| It’s cold—the plants in the greenhouse are | | | | But tougher vegetation evolved in colder climates has |
| thriving—their glossy leaves in stark contrast to | | | | adapted. Some savvy plants move water from within |
| the view beyond the glass. Outside, brown and gray | | | | their cells to between the cells, where there is more |
| bare stems and drooping evergreen leaves are | | | | room for expansion. All excess water goes from the |
| rimmed in ice. Have you ever wondered—what | | | | roots into the surrounding soil. What’s left behind |
| mechanisms make those outdoor plants survive | | | | has higher concentrations of sugars that act like |
| beyond the greenhouse walls? And why is one plant | | | | antifreeze. Colder zone plants produce more of this |
| designated a Zone 7 and another a Zone 3? | | | | antifreeze protection. Conifers have quite a bit. |
| I checked out these questions and learned that one | | | | Greenhouse tropicals have none. |
| of the main factors for cold survival is how plants | | | | How Gardeners Can Help |
| handle water. Then I called Ross Penhallagon, at the | | | | When plants are in this self-induced dry state, |
| Oregon State University Extension Service office. He | | | | protection from wind can be a plus. However, |
| confirmed what I had discovered. | | | | it’s common gardening advice to water plants |
| Ross told me that the first aspect of cold survival is | | | | well before a frost. Maybe that’s true in parts of |
| acclimation. Plants do best when they get several | | | | the country where freezes are seldom |
| weeks of exposure to near-freezing temperatures | | | | expected—orange groves are watered overhead |
| before a frost. This signals them to prepare. | | | | so forming ice protects the plants from lower than |
| Dry Strategies Work | | | | 32 degree temperatures. But unless the ground is |
| One preparation method? Plants purposely put | | | | bone dry, Ross confirmed for me that watering the |
| themselves in a state of desiccation. They remove | | | | soil before a frost may do more harm than good. |
| excess water from their leaves—in the case of | | | | After all, the plants are doing their best to get rid of |
| evergreens like rhododendrons and conifers—or | | | | water, right? |
| from buds and stems. It’s similar to draining | | | | So when you’re in your cozy greenhouse, raise |
| exposed pipes so that ice won’t expand and | | | | your watering can in salute to those denizens beyond |
| burst them. In plants, the forming ice plays havoc | | | | the glass that display nifty strategies to survive the |
| with unprotected cellular structures—why tomato | | | | cold. |
| vines are mush after a first frost. | | | | |