Fruit tree critical temperatures
Have you ever heard the term
"nipped in the bud"? That's precisely what we hope won't happen
to our baby peaches, pears, and nectarines tonight, when the low is
forecast to be in the 20s. This is the one case where we're lucky
that we live on the shady side of the hill, since our fruit tree
flowers (mostly) haven't opened up yet, unlike the trees on our movie
star neighbor's farm, which are in full bloom.
As a fruit tree bud
comes to life, it is less resistant to cold weather with every passing
day, and scientists have come up with charts of critical
temperatures,
telling us when we should kiss those summer peaches goodbye.
Apples
|
Silver
Tip
|
Green
Tip
|
½
inch
green
|
Tight
Cluster
|
First
Pink
|
Full
Pink
|
First
Bloom
|
Full
Bloom
|
Post
Bloom
|
10%
kill
90% kill
|
15
2
|
18
10
|
23
15
|
27
21
|
28
24
|
28
25
|
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
|
10%
kill
90% kill
|
15
0
|
20
6
|
24
15
|
25
19
|
26
22
|
27
23
|
28
24
|
28
24
|
|
Peaches
|
Bud
Swell
|
Calyx
Green
|
Calyx
Red
|
|
First
Pink
|
First
Bloom
|
Full
Bloom
|
Post
Bloom
|
10%
kill
90% kill
|
18
1
|
21
5
|
23
9
|
|
25
15
|
26
21
|
27
24
|
28
25
|
European
Plums
|
Bud
Swell
|
Side
White
|
Tip
Green
|
Tight
Cluster
|
First
White
|
First
Bloom
|
Full
Bloom
|
Post
Bloom
|
10%
kill
90% kill
|
14
0
|
17
3
|
20
7
|
24
16
|
26
22
|
27
23
|
28
23
|
28
23
|
Sweet
Cherries
|
Bud
Swell
|
Side
Green
|
Green
Tip
|
Tight
Cluster
|
Open
Cluster
|
First
White
|
First
Bloom
|
Full
Bloom
|
Post
Bloom
|
10%
kill
90% kill
|
17
5
|
22
9
|
25
14
|
26
17
|
27
21
|
27
24
|
28
25
|
28
25
|
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
|
|
You can probably guess what
stage your fruit trees are at just based on the descriptions, but I've
included some photos here to help you decipher the differences.
Our peach trees are in the red calyx stage (10% kill at 23 degrees and
90% kill at 9 degrees), our pears are in the first white to full white
stage (10% kill at 25 to 26, 90% kill at 19 to 22), and our nectarine
has buds ranging from red calyx to full bloom (10% kill at 23 to 27,
90% kill at 9 to 24 degrees.)
As you can see, you often
find an array of bud stages on a single tree, which is good for us
because it means that a late frost is less likely to kill off all of
our fruit. Even though the currently open nectarine buds and
nearly open pear buds are probably going to die tonight, the less
precocious buds on each tree might pull through, and I'm not overly
concerned about our peach buds.
All of that said, I'm
not sure I expect pears this year. Although my sample size is
very small, I've found that each of my fruit trees has produced flowers
but no fruit the first year it blooms. Perhaps the trees aren't
quite ready to pour that much energy into making fruits but are willing
to make flowers in hopes that their pollen might pass on the tree's
genes using someone else's energy budget? I'd be curious to hear
if you've seen a similar strategy in your own young fruit trees.
If my hypothesis is correct, we should see peaches from the tree that
fruited last year and also from the tree that only bloomed last year,
nectarines from the tree that bloomed last year, but no pears.
Assuming we don't get any excessively cold weather in the next few
weeks, that is....
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About us:
Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.
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