are a few thoughts I have after watching plants starting to grow this
spring after an extremely cold winter in southern New England. I think
one of the most interesting aspects of our situation this year is comparing
it with damage we noticed a year ago. The winter of 2002-2003 had very
cold weather in November when we experienced 7 inches of snow and 10
degrees F cold on Thanksgiving Day. In contrast, we had relatively normal
autumn temperatures this past winter, 2003-2004, but we experienced
extremely cold weather during the month of January. At Summer Hill we
experienced minus 7 degrees F twice during January and one morning of
minus 10 degrees F. There were also several periods where the temperature
went down to zero and 2 degrees below.
A year ago, we experienced practically no damage on flowering dogwoods, but this past winter caused considerable damage to older trees. Younger trees seemed to have survived all right, but the older ones have been very badly hurt. Perhaps this is because they went into the winter stressed from a very heavy fruit set and could not contend with the extreme cold. Albizia julibrissin 'Rosea' has been very badly damaged this winter; however, they experienced only slight damage in 2002-2003. One of our trees was just barely breaking into growth during the last week in May. Taxodiums are alive but are breaking dormancy very slowly, which is typical of their being stressed by extreme cold.
A plant that has surprised me very much is Corylopsis pauciflora. We had given up growing it in past years because of a good bit of damage during normal winters. This year it appears that it was not hurt at all as it was covered with flowers. Corylopsis spicata and C. sinensis 'Calvescens' also bloomed quite profusely. Cercis canadensis has been very badly damaged this year. We had two large trees, over ten years old, in front of our house. The largest tree is still alive but growth is coming slowly, and there were practically no flowers, so I know there will be a lot of dead branches. The smaller tree, which had a caliper of about 4 inches, is totally dead.
Heathers and heaths showed next to no damage after 2002-2003, but were badly damaged this past winter, probably because of the minus 7 degrees morning before there was any snow cover. Japanese maples seem to have survived this past year quite well. Also, I am very happy to report our Ilex aquifolium 'Beanie Johnson' has live wood right up to the top and has made new shiny leaves up and down all the branches, although it showed some leaf damage on the south side. Clethra, in the nursery, showed a good bit of damage with a lot of dead wood at the tops. We find damage to Clethra hard to understand since it is native to this area and usually shows very little, if any, damage in the wild. Other nurseries have also experienced the same damage this year, and we think that it is because of the fertilization we all give these plants to have them grow at a fairly rapid rate. The variety I found in Rhode Island that I've named 'Ann's Bouquet' showed the least damage of any of the varieties we grow. We will continue to grow more and more of this variety as it makes a very nice plant and is showing more hardiness.
In my garden, I see quite a bit of top damage on Itea virginica 'Henry's Garnet'. They showed a bit of damage a year ago but a bit more this spring. The plants have not died entirely, but all of last season's growth has been damaged. We are definitely pushing this plant's northern limit. The most protected plant we had of Hypericum 'Sunburst' shows a lot of branch damage; however, the ones that were more exposed are showing no damage at all!
Pieris japonica came through the winter extremely well. I made some notes on the amount of damage there was to the flower buds in our trial gardens. Most damage came on 'Valley Valentine' and 'Valley Rose' where at least two-thirds of the flower buds were killed. There was also a fair amount of damage on 'Spring Snow' and a good bit of damage to 'Karanoma'. I would say the other varieties we grow bloomed about 80% with damage limited to the top third of the plant. 'Summer Hill' showed practically no damage at all with just a few buds hurt near the top. The only plant that showed no bud damage whatsoever was 'New Red'.
Regarding bamboo - last fall I planted out one each of all the varieties of Fargesia we are growing at this time. F. murielae and all the F. nitida forms came through without any damage. This planting was under some large pine trees where they were in the shade for the entire winter, and they came through in excellent shape despite the fall planting. Fargesia robusta died to the ground as I would have expected since it is rated hardy to only 0 degrees F. However, at this point, it is shooting two strong culms from the base so the roots were not hurt. Fargesia rufa showed a bit of leaf damage but is also shooting strongly from the base and is making new leaves from the culms. F. dracocephala showed a fair amount of leaf damage but has made a great number of new leaves at this point, and the culms appear to have come through 100%. Our Phyllostachys aureosulcata varieties all came through with no problem. The leaves all turned tan, but the culms and branches were not hurt and are breaking into new growth normally. Phyllostachys bissetii is in the same category. P. decora has a good bit of culm damage but is shooting from its roots. Also, P. nigra and P. nigra hale were both killed to the ground. Sasa veitchii, Pleioblastus distichus and Pleioblastus variegatus have tops that were badly hurt, but we mow those each year anyhow and they are all coming up very strongly from below ground.
All in all, I can say that I'm surprised that there is so little damage to plant material both in the nursery and in the landscape after such a severe winter. The reason being, I feel, is because the cold came during the month of January when just about all our plant material can best take harsh temperatures. I still say that most of our "winter" damage comes with severe temperatures in either the spring or the fall when most plants are not ready for it.