Words by Adrian Higgins, The Washington Post
May is the month to assemble pots and containers for the rest of the growing season. Lushly planted containers bring the joy of gardening to the smallest of urban spaces. They also have an important design role, in announcing an entrance, softening corners and even screening unwanted views.
The popular formula for composing a garden in a pot is to observe the mantra of “thriller, filler, spiller.” The reference is to a single upright specimen (thriller), annuals that trail over the lip (spiller) and others that fill the remaining gaps (filler). Whatever compositional approach you favour, there are general techniques for success.
First, look for annuals that have been branded as superior performers, especially among petunias, calibrachoas and verbenas. They are sold as trademarked series. They tend to flower more and longer and shrug off the stresses of heat.
Stand-alones: Sometimes all you need is one starring plant in a pot. It should be dramatic in its growth habit, upright, and sculptural or cascading, for example. Discover its end-of-season size before picking its pot – plant and container should be similarly scaled.
There are plenty of choices for stand-alones in either sun or partial shade, including palms, papyrus, elephant ears (alocasias and colocasias), banana “trees,” angel’s trumpet, cordylines and bromeliads.
Nesting: Another approach is to assemble plant combinations – but in separate pots. That is, have a cluster of containers with each holding its own plant. For best effect, limit the number of containers to three or five, mix up the sizes, and have a clear starring pot.
Succulents: Succulents remain popular for their shapes, colours, low cost and ease of care. Tender succulents work well outdoors during the growing season and free you of the regular watering regime.
Choosing a container
The pot size drives the quantity of plants in the composition, but it also has a direct bearing on how well they do. The larger the pot, the less stress is placed on the plants; soil temperatures are cooler, the soil dries out more slowly and roots can go deeper.
Metal pots or outer containers can get too hot for plants in the summer, especially if they are dark-hued. Otherwise, the material of the pots is purely a function of your aesthetics and purse. The plants don’t care, except that terra-cotta pots can wick moisture away from the soil and dry out more quickly than, say, plastic.
Pots are best irrigated with a watering can, in which you can add soluble feed, or with a wand attached to a hose. Don’t use a regular hose nozzle, which will either dislodge soil from the pot or, if used as a fine mist, be ineffectual or even harmful. Water at the base of the plant and try to avoid getting leaves wet to minimize fungal diseases.
Correct soil is essential to success. Do not use pot soil left over from last year, which is compacted, full of fertilizer salts and possibly diseased. Do not use soil from the garden. Do not use bags of topsoil or seed-starting mix. Use freshly purchased potting soil. Potting soil typically consists of a mix of organic matter, peat moss and perlite. Many branded mixes also contain slow-release fertilizer, either synthetic or organic.
The root systems of new plants should be teased open to encourage deep rooting, but use your hands and be gentle; many young annuals have delicate root systems. After planting and watering, the surrounding soil may have receded. Check and add new soil if necessary to prevent root exposure. Then add a shallow mulch layer to retain moisture.
For an unexpected container, select edible plants with ornamental qualities. The U.S. Botanic Garden suggests this mix for a large pot: pineapple sage Golden Delicious, Swiss chard Ruby Red, bronze fennel Rubrum, sweet basil Purple Delight, nasturtium Tip Top Mahogany and sweet potato vine Molokai Purple.
Images: Proven Winners and Harnek Singh/Wave Hill for The Washington Post