Come on Growing Season!

For wetland professionals, the beginning of the growing season means that we can once again feel comfortable doing wetland delineations. I've been asked many times how one determines when exactly is this?

Our first stop to figuring this out is the US Army Corps of Engineers delineation manual and its applicable supplement (USACE 1987, Midwest Supplement 2010):

Growing season. In the Midwest Region, growing season dates are determined through onsite observations of the following indicators of biological activity in a given year: (1) above-ground growth and development of vascular plants, and/or (2) soil temperature (see Chapter 4 for details). If onsite data gathering is not practical, growing season dates may be approximated by using WETS tables available from the NRCS National Water and Climate Center to determine the median dates of 28 °F (−2.2 °C) air temperatures in spring and fall based on long-term records gathered at the nearest appropriate National Weather Service meteorological station.

In our Chicago area, the average last day of frost is April 15 and the average first day of frost is October 15. So those dates have been used to denote the actual growing season. But not so fast...Our delineations require a floristic quality assessment (FQA) and the Lake Co. Watershed Development Ordinance requires those to be conducted after May 15 and before October 1. So technically, one could do a wetland delineation before May 15th, but will likely have to revisit the site during the growing season to take vegetation data.

So this year has been pretty warm...soils may not be warm enough yet but vegetation is GROWING. We are really close, come on GS.

U. S. Army Corps of Engineers. 2010. Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Midwest Region (Version 2.0), ed. J. S. Wakeley, R. W. Lichvar, and C. V. Noble. ERDC/EL TR-10-16. Vicksburg, MS: U.S. Army Engineer Research and Development Center.