The question about when to plant tomatoes is long debated between gardeners, and I consider it to be one of the top five gardening questions for this area.
The answer varies depending on your soil type, exactly where you live, microclimates, and what kind of protection you are willing to give the plants. Tomato plants could be fine given the right conditions. Would I plant my tomatoes yet? No.
You have probably already been to the garden centers, where the tomato plants are sitting out and crying to be taken home. “I’ll add color and life to your salad!” they shout. “Are you ready for a BLT?”
Giving in to fresh, green, healthy plants looking for a home is admirable. Taking them home and setting them out into adverse conditions could be detrimental to a plant’s health, however, with tomato plants being particularly vulnerable.
The bottom line is to pay more attention to soil temperatures and nighttime temperatures than to the calendar. Soil should be at least 60 degrees Fahrenheit, measured consistently rather than on one warm day. Soil temperature thermometers are available for less than $10.
Nighttime temperatures should be consistently 45-55 degrees Fahrenheit or above. Cooler weather inhibits growth on tomato plants, making them more susceptible to root rots and root damage.
Row covers, black plastic, and/or water tubes like Wall O’ Water can be used to warm the soil and protect the plants if you are serious about early tomatoes. Commercial growers use high tunnels (unheated greenhouses) to produce early crops.
Another option for gardeners who are simply eager to start picking tomatoes is to plant early ripening varieties. Seed packets and plant labels typically list the number of “days to maturity.” This number of days is the average length of time it should take to get ripe fruit after planting the seed. Days to maturity can be offset by adverse environmental conditions, such as low soil temperatures.
Many tomato varieties require one hundred or more days from seed to maturity. Some varieties will, however, produce ripe fruit in 60 to 70 days. Sungold and Yellow Pear are early ripening varieties that are on my planting list anyway because of their delicious fruit, and Celebrity and Early Girl are long-standing favorites amongst gardeners.
Gardeners debating the when-to-plant rule often cite the “rules” about the average date of last frost and the frost-free date. Since the dates themselves seem a bit laden with misinformation, let me clarify. According to the K-State Research and Extension Weather Data Library, the average date of last frost in Lawrence is April 10. The frost-free date in Lawrence is May 2. The average date of last frost is just what it sounds like — the average date. The frost-free date is the day when there is a 95 percent chance that frost will not occur on or after that date.
Because frost kills tomato and other warm-season plants, planting them earlier just means there is more risk involved. Some gardeners I know generally wait until Mother’s Day or even Memorial Day to transplant tomatoes into the garden. Within reason, later is generally better.
And, in case you are wondering, the other four of my top five gardening questions are, in no particular order: “What’s wrong with my tree?”, “How ‘bout this weather?”, “Is this a weed or a plant?” and “How do I get rid of those pesky moles?”