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CHAPTER 1

Gardening with Tenders

Tender perennials are an amazingly adaptable and diverse group of plants.

Because they've arrived in our gardens from so many different corners of the world, tenders introduce wonderful complexities and variations — of texture, bold color, and sheer drama. Caring for them is surprisingly simple when you consider all that they offer the gardener. The diversity of tender perennials lends them to a marvelous variety of uses — these are plants that range from delicate twiners to those that make bold statements, exceeding 10 or 12 feet in height. We suggest that you use your imagination and take your cues from the plants themselves.

What Is a Tender Perennial?

Put simply, a tender perennial is a plant that, though hardy in its original habitat, will not survive the winter outdoors in the climate of the gardener. Tender perennials in one zone may be perfectly hardy in a different location. But for gardeners in any location other than a truly tropical one, chances are that some plants are tender perennials.

Some tender perennials are, in fact, tropical. But many others come from relatively moderate climates where winters just don't get as cold or, perhaps, as wet as they do where you live. From the temperate climates of the Mediterranean come marvelous gray-leaved plants — like helichrysum and santolina — that require dryness in winter. From New Zealand there are trees and shrubs, even grasses and sedges like Carex comans, that make delightful indoor plants. Both South Africa and the South American continent have wonderful plants that simply won't survive outside year-round in other locales, but which (we think you'll agree) can enrich your gardening experience tremendously.

Will tropical and semitropical plants look out of place in your garden? We've spoken with gardeners who worried that this might be the case. We suggest you experiment — you might be surprised. After all, the geographic origins of most hardy perennials are already quite diverse. In our experience, the visual characteristics of plants — their form, texture, and color — are far more important in creating a visually unified and satisfying garden picture.

Location Makes a Difference

The word tender suggests that these plants will not survive frost. But many tender perennials tolerate light or sometimes even heavy frosts. They are called tender in a particular place simply because they are unlikely to survive an entire winter in that climate. This distinction may be confusing, but it really needn't be. Even hardy plants respond to freezing temperatures in different ways. Any plant's tolerance of frost and cold is influenced by a variety of factors: hydration, stress, and the plant's recent history. In general, only plants that originate where frost is a common occurrence will withstand it consistently, and even this is not always the case.

Most gardeners have noticed that the ubiquitous hosta, though reliable and quite hardy in a Zone 5 garden, is prone to react extremely to late-spring frosts. In years when these occur, hostas will generally grow an entirely new set of leaves to replace those that succumbed. Although a plant's appearance may be affected for the duration of the season, this doesn't mean that it's not hardy. It's just an indication of the structure of hosta leaves and stems, and shows that once they've begun to grow, hostas are sensitive to frost, despite being hardy to much colder temperatures while in a dormant state. It's also an indication that in their Japanese homeland, frosts rarely occur once the plants have leafed out.

Other plants seem unaffected by cold nights. Some salvias, for instance, will continue as before, generally blooming and carrying on as if nothing has happened. This is a reminder that frost does occur in the desert, where salvias originate, and also that although most tender salvias cannot survive the winter in many colder zones, they are well adapted to life in the spring, summer, and fall in those places.

Origins Are Important

Tender perennial plants come from every corner of the world, and — as the hosta and salvia examples illustrate — it is important to consider a plant's origins in order to understand the best conditions for growing and overwintering it. A desert plant will be happiest in sunny, well-drained conditions of low humidity; one from the Amazon may require both protection from the sun and extra humidity, along with warm temperatures.

Having grown tender plants over the years, we find it fascinating to learn more about their origins. Gardening is one of the most tangible ways there is to gain a deeper appreciation and sense of place through interaction with your very specific plot of land. But it is also a wonderful way to travel imaginatively through both time and space — and to contemplate where in the world a particular plant grew before it arrived in your own garden.

Selecting Which Plants to Keep

Most house interiors tend to be warmer and drier than is ideal for many plants in containers. Are you willing to adjust the thermostat down to 55 or 60°F (13 or 15°C)? Will you remember to water your containers once a week? (Don't forget to provide saucers for all the pots.) These are basic but important questions to consider before you start hauling around those heavy pots.

As tempting as it may be to save everything from the summer patio, be realistic about the storage space you have. A smaller number of plants with more space around them will be easier to keep healthy than a jungle of plants crammed into an area that's too small to accommodate them all.

Your available space for plants is an important factor in determining what will be manageable for you. Assuming that you're considering only those plants that have performed well, begin your selection with ones that would be difficult to replace. A plant might be expensive or relatively rare where you live. Perhaps you grew it from seed that took a long time to germinate or was difficult to obtain. Or maybe the plant was given to you by a close friend or relative and has sentimental value. Everyone has his or her own reasons for wanting to keep a particular plant.

Some plants are so inexpensively and readily available that it doesn't make sense to keep them from one season to another. When such a plant is winter blooming, however, or has particularly attractive foliage and form, it may be worth keeping, especially if it is also easy to care for. Cacti, succulents, durantas, and anisodontea, along with many convolvulus and most kalanchoes, fall into this category.

How you define low-maintenance is highly personal and depends quite a bit on the specifics of your space. In a cool sunroom or porch, keeping rosemary happy should be easy. But overwintering the same plant in a warmer, heated living area is guaranteed to be a challenge. In the dry, warm air of most homes, it's easy to miss the early signs that this plant needs to be watered, and serious damage may occur before you notice its distress. In a warm space without good air circulation, conditions will also be ripe for the development of mildew or for the proliferation of pests like aphids. By the same token, keeping a brugmansia healthy in a cool, sunny space might not be so difficult — but try it in a warm room and you'll be inviting an infestation of whiteflies. The decision of what to keep for the winter and where to situate it will be informed by many factors. Give each plant some thought well before you need to take action. Remember that when they're happy, plants have a way of growing, and will, in time, occupy more space than they were originally allotted.

Why Grow Tenders?

"Oh, I grow only hardy plants," we've been informed by more than one gardener. And there are certainly arguments to be made for doing this. In general, despite the occasional winter that decimates much of the perennial garden, planting exclusively hardy plants simplifies gardening activities.

But it does limit your options. Even your grandmother probably grew plants in her garden or on her windowsills that were neither annual nor hardy. If she hung her geraniums in the cellar for the winter or kept a sweet-smelling heliotrope in a pot on a windowsill, she was simply overwintering her tender perennial plants. Many gardeners a century ago were familiar with a far greater variety of plants than most are today. One reason is that European and American gardeners of earlier periods were very curious about the many distant places that were still being opened to the eyes of the Western world by plant collectors. Growing the exotic plants that resulted from expeditions to those lands was a tangible way to share in the latest discoveries.

Save Money

In our own consumer culture, plants are viewed as replaceable commodities. Many gardeners simply rely on garden centers and catalogs to supply them with plant products to fill up their gardens each season. These merchandisers produce only those plants that will provide instant and predictable results, regardless of the skills of the gardener. Overwintering tender perennial plants can be a way to save money and to achieve a measure of independence from commercial marketers at the same time. And saving money by not buying the same plants year after year will extend your gardening budget.

Give and Receive

Tender perennials make great gifts for friends and neighbors. Winter bloomers, such as the stunning white-flowered Convolvulus cneorum, will remind them of you each winter when their buds open. Or if the summer garden is the plant's moment to shine, your friends will remember your kindness at the height of the seasonal spectacle.

Giving away plants is practical, too. It's common wisdom among professional propagators that you never know when you'll need to ask for a piece of something back. What if you forget to water during a critical time or the power goes off during a prolonged cold spell? If your friend still has the plant you shared with her, she'll be more than happy to return the favor.

Learn New Skills

In the process of learning to grow tender perennials, you'll acquire new propagating skills as you maintain original plants and increase your stock. Saving any kind of plant also increases the amount of control you have over the selection of plants you're growing and of those you will perpetuate for the future. You may have more time to notice your plants when they're indoors, too, and there aren't the million distractions of the summer outdoors. You'll learn more about the varying needs of plants, which change with a specific plant's place in its own life cycle as well as with the season.

See Plants at Their Best

Saving and storing tender perennials also gives the plants more than one season to mature. Aside from the brevity of the growing season in a place like Zone 5, where we live, many plants just don't reach their full potential in a single season. Some withhold bloom until their second year, and others simply require time to grow large and impressive. Some plants are actually herbaceous in their first season and woody in the next. The young growth of many tender perennial plants — such as salvias, strobilanthes, and durantas — is soft and herbaceous, turning woodier in time. You'll probably learn more about insects, too, as you monitor your plants and keep them healthy. In their second season, they will be ready to create an altogether different and dramatic effect in the garden.

Fill in the Gaps

Many tender plants bloom during those famous gaps in the hardy-perennial bloom cycle. Tender salvias, daturas, and tibouchinas: these and other plants kick in just when most of the perennial border is giving up the ghost. You may be surprised at how much more interesting the August/September garden is when tender perennials are added to your plantings. Their contributions don't necessarily end with the first frost, either. In the chapters that follow, we will show you how to grow and save your favorite plants, and in many cases, how you can continue to enjoy their beauty even through the coldest months of winter.

Who wouldn't want a room full of sweet-smelling flowering plants to enjoy in the dead of winter? No matter where you live, and no matter what your budget, if you choose carefully and consider realistically the conditions of your living space, you'll be pleasantly surprised by the possibilities of your own indoor winter paradise.

CHAPTER 2

Overwintering Your Plants

With all the various ways to overwinter plants, there's sure to be an option that will work for every gardener.

We hope that by now you're convinced that overwintering your tender perennials is worthwhile. You'll save money when you buy plants next year, because you'll already have several to put out into the garden. Many of these plants will have become much larger — ready to be either impressive specimens in the garden or some of the striking elements of your containers.

Overwintering 101

The key to successfully bringing a plant through the winter indoors is understanding its natural dormancy cycle. Some plants continue to grow during their indoor vacation and thus need a warm, sunny location. Others enter a stage of partial dormancy and are more suited to a spot that's sunny but cool. Some plants go completely dormant and simply need to be properly stored for the winter.

What Kind of Space Do You Have?

Anyone can overwinter tender perennials, but your available facilities will limit and define the possibilities. The options you choose will then depend on how elaborate you want to get and also on your personal preferences.

There are three basic ways to store tender perennials. Each is best suited to certain types of plants. This doesn't mean there is only one way to store each plant, however — just that there may be only one best way.

A Sunny Windowsill

Some tender perennials — many of them tropical plants like begonias and alternantheras — will be perfectly happy on a sunny east-, west-, or south-facing windowsill. Treat these as you would a houseplant, watering and fertilizing on a regular schedule. If you keep the thermostat between 65 and 70°F (18–21°C), the temperature inside your house will remind these plants of winter in the tropics. This may cause their growth rate to slow slightly, but for the most part, the plants will continue to be in active growth. They will need every bit of sunlight you can supply. Lacking sufficient sun, you might keep them happy with a supplemental source of light, like the fluorescent lights that many gardeners use for vegetable seedlings.

A Cool, Bright Spot

Another group of tender perennials benefits from a period of relative dormancy in winter, and would be happiest in a very cool but sunny part of your house, such as an unheated porch or a rarely used bedroom. These plants originate in parts of the world that experience dry, cool winters, such as the high elevations of South Africa and parts of the Mediterranean region. They are happiest in a temperature range between 40 and 50°F (4–10°C), accompanied by bright sunlight. The greatest number of tender perennial plants will find these conditions agreeable.

A Dark Basement or Closet

Some plants prefer the dark and will survive the winter in your basement. Most of these can be classified as corms, bulbs, and tubers. Others, such as cannas, like their darkness on the damp side. Still others, like dahlias, will fare better if the conditions are drier. Certain plants from other groups can survive a period of dormancy in the dark almost as well as they might in bright sunny conditions. Some salvias, brugmansias, bananas (Musa), lemon verbena (Aloysia), Sinningia, and Bouvardia ternifolia can overwinter in the basement just in their pots.

A subset of the bulbs-and-corms group can be left in the pots they grew in all summer or can be transferred into paper bags. Because they will tolerate warmer temperatures and will not grow until watered, move them into a closet, where conditions will be dark and dry enough to maintain their dormancy. This group includes bessera, Begonia sutherlandii, amorphophallus, and certain oxalis.

(Continues…)

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Excerpted from "Saving Container Plants"
by .
Copyright © 2014 Brian and Alice McGowan.
Excerpted by permission of Storey Publishing.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

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