When to Plant Tomatoes

When is it safe to transplant tomatoes outdoors?

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.

Wait for these temperatures

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.

When you can ignore this advice

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:

Buying tomato seeds

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 icon because they have the largest selection of hybrid tomatoes and other plants including heirloom tomatoes and other garden vegetables.

90% Probability of Last Spring Frost - U.S. Cities

(Source: U.S. Dept. of Commerce National Climatic Data Center)
City State Avg Last Frost (90%)
Birmingham Alabama Apr 19
Mobile Alabama Mar 21
Anchorage Alaska May 19
Juneau Alaska May 24
Flagstaff Arizona Jun 23
Phoenix Arizona Feb. 9
Tucson Arizona Feb. 24
Fayetteville Arkansas Apr 25
Little Rock Arkansas Apr 9
Pine Bluff Arkansas Apr 3
Los Angeles California *
Sacramento California Mar 20
San Francisco California Jan 23
San Diego California *
Colorado Springs Colorado May 15
Denver Colorado May 13
Grand Junction Colorado May 9
Hartford Connecticut May 10
Wilmington Delaware Apr 21
Miami Florida Jan 16
Orlando Florida Mar 5
Jacksonville Florida Mar 21
Tampa Florida Feb 22
Atlanta Georgia Apr 14
Columbus Georgia Mar. 28
Dalton Georgia Apr 15
Honolulu Hawaii *
Boise Idaho May 8
Coeur d'Alene Idaho May 22
Kellog Idaho May 27
Carbondale Illinois Apr 29
Chicago Illinois May 6
Springfield Illinois Apr 25
Indianapolis Indiana May 4
South Bend Indiana May 11
Des Moines Iowa May 2
Mason City Iowa May 15
Kansas City Kansas Apr 21
Topeka Kansas Apr 21
Wichita Kansas Apr 21
Bowling Green Kentucky Apr 26
Louisville Kentucky Apr 21
Baton Rouge Louisiana Mar 19
Ruston Louisiana Apr 8
Bangor Maine May 23
Portland Maine May 15
Baltimore Maryland Apr 22
National Arboretum Maryland Apr 20
Boston Massachusetts Apr 21
New Bedford Massachusetts Apr 26
Dearborn Michigan May 17
Detroit Michigan May 10
Marquette Michigan May 26
Duluth Minnesota Jun 8
International Falls Minnesota Jun 8
Minneapolis Minnesota May 12
Gulfport Mississippi Mar 16
Jackson Mississippi Apr 8
Tupelo Mississippi Apr 22
Columbia Missouri Apr 21
Kansas City Missouri Apr 21
St. Louis Missouri Apr 19
Springfield Missouri Apr 29
Billings Montana May 17
Butte Montana Jul 7
Helena Montana Jun 4
Missoula Montana Jun 15
Lincoln Nebraska May 12
North Platte Nebraska May 23
Omaha Nebraska May 9
Las Vegas Nevada Mar 19
Reno Nevada Jun 13
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

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City State Avg Last Frost (90%)
Bismarck North Dakota May 28
Fargo North Dakota May 21
Minot North Dakota May 22
Cincinnati Ohio Apr 27
Cleveland Ohio May 16
Columbus Ohio May 9
Dayton Ohio May 6
Lawton Oklahoma Apr 11
Oklahoma City Oklahoma Apr 13
Tulsa Oklahoma Apr 8
Bend Oregon Jul 14
Eugene Oregon May 24
Medford Oregon May 17
Ontario Oregon May 13
Portland Oregon Apr 15
Altoona Pennsylvania May 17
Philadelphia Pennsylvania Apr 19
Pittsburgh Pennsylvania May 10
Williamsport Pennsylvania May 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
Memphis Tennessee Apr 9
Nashville Tennessee Apr 21
Amarillo Texas May 1
Austin Texas Mar 15
Brownsville Texas Feb 13
Dallas Texas Mar 28
Houston Texas Mar 18
San Antonio Texas Mar 21
Logan Utah May 20
Salt Lake City Utah May 8
St. George Utah Apr 11
Burlington Vermont May 20
Rutland Vermont May 26
Richmond Virginia Apr 21
Roanoke Virginia Apr 27
Norfolk Virginia Apr 7
Chelan Washington Apr 25
Richland Washington Apr 21
Seattle Washington Apr 4
Spokane Washington May 18
Wenatchee Washington Apr 24
Green Bay Wisconsin May 12
Madison Wisconsin May 27
Milwaukee Wisconsin May 10
Charleston West Virginia May 8
Casper Wyoming May 22

* Frosts do not occur every year.

For even more U.S. cities visit the National Climatic Data Center or click here for average last frost dates in Canadian cities.

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!

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