Often called the "gateway drug" into gardening, there are few plants that pull someone into gardening like tomatoes do. In Chicago, I've noticed that people who would never call themselves gardeners always seem to make room for one or two tomato plants in their yards, decks, porches and patios. The trick with growing tomatoes here is knowing when to plant tomatoes in Chicago.
Like many gardeners, I diligently start my tomato plants from seed indoors in February to pamper along until the average last frost date for the Chicago area which is somewhere around May 15th every year. On Mother's Day weekend, public gardens, garden clubs, community gardens and garden centers start selling all manner of plants to kick off spring. The alluring tomato being the most popular at this time.
But even though the threat of frost has passed by this time, May is still too early to plant tomatoes in Chicago. Tomatoes shouldn't be planted in the ground until the soil temperature are consistently between 55-60 degrees. You'll need a soil thermometer to get the best accurate reading. Planting tomatoes when the soil temperatures are still cool will result in sullen tomatoes. They'll sit and do nothing at the least and at worst they may rot if we experience is a cool and wet spring and summer.
This year we have had one of those wet and cold starts to summer. My tomatoes are finally starting to produce fruit in the middle of July. These tomatoes have been planted in my self-watering planters in the porch garden in full sun since the end of May and the fruits are barely half the size of golf balls.
Earlier in July, I made a run to a garden center in the suburbs of Chicago with a friend who was just getting her garden planted. On a lark I brought back a tomato plant and planted it in a container. That tomato plant is starting to set fruit and outpace the tomatoes I planted at the end of may and I'll get a decent harvest out of that plant judging by the explosion of tomato flowers and little fruits starting to set. This year, the weather here is just starting to hit that "sweet spot" for growing tomatoes. It's annoying for me, because I've had my tomatoes planted for months, but it's a blessing to gardeners who are wondering if July is too late to plant tomatoes in Chicago.
Obviously, it is too late to start tomatoes from seed here, but you can still buy tomato plants that have been sitting around a garden center. To account for the shorter growing time by planting late, I recommend picking up indeterminate tomato varieties rather than determinate tomatoes.
Determinate tomato varieties are also known as "bush" tomatoes. These are compact tomatoes and grow too about 4 feet. These tomatoes stop producing fruits when they set fruit on the terminal bugs. Then the tomatoes will all ripen around the same time over about two weeks.
Indeterminate tomatoes are different in regards to determinate tomatoes in that they are vines and will not stop producing tomatoes until they are killed by a freeze. Indeterminate tomatoes are "vining" tomatoes and usually grow between 6-10 feet and will produce tomatoes until the cold comes. Chicago's first freeze usually happens between October 11 and November 6th.
If you're wondering if you can plant tomatoes in July in Chicago, by all means go ahead and plant some bush tomatoes now. Like I said, my bush tomatoes are just barely getting started and the plant I bought a couple of weeks ago is starting to pick up steam. But your best bet if you're looking for a tomato harvest this year is to go with indeterminate varieties.
There's something oddly satisfying about going out into the garden and harvesting a handful--as small as it may be--of some cherry tomatoes in late October.