I'm all for fellow combatants fighting the good fight for local food, but I have a fatally low tolerance for seasonality guides that are off. For whatever reason, it makes me especially pissy when you send someone off to the market now looking for plums (plums are a fall fruit). I find it highly unlikely also that any area farmer's market will have horseradish now. I only like to show off a bit, but I really do believe that when it comes to knowing what's in season, I've got the best guide around to what's in season for Chicago area locavores.
The Chicago Locavore site also published a calender. I am not gonna edit it line by line, but in general, I find it, like most seasonality guides, to be quite off for Chicago farmer's markets. Some glaring errors: grapes in June; don't expect grapes until late September; kale in the heat of the summer, when kale's a cool weather crop; no turnips now when the markets are awash with them. Etc.
Seasonality guides tend to be off these days also because they are not recognizing indoor farming and winter markets, or are they? The calender noted above has some crops listed as in season in odd months like salsify for January--granted I have never seen a salsify plant in a local market, what do they mean by January. Is it a plant growing in January or a storage plant. I am not sure if the calender in general is referring to crops from storage, for instance when it covers potatoes in January or sunchokes in February it means storage right? but if it does, why are apples not listed for the winter months as keeper apples are surely around all winter. Likewise, the calender does not cover greenhouse crops that one can find through CSAs or winter markets. The shopper with access to those, or even a shopper who visits Cassie's Green Grocer, will find stuff in months not shown on this calender. Here's what was in season in April, March and February.
One final thought. I think a static calender, regardless of how good its sources are, is an imperfect vehicle for knowing what's out there. The problem is that seasonality changes each year based on weather and other factors. In general, our crops are quite behind this year because of the cold spring. In addition, the heavy rains have wrecked havoc on fields. A farmer today was telling me how her watermelons were destroyed in heavy rains and needed re-planting. When I am writing about seasonality, I am trying to base it on what's actually in season, on what I see at farmer's markets and what farmers and other vendors tell me. This means I may not be able to predict what you will totally see in a few months, but it will mean I should be able to predict what you'll see now.