Tuesday, June 9, 2009

June 9th. Cool weather on both coasts leads to great floral displays this month

This past few weeks I had the opportunity to look at the phenology of plants in both the northern Atlantic and Pacific coastal regions. Both regions have had somewhat cooler than normal springs, with parts of the northeast being quite dry, but recent rains are quickly compensating for this in both areas. On Washington’s Olympic Peninsula last week I actually saw plants in the rainforest wilting from the extraordinary heat and dry conditions there! This followed with heavy rains over the past few days. Even here in Montana we have had cool rainy weather to start out the Month of June which is usually our wettest month.

We have written here before that temperature is a key factor which generally determines when most plants start growing in the spring. When we have a cool spring as many places have seen this year, plants generally come out later. Here in Montana for example while a series of warm springs over the past 10 years or so has led to flowers coming out as much as 2-3 weeks earlier than in the past, this year plants are coming out right at about the average date (the first time flowering dates have been “normal” in nearly a decade). The other good thing about this cool wet weather for gardeners, and also for those that appreciate spring wildflowers is that this also tends to extend the flowering season. We have seen flowering periods extended a week or more for serviceberry and many garden bulbs this spring here in the northern Rockies, while chokecherry was flowering during a warm period recently, so it only lasted a few weeks.

In New York if your travels allow you to visit the New York Botanical Gardens in the Bronx, now is a great time to check out early summer wildflowers and the last of the spring wildflowers. When I was there over Memorial Day weekend Rhododendrons were in full bloom all over the gardens, and azaleas were in full bloom as well on the margins of their amazing old growth forest reserve. Tulip poplars were in full bloom too, although flowers were beginning to fade on some trees. Most pines including eastern white pine were at the first needles stage. Woodland wildflowers such as blackberries, solomon’s seal, viburnum, and mountain laurel were beginning to show. Native flowering dogwoods are done flowering, but the ornamental Cornus kousa, from China and Japan was beginning to reach full bloom in the main garden areas.

In Washington’s Olympic Peninsula by contrast Rhododendrons just recently came into full bloom. In Washington Rhododendrons grow so well they are sometimes considered weeds. I saw some shrubs 10’ or more high there, all covered with red or purple blooms! Spring wildflowers such as trillium are still in bloom there, and the raspberry relative which is native to the coast, salmonberry (Rubus spectabilis), is just beginning to flower. Volunteers in Alaska report that further up the coast spring and summer are quite late this year as well. Spring is just starting up there.

The same varieties of Rhododendron just came into bloom last week here in Montana, at least two weeks behind those in New York. A common ornamental dogwood here, called the pagota dogwood (Cornus alternifolia) is actually native to woodlands in New York.

But because of the cooler weather here it is still in full bloom weeks after it was done flowering in its native range (at least in the Bronx). All of this points to value of making budburst observations not only of native plants where we get the most useful information on the ecological effects of climate change but also your garden plants since varieties of perennials or trees and shrubs are genetically similar, so any differences you see in flow ering dates around the country should directly reflect climatic differences. Make sure you note which varieties you have when you register these plants! (enter in the notes field).

Modern interest in phenology and citizen science actually comes from the observation that most homeowners or residents of dry cold northern areas, such as Montana are quite aware, and usually keep track of when lilacs first come into bloom into spring. Finally some color to contrast with the brown of a long winter! By just organizing volunteers to keep track of the day of first flowers of these shrubs has resulted in an invaluable dataset for looking at how weather affects plant phenology (for more information on the history of this see http://www.usanpn.org/?q=node/36).

A good example of looking at effects of weather on regional patterns of phenology comes from red maple. Native to the eastern US, but widely planted as an ornamental across the country it can be used to show how plant phenology varies as you move across the country. According to budburst observations from volunteers this year it started flowering in Houston, Texas on January 23rd. Nearly a month later it started flowering in Arkansas on Feb 15th. In New England it started flowering in by the second week of March to early April. In Montana it was flowering even later, in mid-April. If you live in the Midwest or west and have a red maple or black locust planted near you please keep track of when it flowers next year. It will be interesting to see what pattern it has across the diverse range of climates in the West.

Paul Alaback

1. Azalias and rhododendrons at New York Botanical Garden during early June
2. Flowering dogwood in early spring at edge of old growth forest preserve at edge of botanical garden
3. Tulip poplar blooms during full bloom over Memorial Day weekend
4. White pines at first needle phenophase in New York
5. First flower phenophase for red maple in Montana

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