When can i start planting in chicago?

1st of April. Start seeds on top of refrigerator. Nice warm spot. In trays. Once up move to windows. May in the normal dry spell before rain starts. This varies every year the weeks. Till and fertilize. Once a oak trees leaves are the size of a mouses ear. Or larger. Wait 1 week and plant. Frost danger should be over. Or if planting seeds. When a oak trees leaf is the size of a mouses ear plant your seed. Learned that from my Grandfather and it has held true. Unless you wish larger plants. In pots then move date back in 2 week intervals for size. I am talking about the small cups. Large pot larger plant. More time. I will start the 2nd week of Feb with some plants indoors. But I have a green house to move them to. In central IL. And you are 2 weeks behind me in Chicago. That is for large plants Tomatoes with blooms and a occasional tomato on them when planted. And 18 inch pepper plants tall. I start 2nd week of Feb. You would do the first day of March. But I always have a good serving of garden ripe tomato's for the 4th of July. While other folk naw on those store bought ones.

Your last frost date is end of April...start seeds indoors mid March. Hope your big window is South facing, any other direction will not get enough sun for strong seedlings...then you'll need a couple of weeks to harden them off before planting outside.

April, or possibly late March.