Parrotia persica

Features - Plants

Every garden has a niche for Persian ironwood

December 7, 2012
Michael A. Dirr

What a great small tree. While roaming the University of Georgia campus in early March, specks of bronzy green are emerging from the dusty gray buds. Leaves will be fully formed by early to mid-April and persist until November-December when full color signals time to rest. Leaves are tremendously frost tolerant — I estimate around 25°F. This is also true for Fothergilla, Hamamelis, Disanthus and other Hamamelidaceae taxa.

The remarkable aspect of these early leafing campus trees is their survival. At the university, there are three in a triangular traffic island: hot, dry, compacted (as students walk between the trees). For more than 25 years they have defied the laws of stress. Why not more widely utilized? From Boston to Chicago to Portland and south to Athens, I’m aware of many successful plantings.

Every garden has a niche for a Parrotia. The Dirr garden has three P. persica and the recent introduction P. subaequalis, Chinese parrotia. Traveling and literature treasure hunts have unearthed more cultivars than I knew existed. In February 2010, I walked rows of seedling Parrotia persica at John Malone’s Summershade Nursery in Good Hope, Ga. I noticed variation in leaf retention, most with brown leaves, enough without, that this would be a quality selection trait, also tied to fall color. In a previous Dirr garden, the seedling Parrotia ranged from yellow to orange-red, but never consistent. A brilliantly colored (listing toward red) selection would have market prominence akin to the best red maple cultivars like October Glory and ‘Red Sunset.’


A global reach

P. persica is native to the Caspian forest of Northern Iran and Azerbaijan where 60-foot tall trees are recorded. Too often in cultivation the species is low-branched and multi-stemmed. Single-trunked trees would suffice as small street and lawn elements. I envision an allée along a garden path, the lowest branches 5 feet above the ground and beautiful exfoliating gray, cream, green-barked trunks.

Typically, height ranges from 20 to 40 feet, spread 15 to 30 feet, yet I observed many specimens wider than high. The tallest was about 60 feet high at the Jardin des Plantes in Paris. Wide-spreading specimens, often with multiple trunks, were noted at the Arnold Arboretum, at Kew Gardens and at the Biltmore House and Gardens. The mature, large-trunked trees develop the exfoliating bark mentioned above. Branches show this character in the 4- to 8-inch diameter range.


Parrotia characteristics

Newly emerging leaves are reddish-purple or with a marginal purplish halo. In summer, leaves are a lustrous medium green to dark green, turning to yellow, orange, red, solely or in permutation in fall. Foliage withstands all manner of abuse, but Japanese beetles relish the leaves.

Flowers and fruits do not overwhelm. The former, apetalous, either male or hermaphrodite (male and female parts) open on naked stems in February and March. Flowers are composed of 5-15 crimson-maroon stamens that provide a dollop of color. Fruit is a woolly, brown, two-valved dehiscent capsule, ½-inch high that contains two, 3/8-inch brown seeds. Seeds are released (ejected) at maturity, so they must be collected before the capsule opens. In 2009, tremendous fruit set occurred on ‘Jennifer Teats’ growing next to a seedling at the Horticulture Farm. I missed the collection mark, but this was the most abundant fruit set I’ve ever observed. Perhaps two different clones, in close proximity, are necessary for cross pollination.

Widely and wildly adaptable to sun or shade; and acid, neutral, moist to drier soils. It’s readily transplanted from containers or balled-and-burlapped and adaptable from USDA Hardiness Zones 4-7, and Zones 8-9 on the West Coast.

With the above quality character traits, why is the species seldom available? It propagates easily from cuttings and has been rooted numerous times in our shop. Take cuttings in late May-June with 3,000 ppm IBA, light fertilizer after rooting and extended photoperiod to induce a growth flush and subsequent overwinter survival. I have yet to germinate seeds and now have seeds in a three-month warm/three-month cold stratification.


Cultivars and types

There is a quixotic assortment of cultivars from weeping to upright and even variegated selections. The list includes ‘Biltmore,’ ‘Burgundy,’ ‘Felicie,’ ‘Globosa,’ ‘Henny’s Dwarf,’ ‘Jennifer Teats,’ ‘Jodrell Bank,’ ‘Lamplighter’ (variegated, unstable), ‘Pendula,’ ‘Persian Lace’ (variegated), ‘Purple Halo,’ ‘Purple Moon,’ ‘Purple Rim,’ ‘Ruby Vase,’ ‘Summer Bronze’ and ‘Vanessa.’ Additionally, several unnamed forms are cloistered in gardens and nurseries.

‘Jennifer Teats’ and ‘Vanessa’ are upright forms with superior foliage compared to row-run seedlings. The latter developed rich golden yellow fall color in late November-early December in Coach Vince Dooley’s Athens garden. For areas where lateral room is restricted, both make great elements. In fact, logic says (to me) that they may be better choices than the ubiquitous Carpinus betulus ‘Fastigiata,’ upright European hornbeam.

The Kew weeping form is the best I know as it truly weeps. Several semi-weepers to almost plagiotropic branch forms that neither weep nor inspire are known.

Only chanced upon ‘Ruby Vase’ on the West Coast, the new leaves ruby-red, habit upright vase-shaped, 30 feet high by 12 feet wide according to Carlton Plants, the introducers.

The purpleleaf types do not hold the color as the leaves mature, but I believe that a seedling from these could be “the one” with persistent purple foliage like one of the purpleleaf European beeches.

The tenor of this article should resonate with readers that any Persian ironwood is a worthy garden element. ‘Vanessa’ and ‘Henny’s Dwarf’ are part of the new Dirr garden and I plan to add others. In 2010, P. subaequalis, Chinese parrotia, was added and the intergeneric hybrid ×Sycoparrotia will soon join the family as I have a population of seedlings under evaluation.


 

Michael A. Dirr is a retired professor of horticulture at the University of Georgia; and partner in Plant Introductions Inc., www.plantintroductions.com.