How weather affects spring buds and leaves

A tree’s buds are made the summer before, but what happens to them over the next nine months is up to the weather. Here’s how a harsh winter, a mild one, a warm spell that comes too early, and a freeze after the leaves are out each affect spring buds, and how trees recover.

Does a harsh winter hurt buds?

For most trees that are native to a region, an ordinary winter isn’t a problem. The maples, tulip poplars, and sweetgums in one Purdue report, for example, tolerate roughly −20 to −35°F (Purdue Landscape Report). Flower buds are more tender. University of New Hampshire Extension puts the point where flower buds of hardy forsythia varieties start dying at about −5°F, peach and sweet cherry buds at about −15°F, and many plums at −20°F or lower. The further a bud has developed, the less cold it can take (UNH Extension).

Timing matters as much as the low itself. In New Hampshire in the winter of 2022–23, an unusually warm January softened buds, and an early-February cold snap that dropped parts of the state to −20°F or lower then killed the exposed ones. Buds buried under snow survived, so forsythia and weeping cherries bloomed only at the tips of long branches that had been covered by snow, a “halo” effect (UNH Extension). Forsythia shows this clearly: flower buds killed in winter turn brown or black and never open, while buds below the snow line still bloom, and the leaf buds usually open normally (University of Minnesota Extension). If you cut a winter-killed bud open, its center is brown (Purdue Extension).

Snow helps in another way. A good snow cover limits how deep the ground freezes. After a snowless winter in southern Wisconsin, soil froze deeper than usual, and the root damage showed up later as sparse leaves, dieback, and even dead plants (University of Wisconsin–Madison Extension). Purdue specialists warned in 2018 that some plants may leaf out with no sign of injury and later wilt as if in a drought, usually a sign that their roots froze (Purdue Landscape Report).

Does a cold winter delay spring? Not necessarily. Trees need a certain amount of winter cold, usually counted in hours between about 32°F and 45°F, and the more of it they get, the less spring warmth they need before their buds break (Purdue Landscape Report). So a winter with plenty of time between about 32°F and 45°F tends to leave trees ready to respond quickly once spring warms up.

What a mild winter does

Too little cold can be the bigger problem. Temperatures from about 32°F to 45°F count best toward a tree’s chilling, colder temperatures add little, and long spells above 60 to 70°F can cancel chilling already gained (UF/IFAS Extension). Trees that come up short are slow to leaf out (UF/IFAS Extension). Texas A&M reported a Hill Country season when traditional counts said peach trees had received about 830 chilling hours, but the trees behaved as if they’d had only about 530, partly because hours below freezing during an ice storm didn’t count. The trees were slow to leaf out (Texas A&M AgriLife). In Georgia, about 80 percent of the 2017 peach crop was lost, and about 70 percent of those losses were blamed on too little chilling (University of Georgia).

Not every patchy spring is a chilling problem, though. In 2025, Purdue specialists looked at maples, tulip poplars, and sweetgums in northern Indiana that leafed out late and unevenly, and some not at all. The trees had received plenty of chilling. The specialists pointed instead to spring weather that swung back and forth between warm spells and cold snaps (Purdue Landscape Report).

False springs

A false spring is an early spring followed by a hard freeze. A run of warm days pushes buds open ahead of schedule, and then a freeze returns and catches the tender new growth (USA National Phenology Network).

Two recent examples show how costly that can be:

• 2007. March 2007 was the second-warmest March on record for the United States, with parts of the East running up to 27°F above normal. Then, in early April, four to five nights fell below freezing, some into the teens, breaking more than 1,200 daily low-temperature records (NASA Earthdata). Researchers found the freeze killed new leaves, shoots, and flowers on wild plants across the region; white oaks were hit hard, and yellow-poplar was slow to leaf out again (ScienceDaily, on research by Gu and others).
• 2012. March 2012 broke heat records at more than 15,000 sites across the U.S. When a hard freeze followed in early April, Michigan’s tart cherry crop collapsed from about 135 million pounds in 2010 to 5.5 million (Cornell University).

When a cold snap hits after buds open

A bud loses cold tolerance as it opens. The best data come from fruit trees, whose growers watch every degree. Michigan State University Extension’s widely used table shows apple buds surviving about 15°F at the earliest “silver tip” stage, but only about 27 to 28°F once the flower buds are clustered or in bloom; those are the temperatures at which about 10 percent of buds are killed (Michigan State University Extension). Penn State notes that such critical temperatures assume the cold lasts about 30 minutes or less (Penn State Extension).

For ordinary trees and shrubs, Iowa State Extension says new growth usually handles temperatures in the low 30s and upper 20s, and damage becomes likely in the mid-20s or lower (Iowa State University Extension). Damaged new leaves shrivel, go limp, turn brown or black, and drop.

Not all cold nights are equal. On calm, clear nights, the ground loses heat to the sky and cold air settles near the surface and drains into low spots, a radiation frost. A windy freeze, when a cold air mass moves in, is harder to protect against. Plants in valley bottoms and frost pockets take the most damage, and a slow, gradual thaw the next morning may reduce it (Penn State Extension).

How trees recover

A freeze that kills new leaves rarely kills a healthy tree. Established plants generally put out new growth within a few weeks (Iowa State University Extension), drawing on buds held in reserve, which can stay dormant for years as a kind of life insurance (Nebraska Extension). It isn’t free: the tree has already spent stored food on the leaves it lost and has to spend more to replace them (University of Tennessee Extension). See what are leaf buds? for the backup buds that make this possible.

Recovery can take a while. After a May 2011 frost of about 23 to 24°F damaged nearly all the new leaves in a German beech forest, the trees began growing new ones 19 to 38 days later, and their crowns had largely filled back in by early summer (Menzel and others, Frontiers in Plant Science). In 2010, after a spring about 5°F warmer than average, a frost across higher-elevation forests of the northeastern U.S. stripped many sugar maples of their new leaves while beech and yellow birch were largely spared, cutting the forests’ growth that year by 7 to 14 percent (Hufkens and others, Global Change Biology). The effects can carry into the next year too: a study of 870 tree species found a late frost delayed the following spring’s leaf-out by about a week on average (USA National Phenology Network).

What to do after a spring freeze

Extension specialists give fairly consistent advice:

• Wait. Give plants a few weeks to leaf out again before deciding anything is dead (Nebraska Extension).
• Hold off on pruning. The Missouri Botanical Garden suggests waiting until midsummer, when it’s clear which wood is actually dead (Missouri Botanical Garden).
• Skip the fertilizer. Extra nitrogen adds stress to a tree that’s already replacing its leaves (University of Tennessee Extension, Nebraska Extension).
• Water during dry spells, especially trees and shrubs planted in the last three to five years (Iowa State University Extension).
• Covering small plants can help. For short trees and shrubs, a light blanket that reaches all the way to the ground can help (Utah State University). Fully protecting trees and shrubs isn’t practical, and Iowa State notes it isn’t necessary for healthy plants (Iowa State University Extension).

Lost flowers are a different matter: woody plants don’t make new flower buds that season (Nebraska Extension), so a frosted magnolia or pussy willow may skip its bloom for the year without any lasting harm (Iowa State University Extension).

Rain, drought, and spring snow

• Cool, wet springs favor anthracnose, a fungal leaf disease that can strip a sycamore of most of its first leaves and also attacks ash, maple, and oak. Trees usually have a full canopy again by late June or early July (Iowa State University Extension).
• Last summer’s drought can show up this spring. Because buds form the summer before, buds made during a drought hold fewer and smaller leaves and shorter shoots (Purdue University).
• Heavy, wet spring snow can break limbs (Utah State University). Brush snow off upward rather than pulling branches down, and let ice melt on its own instead of knocking it off. Weak-wooded trees such as silver maple and Siberian elm are most at risk (Iowa State University Extension).

Are false springs becoming more common?

The answer isn’t settled. The USA National Phenology Network says false springs are predicted to increase (USA National Phenology Network). A U.S. Geological Survey study projected that under high emissions, spring could arrive a median of 23 days earlier by late this century, with false-spring risk rising in the Great Plains and parts of the Midwest but staying flat or falling elsewhere (U.S. Geological Survey). And looking back, a study of 1959 to 2017 found late-frost risk actually decreased in North America while it rose in Europe and Asia (Zohner and others, PNAS).

For the stages a bud goes through and when trees typically leaf out, see when do trees bud and leaf out?