Effective Winter Protection for Hydrangeas: Capturing Ground Heat with Black Plastic Covers

Hydrangeas are beautiful in summer but flowering can be damaged by cold winters. Particularly damaging: a winter warm spell followed by a hard freeze. I've seen bushes wrapped like lollipops with sheets and quilts flung over shrubs. Neither helps much beyond psychological comfort. The plant won't benefit from a pink chenille bedspread on its branches.

The best protection captures the earth's scant heat under an impermeable cover. Most use plastic; a big cardboard box might suffice.

I use black (not clear) plastic for cold emergencies. Clear plastic creates a "greenhouse effect" whenever sun shines—even on frigid days—requiring removal on bright days. Black reflects sunlight; air temperature underneath seldom rises more than a few degrees. I can leave it for several days without harm. Anchor edges firmly (firewood, earth, bricks, rocks).

Option: replace common hydrangeas with reblooming varieties:

• 'Blushing Bride' – white with blue/pink tints; from Endless Summer®
• 'David Ramsey' – hardy to zone 4; compact to 4 ft
• 'Decatur Blue' – exceptional hardiness for northern gardeners
• Endless Summer® 'Bailmer' – first remontant introduced
• 'Mini Penny' – from 'Penny Mac'; very compact
• 'Oak Hill' – similar to Endless Summer
• 'Penny Mac' – from Penny McHenry (founder, American Hydrangea Society)
• 'Forever & Ever' – hardy to Zone 4, compact 3 ft tall/wide
• 'Forever & Ever Double Pink' – compact for small gardens/containers
• 'Forever & Ever Red' – first red-flowering, compact