One of the most common questions we hear from northern gardeners in the spring is: When can I plant tomatoes?
Our advice is: Don't rush it.
The University of Minnesota Extension Service recommends waiting until "after all danger of frost has passed and soil has warmed." The last-frost date in Minnesota is generally between May 5 and May 30, depending on where you are in the state. However, even in the southern part of Minnesota, it may make sense to plant tomatoes later in May, rather than early. If planted in cold temperatures, tomatoes tend to just sit there, rather than growing. And, if it is cold and damp, you may be setting the stage for fungal or other diseases.
Horticulturists generally recommend gardeners wait until day-time temperatures are reliably into the 60s or 70s and night-time temps are not below 50. You can also plant based on soil temperatures, using a soil thermometer. Soil temps should not drop below 50 at night and should be in the 60s or above in the day.
If you use phenology (or the study of nature signs) as your guide, the recommendation is to plant tomatoes "when dogwoods are in peak bloom." In the middle part of Minnesota, that would usually be late May or early June, which sounds about right.
Other gardeners go strictly by the calendar when deciding when to plant tomatoes. While some folks plant on Mother's Day, Memorial Day is a safer option for planting tomatoes. You could even go into early June, as long as you "pot up" and plants you have so they have plenty of room for their roots to grow.
As for how to plant tomatoes, we have linked to this video of our own Tomato Guy planting them before, and it's worth watching before you go out to plant your tomatoes. The best tip, however, is to plant your tomatoes deep. Tomatoes will form roots all along their stems, so plant them deeply to encourage good root formation.
When will you be planting your tomatoes this year?