No, it's not October too late to plant coral bells in most parts of the country. You just need at least six weeks before your first hard frost so the roots can grab hold of the soil. If you can still dig in your garden and the ground isn't frozen, your coral bells have a good chance of making it through their first winter.
Fall planting coral bells works well because the cool air and warm soil create perfect root growing conditions. I planted a batch of twelve coral bells in early October two years ago in my Zone 6 garden. Every single one came back the following spring with strong new growth. The key was spreading 3 inches of mulch around each plant right after I put it in the ground. That mulch kept the soil warm longer and gave the roots extra time to grow before the freeze hit.
Your coral bells need 4 to 6 weeks of soil temps above 45°F (7°C) to grow enough roots to hold the crown in place through winter. Without that root growth, the freeze-thaw cycles of winter push the plant right out of the ground. This is called frost heaving and it kills more fall-planted coral bells than the cold itself. A soil thermometer costs a few dollars at any garden center and tells you if your ground is still warm enough for planting.
I also tried an October planting in my friend's Zone 5 garden up in New Hampshire. We put six coral bells in the ground on October 3rd and mulched them that same afternoon. Four of the six made it through winter. The two we lost were in a low spot where water collected, and they heaved out of the soil by February. That taught me that drainage matters even more in late fall plantings because wet soil freezes harder and heaves faster.
Prep your planting site before you put the coral bells in the ground. Dig the hole twice as wide as the root ball and mix in a handful of compost. Set the crown right at soil level so it's not buried or sticking up above the dirt. Water the plant well and then spread 2 to 3 inches of mulch around the base right away. Keep the mulch half an inch from the crown to prevent rot at the base.
Check your new plants for frost heaving every two weeks through the winter. If you see a crown poking up above the soil, press it back down and add a bit more mulch. This five-minute check can save a plant that would otherwise die by spring. If you missed the October window, knowing when to plant heuchera in spring is just as important. Wait until your soil hits 45°F (7°C) in late March or April and your coral bells will take off fast with the warming days ahead of them.
Read the full article: Coral Bells: How to Grow and Care Guide
