Q: My new deck, which gets full sun all day, has made me interested in container gardening in a major way. I’ve tried the usual bedding plants but would rate my results as merely okay. What interesting flowers do you recommend? — David Jaglowski, Grand Rapids, Mich.
A: Given enough water and fertilizer, just about any flower will thrive in a container. But the right amount of both is often a lot more than you think, so I suspect that upping your level of care will yield better results than just changing the mix of plants will. Annuals require more care in containers than in flower beds. Start with a commercial peat-based soilless mix, which holds a lot more water than potting soil or garden soil. You should also use time-released fertilizers in the mix, then supplement that with liquid fertilizer once a week. But nothing beats new and unusual plants. Here are some that I’ve found to be outstanding in containers.
Don’t be snobbish about impatiens (for shade) and petunias (full sun) if you want color. No other plants can match them for full-tilt flower power. The best petunias, in my experience, are the strains called Supertunia and Surfinia. These far surpass even the Wave petunias in containers (but not in beds, where the Waves do better). In impatiens I have seen no such differences. All do well in containers, although the New Guinea types can take more sun (and have more colorful foliage) than regular impatiens.
My other annual all-stars are less common and, like the Surfinia and Supertunia strains, are grown from cuttings, not seed. Thus they are a little more costly, but their superior performance makes them well worth the money. At the top of my list is Scaevola aemula, an Australian seaside plant that never stops pumping out purple-blue flowers in the face-off in the fierce heat or cool sea winds. Almost as good is Calibrachoa parviflora (million bells), a scaled-down petunia look-alike and relative. Available in six colors (white, dark purple, light purple, pink, red, and terra-cotta), the compact plants trail over the sides of containers and produce abundant flowers regardless of heat or cool weather. Another excellent trailer is Sutera cordata (sometimes labeled bacopa). Its foliage makes a tight, cascading mat spotted with tiny, white starlike blossoms. The Tapien series of verbenas, available in three colors, far surpasses any others I have tried. They spread laterally, weaving appealingly through companions, and are highly mildew-resistant.
For two years I have grown Torenia ‘Summerwave,’ and I now consider it a mainstay. These vigorous trailers produce huge numbers of bluish flowers that remind me of large snapdragons. This is an invaluable companion for impatiens and other shade lovers, but it does well even with a half-day of bright sun. Sweet potato vines, Ipomoea batatas, are almost too vigorous for full sun, but the colorful leaves of ‘Blackie’ (deep purple) and 'Margarita’ (chartreuse) are worth a little pruning. Just be ready to chop them back at least once in midseason. The more open, airy foliage of the licorice plant (Helichrysum petiolare) tends to disguise its propensity to dominate, but that’s easily cured with a few snips every couple of weeks. Finally, among the taller plants I’ve grown, Fuchsia ‘Gartenmeister Bonstedt’ is a standout for both its heat tolerance and its foliage. The slender, brick-red trumpet flowers are stunning, but even without them the plant’s purplish leaves and heat resistance would make it worthwhile.