I got an idea from On the Way to Critter Farm or more directly form the site they linked to Wintersown.org. I had heard about winter sowing. Winter sowing is basically to make a small greenhouse out of a jug or bottle and plant seeds of the appropriate crop in it. You then place the bottle outside and let the spring weather do the rest. I will be trying this with a few tomato plants this year as last years volunteers did quite well without any help.