Growing vegetables from seed in our short Wisconsin growing season can seem challenging. Understanding the growth requirements of various vegetable plants will help you plan your seed-grown gardens. Let’s look at the difference between cool and warm season vegetables.
What’s the difference between cool and warm season vegetables?
Simply stated, cool season vegetables tolerate colder temperatures and warm season vegetables are less tolerant of cold, requiring warmer temperatures.
Dates to remember (Cedarburg, WI) Average last spring frost May 18th Average first fall frost Sept. 27th Average growing season length: 131 days
Why is this important? Vegetables have different timeframes from seed to edible, and that hinges on temperatures.
Cool Season Vegetables
Cool-season vegetable seeds can germinate in colder temps, so you can directly sow in your garden.
These crops prefer daytime temperatures between 55° and 75° F, so you plant them in spring so the veggies mature before daytime temperatures get over 80° F. Cool-season vegetable seeds are usually directly sown in the garden as they can germinate in soil temperatures as low at 40F°, although ideally soil should be closer 60°. Time the starting of your cool-season crops so that they will mature before the hottest summer temperatures arrive. The overly hot temperatures may cause your cool-season crops to develop bitter flavors or to go rapidly to seed (“bolt”).
Sowing Cool Season Crops in Late Summer
Cool-season vegetables can also be planted in late summer, for fall harvest. Aim to sow your summer seeds so that plants will start to mature when the weather cools off in the fall. Many cool-season vegetables can withstand a light frost. In some cases, such as Kale & Brussel Sprouts, the flavor improves after a frost!
Direct sow cold season veggies because the seeds can germinate in cooler weather.
Warm Season Vegetables
Warm-season vegetables cannot germinate in colder temps, so you usually start these indoors.
These crops require daytime temperatures between 65° and 95° F. Since they don’t tolerate cold soil temperatures and they usually take longer than our average growing season to go from seed to edible, you’ll typically start seeds indoors. Then, you will transplant them to the garden when the air and soil temperature are more appropriate.
Examples of warm-season vegetables for Wisconsin:
Start warm season veggies indoors because the seeds cannot germinate in cooler weather.