Tuesday, June 21, 2011


Blanketflower (Gaillardia aristata) is usually a good sign that summer is on its way in
its native Rocky Mountain region

Summer is a great time to be outdoors exploring and also a a good time to make budburst observations. We don't usually get as many summer observations as spring ones, but it would be valuable to have a better record of how plants vary in their flowering patterns in the summer. In warm climates it is often assumed that the timing of flowers varies mostly as a function of moisture availability, not heat. Observations from the mountain West suggest that this may not always be true. The heat of the summer often leads to flowers that normally come out in the fall to actually emerge in the middle of the summer, like some aster species. Perhaps there is a lot more to learn about what influences summer flowers and especially how it varies from place to place in the country

Here in Colorado our trees and shrubs are very active in the late spring, Many put out their leaves in early May and flower a week or two later. Just this past week the last of our pines, eastern white pine, pinyon pine and bristlecone pine have started to disperse their pollen and send out new leaves. In the past few days catalpa trees have put out their showy white flowers, covering whole trees with blooms. The principle tree left to flower now are the various linden species (Tilia). Interestingly they have seemed to be in slow motion lately. Their odd strap like appendage and stalk for flowers has been out for nearly a month, but the flower buds are tightly rolled up in their buds. Maybe in another week or two they will finally be out. Lindens, in case you have not had the pleasure, are popular ornamental trees in most parts of the country not only because of the good shade and form of these trees but also because of their wonderful flowers. When in flower a whole yard can be filled with the fragrance of these flowers, and are a major attractant for bees as well.

In the summer many other budburst species first come into flower, in particular wildflowers. This year we also have the occasional observer protocol so you can make observations of wildflowers in your summer hikes or travels across the country. While on a road trip from Colorado to Arkansas a few weeks ago, for example, I was able to see lots of interesting patterns in phenology with species that were planted in many places along the way. Down there summer grasses were already in flower and spring wildflowers were either gone or well into the fruiting stages. Ponderosa was a common roadside tree all across Kansas and you could see it with fully developed new needles in the east, where the warmest temperatures occurred. Then going westward the phenology went back in time as we slowly climbed up towards Colorado. By the time we got back to the front range, north of Denver, ponderosas were back to the budswell stage, and it would be weeks before new needles emerged. Similarly a few weeks ago I took a trip up to Estes Park, at 7500' elevation where chokecherry and lilac were in full bloom. They have been done flowering for weeks at our more moderate elevation of 5030'.

Enjoy your summer adventures outdoors, and we look forward to seeing your observations. Maybe they can help us explain how these plants respond to the odd weather we have been having lately.

The first flowers of catalpa (Catalpa speciosa) came out in late May in Salida Kansas,
and on June 19th in Berthoud, Colorado.

Paul Alaback