There are GDD calculators available on line for most regions and even many states. And many of the state university extension websites have graphs for their local areas.

Are you New Mexico or where?

Dave

Dave, I'm not trying to calculate GDDs; I've got that. What I'm trying to do is tie the number of days listed in a seed catalog to GDDs. I think that at one time Territorial Seeds listed these (I'm guessing on the numbers); extra early tomatoes (65-70 days) were 1100 GDDs, early (75-80 days) were 1300 GDDs, etc. We have pretty low GDDs (2100 at 50F) & I'm trying to explain how that impacts vegetable selection to a Master Gardener class.

Andy in Northern NM

NMAndy, I looked online for a tomato GDD chart and didn't see one, though there are a few numbers here and there for one or two tomato DTM types (and it seemed to me that they didn't always agree).

http://forums.gardenweb.com/forums/load/tomato/msg0816021516605.html

http://swroc.cfans.umn.edu/prod/groups/cfans/@pub/@cfans/@swroc/documents/asset/cfans_asset_330307.pdf [page 9]

http://www.helpfulgardener.com/phpBB2/viewtopic.php?t=31447

http://www.walterreeves.com/gardening-q-and-a/tomato-how-long-to-ripen/ [not much]

Found this info on another board we can't link to:

From Territorial 2002 catalog:
Ultra-Early: 1100 heat units (=GDD)
Extra-Early: about 1300 heat units
Early: up to 1500 heat units

With that you could pull up the DTM on several varieties and get a rough comparison.

Then found this site for NM that lets you pick location within state and it will give you the cumulative GDD for that area for the year you pick. ie 2012 in Alamogordo broken down by months.

Dave

Here is a link that might be useful: IPM Models Weather Data

missingtheobvious - thanks, helpful

Dave, thanks. I like the link but it's obviously geared towards commercial growers since it's got pests, grains, etc.

Looks like I've got the basics to prove you can't grow late tomatoes here w/o season extension.