Hardiness Zone Map for the United States We have included your USDA horticultural Zone (HZ) on the order form and the varieties for your climate. If you are in a climate that is too cold for a variety, don't be afraid to experiment with a small planting: apply a good 4" layer of mulch after the ground freezes. If you are in zone 8 or warmer, precool your bulbs for at least ten weeks prior to planting to promote good root development. Please contact us or a good, local horticulturist if you have any questions about your micro-climate (due to elevation or proximity to water) or about precooling your bulbs. Range of Annual Minimum Temperatures Zone 1Below -50ºF Zone 2-50º to -40ºF Zone 3-40º to -30ºF Zone 4-30º to -20ºF Zone 5-20º to -10ºF Zone   6-10º to 0ºF Zone   70º to 10ºF Zone   810º to 20ºF Zone   920º to 30ºF Zone 1030º to 40ºF Hardiness Zone Map for the United States Naturalizing Flower Bulbs Bulbs for warmer climates Heirloom flower bulbs Moist soil conditions Shady conditions Fragrant flower bulbs Rockgardens Deer proof bulbs