Spring is at its peak right now in Chicago.
The Chicago Botanic Garden is in full bloom. In the last ten days I saw the first flowers open for several trees and shrubs, including lilacs (Syringa vulgaris), juneberry (Amelanchier canadensis), and redbud (Cercis canadensis). The magnolias (Magnolia spp.) are waning and the crabapples (Malus spp.) are just starting to open their colorful blossoms. The spring ephemerals such as bluebells (Mertensia virginica), white trillium (Trillium grandiflorum), and dogtooth violets (Erythronium americanum), rue anemone (Thalictrum thalictroides) and celandine poppy (Stylophorum diphyllum) are in full bloom in the region’s woodlands. Most of these observations were within a few days of last year’s observations of these phenophases.
We expect to see the greatest variation in the early spring phenophases. Plants that bloom early in the spring and leaf budburst for many species are tightly correlated with temperature. For plants that bloom in mid-summer, bloom time is more often cued by daylength rather than temperature. As our dataset grows, we will be able to test these predictions. Do we see a greater spread in the first flower opening date for something like Forsythia (Forsythia x intermedia), one of the first spring bloomers, compared to a grass like big bluestemAndropogon gerardii) which typically blooms in the summer.