Container Gardens -June 2008

by: Hilary Newell

The decks, patios and porches of Nantucket lend themselves perfectly to gardening above the soil line. A single step in front of your house or apartment can provide enough space for an overflowing color display. Or, if that’s not your style, a single elegant evergreen boxwood, or feather grass in an urn on either side of your front door, might be the answer.

Container gardening has been around for years. Whether it’s a single geranium in a clay pot or an abundance of large decorative pots or window boxes, Nantucket gardeners have rediscovered the joys of overflowing flower-filled vessels. 

According to a garden guru friend, container gardening is the fastest-growing area in the gardening world. The reasons vary. Many Nantucket homes don’t have an area large enough to dig a garden, whether it’s for vegetables, herbs or flowers. But everyone has a front door, and that’s a fine place to start.

Gardening above the soil line needn’t be limited to those with diminutive properties though. Some of the largest gardens I’ve visited included sizable cast-iron urns with blooming shrubs, highly-crafted Italianate pottery with ancient topiary or simple clay pots brimming with colorful annuals.

When I visited The Butchart Gardens in Vancouver, British Columbia I found an assortment of highly-blooming plain terra cotta pots dotted around the piazza, and large pots of blooming roses near the rose gardens. Drummond Castle in Muthill, Creiff, Scotland has very formal clay and concrete urns that are strategically placed in the gardens, intended to draw your eye to an interesting feature. 

At a Midwestern university I visited, I observed a brilliant use of planted pots that solved two problems. The area was exceedingly hot, and appeared to be difficult to get at with a hose. They had planted simple concrete bowls with a variety of succulents like SempervivensJovibarbaSedumsCrassula and Escheveria, relatives of the jade plant and “Hens and Chicks.” An inspired solution . . . the succulents don’t need much water and they love heat and sunshine. 

Creative skills will come in handy, but are not a requirement, when planning and planting containers. Using a combination of grasses, foliage and flowering plants together, you can create a stunning display that is quite easy to maintain. There are so many versatile plants that can be used in boxes, pots and containers, sometimes it’s hard to decide what to use. Even if a property has plenty of room to put a garden in the ground, there’s always room to spruce up a corner somewhere with a pot of colorful begonias or some greenery in a decorative tub. The website has hundreds of photos and recipes for interesting combinations using plants that are readily available.

The flexibility of changing containers with the season though, may be one of the best reasons for container gardening. In the spring, choosing hardy annuals and early perennials that can tolerate cold, early-spring temperatures is a great way to provide a much-needed glimpse of color that we all need after a Nantucket winter. Good choices are Primulas, Violas, Erysimum, (wallflower) and some early-blooming perennials likeAquilegiaBellis (English daisy), Pulmonaria (lungwort), Arabis (rock cress), Heuchera (coral bells), and Acorus (sweet flag). These will look good until the weather gets quite warm.

Flowering window boxes are one of the stars of summer, so using annuals for a maximum show of color is ideal, and there are scores of choices. Using plants that bloom profusely is a good way to narrow the choices when deciding what to plant. There are so many outstanding annuals that a trip to the garden center to see them in person may be the best way to make your choices.

Some important details to pay attention to before you make the trip: How many hours of direct sun will the container get and how exposed to the wind will the pot or window box be? Armed with good information, you will be able to choose your best options.

The first “must-have” is Euphorbia diamond frost. A heat- and drought-tolerant plant, it produces clouds of airy white flowers all season and into the fall and its low maintenance makes it even more attractive. It mixes with absolutely everything, and has even been used to plant with poinsettias at Christmas. Diamond frost is one of the top award-winners within the plant community and in 2007 received at least 29 awards from various judging bodies including The Smithsonian Institution (Top Performer) and numerous universities, arboreta and botanical gardens.

Petunias were first discovered in the 1700s in South America. They migrated to Europe where hybridizers transformed them from lanky plants with small flowers to what I refer to as “Grandmother’s petunias.” Simply colored and needing to be deadheaded to continue to bloom, Petunia x hybrida was a staple in gardens through the 20th century. Easily grown from seed, they provided long-lasting color for pots or gardens. The petunia family has now grown into a comprehensive group of flowering plants that includes the Supertunia. These are a great choice for long-lasting color in containers and window boxes. They provide non-stop color through the whole season and continue to bloom into the fall and past the first frost. These are not your grandmother’s petunias. They need lots of feed, but they don’t need to be deadheaded to keep blooming and the color choices out there will make your head spin. Supertunias are propagated by cuttings and have better longevity than their seed-grown ancestors. They are also self-cleaning so you don’t have to pick off the spent blossoms.

A close relative of the petunia is the calibrachoa. It’s actually in the nightshade family, but is often referred to as a trailing petunia or superbell petunia. One of the early series of this plant was called Million Bells and it certainly lives up to its name. Extremely heat-tolerant and long-blooming, calibrachoas are an excellent colorful choice for window boxes. They are also self-cleaning.

Verbenas, with their red, blue, pink, white and purple tones, also help keep a window box or your favorite pots blooming all summer. Their trailing or mounding habits make them very useful in sunny situations. Seeing them spill over the fronts of all the boxes on a house is a dramatic sight.

Lobelia is another old-fashioned favorite, but it too has changed in the last 15 years. Lobelia grown from a cutting is another example of an annual that when grown this way, outshines its seed-grown cousins by a mile. Older varieties that are grown by seed tend to burn our early in the season, while the newer varieties will bloom throughout the whole summer, and keep on going well into the fall.

Gaura lindheimerii is a perennial that has found its way into container gardening in the last several years. The white form Stratosphere White can go in the center of a sunny pot and when everything else is done blooming and has faded away, the Gaura keeps on blooming until frost. It holds its flowers at the end of graceful, arching stems, and from a distance, the flowers look like small white butterflies whirling around the pot. 

There are lots of appealing foliage plants to use, too. The Euphorbia family has expanded over the years and the range of color, height and form gives a wide choice of looks for whatever container you’re using.Euphorbia amygdaloides hybrid Efanthia, and Euphorbia hybrid Kalipso both lend themselves to mixed containers with their interesting colors and habits. Heuchera (coral bells) comes in just about all the colors of the rainbow. With names like Blackcurrant, Crème de Menthe, Key Lime Pie and Peach Melba, their colors help bring the other elements of the container together.

Grasses provide movement and greenery to containers through the entire season. Calamagrostis x acutifloraOverdam grows two to three feet with pink foliage that turns white in the summer and looks great right through the fall. Carex flagellifera (Toffee Twist) is a distinctive mahogany-colored grass that carries itself all summer and into the fall. Anthericum sandersii (St. Bernard’s Lily) is a mounded grass with showy small white blooms shaped like butterflies. More sun produces more flowers all season long. Chasmanthium latifolium has small dangling oat-like spikes, growing four-feet in full sun. The true beauty of any grass is the way the light reflects on it or pours through it, especially after it matures and has its plume of seed heads on.

If you have large tropical or semi-tropical green plants in your home, they can also be moved outside in the summer. Most don’t like cold weather or wind, so a protected, bright covered porch is an ideal spot to put your houseplants in the summer. Houseplants can help transform a simple porch into a charming outdoor living space. In the fall, the plants should go back inside well before a killing frost. Most tropical plants don’t want to be outside when the temperature drops below 40 degrees F. 

Lush foliage plants can make a bold visual statement in a summer window box, especially one in the shade. Variegated foliage is particularly interesting, and there are plenty of choices like Hypoestes phyllostachya(polka dot plant), and Chlorophytum comosum (spider plant.) Most varieties of ferns also work well in the shade. Athyrium niponicum Pictum (Japanese painted fern) is a favorite. 

When fall arrives, there is still a wide choice of plants to use in containers. A fresh planting of supertunias and grasses can keep you deck dressed up well into October or later. Or try a combination of Coral Diascia,OsteospermumCarex Toffee Twist and Salvia (purple sage). If there are grasses left in the pot from summer, they will usually stay nice through the fall, leaving their structure there for winter interest.

I would be remiss if I didn’t mention using pots to grow herbs, greens and vegetables. This is a great solution if your space is temporary, if you have a postage-stamp property or if you love to cook, but don’t have time to do a lot of gardening. Cherry tomatoes are the most satisfying edible that I grow at home. I used to put them in the ground until I acquired a puppy that loved to dig. Now, each year, I plant one healthy golden cherry tomato (Sungold) in a very large clay pot. This sits next to the whiskey barrel full of perennial herbs like thyme and tarragon. 

I replant parsley, dill and nasturtiums in it each year, and in combination with other pots of cilantro and mint, I have a ready supply of fresh herbs for cooking all summer long and fresh cherry tomatoes to snack on whenever I walk by.

Another edible favorite is the Meyer lemon tree that lives on the deck in the summer and in the den in winter. Harvesting a lemon at the peak of perfection is a little bit of heaven in my iced tea. Add a sprig of mint and the satisfaction of growing it myself? Priceless. 

Gardening above the soil line is a fun way to add some color and interest to your landscape. Whether you choose window boxes overflowing with blooms, pots on a patio or whiskey barrels casually placed around your property, containers will add charm and appeal to your outdoor living spaces. 

Hilary Newell is the greenhouse production manager and writes “The Farm Dirt” at Bartlett’s Ocean View Farm.

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