Cheat Your Climate
There are ways to grow plants you "can't."
As gardeners, we can be romantic, irrational and headstrong. If we lose our heads to a certain plant, there's no stopping us. It might be a plant we fell in love with while on a Hawaiian vacation or the pages of a gardening book. We have to have it! And the quest is on...to get the plant and grow it well.
Oftentimes—despite the naysayers in our lives—when there's a will, there's a way. You can succeed in growing that tidy boxwood hedge, fiery-flowered ginger plant or exotic fruit tree, even in the "wrong" climate. But you just might have to cheat...
Rationalizing and Tricks
Your garden is in a certain USDA Plant Hardiness Zone. By all right, any plant not cold-hardy in your area will perish over winter. So you rationalize, "I'll treat my boxwoods, tender rosemary bushes and blue perennial salvias like annuals. I'll buy new ones each year. Expensive, yes. But worth it."
While this is true and possible for some plants, it isn't for all. Some tender and tropical beauties require a long, warm season and will never reach maturity or produce the flowers or fruits you dream of in a shorter, colder growing season.
A way around this is to start plants indoors early in the year, even if you have to provide artificial warmth and light from a fluorescent "grow light" or propagation table like the ones greenhouse growers use. If the plant prospers, you will be able to move that beautiful ginger outside when summer's mild temperatures arrive.
Of course, when colder temperatures return in fall, you will have to haul it back indoors to a nonfreezing spot and reduce water and light in order to keep it in a dormant state until spring returns (ah, what we do for those we love!).
Alternatively, you can buy a larger, more mature (and, consequently, more expensive) plant and have it shipped to you when it's safe to put it outdoors in your climate. Be sure to make your plan clear to the nursery when you place your order.
No matter what zone your garden is in, every yard is unique, and you ought to be able to push the limits a bit. In other words, even if you are in USDA Zone 6, you may succeed with plants touted as Zone 7, 8 or higher—the reverse goes as well, cold-climate plants in hotter zones. How? Pamper and protect them...but first, identify and capitalize on microclimates in your yard.
What is a "microclimate"? It's a small portion or pocket in a landscape whose conditions are a little different. Walk around your yard and assess—you may discover a few variations, even within several feet of one another. A south-facing site is warmer and can host plants that would perish in the cooler soil and air and additional shade of, say, the east or north side of your house. Partially or fully shaded spots are also slower to melt any ice and snow, to drain away rain and to warm up generally. They can, however, experience less dramatic temperature fluctuations and offer somewhat higher humidity. They can be good spots for a southern gardener to try a traditionally northern plant.
There's more. Exposed hills and embankments are drier and warmer, while hollows and valleys, even minor ones, collect moisture and retain cold. Rocky areas or rock gardens offer sanctuaries of warmth and shelter for vulnerable, smaller-size plants. Fences, walls, pavement and stone or brick patios also sport milder temperatures in their immediate vicinity. They absorb the sun's warmth by day and radiate it back at night. So these are obvious areas to try borderline-hardy plants. (A word of warning: Such spots can become too warm, causing potted plants in particular to dry out quickly, so keep an eye out and water as needed.)
Even when you place a borderline-hardy plant in the warmest microclimate in your yard, this might not be enough to help it thrive. Here are a few ideas for providing an extra boost of protection:
Gradual adjustment: Create a period of transition when the plant first arrives...bring it back indoors or cover or shield it on chilly days and at night (with a box or a tent of plastic or burlap or an old blanket); expose it to more sun and heat over a period of a few days or weeks until it settles in.
Apply mulch: Organic mulches keep soil cooler in summer and moderate temperature fluctuations. If you wish to avoid too much moisture—say, if you are growing a special cactus—use gravel.
Raised beds and containers: These warm faster in spring and have better drainage. Plus, you can provide specialized soil that garden soil may not offer.
Raise local humidity: Sometimes it isn't just warmer temperatures that the object of your affection requires; it's also higher humidity (in other words, tropical conditions). If you notice the edges of the leaves browning or flower buds drying out before unfurling, this could be the problem. Luckily, it's easily solved with the following techniques. Spritz the entire plant every day or every few days with water. Put the pot in a tray or dish of pebbles, and either put water in or let water drain in. Place the plant in a sheltered spot so drafts and winds are less likely to dry it out. Grouping plants together can also boost humidity.
Remember, rules are made to be broken. Nature is more flexible, and plants more adaptable, than most gardening books would have you believe. Give any plant you desire extra TLC, and it just may reward your efforts by bucking your climate's limitations and prospering.