Rate fruit tree species in order of flower time/frost sensitivity

I’m thinking of building an overhead sprayer/mister. For blossom night frost protection.

I can’t spray the whole garden/orchard for practical reasons. So I’m thinking of grouping all the night frost sensitive species together in 1 spot.

This is where i need your help.
Could you rate/list from wanting to protect the blossoms most to least the fruit tree species you grow/know off? And mention your climate zone or local variables :slight_smile:

I’m trying to make a list of trees needing the most flower frost protection.
(from most to least protection needed)

So far i got the following. But I’m not sure of the order. And where to place things like pawpaw and jujube?

I’m in zone 7/8 Europe, Netherlands

asian plum
Almond
apricot
aprium
pluot
fuzzy kiwi
sweet cherry
tart cherry
peach
EU plum
Asian pear
hardy kiwi
EU pear
apple
mulberry
quince
medlar (mispilus germanica)
kaki
pomegranate
pawpaw
jujube

what would you change or add?

Thanks for your help.

Some more information on flower frost sensitivity.

At or near the bloom stage, the critical temperature is the same for almost all fruits and flowers. Freezing temperatures of 28 degrees Fahrenheit will result in about a 10 percent loss and 24 F in a 90 percent loss

The percent of flowers killed in a frost may or may not relate directly to lost yield later in the season. With large-fruited fruits such as apples, peaches, plums and pears, the loss of 50 percent of the flower is not devastating since we may only want a small percentage of the flowers to become fruit. For small-fruited fruits such as cherries, blueberries and grapes, many small fruit are needed for good yields and a full crop. Crop losses due to freezing temperatures are almost always significant in cherries.

These statements make me think it’s most important to protect those that flower earlier. And those that have smaller fruit.

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Zone 8. Texas. I’ll give it this a shot, but for a couple of fruits it really depends on cultivar. We can have apples blooming in January, and other varieties blooming in April. Same thing with peaches.

So, here is the list of what blooms first if you plant the recommended varieties for the region:

Strawberry
Wild Plum
Plum, Pear, Peach
Persimmon
Pecan, Apple
Pomegranate
Elderberry

Peach and strawberries seem to be the most frost susceptible.

If I was going to protect flowers:
Peach

Persimmons, some apple varieties, elderberries and pecans bloom after frost. Our frosts are not normally hard enough to hurt pears, and the plum varieties we grow here are usually bloom so much that fruit lost to frost isn’t that big an issue.

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Your list looks good to me @oscar … I would add to the bottom pomegranate, pawpaw, then jujube (they never have problems and not completely sure on the order there). Fuzzy kiwi are up with the Asian plums and hardy kiwi maybe with Asian pears.

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Agreed.

Jujube are the last ones- mine just started opening in the last couple days. The few pawpaw I have were done a week or two ago. There may still be some Kaki open, but it’s been spread out over a while- probably similar to pawpaw.

I’m not sure if it is just because of the cold spring, but my hardy kiwi are just finishing flowering now. AP were done a long time ago and are now sizing up.

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I should have mentioned that my kiwi dates were not bloom dates, I was more thinking of frost sensitivity. They can easily die back before blooms open since all the blooms are on this years “wood” (on the sides of new shoots) unlike tree fruit.

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intresting scott. Even though it’s not directly flower frost protection you exactly got the spirit of the topic :heart:

I have never seen my hardy kiwi’s blossem get frost damage. but have seen damaged leaves when they leafed out early due to heat early in the year followed by night frost.

Will the regrowth also flower? But just cause a later harvest? or if the primary growth gets frost damage, it’s no fruit that year? My hardy kiwi’s where still young and neglected so i did not pay much attention last years to frost flowers and fruit.

It depends how late the frost hits… if the shoots are quite elongated it is likely you will lose the whole crop. If they are shorter there may be some shoots not budded yet so you can get a small crop.

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thanks scott.

Do you know by chance the mechanism? How does the kiwi know when to make flowers on a new shoot and when not? Or are the flowers starts already there in the buds that grows the shoot, like in grapes? And thus like virtually all other fruits the flower start/bud develops pre dormant season.

Basically, do the flower buds develop in the spring? or do they develop pre dormant season, but are they packed together in a single bud that grows into a shoot with flowers?

I think it is like grapes, the flowers are already in the shoot buds in some microscopic form.

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Here in my USA, Tennessee zone 7a Jujube bloom end of May into early June. Our last frost is normally mid April… occasionally as late as 4/20 or 25.

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You only mentioned fruit trees…

But just a FYI… many berry bushes produce lots of nice fruit and for most I think (for me for sure) are much less succeptable to late frost.

Last spring we got a hard frost on 4/15… wiped out all my apples peaches grapes…

But did not affect my blackberries raspberries blueberries at all.

Have you considered Figs ?
My Chicago Hardy Fig starts producing fruit in July… and we picked our last Dec 3.

TNHunter

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thanks for the reply TNhunter.

My goal for starting this topic though was determining which fruit’s need most protection, so i can put those close together. That way i can spray/mist them if a freeze is predicted during flowering.

Those that flower late i ofcourse won’t protect.

Rubus phoenicolasius (Japanese wineberry) just started flowering for me. While my tayberry’s are already quite large and developing colour.
Thats another late flowerer.

Would you prefer if i also add berry’s figs and grapes to the list? My goals was to make a list of things that need/like flower frost protection. So i left quite a few off that i know flower late enough. But if it’s more useful to other member I’ll gladly add things that don’t need protection to the list to.

@oscar - no need to add those… I see what you were working out there now.

I do think your list above is about right…

Here in Zone 7a Tennessee our average last frost date is 4/15 per extension.tennessee,edu.

Of those in your list I have these…

Peach, Rising Star - opened first bloom 3/16 this year
Peach, Reliance ? - opened first bloom 3/17 this year
Apricot, Morepark - opened first bloom 3/17 this year
Peach, Early Elberta - opened first bloom 3/19 this year
Sweet Cherry, Lapins - opened first bloom 3/24 this year
Apple, Macintosh - opened first bloom 3/26 this year
Apple, Gold Rush - opened first bloom 4/10 this year

I have had Japanese/Asian Plums in the past and both of them started blooming Mid to Late February.
In 11 years, we got one good crop off of them, and in 2 other years small crops.

In my location, the Japanese Plums bloomed much earlier than my Moorpark Apricot does.
Unfortunately at this point I am not sure what variety of Japanese Plums it was that I had, one ripened a nice dark purple color and the other was golden. They were both delicious and both trees died after 11-12 years.

I replaced them in 2018 with European Plums… which by the way have not bloomed yet.
I hear they are supposed to bloom much later, so I am giving those a try.

Good Luck with your frost protection project.

TNHunter

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that’s a nice list of flowering times.

It seems peaches are earlier then apricots for you?

our last (night) frost date is 15/05. So I’m jealous of your longer growing season. Or does frost come earlier for you in the winter? (what’s you first frost of the winter?) for us it’s usually end of oktober/november
Not this year, but last year we had night frost on the night of 14/05 to 15/05 a lot of people here had a foot+ sized potato plants with frost damage. That year we had a warm winter, and i even saw a Japanese plum flower in december.

@oscar

Again per extension.tennessee.edu…

Tennessee Vegetable Planting Guide
Frost Dates:
Average Last Frost: April 15th
Average First Frost: October 14

The official average first frost date is Oct 14 per them… but that could be a very mild frost and it may take a hard frost to stop fruit production.

For example last year, we harvested everbearing raspberries and figs, until Dec 1 and Dec 3.
It was not until then that we had our first really hard frost, that took those out.

I had Greens, and Carrots, and Beets in my garden past Christmas.
It may be sometime in January before my hardy greens in the garden are gone.

TNHunter

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Peach, Rising Star - opened first bloom 3/16 this year
Peach, Reliance ? - opened first bloom 3/17 this year
Apricot, Morepark - opened first bloom 3/17 this year
Peach, Early Elberta - opened first bloom 3/19 this year


Yes my Peaches and Apricot opened first bloom within just a few days of each other.
The Early Elberta and Reliance ? are 20 year old trees.
The Rising Star and MoorPark Apricot are 2 year old trees.

The Rising Star boomed and set fruit (hundreds of blooms).
The MoorPark Apricot, opened 3 blossoms in the very tip of the tree, and set no fruit.
Perhaps next year.

Note… I say Reliance ? (with a question mark). I ordered a Reliance, it came labeled as a Reliance, I planted it and have grown it thinking it was a Reliance, but this spring when I posted pictures of it on this board (in bloom) found out that my tree has extra showy blossoms, and that Reliance trees do not.
So, I have no idea exactly what variety of peach it is… or what to call it, so I just call it Reliance ?

:slight_smile:

TNHunter

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I live in New Mexico in the US and we have very warm weather in early spring but late frosts so it is very challenging to protect flowers and young fruits here.

Almonds are very early flowering and can be problematic because they are open for a longer period of time during the cold weather.

Fuzzy kiwi is not very hardy. Don’t know about your climate but it might get killed in colder temperatures during the winter. Hardy kiwi is very sensitive to frost once it has leafed out and tends to leaf out early, so it would be very difficult to protect.

Mulberries, pomegranate, pawpaw, and jujube all flower well after the last frost as far as know. It is possible that the same is true of persimmons.

You don’t mention Amelanchiers, which seem to flower late and regularly produce fruit, even though there is sometimes some overlap between frost time and their flowering

My medlar has also flowered late and may do so after the last frost. Same might be true of quince but they might both need a little protection if late frosts are extended.

Tart cherry flowers later than sweet cherry. My Montmorency seems to regularly produce at least some fruit. I have recently planted some of the very late flowering sweet cherries, which may flower almost as late as Montmorency. You would need to look up a chart of flowering times for sweet cherries and try the absolute latest flowering ones.

As for the rest of the standard fruits that you list, I think they would all be in the same category of vulnerability. I haven’t used a spray system. I decided it was not the best approach for me. If you get too much spray in the wrong conditions, it freezes and can actually kill the fruits.

I have mostly young trees. They are small enough that I can cover them with a tree bag. I then place an outdoor halogen spotlight inside the tree bag. This provides enough heat to raise the temperature inside the bag. There are a lot of nuances as to how to do this, which I’d be glad to share with you privately if you are interested. Too much detail for here.

For more shrubby plants I have successfully protected them with a temporary winter wall of straw bales, plus the tree bags.

A related issue is that of plants that are marginally hardy in your area and may need some protection during the coldest temperatures of the winter. Here again tree bags with spotlights are helpful. I have the lights on thermostatically controlled plugs that only turn on if the temperature is below 20 F, as most such plants can tolerate 15 or even 10 F. I protect figs and pomegranates this way.

During the spring I carefully monitor predicted temperatures and actual temperatures each day. I recently discovered that the temperature varies alot depending on which part of my property and specficially on how high I place the thermometer. Whereas it might get to 24 F at a foot above ground, at 4 feet above ground it might only get to 35 F and that level is where most of the flowers and fruits are. Since it’s a lot of work to protect things, I find it helpful to be able to more accurately predict where the damaging temperatures will occur.

I find it quite tricky to get a good forecast. When I use the official forecast for my area, I can be anywhere from a few degrees to almost 20 degrees F colder than that prediction. So even if the predicted low is 48 F, I have to be prepared for the possibility of 24 F!!!

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thanks for that extensive reply jcutts :heart:

I’m lucky since the frosts that damage fruit tree flowers here are almost exclusivly night frosts. And spraying water at night, keeping things wet so there’s always water to freeze will create some 0 Celsius ice. That than easily melts during the day.

If your in an area with both day and night frosts during flowering. Spraying water is probably a bad idea.

Goede daag, Oscar.

The frosts here are at night, usually very early morning, about 5 to 6 am.

I’ve read that under the wrong conditions, the ice that forms from spraying or misting can actually cause injury the flowers, buds, and fruits. You could do a little research. From what I have read, it isn’t a very reliable method but it may be the only thing that could help if you have trees that are too large to cover.

Good luck!

Hello jcutts

The circumstances that could damage the tree’s that have been sprayed for frost protection are when there is low relative humidity and high wind and low temperature/sunshine. Since at that point the ice that’s formed over night that keeps your flower buds from going below 0C (water freezing point) Does not thaw during the day. But actually goes straight from ice into gas (water vapour) form.(sublimation) This sublimation actualy needs heat, and it extracts it from the surrounding. Thus cooling down the surrounding.

Where the water freezing actually releases heat, and thus heats up the surrounding.

So basically using water for frost protection, spreads out the cold/frost over an longer time period, by temporarily releasing some heat by the formation of ice. That later has to be put back in to melt the ice. If it keeps freezing during the day, and the ice does not melt. that becomes a problem.

However as long as the ice does not melt. you want to keep it wet. So it keeps freezing new ice and releasing heat.

Here it is really rare to have long freezes that damage blossom. Mostly just a few hours at night and 5-10 Celsius during the day. So plenty of time for the ice to thaw.

The water spraying for blossom night frost protection works to a lesser degree in really windy times. Luckily most of our blossom damaging night frosts are radiative and not convective from cold winds. So if it’s really windy we usually don’t have a frost. And when there’s practically no wind and a clear sky, we get a radiative frost. And water spray can work excellently to protect against that.

If your in a location that gets convective freezes from cold wind. I would not recommend water spray for frost protection. Also if your in a place where the blossom damaging frost also happens during the day, i think water spray would not be ideal either. Luckily those things are quite rare.