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Results
from winter 2008-2009
I started writing this in late July, 2009 a habit of experienced gardeners in climates subject to real winters, who need to wait until summer to assess the long term effects of prolonged cold, but today is February 6, 2010 and last night what is probably the greatest snowstorm in the history of DC began. Today, 26 hours after continuous snow commenced it is still snowing steadily. At 8 AM we had 22”. I think we now have ~27” and there is much breakage. A least 3 feet has snapped off the top of my Magnolia fordiana. So, another habit of experienced gardeners is to get to indoor tasks when Jack Frost slams the garden.
Notes
from 2009
My Passiflora x ‘Incense’ just sprouted in the first 10 days of July-I was sure it was a goner. The winter was severe with temperatures to + 3 deg F on the 17th of Jan. and 9 days continuously below freezing that month scattered in packets of three days at a time. Since there was virtually no snow, ground freezing was significant, though I don’t know the depth. Another cold wave with single digit temperatures occurred as late as March 3rd and 4th.
It certainly was fascinating to see what thrived and what died. I am one of those people who answer the question “You want the good news or the bad news?” with the reply “Give me the bad news first. That way it can’t get any worse.” Consequently, I will start with the losses.
Starting with xerophytes, one of the biggest disappointments was the loss of three of my four giant South American cacti, species of the (old) genus Trichocereus, now subsumed in the wickedly clumped genus Echinopsis. Trichocereus tarijensis, 2-2.5’, had come through the previous very mild winter, minimum +13 deg F, with no discernable damage and grew vigorously last summer. It was unable to withstand the low single digits, another illustration of the sharpness of many cold damage events. Two of my three 2.5’ Trichocereus pasacana, hardiest and most high altitude of the northern Argentinean species, froze also. The thinner plant, clearly representing a different strain, froze first. The fatter plant actually developed rot near the base on the shaded side, but most of the plant survived. However, it did not fight off the internal infection as the spring progressed. I think this reflects the hybrid origin of these plants here in the states, where seed is collected from plants open pollinated from several different Trichocereus species. The one survivor will be discussed below. Suffice it to say this was its 4th winter and it is pictured on this website. After six winters without damage my Denmoza rhodacantha perished. Next to it an Acanthocalycium violacea, also doing well for six winters, likewise perished. The two large American barrels, Echinocactus hamatacanthus and Ferocactus wislizeni, both having come through several winters (5 previous for the Ferocactus), but both having lost their meristem to ants three years previously, perished. Once again I failed with a young Nolina nelsonii, my third try. I would like to try a large one. I think these plants get much hardier with age. My established Agave schottii were all killed outright as was an old A. scabra in the west bed, where the A. lophanthas were all damaged to one degree or another. However, a newly planted A. schottii in the east bed survived with significant injury, later to die at the end of the summer. My one remaining A. palmeri, weakened by shade was nursed back to a good root system in a pot, and will be returned to the garden in the spring. Almost all of my Lobivias and Echinopsis bruchii hybrids were killed except for one each respectively. The Lobivia is possibly backebergii or, less likely, chrysochete. My failure with large numbers of small lobivias and echinopsis vs. my success with very much larger growing species in the same group and habitat leads me to hypothesize the following. In the very high altitude, high insolation Andean environments wherein these plants are native, I think the plants close to the ground (and large rocks) benefit from a large amount of stored heat absorbed during the day, then re-radiated at night. Even when Antarctic air invades periodically, bringing with it heavy snow to the normally bone dry winter puño environments, the small plants will be buried under the snow. In contrast, larger plants stick up into the air and, snow or not, must thermally equilibrate with the frigid night air of their environment, where temperatures go below 0ºF with some regularity. If this is correct, and so far my data supports it, then it amounts to a delicious horticultural irony: the largest, most flamboyant high altitude barrel cacti are nevertheless the most cold hardy of that group. A number of small echinocerei perished: a fendleri, a very hardy species that is nevertheless touchy in wet acid environments, E. delaetii, a beautiful, relatively rare Mexican species with only one stem out of about five still healthy was a near loss, but its hardiness is still surprising. The most egregious loss appears to be my large Yucca torreyi, after vigorous growth for 7 years. The cause of its demise was mysterious until explained by Sarah Guerra, proprietor of Desertland Nursery in El Paso, Texas, one of my best quality suppliers and a very talented horticulturist. She pointed out that these yuccas develop a very narrow trunk in drought years. If such plants are subsequently transplanted into irrigated landscapes, they then grow rapidly with very thick trunks above the drought induced constriction. Eventually, if they are not plumb straight, they will buckle at the drought narrowed section of the trunk. That is what has happened to my plant. The buckling occurred during the winter and apparently the vascular damage above the bend was sufficiently severe so as to cut off water and nutrients to the crown. I propped it up and I have been hoping it would sprout from the trunk below the stricture, but so far no luck. She is encouraging me to cut it back below the narrow portion next spring.
Among plants adapted to environments more normal by Middle Atlantic standards, losses were surprisingly light. Dacrydium (Lagarostrobus) franklinii finally got so ratty, after 5 winters, that I pulled it up and tossed it. A wonderful southern native shrub, Clinopodium georgianum, that had graced the rear perennial bed with its display of light purple mint flowers early each autumn just became chlorotic this spring and died in early summer. Leptospermum lanigerum, beautiful Australian myrtaceous evergreen, undamaged in two previous winters including a very hard Feb 2007, froze to the ground. Callistemon ‘Woodlander’s Hardy’ perished roots and all in the open. Cinnamomum chekiangense, in the garden since 2004, froze to the ground again in its protected spot against the east wall of the house. It sprouts back from the roots each time to ~ 10’ and is even evergreen in mild winters. I plan to eventually replace it with something more interesting, probably Castanopsis sclerophylla, in the near future. Magnolia insignis ‘red form’ finally died altogether . The pink form stayed evergreen and is over 12’ tall now after 4 or 5 winters. The last of my Hebes pimeloides ‘Quicksilver’ also died. A supposedly hardy strain of Laurus nobilis died in the perennial bed, though success that others have had locally and in Delaware will prompt me to try again ( I love bay leaves in my cooking). Once again Musa sikkiminensis, from Joe Kieffer’s Triple Oaks nursery in NJ failed to survive, as did a supposedly root hardy Dahlia he sold me, but many of the other plants I obtained from him are thriving. John Boggan of DC Tropics provided me with two possibly hardy Sinningia, a gesneriad, but only one returned in mid-summer and was not very vigorous, although it appeared healthy enough in full sun and well drained ordinary garden soil. One of two rare Berberis perished over the summer, a species called Berberis empetrifolia from Chile. It is hardy enough that I will try it again in a more sheltered location in the bed next to the east wall. That’s about it for downers. Now for the uppers.
In the lowest part of the garden, lining the drive seen on the home page of
tucsoneast, Cistus x corbariensis took a beating. ~80% of the leaves and half the wood froze, but subsequent to a hefty spring
pruning it grew back fiercely and is healthier than ever. In the past it has stayed perfectly evergreen and plum purple to
upper single digits. Just next to the Cistus, Nolina ‘La Siberica’ the arborescent Nolina from the highest part
of the Sierra Nevada Oriental in Nuevo Leon, Mexico went through its second winter with superficial leaf burn. It was planted
two years ago as 1 qt. specimen, but it has tripled in size since. This is a very exciting development since this is a young
plant and it is very likely that older plants will be much hardier. On the other side of the drive another southwestern surprise
winner has been emerging. This appears to be a Dasylirion berlandieri hybrid. It does not have the blue foliage of the plants
in the wild, but one of the experts at Yucca Do told me that there is enough interspecific breeding in the wild to make this
plant’s light green color tenable. The leaves are twisted and they weep. This plant will be fascinating to watch as
it ages. Down at the street curb, under the circumscribed shade of Cytisus ‘Lena’ Berberis stenophylla 'Corallina'
has been thriving with its little evergreen rhomboid leaves. Up the slope in the east bed Escallonia ´ langleyensis 'Apple
Blossom' went through its third winter without significant damage. Its little scalloped edged evergreen leaves are quite distinctive,
but it has been a shy bloomer for me. Underneath it Jasminum parkeri continues to thrive next to a Ruscus aculeatus, the European
butcher's broom, none the worse for wear. Also next to it is a very pretty low evergreen Viburnum atrocyaneum which also showed
no damage, though it purples up in the winter and the large evergreen Viburnum cinnamomifolium also is doing well although
neither has flowered or set fruit. Behind them Magnolia insignis had mild leaf burn, but pushed up this summer to 12-14’.
A little further up the slope Magnolia fordiana has regained its healthy 12-14’ and the evergreen Viburnum propinquum
is getting tall enough to show a bonsai-like branching pattern It displays iron hardiness but no fruit because it’s
a male. Near the top of the slope, under the 15’ Tetrapanax papyrifera cv. ‘steroidal giant’ that has never
frozen back is a lovely evergreen Itea chinensis, never hurt. Next to it Pittosporum heterophyllum suffered virtually no leaf
burn and the large Podocarpus chinensis was also undamaged. In the corner of the bed and the fence enclosing the compost pile
the evergreen dogwood, Cornus angustifolia, continues to perform flawlessly except for a decided lack of flower production.
Also in this group is a Trachycarpus given to me as a member of the same group that Kathy Denton marketed as ‘Takil’.
It did not suffer that much injury to the older leaves but the emerging spears were badly hurt. Of course, our lab tests indicate
lethal damage to ordinary Trachycarpus leaves at -16 deg C, but -18 deg C for
the ‘takils’, so any damage at all was a bit discouraging. It has recovered vigorously. As my Bulgarian research
partner says “We live to see”. The very interesting Fuchsia regia
is declining due to shade competition. Late in the season I took all of the stems as cuttings and drove them to Joe Kraut,
head propagator at Brookside Botanic Garden to be stuck in their greenhouses, as I have been unable to find the plant in the
trade. There are also two hardy Gardenia in the bed. One is the well known ‘Kleims Hardy’, which remained undamaged
as it always has. Nearby one of the two Gardenia jasminoides 'Shooting Star', with much larger lighter green leaves was burned
a bit but recovered well, its sister plant in complete shade against the colder north wall was undamaged. This plant not only
sports the standard lovely single white extremely fragrant Gardenia flowers but pretty pale orange fruit as well, resembling
somewhat a narrow cylindrical star fruit (Averrhoa carambola). In back of a large pyracantha, Camellia chekiangoleosa persists
despite the competition. If this particular plant were fuller it would be very handsome with large orange red flowers and
peculiar fruits resembling somewhat the cone of a conifer, or a gnarled nut. Along the north wall of the house Osmanthus americanus
has grown very well, but displayed few of the fragrant small flowers the genus is noted for. Next to it the exquisite Camellia
Japonica ‘Tama-No-Ura’ put on a royal display of red and white flowers. Along the deck, but also in winter shadow
and facing the cold north sky, Jasminum officinale along with Pittosporum illicioides DJHT 99084 from Cistus Nursery in Oregon
performed flawlessly. This superb evergreen resembles a Pieris with undulating leaf edges. Across
a small strip of lawn, against a high railroad tie wall holding back what amounts to a great earthen berm, a number of fascinating
plants reside on what is effectively a south facing wall. Here resides my first success with evergreen Citrus, Citrumelo ‘Winston-Salem’
weathered the winter nearly perfectly, staying entirely evergreen except for two inches of late growth. Next to it is the
exquisite perfectly evergreen relative (also Rutaceae) Choisya x ‘Aztec Pearl’ [Choisya ternata x Choisya arizonica] looking like a miniature marijuana bush (now, how do I know that? Why from the old
Bailey’s Cyclopedia of Horticulture (pub. 1913) of course, which recommends Cannabis highly for the perennial border
because of its graceful foliage and gorgeous aroma……÷) ÷)). About 2 feet away is the completely hardy Hakea microcarpa,
my only completely successful Proteaceous plant so far. It looks like a skinny conifer.
Next to that is the very beautiful and reliably evergreen Quercus hypoleucoides from the mountains of the interior
southwest and leaves full of white down on the undersides. Beyond that is the evergreen strain of our swamp magnolia, Magnolia
virginiana var. australis, a thoroughly underappreciated very reliable evergreen tree. Beyond that is a regular, completely
reliable Choisya ternata, from Joe Kieffer’s Triple Oaks Nursery in southern NJ. This I find very interesting because
the somewhat lighter green strain of same plant grown by Monrovia Nursery in the 60’s and 70’s habitually fried
at +15º F in my parent’s nursery in Toms River, NJ. As is so often the case, this makes one wonder about provenance.
Next to the Choisya is an unidentified Argentinian Schinus (pepper tree) originally from Woodlanders in Aiken, SC. It stayed
evergreen with moderate burn last winter. I have no idea about flowers. The leaves are narrow somewhat willow like, purplish
in cold weather, with ornament serrations on the edges. Woodlanders thinks it is Schinus gracilipes about which I can find
almost nothing. Towering above the Schinus is yet another species of perfectly hardy Pittosporum (why is everybody hung up
on P. tobira??). This one looks like a Takoma Park (Left Socialist) version of a Japanese Holly but with the usual little
yellow intensely fragrant flowers characteristic of the Pittosporum. It fruited a little this fall. The small red fruit sat
in a little burst-open capsule. It looked a lot like Euonymus fruit. Woodlanders did not have a name, just the accession number
from (I presume) USDA: Pittosporum sp (98FB104). A bit further on along the ever
taller railroad tie wall, beyond a venerable Erica carnea 8’ across, is one of my Holy Grails, an Arbutus. Surprisingly
it is andrachnoides. It took some leaf burn on older leaves but was otherwise fine. So this denizen of dry rocky subtropical
slopes in Asia Minor withstands days with lows of +3 deg F and highs of +21 deg F or 10 days in a row continuously below freezing
in soaking wet, though well drained soil. Right above it is a 10’ Yucca treculeana, the bluish-leaved west Texas form,
thriving in the shallow rocky mica schist loam. Next to that the long standing
Chilopsis linearis, 6-8’ tall, that I got as a gift from Ed Aldrich of Alexandria, Virginia 6 years ago. It suffered
a little tip dieback but was otherwise unfazed. Just to the west is a 12-14’
Castanopsis cuspidata. It leaned over for no good reason 2 years ago and now is rapidly growing replacement leaders. It flowered
this year for the first time-little “Castanea” catkins. The glossy-leaved Magnolia lotungensis [Parakmeria lotungensis]
and M. yunnanensis [Parakmeria yunnanensis] are often cultivated as street trees in their native