January–February
The bare woods of winter murmur and tap with chickadees and woodpeckers, while the prairie rustles and chirps as the sparrows and juncos scratch for seeds and flutter through the tall grass. This is a good time to observe hawks and is when owls are most likely to be active during the day. The end of February brings the first woodland wildflowers, including the native harbinger-of-spring and naturalized Eurasian snowdrops.
March
Varying from year to year, the first really spring-like days come in the first to the third week of March. Dutchman’s breeches, hepatica, violet and spring beauty first appear, along with the early flying butterflies that pollinate them. Garter snakes, which gather in rock crevices for the winter, emerge from the dens to mate and disperse on these first warm days. Listen for spring peepers (small frogs) on warm, cloudy days or in the evening. The orange tip butterfly appears at the end of the month and remains for a mere two or three weeks.
April
In the first half of April, the Pinetum is dazzling with its thousands of daffodils. The spring wildflowers of the woodlands appear in earnest this month. Bluebells, phlox, Mayapple, celandine poppy, bellwort, and many others join those which started earlier, while wild strawberry, yellow star grass and yellow rocket bring color to prairie, glade, and field. Insects and reptiles become active. In warm years, redbud and dogwood flower early in the month, but most years they bloom later.
May
The first half of May is the peak time for viewing migrating songbirds. Warblers, tanagers, orioles and thrushes flit about the tree tops eating the abundant insect life on the newly forming leaves. At ground level ants busily reconstruct their mounds and grasshoppers abound, these becoming the main food for hungry baby bluebirds in the numerous nest boxes at the Nature Reserve. In May, the woodland wildflowers mature and by the end of the month give way to the spring flower show in the glade with Indian paintbrush, birdsfoot violet, Carolina larkspur, and orange puccoon conspicuous among the many kinds blooming.
June
Some wildflower enthusiasts refer to June as the "green lull" between spring and summer. Many of the more conspicuous wildflowers of June are white, including white wild indigo, smooth penstemon, dogbane, and the introduced Queen Anne’s lace and oxeye daisy. Pink-flowered Bradbury beebalm and European red clover, and blue-flowered spiderwort are notable exceptions. June is when the plant and animal life in the prairie and wetland areas begins its ascending spiral of growth and activity, which continues until the short days and cool nights of Autumn take hold.
July
The hottest days of the year usually occur in early July. These bring to an end the chorus of frog and bird songs of early summer and bring forth the varied buzzes, chirps, and trills of the singing insects. The heat also brings forth the beginnings of the riot of color that characterizes the prairie in ever-changing hues from July through September. The whites of June give way to the yellow of grayheaded coneflower and black-eyed Susan, pink milkweed and the brilliant orange butterfly milkweed, purple leadplant and magenta ironweed. Late in the month, tall purple spikes of prairie blazing star begin to flower, and are visited by the year’s greatest abundance of swallowtail and other butterflies. Listen for the rare Henslow’s sparrows and sedge wrens in the prairie.
August
During August, the prairie grasses attain their maximum height as they reach upward to take maximum advantage of the wind for dispersing their pollen. Some asters, sunflowers, and goldenrods show their first blooms. At the wetland, boltonia, tickseed, cardinal flower, wild hibiscus and water lilies bloom as the water warms and its level drops around them. The exposed mudflats are home to a multitude of small frogs, and become coated with the first small growth of the opportunistic plants that grow on them when they dry out each summer. The quacking nocturnal call of the woodland katydid peaks this month.
September
As summer wanes, the grasses of the prairie take on purple or golden tones while the asters, sunflowers, and goldenrods come into their full flourish of bloom. Migrating monarch butterflies peak at or just before mid-month, following the first cooling northerly weather fronts, taking advantage of the nectar of these prairie flowers to nourish them for their long journey south. The bluest of all our flowers, prairie gentian, begins to bloom at the end of the month. Only 1–1.5 feet tall, this plant is often well hidden among the four- to eight-foot vegetation around it.
October
October brings the first frost and the fall colors. New England aster, showy and stiff goldenrods, and prairie gentian continue to bloom through the month, while the sumac leaves turn scarlet, and maple, sassafras and oak in the nearby woods turn gold, salmon and crimson. Gossamer spider threads and fluffy seeds on the warm afternoon breeze are other signs of fall.
November–December
There is little flowering at this time, but a lingering gentian in the prairie, a dandelion in the mowed areas, or Eastern witch hazel in the woods may delight the eye of the flower hunter on a warm afternoon. The reddening of broomsedge, little bluestem and switch grass intensifies during this period, resulting in a mosaic of russet, tan, and gold in the frost-cured prairie.