Apple blossoms before a frost

Frost is possible the forecast night (forecast low 30°F). Your latest note for this tree: that stage. Flowers and small fruit can be damaged at about 28°F, and a few degrees colder can kill most of them. A tree needs only a small share of its blossoms to set a good crop, so some loss is normal.

When we suggest this

• ForecastA night at or below about 30°F is forecast for tonight or the next 2 nights.
• Your noteYour note: stage is flower buds in a tight cluster or flower buds showing pink or blooming or petals falling or small fruit forming.

What would stop us suggesting it

• The morning after the forecast night passes (or when a fresh forecast no longer shows it).
• When you mark it Done or Doesn't apply. "Doesn't fit my setup" stops it for that plant this season.

What to do

1. For a small tree, drape a frost cloth, old sheet, or burlap over it in the late afternoon so it reaches the ground all around.
2. Keep plastic off the blossoms. It protects poorly and can damage what it touches.
3. If the soil under the tree is dry, water it during the day. Moist soil holds more heat.
4. Take the cover off late the next morning, once it's above freezing.

What we can't know

• How cold it gets at your tree. Low spots can be several degrees colder than the forecast.
• How many blossoms your tree has. A heavy bloom can lose some and still crop well.

WSU and Penn State tables ('Red Delicious', 30 minutes of exposure) give about 10% kill at 27°F at tight cluster and 28°F from pink through post-bloom, and 90% kill at 21–25°F. A UMN chart lists 25°F at tight cluster, and Penn State's Marini puts full-bloom kill at about 27°F; 'Golden Delicious' is about 1°F and 'Rome Beauty' about 2°F hardier until petal fall. We trigger at a forecast low of 30°F because buds on clear, calm nights run a few degrees below measured air temperature (up to about 5°F) and yards differ from the forecast point. Sources disagree on how much covering helps: USU recommends covers for backyard trees, Texas A&M says covers help on calm nights but little in windy freezes, and Iowa State says little can be done in most backyard orchards.

Where this advice applies

All US regions.

Any US garden where frost can come after apple buds reach tight cluster, most often near the typical last spring frost.

Cold air drains into low spots and slope bottoms, which can be several degrees colder than the forecast; trees against a warm south or west wall may bloom earlier.

Exceptions

• Trees you haven't noted as flowering yet (answer the stage check-in).
• Trees with fruit already coloring.
• Trees you've marked finished for the season.

Related guide sections

• Growing apple trees: seasons

Reviewed

Sources checked Sept 2026 · awaiting expert review

Gardenplanner research (AI-assisted), pending extension-qualified review

Rule id and version: apple.bloom-frost@1