Wait for Warmth: Soil Temperatures Key to Success
- Chelsey
- Apr 26
- 2 min read
Spring Fever Can be a Real Problem!
Thinking about planting directly in the ground? Don't underestimate the vital role of soil temperature! Jump the gun too early, and you risk stunting your plants and impacting their food production.
This is a tried and true test by your very own Queen Bee– as someone who farmed up to seven acres of chemical-free produce from 1996 to 2018, first with my parents and then independently, I learned this lesson firsthand. We constantly experimented to get the first harvests, but the early tomatoes we managed were never as robust as those planted later.
Why? It is all about the soil temperature. While it's relatively easy to protect young tomato or pepper plants from the Iowa spring temps and wind above ground, warming the soil is far more difficult.
Did You Know?
Tomatoes, peppers, cucumbers, and watermelons are actually tropical plants so we need to treat them as such. They love warm temperatures!
Tip: A simple trick to both suppress those million pesky little weeds and give your soil a little temperature boost is using black plastic or landscape fabric in your planting beds.
What can you plant early?
Cole crops - aka cruciferous vegetables like cabbage, broccoli, cauliflower, Brussels sprouts, kale, and kohlrabi - can be planted early but it is still better to wait until the soil temperature is consistently in the mid 50s and ambient temperatures not below 40’s or you run the risk of frost damage.
Seeds
Radishes, lettuce, spinach, onions, cole crops.
Potatoes as long as it’s not cold and wet or they will rot before they start to come up
For example, 60-70 degree daytime temps are recommended for lettuce to germinate. With an estimated 7-14 days to germinate.
What about Annuals?
Annuals that you can plant early without much fear are:
Snapdragons
Pansy
Violas
Petunias
Calibrachoa
Alyssum
Avoid These Sensitive Ones
Do not plant these early because they're extremely frost and cold temperature sensitive.
Basil
Sweet Potatoes
Begonias
Coleus
Impatiens
What does Frost or Cold Damage Look Like?
Brown or black leaves or leaf edges
Wilted, limp and starting to collapse
Portions of leaves turning white
After all it is Iowa!
Just because it’s nice one day doesn’t mean it will stay like that. It’s spring in Iowa which means we can have summer spring and winter all in one week or even one day!
Watch the forecast closely this week to determine if it will be warm enough to gamble!
Source: Iowa State University: Germination Requirements for Annuals and Vegetables, Cold and Freeze Damage to Garden Plants
