Russel Allen Garden Day
Cool season gardening extends the growing season for gardeners

[March 18, 2025]    At the Russel Allen Garden Day on March 15th, University of Illinois Extension Horticulture Educator Jennifer Fishburn led a discussion on cool weather gardening.

Fishburn noted to the audience that there are many gardeners who enjoy the mid-season vegetables they grow such as green beans, cucumbers, tomatoes and more. However, many gardeners are a bit intimidated about gardening in cooler temperatures. There is an uncertainty about planting in the colder climate that gives gardeners pause because they have the mid set that plants need warm temperatures to grow and thrive.

However, some vegetables grow better and even have a better taste after harvest when grown in those cooler conditions.

Fishburn talked briefly about different styles of growing, from the traditional garden to using fabric pots, raised beds and “salad tables.” She dwelt a bit longer on salad tables explaining they can be built waste high to save on time on the knees and stress on the back. The tables are good for shallow root system crops such as lettuce and spinach, thus the name salad table. They can also be a good place for radishes.

The tables have a fine mesh wire bottom for drainage and the air that passed underneath the table serves as a natural pruner for roots.

She also talked about the “soil” to use in raised beds and container gardens and said it was best to use a soilless potting mix. Later in the session she was asked to define a soilless mix. She said the gist of it is not to go out to the garden or a field and scoop up soil for the beds. She said it would cause too much compaction and hinder the growth of the roots and plants. She said that Master Gardeners do not recommend specific products, but she uses a lot of the Miracle Grow soilless potting mix. Choices are to purchase a premixed product, or to make your own using ingredients such as vermiculite, Spaghnum Peat Moss, organic matter from the compost pile, and shredded leaves. She said the point is to use material that will not compress, but rather will stay light and loose.

She also issued one word of warning concerning use of manure. She said that cow or horse manure from the farm should be used with caution. Fishburn explained that for the garden, the manure product should be well aged or cured. It should look more like soil than waste. She told guests that a good rule of thumb would be if you don’t want it on your hands, you don’t want it on your garden. The reason for the caution, she said that manure that is not well aged carries the opportunity for EColi, and that putting it on the garden can contaminate the vegetables.

Fishburn said that one good hint is to buy all your garden seed early in the season, even if it is a fall weather seed. The reason being that most retailers will remove their seed displays in the early summer, so by summer’s end, it is impossible to find seeds for those fall crops.

She also shared that there are many spring seeds that can be planted in the very near future such as radish, carrot, and onion. She said for summer seeding, the best rule of thumb is not to plant anything that needs warmth of soil and air temperature for proper germination before Mother’s Day.

Radishes, carrots, lettuce, spinach, and peas can be planted after the last freeze but before the soils are warmer.

For fall crops, a good plan is to look at the predicted frost date in the area, then count backward according to the seed packets recommended days to maturity. She added that some plants will actually taste better if harvested after that first frost.

Fishburn went through a PowerPoint presentation talking about several vegetables that can be grown in the early spring or late fall. She offered guidance on some of the issues that can occur.

She talked about growing carrots and said that they needed loose soil. One warning she gave was that they have a long germination date, so don’t loose patience waiting on them to sprout. She also warned gardeners to be aware of raised shoulders on the carrots. The portion that sticks above the ground is not good to each, so soil should be pulled up against the plants when they are growing.

She said that carrots can grow into the late fall. The cooler temperatures also increase the sweetness of the carrot, making it more flavorful.

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Another good product for fall harvest in Cauliflower. She did warn that gardeners should be alert to the cauliflower heads. Many times, the plant will naturally grow a wrapper around the head protecting the vegetable from sunlight. She said if that wrapper doesn’t come naturally, gardeners should pull outer leaves up around the head and secure them with ties or clips.

Fishburn also talked about cabbage. She said to watch the heads and when they are the right size and the leaves are nice and tight the heads can be harvested. She warned that if gardeners have heads ready to harvest and rain is predicted, to get out there and do that harvest because once the heads are tight, rain will cause them to split.

She added that when harvesting, if one cuts the head off high on the stalk, additional cabbages may grow.

Fishburn addressed growing several other cool to cold weather vegetables such as Kohlrabi, Kale, Turnips, peas and potatoes.

A final bit of advice that she offered was that gardeners should pay head to the growing instructions on seed packets. She said it was the best guide to when to and how to plant various vegetables throughout the season.

At the end of the session, she opened the floor for questions and comments. Guests shared questions about soil compaction and organic matter. Fishburn said a good soil test will not just give nutrient levels but will also tell gardeners how much organic matter is in their soils.

Another guest said that she plants radishes and plants together. She said radishes harvest earlier than carrots, but having that fellow root crop helps break up the soil for the carrot growth.

Fishburn also shared a couple of websites gardeners can utilize and added that the guest packets handed out at registration has additional websites listed.

[Nila Smith]

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