LISLE, Ill. (March 18, 2026)—With March 20 marking the first official day of spring, the tree and plant experts at The Morton Arboretum say the Chicago region is currently on track for an average arrival time of spring blooms, despite weather fluctuations over recent days and weeks.
“As the Chicago region transitions from late winter to early spring, there is very rarely a steady warm-up,” said Arboretum Forest Ecology Research Scientist Christy Rollinson, Ph.D. “When we are trying to predict the timing of spring bloom or leaf-out, we look at temperature accumulation as opposed to any individual day. The weather can be volatile in the short term, but it usually evens out into more recognizable patterns, or climate trends, over time.”
One warm or cold day now won’t dramatically speed up or slow down the trajectory of spring blooms, but as time progresses closer to the growing season, such spells will start to bear greater influence on whether plants emerge early or late. Think of it like a diving board, Rollinson said – jumping at the base doesn’t do much, but by the end, when a diver is about to spring off, every little movement sends the board up and down.
“It’s a similar principle. In ecology, we call it thresholds,” she said. “As you get closer to that threshold, the impacts of daily weather events on the timing of spring blooms and leaf-out become more amplified.”
The same goes for rain and snowfall – steady precipitation over a span of time affords more stability than one single event, especially one dramatic downpour. While the Chicago region has remained clear of current drought conditions affecting much of the country, the U.S. Drought Monitor lists most of central Illinois under moderate to severe drought as of late last week. New data is published each Thursday.
“The rain is good for plants at the moment, as will be the snowmelt,” Rollinson said. “But as we move forward in the growing season, we’re going to want to have moist soils, not sopping wet soils, which tend to spread disease.”
Based on data from years past, areas experiencing drought can expect trees to leaf out more slowly with sparser canopies. Once more rain falls later in the season, trees can often take full advantage of it, according to Rollinson.
“What happens in the spring can prime things for the rest of the growing season, but it doesn’t necessarily define it,” she said.
Spring showstoppers
What is normal bloom timing? Historical records indicate that, on average, peak spring blooms in the Chicago region can be expected to occur around mid-April to May, according to Arboretum experts. This is when woodland wildflowers, daffodils and the majority of flowering shrubs often offer their best show, and redbud, crabapple and magnolia trees become big attractions at the Arboretum.
The Arboretum anticipates resuming its annual Spring Bloom Report on the mortonarb.org website in the coming days, at which point viewers can check back for weekly updates on the spring flowering underway on its grounds.
Protecting plants during spring weather swings
At this stage of the season, Rollinson assures homeowners and gardeners that they don’t have to worry about temperature drops and snowfall just yet for most plants. In fact, the latest snow cover acted as a layer of protection for plants against the sharp cooldown. The first step is to simply check which trees and plants have begun budding and sprouting.
“In general, things that leaf out or emerge early in the season evolutionarily know they do so at a risk, and so they tend to be pretty well adapted to cold spells,” she said. “There’s a reason snowdrops are called snowdrops—they have adapted so that they can freeze and not die.”
If plants that normally flower toward late March or April show activity early, it is recommended to insulate them. The Arboretum’s Plant Clinic advises spreading leaves or mulch over any green sprouts in the garden. Before an anticipated frost, cover small trees and shrubs, to the ground, with sheets or lightweight tarps for protection, then remove them in the morning once the worst of the cold subsides. Signs of freeze damage in plants include sudden discolored tissue that appears water-soaked and withers within a short time.
For more information, visit the Arboretum’s webpage about protecting plants from cold spells. The Plant Clinic is available to provide free tree and plant care advice Monday through Friday by phone at 630-719-2424 or walk-ins at the Arboretum (with paid admission) from noon to 4 p.m., or by email at plantclinic@mortonarb.org.