A question about chill hours.

What temperature is referred to when talking about chill hours? We have chilly weather here during the winter but it rarely freezes. Can anyone clarify this for me?

Thanks,
katiebear

Katiebear, its the number of hours of cold it needs to set fruit. :)

I understand that. I want to know how cold is "cold"?

kb

Chill is the number of hours below 45�F from November to mid February.

kb, it the number of hours between 32ºF and 45ºF, but it can be complicated to calculate because warm weather changes how the numbers are added up. Fruiting trees and shrubs need a certain amount of cold weather in order to break dormancy properly. If the plant doesn't get enough cold weather, it won't break dormancy properly and the flowers may be damaged. This will lead to a stressed and weakened plant that will eventually die or fall prey to pests and diseases. Is there a governmental agency or a university system that specializes in agriculture that you could contact?

That's what I was wondering. We have several months when it's cold but not freezing. I think I will have to learn by experimenting. Some things may fruit here even though it rarely freezes.

I don't know of any government or university agencies that could help like they do in the States.

Thank you both for the information.

katiebear

You might want to try growing some of the low chill varieties that are recommended for the southern states. Something that requires less that 400 hours

What are you trying to grow?
What part of Mexico?

I'm growing a lot of cirtus. Also mangoes, pomegranites and papayas. I have a lot of small macadamia nut trees. I'm looking for other fruits and nuts which might do well here.

I am in Baja California, halfway down (600 miles from San Diego) on the Sea of Cortez side. I am very close to the sea so the soil is alkiline and salty.

katiebear

If you can grow citrus, you will need low chill cultivars of the more northern fruits like peaches, blueberries. Those developed for Florida and the gulf coast or perhaps southern California, These are the ones I am familiar with, but there are breeding programs in Mexico, Central and south America, Australia, India, and Thailand. These typically require less than 200 chill hours. http://www.actahort.org/members/showpdf?booknrarnr=592_13 http://www.justfruitsandexotics.com/ http://www.actahort.org/books/622/622_65.htm

Katiebear, you really need to find out how many chill hours your area gets. The number will vary from year to year. So it would be best to stay under when you buy trees. See if you can find a weather station that records the hourly temperatures in your area. You might be able to get a crude idea of the number of chill hours. Meanwhile, you could stick with trees that require 200 hours or less. This is what I have found so far.
Apples:
Dorsett Golden and Einsheimer require 100 hours
Anna requires 200. All three are self-fruiting.
There is one Plumcot.
All figs.
Persimmons require 100 or 200 hours depending on the cultivar.
There are a few nectarines that require 200 hrs or less.
At least one pear - Hood.
There are a few Japanese plums with requirements that low.

Dave Wilson Nursery provides chill hour requirements if available.
The second link is to a description of a farm cooperative in operation there in Baja. Try contacting them. They would know what their member grow. They might be able to tell you if there is a government or university agency similar to our Cooperative Extension Service
SAGAR is the Agricultural and Rural Development Ministry.
http://www.davewilson.com/br40/sales_catalogFruit.html
http://www.delcabo.com/

Thank you both for the information and the links. Lots of good information.

I forgot to say that I also have bananas and fig trees. Also, lots of gourds.

katiebear

P.S This is one of those times when I asked a question and got responses which, to me, are alone worth the value of my subscription. So thanks, again, to all.

Farmerdill, thanks for those links. When we moved to Texas, I had to rethink how I gardened. We lived in the east hills of San Jose, CA for 22 years and temperature dipped low enough to get a light frost on the grass. The number of chill hours however was high enough that I could grow just about anything. The south bay used to be full of fruit orchards of all kinds until property values sky rocketed. Here, it can get down into the teens although for the last 7 years, the low has been 23ºF. My biggest headache is the very real threat of a late frost in March.