US Freeze Dates by State
USDA Hardiness Zone (click here)
Find Local Temperature Averages/Records (click here)
Hardiness Zones and Frost Dates
Seeds will germinate and grow when their environment will allow, most needing heat, moisture,
sunlight and oxygen. Seed germination success will come when the natural environmental conditions are
reproduced. Once a seed is planted (or sown), the 'window of opportunity' that it has to germinate, develop
into a plant and then produce fruit can be identified by the information below. Some plants can develop in
a short time where others need a longer growing period (ex: peas need 50-60 est. days where tomatoes need an est. 90-110
Once the USDA Hardiness Zone is determined,
identify when the last (spring) frost date and first (autumn) frost date is expected in your area. Then you can determine
when to plant the seeds or seedlings if started indoors, without the threat of frost damage. The dates below are
complied by the United States Department of Agriculture and are classified into long, medium and short growing seasons.
A long growing season would be found in zones 8 &
(Feb 15th - Mar 15th to Nov 15th - Dec 15th)
A medium growing season would be found in zones 5, 6 & 7
15th to October 15th)
A short growing season would be found in zones 3 &
(May 15th to September 15th)
Succession Planting is where you plant certain seeds multiple times during the year. The first
planting grows and provides produce while the second and even third planting is growing or beginning to sprout. An example:
plant the first patch of corn seeds then two weeks later, plant the second patch of corn seed in an adjacent area to the first.
As the corn seed is used from the first patch, the second patch is growing and should be ready to harvest after all the
corn has been picked from the first patch. Another example: plant the first batch of lettuce, spinach, peas early in
the spring and the re-plant in mid to late summer for a second crop to eat during the fall.
seeds have germinated and the second or third set of leaves have appeared on the plant, the process of 'hardening-off'
(acclimatization) is necessary for the seedling to survive the transplant from the container to your garden. This process
is gradual and should take no less than two weeks. A 'cold-frame' is ideal for this purpose where you can place
the seedling inside and allow the temperature to fluctuate while providing protection for the plant. The idea is
to slowly replicate the environment that the thriving plant will be permanently re-located to. As the plant continues
to grow it will be less likely to suffer transplant shock if the 'hardening-off' period is long enough.
To lower the temperature in a 'cold-frame', slightly prop open the lid then use
a thermometer to monitor. Closing the lid will allow the temperature inside to increase. For the first few days, the temperature should not be reduced by more than 5-10 degrees
from the temperature of which the plants are accustom. After this period, slowly reduce the temperature by an additional
2-5 degrees every few days until it matches the temperature outside. The plant will then be ready for transplant.
For more information about 'cold-frames', click on our 'Recommended books/Articles' page and scroll down.
Seed Storage &
All seeds have a limited shelf life. This can range from one year (Parsnips)
to ten years (Tomatoes). To save unused seeds, keep them in their paper envelope (helps to identify them later) and place
them in a cool, and most importantly, dry location. By placing them in a plastic bag or glass jar with a rubber seal,
they can be safely stored in a refrigerator. For long term storage, seeds can be frozen. When you are again ready to sow
the seeds, test them by placing a few seeds in a damp paper towel and then into a plastic bag. Set them
in a warm location checking each day to make sure the paper towel remains moist. Soon the seeds will sprout, an estimate
of the percentage of germination can be made for the remaining seeds in the envelope.
do you know when to plant what? The science of Phenology can be very helpful, although there are no absolute guarantees. Phenology is the study of
periodic plant and animal life cycle events and how these cycles can be used as signals that let us know when the weather
and climate are progressing. From these natural occurances, we can gauge when to plant seeds or transplant seedlings. The
list below are can help:
Plant peas ------ when forsythia and daffodils are blooming
Plant potatoes ------ when 1st dandelions
beets, carrots, cole crops (broccoili), lettuce, spinach ------ when lilac has first leaves
Plant beans, cucumbers, squash
------ when lilac is in full bloom
Plant tomatoes ------ when lily-of-the-valley are in full bloom
Transplant eggplant, melon,
peppers ------ when irises bloom
Plant corn ------ when apple blossoms start to fall from tree
Seed fall cabbage and broccoli
------ when catalpas and mockoranges bloom
Plant cool season flowers (pansies, snapdragons) ----- when aspen and chokecherry trees leaf out
Wisconsin Horticulture - Cooperative Extension
National Gardening Association