oil solution in water, neem oil, or pyrethrins.

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Plant of the Month: Alchemilla mollis ‘Thriller’

Alchemilla mollis (Lady’s Mantle) is probably a well-known plant to many readers here. A perennial border classic, it is celebrated for its magnificent scalloped foliage and its delicate chartreuse-yellow flowers rising on wands above the main clump of leaves. It’s a great edging plant and an attractive visual filler among other flowers.

Alchemilla mollis 'Thriller'

Alchemilla mollis ‘Thriller’

The photo at left is the ‘Thriller’ variety in its second year, grown from one-gallon pots. I’ve grown both the standard Alchemilla and the ‘Thriller’ variety and, on balance, I prefer ‘Thriller’. Descriptions of both varieties can vary in publications or on the internet, but, in my experience, ‘Thriller’ is a larger plant whose leaves are distinctly green rather than gray-green.

Alchemilla mollis 'Thriller' after a rain shower

Alchemilla mollis ‘Thriller’ after a rain shower

The two reasons for making ‘Thriller’ the Plant of the Month are its incredible cold-hardiness and its ability to flourish in miserable soil. Not only did the pictured Alchemilla plants survive an absolutely brutal winter, when they started to put out new growth in spring, they rapidly achieved full size, despite growing in heavy clay. It’s rare to find any perennial that looks its best the second year after planting.

Once established, Alchemilla can tolerate dry soil when grown in light shade. It can survive full sun if planted in a northern or eastern exposure and provided with adequate water. My ‘Thriller’ plants have recently been attacked by the Four-Lined Plant Bug ( a pest that is attacking all my flowers this year), but otherwise these plants are generally pest-free and disease-free. Lady’s Mantle blooms in June and is hardy in Zones 3-7. If the flowers begin to weight down the plants, they can be cut for use in arrangements.

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Final Update on Clethra alnifolia ‘Vanilla Spice’

Clethra 'Vanilla Spice'

Clethra ‘Vanilla Spice’

The Clethra ‘Vanilla Spice’ that began as a garden trial four years ago has matured into a lovely, medium-sized shrub. While not easily found at retailers, this is a highly desirable shrub well worth locating and planting.

Location Requirements

This cultivar grows well in acidic or alkaline soil. The natural environment for Clethras is woody swampland, so they all require constantly moist soil; however, once established, an inch of rainfall per week is adequate to grow ‘Vanilla Spice’. If weekly rainfall is unreliable, choose a location with easy access to supplemental watering. Continue reading

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A Note on Powdery Mildew and Disease Management

Powdery Mildew

Powdery Mildew

“Powdery Mildew on Lilacs” continues to be one of the most read articles on Gardening in the Mud. However, anyone located in Zones 5 and 6 hoping to treat powdery mildew at this time of year has only one control option available–and even that control will only help contain spread of the disease for next year’s growing season:  collect all fallen leaves and either burn them or otherwise permanently dispose of them. Do not compost infected leaves. Powdery mildew fungus overwinters in the leaves, so you want to keep the fungus away from affected plants. Continue reading

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Sport or Sucker?

Rose with yellow sport

Rose with yellow sport

This bicolor rose in my neighbor’s garden has a shoot that is producing a single yellow rose. The majority of flowers on the plant are a combination of orange and yellow, so this particular shoot could simply be sporting back to its yellow rose parent. The plant could also be creating a “sport” that represents a genetic change in the plant material, in which case the shoot with the yellow rose could be propagated as a cutting to see if a new, all-yellow rose bush could be developed, different from the parent. Since this particular shoot isn’t growing from any of the main stems, it could also be a sucker from the rootstock onto which the rose is grafted. However, since most rootstocks produce either red or white flowers on suckers, my guess is that this shoot represents some sort of sport.

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