Thursday, February 3, 2011

Fluxuating Temperatures Wreak Havoc in the Garden by Heather Hodgin

Heather Hodgin, Guest Blogger
A Garden Affair
Endless Summer Hydrangea
Baby its cold outside, and you’re not kidding. According to the National Weather Service, the last time that Denver had a high of minus 1 or lower was January 12th and 13th in 1997. Maybe like me, when you heard the prediction for the metro area sub zero temperatures, your thoughts flew to your (insert name of perfectly lovely, but only semi-hardy plant here). With dread, you worried what that naked spot in your garden would look like next year and fell into a deep pit of despair.

When we talk about hardiness in plants, we are usually referring to the USDA hardiness zone map. To check the map out for yourself, visit The Front Range is generally considered to be Zone 5. Most plants have an associated number on their label that can help you to determine if your plant of choice will successfully over winter here.

 Like most of us, us, you may have been overcome by the draw of plants that might not be as hardy here, such as Hydrangea ‘Endless Summer’ (Hydrangea macrophylla), Swamp Mallow (Hibiscus moscheuots), and the stunning Arizona Cypress (Cupressus arizonica).  You may have put to the back of your mind the knowledge that in a harsh winter they might not make it. The plant palette of adventurous gardeners may indeed be at risk due to these dramatic temperatures. Next Spring, if you find yourself wary of zone crossing, check out these websites for perennial plants that will generally do well here:

What can you do? You may have missed the opportunity to take action this time, but here are a couple of things to try when freakishly cold temperatures loom:

*Winter Watering* Most freezing damage occurs through desiccation. By maintaining a good winter watering schedule, you can help to mitigate freeze damage.
*Under Cover* Protect tender plants by placing an inverted bucket or a thick mulch layer over them when freeze risk peaks. Be sure to remove, once freeze risk has passed.
*Microclimate* There are many great tips for creating microclimates around your favorite plants. For more information on this topic, visit:

The good new is plants are the original rebels. Horticultural rules are meant to be broken. Don’t give up hope, there’s a chance your bountifully blooming butterfly bush will live to see the sunshine again. Give it some time and patience this summer, and be sure to remove portions of the plants that have succumbed to cold. You never know, it may be your garden’s best year yet!

The 2003 US National Arboretum "Web Version" of the USDA Plant Hardiness Zone Map USDA Miscellaneous Publication No. 1475, Issued January 1990