July 2, 2007

Silphium Blooms Early on Leopold Memorial Reserve

"During every week from April to September there are, on the average, ten wild plants coming into first bloom. In June as many as a dozen species may burst their buds on a single day. No man can heed all of these anniversaries; no man can ignore all of them. He who steps unseeing on May dandelions may be hauled up short by August ragweed pollen; he who ignores the ruddy haze of April elms may skid his car on the fallen corollas of June catalpas. Tell me of what plant-birthday a man takes notice, and I shall tell you a good deal about his vocation, his hobbies, his hay fever, and the general level of his ecological education."
-- Aldo Leopold, Prairie Birthday

Estella Leopold and former ALF intern Erin McGraw admire a compass plant (Silphium laciniatum) blooming on the Leopold Memorial Reserve.

The study of these anniversaries is called phenology. Through record keeping, naturalists can track long-term changes in when events happen in the annual cycle. These changes may then be related to larger regional or global changes. From 1935 to 1945, Aldo Leopold kept track of 145 separate phenological events throughout the year in Madison, Wisconsin, and during trips to the Leopold Shack and Farm. In 1976, his daughter Nina Leopold Bradley started recording the first dates of many of the same events at the Shack and Leopold Memorial Reserve. By comparing their records, we can see a number of events are now occurring earlier each year, likely due to global climate change.

"This year I found Silphium in first bloom on 24 July, a week later than usual; during the last six years the average date was 15 July." So Aldo Leopold writes of his phenological records in his essay Prairie Birthday. Today, Silphium is blooming on average three weeks earlier than it was in Leopold's records. This year, it began blooming on June 19.