Why does your neighbor's hydrangea look like a magazine cover while yours sulks? Three times out of four, the answer is below your feet. The soils across Lake Forest, Lake Bluff and the broader North Shore are some of the trickiest we work in — beautiful, ancient, and unforgiving if you fight them.
What's actually under there
Most of Lake County sits on glacial till from the last ice age — a heavy, mineral-rich clay laid down roughly 14,000 years ago by the receding Wisconsin glaciation. In Lake Forest specifically, you'll typically find a thin layer of dark prairie loam (10–18 inches) sitting directly on top of dense, slow-draining clay subsoil.
This sounds bad. It's not. Glacial clay holds nutrients beautifully — it's why the Midwest grows corn. The problem is drainage and root penetration, not fertility.
Three soil types we see most often
1. Morley silt loam (the western corridor)
Deep, well-drained on the surface, clay subsoil starting around 18 inches. This is the soil under most of Mundelein, western Libertyville, and parts of Vernon Hills. Forgiving for almost anything if you respect the subsoil.
2. Beecher silt loam (central Lake County)
Heavier, slower draining, clay closer to the surface (often within 12 inches). Common across central Libertyville, much of Mundelein, and lower-lying Lake Forest neighborhoods. Plant clay-tolerant species and amend generously.
3. Lake-bluff sandy loam (within a mile of Lake Michigan)
Lighter, faster-draining, often acidic. The Sheridan Road and Green Bay Road corridors. Wonderful for blueberries, rhododendrons and hollies; needs more frequent watering for thirsty perennials.
How we work with it (not against it)
Mound, don't dig out
The classic mistake is to dig a deep hole in clay, fill it with bagged garden soil, and plant. You've created a bathtub. Water flows in, has nowhere to go, and the plant rots. Instead, we plant slightly above grade and mound generously around the rootball.
Amend wide, not deep
For a new bed, we till in 3–4 inches of compost over the entire footprint, not just the planting holes. This raises the bed slightly and improves drainage across the whole root zone.
Choose plants that evolved here
Native prairie plants — coneflowers, little bluestem, butterfly weed, baptisia — descended from species that thrived in exactly this clay. They have deep tap roots that punch through the subsoil and bring up nutrients.
Skip the pH panic
Most North Shore soils are mildly alkaline (pH 7.0–7.6). For 95% of plants this is perfectly fine. Don't waste money trying to acidify the whole property — just choose acid-loving plants for one dedicated bed and amend that one heavily with pine fines and elemental sulfur.
The biggest favor you can do your garden is a $25 soil test from the University of Illinois Extension before you spend a dollar on plants. We bring tube samplers to every site visit.
What about that sulking hydrangea?
If your established hydrangea looks tired, the cause is almost always one of three things: not enough water in late summer, planted too deep eight years ago, or buried under five layers of accumulated bark mulch. Pull the mulch back to the original soil line, water deeply twice a week in August, and give it one season. They're tougher than they look.
If you'd like us to come walk your property and tell you what's underneath, that's exactly what a complimentary site visit is for. Schedule one here.