The common advice for when to plant tomatoes is after the last frost date. The problem with this advice is that 50% of the time the last frost falls after this date! Tomatoes will not tolerate frost and you'll have to use frost protection measures if freezing temperatures threaten.
Better advice is to wait until two weeks past your average safe date before planting. The safe date is the day on which in meteorological records the last frost date had already occurred 90% of the time. See the table below for many U.S. cities. If you're conservative and wait a little longer until the weather is warmer you'll be rewarded. Your plants will invariably bear more and longer than plants set out very early.
At SeaTac Airport in Seattle, for example, the average last frost date is March 10th and the average 90% safe date is about four weeks later -- April 4th.
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Not only should you wait till after the safe date, it's best to wait until the soil and air temperatures are no lower than 45˚F (7˚C) at night unless you're prepared to cover your plants. The daytime temperature of the soil should be at least 55 to 60˚F (13 to 16˚C) before transplanting outdoors.
For peace of mind, why not consult your nursery or your local newspaper's garden columnist for when to plant tomatoes? Here in Seattle that would be a colorful character by the name of Ciscoe who authored an excellent gardening book, Ask Ciscoe: Oh, la, la! Your Gardening Questions Answered. Ciscoe recommends setting out tomato plants around Mother's Day (second Sunday in May) in Seattle unless you're planning to use cold frames or some other early-tomato tricks.
You've read advice on when to plant tomatoes but if you want to have the first ripe tomatoes in the neighborhood you can gamble by setting your plants out early. You'll want to be ready with some frost protection strategies if a late frost looms. Two passive techniques to keep tomatoes warm and protected are to use covers and heat-storing water containers. Some common frost protection methods and devices:
The local expert at your favorite garden center will know what varieties grow best in your vicinity. If you like to shop online my favorite source is Burpee Tomato Seeds because they have the largest selection of hybrid tomatoes and other plants including heirloom tomatoes and other garden vegetables.
|City||State||Avg Last Frost (90%)|
|Little Rock||Arkansas||Apr 9|
|Pine Bluff||Arkansas||Apr 3|
|San Francisco||California||Jan 23|
|Colorado Springs||Colorado||May 15|
|Grand Junction||Colorado||May 9|
|Coeur d'Alene||Idaho||May 22|
|South Bend||Indiana||May 11|
|Des Moines||Iowa||May 2|
|Mason City||Iowa||May 15|
|Kansas City||Kansas||Apr 21|
|Bowling Green||Kentucky||Apr 26|
|Baton Rouge||Louisiana||Mar 19|
|National Arboretum||Maryland||Apr 20|
|New Bedford||Massachusetts||Apr 26|
|International Falls||Minnesota||Jun 8|
|Kansas City||Missouri||Apr 21|
|St. Louis||Missouri||Apr 19|
|North Platte||Nebraska||May 23|
|Las Vegas||Nevada||Mar 19|
|Concord||New Hampshire||Jun 6|
|Nashua||New Hampshire||May 20|
|Atlantic City||New Jersey||May 10|
|Alamogordo||New Mexico||Apr 14|
|Albuquerque||New Mexico||May 3|
|Buffalo||New York||May 6|
|New York||New York||Apr 13|
|Fayetteville||North Carolina||Apr 13|
|Raleigh||North Carolina||Apr 25|
|City||State||Avg Last Frost (90%)|
|Bismarck||North Dakota||May 28|
|Fargo||North Dakota||May 21|
|Minot||North Dakota||May 22|
|Oklahoma City||Oklahoma||Apr 13|
|Providence||Rhode Island||Apr 29|
|Charleston||South Carolina||Mar 8|
|Columbia||South Carolina||Apr 20|
|Aberdeen||South Dakota||May 20|
|Rapid City||South Dakota||May 25|
|Sioux Falls||South Dakota||May 19|
|San Antonio||Texas||Mar 21|
|Salt Lake City||Utah||May 8|
|St. George||Utah||Apr 11|
|Green Bay||Wisconsin||May 12|
|Charleston||West Virginia||May 8|
* Frosts do not occur every year.
Planting your tomatoes outside no earlier than two weeks after the dates in the above table while being mindful of the best temperature conditions described above will set you up for an excellent start to the growing season!Back to Top