Wednesday, May 30, 2012

Native Plants: Early Spring Woodies (Part 2)

Cornus florida (Flowering Dogwood)
 Despite my affection for all the native woody plants in my garden, I have to admit to some degree of favoritism. Perhaps its due to the challenges I've encountered with these trees - partly due to the choices I've made, partly due to conditions beyond my control. It's partly that, but it's also that these are, in my opinion, amongst the most exquisite of our native species.

Flowering Dogwood (Cornus florida) is a beautifully architectural understory - what we call, in landscaping parlance, an ornamental - tree characterized by a candelabra-like branching structure which makes for a dramatic sculptural quality throughout the year. The tree bears showy bracts of either white or pink (what most people think are the flowers) surrounding a cluster of inconspicuous chartreuse green flowers which evolve into showy red fruit much like Spicebush (Lindera benzoin). I have up-lit my dogwood to great effect throughout the year, as it transitions from a cloud of white, to lush green foliage, through a dramatic burgundy color change in fall, accented by its red berries, to its sculptural zenith in winter.

As an understory species, Flowering Dogwood should not be planted in full sun. The introduction of exotic Kousa Dogwoods (Cornus kousa) carrying anthracnose (Discula spp.) pathogens to which our dogwoods have no resistance have wreaked havoc on  native populations. Unlike anthracnose in native Sycamore (Platanus occidentalis), which is primarily an aesthetic condition which causes the trees to defoliate prematurely (after which they put out new leaves), anthracnose in native dogwoods, once it becomes systemic (enters the tree's vascular system) is generally fatal. (Pink varieties seem to be more susceptible than white.) For this reason, I have planted my Dogwood in full sun, thereby minimizing the risk of fungal disorders (including anthracnose) and taken other steps to maximize the other aspects of its cultural circumstances.

Cercis canadensis (Eastern Redbud)
Perhaps another reason I favor the white Dogwood over the pink is that its bloom time overlaps that of our Eastern Redbud (Cercis canadensis), which generally blooms in a cool pink that doesn't seem to harmonize very well, to my artist's eye, with the more salmony pinks characteristic of Flowering Dogwood. (There are a few exceptions, but I'm not much of a pink person anyway!) Redbud is a member of the pea (Fabaceae) family and has characteristically pea-shaped flowers, usually pink but also white (Cercis canadensis 'Alba', a naturally-occurring variation), that emerge before the foliage; the fruit, when ripe, is a brown, flattish pod with a number of small pea-like seeds. The flowers are not just borne at the tips of the tree's twigs but also right on major limbs and the trunk. The beautiful heart-shaped leaves - which provide "baby blankets" for leaf-cutter bees - mature to a beautiful mid-green, burning almost butter yellow in the Fall. The tree's unique branching architecture assures its year-round interest, complemented by beautiful grayish bark.

My Redbud flowered for the first time this year, after many years in my garden, partly because of its exposure - the surrounding Silver Maples (Acer saccharinum) may be giving it a bit more shade than it really wants - and damage it has endured at the hands our intrepid DTE-affiliated tree pruners. (The Redbud itself is an excellent tree choice near electrical wires, as it does not get exceptionally tall; the problem is that those individuals pruning the surrounding maples, which are not good choices near wire, drop the maple limbs on my poor little Redbud.) Needless to say, I was delighted to see it put out two small flower clusters; I hope to see more in years to come.

Aronia melanocarpa (Black Chokeberry)
A less-commonly-seen shrub, Black Chokeberry (Aronia melanocarpa) is a delightful highlight of my front garden. Not a particularly large plant, usually about 4 feet, which can sucker - but not particularly aggressively, in my experience.  A member of the Rosaceae family, the bush has typical white five-petaled flowers with distinctive pink anthers which darken as the flower ages. The flower buds look like little balls before they pop open and the flower clusters make a cheerful display in my front foundations. The fruits ripen to a deep blue-black but are not edible (although they are not toxic) for humans due to their astringency. (They can be used to make wine, jam, syrup and other cooked foods.) Birds feed on them freely, as they do not taste astringency, dispersing the seeds in their droppings. Fall color is in the red range and is quite lovely. Wintertime structure is "typical shrubby", making an excellent backdrop to the rest of my garden, which I do not cut down until Spring.

I understand that birds opt for more desirable fruits earlier in the season, utilizing less tasty fare as menu selection shrinks. Some fruits convert astringent starches into sugar with a good frost, after which the birds consume them with abandon. (It is in a bird's best interest to select the ripest fruit with the highest sugar content: birds require a lot of calories daily to sustain themselves; hence, the phrase "ate like the bird" is really not accurate in its common usage.) I have tried Black Chokeberry fruits, both before and after frost, and, as far as I can tell, they don't improve with age!

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