What's up with the Upper Valley clay belt?

If you've ever spent any time digging around the Upper Valley area (and believe us, we have!), you might have noticed something about the soil, especially around the Norwich/Hanover area... it's so full of clay that you could probably make a pot out of it! But have you ever wondered why? Today's post is going to take a deep dive through the past to investigate our soils.

This map shows portions of Hanover and Lebanon- blue areas show deposits from Lake Hitchcock.

The story begins about 15,000-16,000 years ago. A giant glacial lake called Lake Hitchcock spread across much of the region, spanning from the middle of Connecticut up to St. Johnsbury, VT. As the lake sat there, sediment slowly settled out of the water, creating layers of clay/silt that was deposited during the winter and silt/sand that was deposited during the summer when melt water brought additional sediment into the lake. This process occurred for around 3,000 years until the lake drained... which left a buildup of up to 250 ft of sediment! These deposits developed into the clayey soils that we have today.

So what are clay soils exactly?

Soils are made up of multiple particle sizes, the smallest of which is clay, coming in at less than 2 microns, which is very very small. For context, this is 10x smaller than the finest human hair. Any soil that has a clay content greater than 30% is considered relatively high clay content. Clay soil has some special properties: due to its small size, water doesn't move through it easily; once saturated it takes a long time to dry out; air doesn't move easily through saturated soil; it is easily compacted when wet; and although it retains nutrients well, they may be bound up and not available to plants.

Can plants thrive in clay soil?

Yes! There are many plants that are adapted to clay soils. They need to be able to tolerate waterlogging, poor aeration, and/or compaction. Plants that have deep, strong roots can break through compacted soils and may be a good choice if your soil isn't consistently wet. These include species such as switchgrass (Panicum virgatum), Coneflower (Echinacea spp.), and Black-eyed Susans (Rudbeckia spp.).

Plants with fiberous roots can spread horizontally, stabilizing soil and reducing compaction. These might include Creeping Phlox (Phlox sublata), Hostas (Hosta spp.), and Stonecrop (Sedum spp.). Wetland plants, such as Cardinal Flower (Lobelia cardinalis), Joe Pye Weed (Eutrochium purpureum), and Swamp Milkweed (Asclepias incarnata), have evolved to deal with inundation, so they could also be a great choice for a clay soil.