Cold Tolerance

       Some few veggies are so cold tolerant that they can overwinter unprotected here in Zone 7A in northern Delaware.  Others can go in before the last frost date of spring, which here is around May 10th.  Last year was warm for weeks before May 10th, then zap, that morning was cold.  So beware the desire to put out the warm weather stuff too early.

The following useful info was from the website:     

              http://aggie-horticulture.tamu.edu 

                    Cold Tolerance in Vegetables

Q. You have often mentioned cold tolerant vegetable crops and those which are very susceptible to frosty injury. Could you list these and temperature lows which they can tolerate?
     This is very difficult to do and be accurate since cold tolerance depends on preconditioning. For instance, if broccoli has been growing in warm conditions and temperatures drop below 22 degrees F., it will probably be killed. If these same broccoli plants had experienced cool weather, they would probably survive the sudden cold.
   A:   In general, a frost (31-33 degrees F.) will kill beans, cantaloupe, corn, cucumbers, eggplant, okra, peas, pepper, potatoes, sweet potatoes, squash, tomatoes, and watermelon.
   B:   Colder temperatures (26-31 degrees F.) may burn foliage but will not kill broccoli, cabbage, cauliflower, chard, lettuce, mustard, onion, radish, and turnip.
   C:   The real cold weather champs are beets, Brussels sprouts, carrots, collards, kale, parsley, and spinach.

      So right now, Groups B and C could be direct seeded or transplants put in.  Resist the urge to put in Group A until after May 10.  It won't really be warm enough to have them grow well until that date anyway.  Fedco Seeds is one of the two seed catalogs that I use, the other being Territorial Seed Company.  I wish I got some money for backing these two, but that is just a pipe dream.  Fedco has free shipping on orders over $30, usually easy enough to reach.  And they are a co-op that includes YOU as the buyer!  That meant that I got a $3.12 check back in the mail as my share of the profits on my order.  Pretty neat.
      Being located in Maine, Fedco offers a lot of seed that can handle colder conditions.  In particular, on page 53 of their 2011 catalog they have a listing of season-extending greens.  They say that with protection the greens can survive the entire winter in Zone 6 and south.  I am experimenting with the following varieties, and will probably add more of their list for the fall of 2011.  Some of their seeds are sold out, so if you want to try some, don't delay your orders.  The following list includes plants that I now have started of these  hardiest of greens.
      Here is the website for Fedco:  http://www.fedcoseeds.com/seeds.html 

Plant	Description	Supplier
Arugula	Ice-Bred Arugula	Fedco
Arugula	Sylvetta Arugula	Fedco
Claytonia	aka Claytonia perfoliata	Fedco
Collards	EvenStar Champion	Fedco
Corn salad	Bistro	Cook's Garden
Kale	Red Russian	Lake Valley
Kale	Redbor	GWD
Kale	Rainbow Lacinato Kale	Fedco
Kale	Beedys Camden Kale	Fedco
Lettuce	Tango Lettuce	Fedco
Lettuce	Winter Marvel	Fedco
Lettuce	Rouge d'Hiver	Fedco
Minutina	Minutina	Fedco
Mustard	Pink Lettucy Mustard	Fedco
Mustard	Pink Lettucy Mustard	GWD
Mustard	Green Wave Mustard	Fedco
Mustard	Tenderleaf Hardy Green	Fedco
Mustard	Chinese Thick-Stem	Fedco
Senposai	Senposai	Fedco
Spinach	Tyee	Lake Valley
Spinach	Olympia Hybrid	Lake Valley
Spinach	Bloomsdale	Burpee & Livingston
Spinach	Bloomsdale	Alexander's Bulk
Spinach	Space Spinach	Fedco
Spinach	Giant Winter Spinach	Fedco
Spinach	Giant Winter Spinach	Heirloom
Tatsoi	Tatsoi	Fedco
Tatsoi	EvenStar Tatsoi Gene Pool	Fedco