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An illustrated guide to the signs of Minnesota spring

Phenology fiends, rejoice.

The snow is melting. The birds are chirping. Minnesotans are wearing shorts (yeah, yeah, some of them never stopped). It must be spring, right?

If you’re as antsy as us about spring, though, you want to know about the real deal: When are the geese coming back? When will the lilacs bloom?

The Minnesota Phenology Network has a better idea of these things than most. They’re a group of naturalists who record the timing of seasonal flora and fauna events across the state of Minnesota. The group formed in 2010 and compiles observations from independent phenologists, with some records going back to the 1940s.

MinnPost analyzed the network’s dataset to find the average dates of a selection of signs of spring in Minnesota. Because the date things happen in a given year can vary wildly based on location, we’ve limited our analysis to observations in the seven-county Twin Cities metro area and to phenomena that have three or more recorded observations over time.

All illustrations by Greta Kaul.

Maple sap flowing

March 13

In cold climates like Minnesota, maple trees go dormant in the winter, storing up their food as starch during the cold months. But once temperatures warm, sugary sap starts to flow.

Earliest observation: February 28 (1987)
Latest observation: March 25 (1986)

Canada goose spotted

Branta canadensis
March 15

Some Canada geese are year-round residents of Minnesota, but when you look to the sky and see flock after flock of these big honkers coming north from parts south, it's a sure sign of spring.

Earliest observation: March 2 (1983)
Latest observation: March 24 (1984)

Woodcock spotted

Scolopax minor
March 21
“Up and up he goes, the spirals steeper and smaller, the twittering louder and louder, until the performer is only a speck in the sky. Then, without warning, he tumbles like a crippled plane, giving voice in a soft liquid warble that a March bluebird might envy. At a few feet from the ground he levels off and returns to his peenting ground, usually to the exact spot where the performance began, and there resumes his peenting.”

This short, stout gamebird whose mating dance Aldo Leopold immortalized in 1949’s “A Sand County Almanac” makes its return from the southeast around mid-March.

Earliest observation: March 6 (1983)
Latest observation: April 2 (1984)

Active mosquitoes

April 4

Everybody knows mosquitoes — not loons — are the real Minnesota state bird. Mosquito eggs hide out in the soil during the winter, but they generally start hatching around early April.

Earliest observation: March 4 (1983)
Latest observation: May 10 (1984)

Flowering snow trillium

Trillium nivale
April 7

This rare woodland flower is one of the earliest ephemerals to appear — sometimes while there’s still snow on the ground. Other varieties of trillium can be found later in the spring.

Earliest observation: March 26 (1987)
Latest observation: April 22 (1965)

Active wood ticks

Dermacentor variabilis
April 12

It wouldn't hurt to start checking for ticks mid-April, when wood ticks re-emerge from their winter inactivity. (You should also be checking for deer ticks, the tiny ones that transmit Lyme disease).

Earliest observation: March 29 (1981)
Latest observation: April 29 (1983)

Flowering quaking aspen

Populus tremuloides
April 10

Look closely at the tips of trees and you might start to see green in the first few weeks of April. Catkins — bright, green shocks that develop at the ends of quaking aspen branches — emerge around that time. They are the tree’s flowers and are a sign that the trees will leaf out to quake when the wind blows in the summer months.

Earliest observation: April 1 (1963)
Latest observation: April 22 (2011)

Flowering white trout lily

Erythronium albidum
April 20

If you’re looking to do some trout lily fishing in America — Minnesota, at least — mid-to-late April is usually a good time to start. These native plants with drooping flowers are found in colonies in shady, wooded areas. The dwarf trout lily, which resembles the white one, is endangered, so it's best not to touch these.

Earliest observation: April 7 (1988)
Latest observation: May 2 (1965)

Flowering Dutchman’s breeches

Dicentra cucullaria
April 23

These white and pink wildflowers, native to Minnesota, derive their name from their resemblance to pairs of pants hanging upside-down. They can be found in shady wooded areas.

Earliest observation: April 13 (1977; 1985)
Latest observation: May 6 (1975)

First dandelions

Taraxacum officinale
May 1

May Day brings bad news for fastidious lawnkeepers: dandelions are coming. These non-native weeds’ name comes from the French dent de lion, meaning lion’s tooth. They flower pretty much all summer long.

Earliest observation: April 10 (2012)
Latest observation: May 17 (2013)

Flowering apple trees

Malus domestica
May 5

Apples may be a sign of fall, but their blossoms are a sure sign of spring. Look out for them in the first week of May.

Earliest observation: April 16 (1987)
Latest observation: May 21 (1950)

Flowering prairie smoke

Geum triflorum
May 7

These native plants are some of the first prairie flowers to bloom in the spring, with wispy, tufted tips.

Earliest observation: April 17 (1958; 1963)
Latest observation: May 25 (1968)

Flowering lilac

Syringa vulgaris
May 12

Lilac, with its distinct, sweet smell, tends to bloom during the last few weeks of school.

Earliest observation: April 25 (1987)
Latest observation: May 26 (1950)

Flowering jack in the pulpit

Arisaema triphyllum
May 24

These sneaky woodland flowers, which do, in fact, kind of look like a person standing in a pulpit, are often found by morel mushroom hunters in May.

Earliest observation: May 1 (2012)
Latest observation: June 20 (2011)

Flowering white lady’s slipper

Cypripedium candidum
May 30

The white lady’s slipper, a small, delicate woodland orchid, starts to bloom around the end of May. Its relative, the pink and white showy lady’s slipper, is Minnesota’s state flower.

Earliest observation: May 20 (1962)
Latest observation: June 5 (1966)

All data supplied by the Minnesota Phenology Network and its volunteers. For more information about the network, visit