City of Oak Park issued the following announcement on Apr 7.
Yard waste and brush collection has begun!!! Leave them out for collection on your regularly scheduled waste days.
YARD WASTE: Yard waste includes grass clippings, leaves, small twigs (¼ inch in diameter or less), shrub trimmings, weeds, and general yard and garden waste materials. Separate yard waste from regular refuse and set out for pick up in either a 30-gallon brown paper kraft bag or a refuse can with an Oak Park Yard Waste Recycling decal attached.
LARGE BRANCHES/BRUSH: Branches less than 6 inches in diameter and between 4 feet and 8 feet in length may be stacked and set out at the curb for pickup by the chipper truck. Branches should be stacked with the cut ends facing the same direction. The following materials, however, are NOT ALLOWED for curbside brush pickup: materials produced by commercial landscapers and tree trimmers and materials produced from tree removal projects (including stumps, logs, and roots removed by the resident or a private firm.)
SMALL BRANCHES/BRUSH: Branches and woody materials that are less than 1½ inches in diameter can also be cut into 4 to 4½ foot lengths, bundled with twine and placed at the curb to be collected as trash. (40 lb. weight limit per bundle).
Original source can be found here.