Another consideration is the date of the first fall frost/freeze. In northern latitudes, where summers can be short, the length of time some species take to reach maturity (most notably tomatoes and peppers) make it necessary to plant seeds indoors and then transplant the seedlings outside at the appropriate time.
Other vegetables and fruits, such as winter squashes and some melon varieties, seem to do better when planted as seeds directly where they are going to stay. With maturation times up to twelve weeks, it may be critical to get seeds planted as early as it is safe to do. If you have a short growing season, and wish to grow these crops, choose varieties that will reach maturity within a safe time period for your area.
My personal observation has been that seed crops planted at their earliest safe date are less likely to fall victim to insects than later plantings. If you have a small organic garden itís not too difficult to reseed if a surprise late frost damages a particular crop.
Many vegetable plants that are planted in the spring can be planted again towards the end of the season. Again it is important to know what date you can expect the first frost.
By understanding the times and length of frost free weather in your area you can have a better chance for success in your organic vegetable garden.
The National Climatic Data Center has a data sheet online that can be downloaded as a pdf file or viewed online. The data sheet contains frost/freeze information for over 3000 U.S. locations. The information is presented as a table, listed in alphabetical order by state and then selected towns within each state.
National Climatic Data Center: Frost/freeze Occurrence Data Table.
The left hand column lists 3 different degree points: 36, 32 & 28 degrees for each area listed. This is followed by dates corresponding to the probability that the preceding temperature will occur after that date.
For example: on Block Island, Rhode Island there is a 90% chance that a late spring light freeze (32F.) will occur after March 31 but only a 10% chance after April 20th. This means that April 20th is the better date to put out vegetable seedlings that canít take a light freeze.
Conversely, the next 3 columns give the probability of a frost/freeze occurring before a certain date.
In this case, Block Island has a 10% chance of getting a moderate freeze (28F.) by Nov. 10th and a 90% chance by Dec. 6th.
The next three columns relate to the number of days you can expect to be frost/freeze free.
Using the same location, Block Islanders can expect a 90% chance of having 195 days of temperatures above 32F. in a row.
Be aware that this information is based on 29 years of data gathering from 1951 to 1980, and that they are statistical in nature and cannot unequivocally predict exact dates for any given locality in any given year.
Biodynamics and Phenology use astrological and natural occurrences to discern clues about the best time to plant and harvest vegetables. Native Americans and other earlier civilizations used similar techniques.
Most areas consist of microclimates that vary by elevation, exposure and proximity to large bodies of water. The Freeze/Frost Tables are a good reference point, but it makes sense to keep track of temperature and other factors in your particular vegetable garden location if you want to truly understand when it is actually the best time to plant your vegetables.
To View or download The Frost Freeze tables; click on the
Chip Phelan, a contributing editor for Organic Gardening Review, is an organic gardener living in Rhode Island. He has been gardening organically for 30 years while working as a sculptor and photo imager. He has recently created a research garden to experiment with organic and small scale sustainable gardening techniques.
Organic Gardening Review is a resource center for organic gardening enthusiasts and features his efforts and interests in all aspects of organic gardening.
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