Extension News

Cool Season Gardening


Note to media editors: This is the Garden Column for use during the week beginning April 10.


By Cindy Haynes
Extension Horticulturist
Iowa State University

April is the time to start planting. Yes, planting! Believe it or not - there are several cool-season crops that do best when planted in April in Iowa. Below are a few questions novice gardeners often have about cool-season crops.

What is a cool season crop?
A cool-season crop prefers the cooler weather of spring. Some common examples are lettuce, spinach, radish, beets, carrots, peas, broccoli, cauliflower, and cabbage.

When, in April, are cool season crops planted in Iowa?
Central Iowa gardeners normally plant their cool season crops in mid April. Southern Iowa gardeners plant a week earlier and northern Iowa gardeners usually wait until late April for planting. Because cool season crops are planted so early, they are usually harvested before the summer heat of late July and early August.

Where are cool season crops planted?
Any sunny site with fertile, well-drained soil is suitable for a vegetable garden and cool season crops. Locate the garden as close to the house as possible while maintaining full sun. Close proximity will make it easier to see what maintenance tasks are needed. It will also keep the garden close to a water source when needed.

How are cool-season crops sold and planted?
Some cool season crops like lettuce, spinach, beets, peas, radish, carrots, and kale are directly seeded into the garden. They are sowed thickly in shallow rows and thinned later. Over-sowing is used because germination this time of year can be dependent on the weather. Ideally, the frequent (but light) showers of April assist in germination. Thinning, or removal of excess seedlings, allows proper spacing of the remaining plants and promotes full development. Peas are often sowed near a trellis or fence or some form of support. Many pea cultivars have a vining or sprawling habit; therefore they should be to some form of support to maximize space in the garden and make harvesting easier.

Transplants – or young plants – are used for cabbage, cauliflower, and broccoli. Seeds of these crops are sown indoors several weeks prior to planting. Many garden centers offer these transplants for sale to gardeners in April. Transplants should be acclimated for a few days to outdoor conditions prior to planting.

 While seed and plants of onion are sold, many gardeners will buy sets – or small, immature bulbs - for planting directly in the garden. Onion sets are sold simply as yellow, white, or red while seeds and young onion plants usually have a cultivar name. Potatoes are truly unique. They are sold as seed pieces, even though they are not seed. Small potato tubers or sections of larger tubers are sold to start new plants. These pieces are buried 3-4 inches and may take a couple of weeks to emerge in spring. As the potatoes continue to grow, gardeners will often mound extra soil around the base of the plant to create a small hill. This extra soil will protect the developing tubers from light and prevent them from turning green.

Why plant cool-season crops?
There are a couple of good reasons to grow cool-season crops. First, they are relatively easy to grow. As with any crop, there are a few particular maintenance chores that keep each species productive – but these tasks can be researched and performed with little effort and money. A challenge when growing some cool-season crops is keeping the rabbits away. Gardeners are strongly encouraged to set up fencing around cool season crops like spinach, lettuce, carrots, etc. to prevent rabbit entry into the garden.

A second reason to plant cool season crops is they are ready to harvest before warm season crops like tomatoes. This means that not only are you enjoying the “rewards of gardening” early in the growing season, but that space in the garden can be used for another planting. A second planting of lettuce spinach, carrots, beets, and radish may be made in late July for harvesting in fall. The ability to grow multiple crops in the garden makes efficient use of garden space.

Growing a few cool-season crops is also a great idea for those “impatient gardeners” like myself that are ready to get into the garden. I hope we just had the last snow for the season and that planting my cool season garden is not delayed…much.


Contacts :

Cindy Haynes, Horticulture, (515) 294-4006, chaynes@iastate.edu

Del Marks, Extension Communications and External Relations, (515) 294-9807, delmarks@iastate.edu

A high-resolution photo of a broccoli plant is available for use with this week's column:  broccoli.jpg [400 Kb]