Spring Frost Damage Thresholds (text version)

Critical Spring Temperatures for Tree Fruit and Small Fruit Bud Stages
Compiled by Mark Longstroth, District Extension Horticulture Agent, MSU Extension

Pome Fruit
Apples	Silver Tip		Green Tip			½ inch green		Tight Cluster			First Pink			Full Pink				First Bloom		Full Bloom		Post Bloom
Old temp 10% kill 90% kill	16 15 2		16 18 10			22 23 15		27 27 21			27 28 24			28 28 25				28 28 25		29 28 25		29 28 25
Pears	Bud Swell		Bud Burst					Tight cluster			First White			Full White				First Bloom		Full Bloom		Post Bloom
Old temp 10% kill 90% kill	18 15 0		23 20 6					24 24 15			28 25 19			29 26 22				29 27 23		29 28 24		30 28 24
Stone Fruit
Apricots	Bud Swell		Bud Burst			Red Tip			First White			First Bloom				Full Bloom			In the Shuck			Green Fruit
Old temp 10% kill 90% kill	-- 15 --		23 20 0			-- 22 9			25 24 14			-- 25 19				28 27 22			-- 27 24			31 28 25
Peaches	Bud Swell		Calyx Green			Calyx Red						First Pink				First Bloom			Full Bloom			Post Bloom
Old temp 10% kill 90% kill	23 18 1		-- 21 5			-- 23 9						25 25 15				-- 26 21			27 27 24			30 28 25
European Plums	Bud Swell		Side White			Tip Green			Tight Cluster			First White				First Bloom			Full Bloom			Post Bloom
Old temp 10% kill 90% kill	-- 14 0		-- 17 3			-- 20 7			-- 24 16			23 26 22				27 27 23			27 28 23			30 28 23
Sweet Cherries	Bud Swell		Side Green			Green Tip		Tight Cluster			Open Cluster			First White				First Bloom		Full Bloom		Post Bloom
Old temp 10% kill 90% kill	23 17 5		23 22 9			25 25 14		28 26 17			28 27 21			29 27 24				29 28 25		29 28 25		30 28 25
Tart Cherries	Bud Swell		Side Green			Green Tip		Tight Cluster			Open Cluster			First White				First Bloom		Full Bloom
10% kill 90% kill	15 0		24 10			26 22		26 24			28 24			28 24				28 24		28 24
Small Fruits
Concord Grapes		First Swell		Full Swell			Bud Burst			First Leaf			Second Leaf				Third Leaf				Fourth Leaf
10% kill		13		21			25			27			28				28				28
90% kill		-3		10			16			21			22				26				27
Strawberries		Buds Emerged					Buds Closed								Bloom						Small Fruit
Damage		10					22-27								28						28
Blueberries		Bud Burst			Pink Bud					Open Flower					Petal Fall						Green Fruit
Damage		< 20			< 25					27					28						28

Old standard temperature is the lowest temperature that can be endured for 30 minutes without damage.
This chart also shows the temperature that will kill 10 % and 90 % of normal fruit buds.
These numbers were taken from Washington (WSU), Michigan (MSU) and North Carolina (NCS) Extension Bulletins. Apple - WSU EB0913, Pears - WSU EB0978, Sweet Cherries - WSU EB1128, Peaches - WSU EB0914, Apricots - WSU EB1240, Tart Cherries - MSU Research. Rpt. 220,
Portions of these bulletins are posted at Gregg Lang's Fruit Bud Hardiness Page at the MSU Horticulture Department
Two others are posted on the web: Concord Grapes - WSU EB1615, Bluerries, NCS- HIL-201-E