Do I have wait for Mother's Day?
“When should I plant my tomatoes?” A common answer in central Iowa is “any time after Mother’s Day”. But does that rule of thumb still apply this year? The best planting time for tomatoes depends on your weather conditions, but here are a few guidelines that can help you decide when to plant regardless of where you live.
The first thing to understand about planting tomatoes (and peppers, eggplants, melons, and squash) is that they are warm weather plants. Tomatoes will not grow in temperatures below 50 F. The first sign that it is warm enough to plant is the night time temperature stays consistently above 50 F. The ten-day weather forecast for my town in central Iowa indicates we won’t reach those temperatures in the next 10 days.
Why should I care about the soil temperature?
The second thing to consider is the temperature of the soil about 4" deep. Ideally, tomatoes should be planted when the soil temperature is at least 60 F in the early morning. You can use a soil thermometer, a kitchen thermometer, or just stick your finger in the soil for a minute and see if it feels cold (if it feels uncomfortably cold it is probably below 60 F). So far this year, even the maximum temperature at the closest station taking soil temperatures hasn’t reached 60 F.
Why should I care about the weather forecast?
The third thing to consider is the weather forecast. Even if there have been a few warm days and nights and the soil temperature warms to 60 F, a forecast for significant cold weather indicates it may be better to wait to plant until warmer temperatures are in the forecast.
What about this year?
So where does my garden in central Iowa stand on these 3 considerations? Our night time low temperatures this week have been in the upper 40's most nights. The soil temperature in my west-facing raised garden beds this morning has warmed, but the night time lows in the 10-day forecast has a mix of 40's and 50's. All of that suggests I should wait another week or two, which puts us pretty close to….Mother’s Day.
What about Peppers, Eggplants, Squash and Melons?
If you are like us, tomatoes are not the only type of plant we like to grow. We also grow peppers, eggplant, squash, and melons. Add 10 degrees to all of the tomato temperatures above when deciding when to plant peppers, eggplant, squash, and melons. Cool season plants like peas, potatoes, onions, celery, kale, carrots, broccoli, and cabbage can be planted now if not already done.
If you haven’t purchased tomato, pepper, strawberries, herbs, or squash plants yet, check out our plant sale page at https://www.iowabackyardfarmer.org/springplantsale.html