Category: Horticulture Highlight

…Yellow, yellow, yellow

it eats into the leaves,

smears with saffron…

            -William Carlos Williams

Autumn at Mount Auburn is full with an impressionistic cornucopia of changing landscape colors. During this weeks-long period, different plants pass the mantle of being the “plant of the day.” One plant providing outstanding yellow is Amsonia hubrichtii, thread-leaf blue star.

The genus Amsonia includes about 20 species of clump-forming, herbaceous perennials, primarily native to North America, with one species each also native to eastern Asia and Europe. The name commemorates John Amson (1698-1765), English physician and botanist, who was the one-time mayor (ca.1750) of Williamsburg in Colonial Virginia.

Amsonia hubrichtii, thread-leaf blue star in May displays pale blue flowers atop of three-foot-high stems. Its leaves are uniquely narrow, finely textured, adding contrast next to any companion plants. In breezes, there are kinetic, delightful sways of this billowy foliage. October provides further grandeur as these leaves slowly morph into a butter-yellow or vibrant gold color that will persist for 2-3 weeks. This was the Perennial Plant Association’s “Plant of the Year” in 2011.

We also grow Amsonia tabernaemontana var. salicifolia, blue star that likewise produces blue springtime flowers and outstanding yellow fall foliage. The lanceolate, willow-like leaves are wider than thread-leaf. These two stars are problem free, three-season, reliable perennials. On your next visit to Mount Auburn look for these on Central Avenue, Narcissus Path, at the flagpole and in Asa Gray garden among other locations.

…Yellow as a goat’s wise and wicked eyes,

yellow as a hill of daffodils,

yellow as dandelions by the highway,

yellow as butter and egg yolks,

yellow as a school bus stopping you,

yellow as a slicker in a downpour…

            -Marge Piercy

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…Something in me isn’t ready

to let go of summer so easily. To destroy

what I’ve carefully cultivated all these months…

            –Karina Borowicz

The common onion, Allium cepa would not make many lists of beautiful ornamental plants. Nor would the garlic, Allium sativum, chives, Allium schoenoprasum, or leeks, Allium ampeloprasum. All are members of the large genus Allium, which depending on taxonomic interpretation include 750 or 850 or more species, primarily native to the temperate climates of the Northern Hemisphere. In historic times this genus’ place was in the kitchen or vegetable garden. In our modern era people began to know the “ornamental onions.” You will find in many nursery catalogues as well as landscapes, ornamental Allium species with exceptional beauty.

One well-known, striking example is the hybrid ‘Globemaster’, with its three-foot tall stems topped with large purple flowerheads. You may recall these from their earlier June display around our flagpole planting bed.

 Allium ‘Millenium’ one of the more recent horticultural hybrid ornamental onions blooms during mid-to-late summer. This 10-15-inch, compact, upright clump, of dark-green, grass-like leaves is topped with 2-inch, rose-purple balls of florets.

This summer floral display may last four to six weeks, attracting many bees, butterflies and other pollinators. When the colorful florets wilt they dry to a tan color still providing texture and accent in the garden. Additionally, this is a drought-tolerant perennial that rabbits and deer leave alone.

Bred by Mark McDonough, a Massachusetts plant researcher, who specializes in growing and selecting Alliums, this was selected by the Perennial Plant Association as the Perennial Plant of the Year for 2018. On your next visit to Mount Auburn look for Allium ‘Millenium’ within our new Asa Gray Garden, just inside our main entrance.

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…the tree

aspires to the sky

one branch, cracked by lighting.

scrapes the earth…

            -Grace Schulman

As beautiful as Mount Auburn is, our professional arborists and horticulturists constantly are coping with problems injuring and compromising plants’ health and/or lives. A cursory list of on-going concerns includes beech decline, viburnum leaf beetle, hemlock wooly adelgid, verticillium wilt, winter moth, fire blight, dogwood anthracnose, bronze birch borer, elm bark beetle, boxwood leaf miner, nectria canker, etc., etc.   A comprehensive list of concerns could fill this whole page. Many of these conditions have been dealt with in the past and our staffs’ extensive knowledge help with prevention strategies, constant monitoring, early diagnosis and appropriate best practices treatments of countless biotic and abiotic plant health issues.

However, one abrupt, unforeseen, injurious agent is lightning. Relatively few trees struck by lightning will be completely shattered or disintegrated by the strike. Some struck trees nonetheless are killed immediately. Some may die later within the same year. Others may linger alive for years before declining in health primarily due to increased stress, secondary pests and/or other problems. We have one of the latter, a red oak, Quercus rubra on Mist Path, struck on July 9, 2016.

Beginning in clouds with electrical sparks created by negatively charged and positively charged particles, there are different types of lightning; intra-cloud lightning, cloud-to-cloud lightning, and cloud-to-ground lightning. Cloud-to-ground lightning represents an exchange of massive electric current and damages and kills thousands of trees annually. The National Lightning Detection Network (NLDN) reported 21 million cloud-to-ground strikes in the lower 48 states in 1999, this averages more than one per second, every second of the year. Various other sources report even higher averages per second worldwide.

Back to our red oak, Quercus rubra on Mist Path, one of five red oaks believed to be as old as the cemetery, with a trunk circumference of almost 14-feet. The morning after this tree was struck the obvious observable damage was a 10-12-inch, scar of missing bark running from the ground up the length of the trunk in a slightly spiral pattern. Most lightning passes through trees because water is a better conductor of electricity than air. Water in trees is concentrated in the cambium tissue just under the bark. Electricity surging through this water results in it boiling explosively, blasting off the bark. That morning we found pieces of its bark as far as 115-feet away from the tree. Shortly thereafter our arborists pruned out the major limb where the strike occurred.

…But if we got struck by lightning –

not a lot; say glanced, or shaved,

there was a chance (we heard)

it wouldn’t be so bad:

a little refreshing,

a little like La Vita Nuova

in a readable translation…

            -Ange Mlinko

Paul Walker, Superintendent of Grounds, an arborist with almost forty years of experience here at Mount Auburn has been monitoring this tree since the lightning strike. He recalled that in his time here there have been 10 trees struck by lightning, including this one, and five of them have been oaks, 3 red oaks, one white oak and one black oak. Other trees struck were white pine, American ash, Douglas fir, black cherry and blue spruce. The spectrum of survivability from these 10 strikes ranges from one tree being killed instantly to another red oak lasting about 15 years before finally succumbing. Trees struck but surviving will suffer from a reduction in water movement capacity at the site of cambium loss, increased stress, lessened defensive capability in tolerating insects, fungi and disease. The lengthy wound on our red oak now measures 21-24-inches at its widest, and will continue to enlarge.

On a future visit to Mount Auburn, stop by and pay a tribute to this notable monarch displaying its will to survive.  

We had so little, yet we had so much:

Thunder and lightning at the lightest touch.

            -John M. Ridland

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Horticulture Highlight: Astilbe, Astilbe sp.

…It is a morning in July, hot and clear.

Out in the field, a bird repeats its quaternary call,

four notes insisting, I’m here, I’m here…

​-Elizabeth Spires

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