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Spring is already here … and why that’s terrible | Chill Hours Explained

Spring is already here … and why that’s terrible | Chill Hours Explained

Spring is here! And it’s TERRIBLE!

The trees in our orchard started to bloom about a week ago. Tiny green leaves and big fluffy blossoms began to pop out all over the place. As much as I absolutely love the spring, I was disappointed to see that spring was already here. Believe it or not, fruit trees actually need the cold days of the winter and we didn’t get enough of them yet! Sure, when that first frost hits in the fall it looks like the tree is going into shock. All the leaves fall off leaving behind a naked and twiggy stick poking out of the ground. It looks sad and pathetic. Fortunately, there’s more going on here than you might realize.

Peach tree leaf and flower buds – mid February 2017

Most fruit trees require a specific number of “Chill Hours” every winter in order to properly develop and prepare the fruit crop for the coming spring. A chill hour is considered an hour between October 1st and February 28th where the temperature is between 32F and 45F. Stephenville, TX specifically falls into the 800 to about 850 chill hours zone. That means that on average we receive about 800-850 hours each winter where the temperature is between 32F and 45F.

Texas Chill Hours Recommedations Map

Folks who understand chill hours take them into careful consideration when selecting and planting fruit trees. If you select a tree that requires chill hours lower than what your area regularly receives, you’ll likely have the tree burst out in bright blossoms just in time for a savage freeze to blow through and kill every single one of them. No blossoms – means no fruit. If you’re in our area and tried to grow something like and Orange or a Lemon, you’ve experienced the result of this firsthand when year after year you have no fruit.

Alternately, if you select a tree that requires a higher number of chill hours than what your area regularly receives, you’ll have far fewer and poorer quality fruit than you would have otherwise received. That’s what Stephenville is experiencing this year. This year we (and likely much of Texas) haven’t even received half of our chill hours. If you’re in Stephenville, you can use this page here which shows the accumulated chill hours in Overton which is in the same hour band as we are. Right now we’re at less than 400. I pulled the below table from A&M’s website at the link above.

So Should We Plant Trees with Lower Chill Hours?

It’s an interesting question, and one that I’ve heard at least twice in the company of educated fruit growers over the last year. To be fair, last year (2015-2016) we came up short on chill hours (from the 800ish estimated for our area) and this year (2016-2017) is looking to be even lower. The answer in both cases was that it takes a lot more than 1 or 2 years of mild winters to change something like chill hour recommendations for an area. A slightly more helpful answer is probably just to look at this table of data that A&M has collected over the last couple decades.

YearDate of Last FrostChill Hours

It’s easy to see that while the last couple years havent exactly hit their mark, the last decade paints a different story.

Dr Jody Worthington (a bonafide peach expert) at his orchard last week answering the question about chill hours.

The Short Version

Too lazy to read everything? Here it is as succinctly as possible. Fruit trees need a specific number of chill hours (hours between 32F and 45F) during the winter. Stephenville usually gets around 800-850. We didn’t get enough this year. That’s bad. There will be less fruit and potentially lower quality fruit this year because of that fact.

Dont sweat it. There isn’t anything we can do about it except just sit back and endure it. Sure, we wont have as good of a fruit crop this year, but chances are good that next year everything will swing back in the right direction.


Trees are awesome. In a world where everything is dominated by instant gratification, working with a tree that must be nurtured for years forces you to slow down and appreciate the value of hard work.

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