Wednesday, April 14, 2010

Clethra

A genus of around 60 species of trees and shrubs widely distributed around the world.
They prefer partial shade, a site sheltered from wind on moist, fertile, humus-rich, acidic soil.
The flowers attract butterflies and hummingbirds.
Clethras are generally not prone to pests or disease, spider mites can occur but are rare. Pruning should be done during late autumn into early winter...spring pruning causes bleeding. Propagation is from seed, cuttings taken mid-summer and layers.

Clethra acuminata ( Cinnamon Clethra )
A deciduous, large shrub or small tree reaching around 22 feet that is native to the southern Appalation mountains in the southeast U.S ( from central Kentucky to southwest Pennsylvania to Virginia, south to Alabama and far northern Georgia ). though thrives much further north, especially in New England. Some records include: fastest recorded growth rate - 6 feet; largest on record - 33 x 22 feet with a trunk diameter of 9 inches. This rare mountain woods native is extinct in the wild in Maryland.
The toothed, elliptical leaves are up to 8 x 4 inches in size. The foliage is rich mid-green and turns attractive orange late in autumn.
The abundant, fragrant, creamy-white flowers are borne on racemes, up to 8 inches in length, during late summer.
The cinnamon-orange color exfoliating bark is extremely attractive, especially with snow on the ground.
Hardy zone 4b to 7 ( should be tested in zones 3 and 4a ) in partial to full shade. Hates heat and drought. It does not enjoy maritime climates and despite being fully hardy in Ottawa, Canada; the wood doesn't harden well in England's cool summers and only reliably survives there in the south.

* photos taken on June 30 2013 @ U.S. National Arboretum, DC

* USDA-NRCS PLANTS Database



Clethra alnifolia ( Summersweet Clethra )
A fast growing, erect, medium size, deciduous shrub reaching around 8 feet that is native to eastern North America ( from Erie, Pennsylvania to northern New York State to southern Nova Scotia and Maine; south to eastern Texas to northern Florida in wet forests, bogs and wetlands. Most of its population is within 100 miles of the Atlantic Ocean and Gulf of Mexico and the wild population in Nova Scotia, Canada is endangered with extinction. Some records include: fastest recorded growth rate - 3 feet; largest on record - 13 x 13 feet.
The toothed, oblong to obovate leaves are up to 5 x 3 ( rarely over 3.5 x 1.5 ) inches in size. The foliage is bright green at first turning to glossy deep green in summer then to yellow and orange during late autumn. The autumn color can persist up to a month. Summersweet Clethra is late to leaf out during spring.
The small, very fragrant, white flowers are borne in upright, terminal racemes, up to 8 inches in length, during mid-summer and lasting up to 6 weeks.
The attractive bark is chestnut-brown on older stems.
Hardy zone 3 to 9 in sun to partial shade. It is hardier than expected considering its natural range, with the most northerly seed source even thriving in southeast Alaska and the Ottawa Valley of Canada. Tolerates swampy soil and salty seashore conditions. Can be cut to ground in March for renovation and will reach 4 feet and bloom by August. Propagation is from seed except for the cultivars which are propagated from semi ripe cuttings. 4 inch cuttings are easily rooted in peat or sand. Cuttings taken in May are flowering shrubs up to 16 inches in height by August. Seeds can be sown on permanent site during early spring.

* photos taken on July 2 2010 in Columbia, MD


* photo taken on October 17 2010 in Howard County, MD

* photo taken on Aug 20 2011 @ Brookside Gardens, Wheaton, MD

* photo taken on Nov 3 2013 in Columbia, MD

* historical archive photo

* photos taken on Oct 23 2015 in Ellicott City, MD

* photos taken on July 11 2016 in Ellicott City, MD

* photo taken Aug 2016 @ Patuxent Research Refuge, Laurel, MD

* photos taken on Sep 22 2016 @ Patuxent Research Refuge, Laurel, MD

* photo taken on Apr 28 2017 in Ellicott City, MD

* photos taken on May 27 2017 @ Meadowlark Botanical Gardens, Vienna, VA

* photos taken on Aug 5 2017 @ Brookside Gardens, Wheaton, MD


'Anne Bidwell'
Moderate growing and compact in habit, reaching up to 8 x 6 ( rarely over 6 x 5 ) feet. The very unusual for a Clethra flower spikes are borne in huge white clusters, up to 6 x 5 inches. The flowers are borne during late summer.

'Creel's Calico'
Moderate growing, reaching up to 4 x 6 feet in 5 years, eventually to 6 x 6 feet.
The glossy deep green foliage is heavily spotted and blotched pure white. The foliage turns to golden-yellow during autumn.
The white flowers are borne in branched clusters up to 6 inches in length.
It does not like full sun or reflected sun.

'Cottondale'
A vigorous cultivar of subsp 'tomentosa'. The leaves are larger and fuzzier than Clethra alnifolia; they also emerge a month earlier. It is semi-evergreen in zone 8 and 9.
The flowers are borne on very large clusters up to 16 inches in length.

'Hummingbird'
A very compact, suckering, medium-size shrub reaching up to 5 x 6 feet ( less in cooler climates, the record is 6 x 8 feet ) Some records include: fastest growth rate - 3 feet; 10 years - 5 x 6 feet.
The foliage is glossy and very deep green; turning golden-yellow during autumn.
The very abundant, fragrant, white flowers are borne during mid-summer, earlier than Clethra alnifolia.
Hardy north to zone 4

* photo taken on Aug 25 2011 @ Scott Arboretum, Swarthmore, PA

* photos taken on July 30 2013 in Columbia, MD

* photo taken on July 8 2014 in Columbia, MD

* photos taken on July 30 2014 in Columbia, MD

* photo taken on July 17 2015 in Columbia, MD

* photo taken on Oct 26 2015 in Columbia, MD

* photos taken on Aug 12 2016 in Columbia, MD

* photo taken on Jul 19 2017 @ Rideau Hall, Ottawa, ON

* photo taken on July 25 2017 in Columbia, MD

* photos taken on Oct 17 2017 in Columbia, MD


'Rosea'
Very dark glossy deep green leaves turning to yellow in autumn.
The flowers are fragrant and pink.
It is otherwise identical to the species.

* photos taken Aug 1 2014 in Columbia, MD


'Ruby Spice'
Vigorous, dense and upright reaching up to 8 x 8 feet. Some records include: 5 years - 6.5 x 6.5 feet; 10 years - 8 x 10 feet.
The glossy deep blue-green foliage turns to orange-yellow for several weeks during autumn.
The fragrant, deep pinkish-red flowers are ruby-red in bud.

* photo taken by Milan Havlis, owner of central Europe's premier plant nursery

* photo taken on July 6 2016 in Columbia, MD

* photo taken on Nov 14 2016 in Burtonsville, MD

* photo taken on Nov 19 2016 @ London Town Gardens, Edgewater, MD

* photos taken on Aug 5 2017 @ Brookside Gardens, Wheaton, MD

* photos taken on Aug 1 2017 in Columbia, MD


'September Beauty'
More compact, reaching a maximum size of 8 x 7 feet, with luxuriant glossy deep green foliage that turns to golden-yellow during autumn.
The extremely fragrant, pure white flowers are borne on erect racemes up to 6 inches in length. They appear over a long season lasting up to 1.5 months during late summer into early autumn.

* photo taken on May 27 2017 @ Meadowlark Botanical Gardens, Vienna, VA

* photos taken on Aug 24 2017 @ U.S. Botanic Garden, Wash. DC.


'Sherry Sue' ( Red Twig Summersweet Clethra )
Vigorous and rounded in habit, reaching up to 9 x 8 feet. Some records include: 5 years - 7 feet.
The foliage is glossy deep green, turning to intense golden-yellow during late autumn.
The typical for Clethra alnifolia, white to pinkish-white flowers appear during mid-summer.
The intense red winter stems add seasonal interest and set this cultivar apart from the other Clethras.
Hardy zones 4 to 9.

* photo taken on Aug 13 2017 @ Howard Comm. College, Columbia, MD


'Sixteen Candles'
Moderate growing, compact, dense and sturdy in habit, reaching up to 5 x 5 ( rarely over 3 ) feet.
The attractive glossy deep green foliage turns deep yellow in autumn.
The fragrant, dense, upright, white flower candles, up to 6 inches in length, last up to 6 weeks beginning mid-summer.

* photo taken on Sep 15 2011 in Howard Co, MD

* photo taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014

* photo taken on July 15 2015 in Columbia, MD

* photo taken on Sep 22 2015 in Columbia, MD

* photo taken on May 14 2016 in Columbia, MD

* photo taken on Aug 1 2016 in Columbia, MD

* photos taken on Nov 14 2016 in Columbia, MD

* photos taken on Aug 5 2017 @ Brookside Gardens, Wheaton, MD

* photo taken on Aug 21 2017 in Columbia, MD


'Sugartina'
Also called 'Crystallina'. Moderate growing, dense and compact, reaching a maximum size of 4 x 5 ( rarely over 3 ) feet.
The glossy, very deep green foliage turns to yellow during autumn.
The fragrant, pure white flowers are borne during late summer.

* photo taken on June 25 2017 in Elkridge, MD

* photos taken on Aug 5 2017 @ Brookside Gardens, Wheaton, MD

* photos taken on Aug 13 2017 in Columbia, MD


subsp. 'tomentosa'
The leaves emerge up to 3 weeks earlier than regular Clethra alnifolia and also persist very late in autumn.
The fragrant, pure white flowers are larger, up to 0.5 inches each. The flowers appear during early autumn ( about a month later than species ).
Not quite as cold hardy, zone 4 to 9

* historic archive photo


'Vanilla Spice'
Also called 'Caleb'. Moderate growing and dense, reaching up to 8 x 6 feet.
It bears very fragrant, very large, pure white flowers ( each about dime size which is double the size of that on regular Clethra alnifolia ) on large panicles up to 12 inches in length.
The foliage is glossy deep green.
Hardy zones 4 to 9.

* photos taken on Aug 13 2017 in Columbia, MD


Clethra arborea ( Lily of the Valley Tree )
A very handsome, densely foliaged, small, moderate growing, evergreen tree to 30 feet that is native to the island of Madiera. Some records include: fastest recorded growth rate - 2 feet; largest on record - 66 x 20 feet with a trunk diameter of 28 inches.
The leaves, up to 6 x 2 inches, are reddish at first turning to shiny deep green.
The fragrant white flowers are borne in long terminal panicles. The flowers attract butterflies.
Hardy zone 8 to 10 and requires a mild climate. In the U.S. it can only be grown on the west coast.

Clethra barbinervis ( Japanese Clethra )
A fast growing, arching, deciduous small tree to 20 feet that is native to mountain woodlands of Korea and Japan. Some records include: fastest recorded growth rate - 4 feet; largest on record - 46 x 27 feet with a trunk diameter of 1 foot. The largest in the U.S. is at Arnold Arboretum in Boston, MA.
The prominently-veined, sharply-toothed, oval leaves are up to 6 x 2 inches in size. The leaves appear early during spring. The foliage is glossy deep blue-green above, bluish-white beneath; turning to attractive maroon-red during autumn. The leaves are clustered near the ends of the stems giving a whorled appearance.
The small, fragrant, white flowers, up to 0.3 inches are borne in terminal clusters up to 6 inches in length during August and September.
The bark is orange and peeling.
Hardy zone 4 to 8, in zones 7 to 8 it requires shade. Japanese Clethra even thrives in the Midwest if its soil needs are met.
It prefers a sandy, fertile, acidic soil. Pruning is rarely necessary. It is not prone to pests or disease and is not eaten by deer. Propagation can be from either seed sown in autumn or softwood cuttings taken in summer.

* photos taken on July 2004 @ Tyler Arboretum near Philly, PA

* photo taken on April 18 2010 @ U.S. National Arboretum

* photos taken on 4th of July 2010 @ U.S. National Arboretum, D.C.



* photo taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014

* photos taken on Nov 19 2016 @ London Town Gardens, Edgewater, MD


'First Snow'
Spectacular creamy-white splashed foliage; otherwise similar to species.

Clethra delavayi ( Delavay Summersweet )
A very ornamental, upright small tree reaching around 33 feet that is native to mountains of southern and western China, India, Bhutan, northern Burma and Vietnam. Some records include: largest on record - 65 x 33 feet.
The handsome, strongly-veined, taper-pointed, lance-shaped leaves are up to 6 x 2.5 inches in size. The foliage is very attractive bronze-red during spring turning to deep green above and downy white beneath. The foliage turns to yellow during autumn.
The small, very fragrant white flowers are borne in dense racemes up to 10 inches in length during mid-summer.
The attractive bark is exfoliating and gray-brown.
Hardy zone 7 to 9 in partial shade on moist, peaty, acidic, well drained soil. Hardiness varies greatly upon seed source. This species generally needs a mild maritime climate to thrive however it may be possible that seed source from high mountains in western China may be hardier to zone 5. The Delavay Summersweet prefers cool summer nights restricting it from most of the eastern U.S. and even warmer summer parts of the Pacific Northwest.
Propagation is from seed in autumn or softwood cuttings taken in June.

Clethra fargesii ( Chinese Clethra )
A beautiful deciduous shrub to small tree, reaching up to 13 x 10 feet, that is native to southeastern China. It is similar in appearance to Clethra barbinervis. Some records include: largest on record - 50 feet.
The sharply-toothed, lance-shaped to obovate leaves are up to 7 x 2.5 inches in size. The luxuriant glossy deep green foliage turns rich deep yellow during autumn.
The fragrant, small, pure-white flowers are borne on large branching clusters up to 14 x 8 inches in size, during mid to late summer.
Hardy zone 5 to 8 () tolerating -20 F ) in partial shade on moist, acidic, fertile, humus-rich, well drained soil.

* photo taken on April 11 2010 @ U.S. National Arboretum

* photo taken on May 8 2010 @ U.S. National Arboretum, D.C.

* photo taken on June 23 2013 @ U.S. National Arboretum, DC


Clethra lanata ( Mexican Clethra )
A tree native to tropical America from southern Mexico to Panama, that reaches a maximum height of 90 feet with a trunk diameter of 16 inches.
The sparsely-toothed, thick leaves, up to 7 inches in length are glossy deep green.
The white flowers are borne in racemes, up to 8 inches in length, during summer.
Hardy zone 9 to 11

Clethra macrophylla
An evergreen, small tree, reaching up to 20 feet.
The obovate leaves are up to 8 inches in length. The foliage is deep green.
The white flowers are borne in clusters up to 6 inches in length.
The blocky, deeply-ridged bark is light gray.
Hardy zones 9 to 10, thriving in coastal regions of California.

Clethra monostachya
It is considered by some to be a subspecies of Clethra delavayi. A large shrub to small tree native to China, reaching up to 20 x 12 feet ( record is 28 feet ).
The handsome, strongly-veined, taper-pointed, lance-shaped leaves are up to 9.5 x 4.3 inches in size. The foliage is very attractive bronze-red during spring turning to deep green above and downy white beneath. The foliage turns to yellow during autumn.
The fragrant, small, pure-white flowers are borne on large branching clusters up to 8 inches in length, during mid to late summer.
Hardy zones 6 to 9.

Clethra pringlei ( Pringle's Clethra )
A spreading, evergreen, small tree reaching a maximum size of 25 x 20 feet with a trunk diameter of 1 foot, that is native to mountains of Mexico. A large tree grows at the San Antonio Botanical Gardens in Texas.
The large, toothed, elliptical to obovate leaves are bronze at first, turning to glossy blackish-green above, silver beneath.
The fragrant, white flowers are borne on long racemes, up to 10 inches in length.
Hardy zones 8 to 10 ( unconfirmed reports of 7 ) in full sun to partial shade on consistently moist, humus-rich, well drained soil. It thrives in both the southeastern U.S. as well as the Pacific Northwest.

2 comments:

  1. Very well-written and informative article. I enjoyed learning of all the different types of this wonderful plant!

    ReplyDelete
  2. Thank you! I just added some additional pics and a new cultivar entry to this posting

    ReplyDelete