AAS Award-Winning Plants for Containers and Window Boxes

Since its founding in 1932, the nonprofit All-America Selections (AAS) has used a network of trial gardens across the United States and Canada to test new cultivars before their commercial release. The organization then helps promote the award winners in the year of their introduction to the public, so that gardeners can make confident choices among unfamiliar varieties. 

Volunteer judges, who are horticulture professionals, evaluate the plants in approximately 80 trial gardens, which exist at universities, public gardens, seed companies and more. The trials place the new varieties alongside comparable cultivars that are already established in the garden trade. The plant being evaluated must show improvement over these standards in two qualities to be eligible for an award. Qualities include health and habit, bloom time and novel color, among others.

Here are some recent winners to consider trying in your containers this year, thanks to their compact habit and lengthy bloom time. To explore more options, see all-americaselections.org.

Related: Choosing, Hanging and Caring for Window Boxes

While it’s common to grow dahlias from tubers, some are raised from seed, including the new Black Forest Ruby. Dark leaves provide a dramatic backdrop to its scarlet to maroon flowers, which can bear single or semi-double petals. Black Forest Ruby achieved an AAS award for its sturdy growth habit and disease resistance. This dahlia also won a Gold Medal in Fleuroselect, a European program similar to AAS.

In the AAS gardens, judges appreciated this two-foot-tall dahlia’s ability to remain upright and compact without staking, while the comparable variety ‘Bishop’s Children’ flopped open. Its resistance to heat, drought and disease also made it a standout, and these qualities along with its small size make it a great choice for containers. The varied shades and shapes of the flowers enhanced its visual appeal.

Start Black Forest Ruby dahlia seeds indoors four to six weeks before the typical last frost date. Move outside after danger of frost has passed, siting in full sun. Expect the first flowers to appear 85 days from sowing. Bloom can continue well into fall; pick the flowers or deadhead spent blooms to promote the best show.

Seed catalogs contain pages of marigold varieties, such that one might wonder if more are necessary. The new Mango Tango, a French marigold that won a Fleuroselect award as well as a National AAS recognition, boasts vivid colors and a compact habit to make it a worthy addition.

Judges remarked on the saturated nature of the yellow-and-red bicolor blooms. The plant’s mounded growth habit—reaching 8 to 10 inches tall and wide—displayed the flowers well. And Mango Tango showed equal tolerance to heat and cold, with flowers occurring throughout summer and into the fall.

Marigolds are simple to grow from seed started indoors four weeks before the last frost, or outdoors after no chance of frost remains. Mango Tango's short stature makes it a natural for pots, though it can also serve as edging for garden beds. Full to part sun, moderate watering and a twice-monthly liquid feed complete its requirements.

Related: Create Annual Planters That Are Dramatic and Full of Color

Nasturtiums beguile gardeners with their unique round leaves and funnel-like flowers, but they can also disappoint with lax growth and lack of blooms. The Baby series of nasturtiums seems to avoid these problems, dazzling AAS judges with their floriferousness and tidy habit.

All three varieties won points for their bold, solid colors and deep green foliage. The plants grew as uniform, compact mounds to just 12 inches tall and wide, perfect for hanging baskets and other containers. Judges especially liked the upright stance of the flowers, which kept them visible above the leaves. Heat tolerance rounded out the accolades for each Baby variety.

Nasturtiums are best grown from direct-sown seed, which can be planted just after the last frost. Soaking the seeds in water overnight before sowing aids in germination. These plants prefer full to part sun and moderate to low water. Avoid rich soil and do not fertilize; nasturtiums grow and bloom best in lean conditions.

Related: Check out ‘Tip Top Rose’ nasturtium, a dwarf variety that also won in All-America Selections

While large or midsize petunias require a sizable patch of soil or a planter all their own, smaller varieties lend themselves to mixed containers. The new Shake Raspberry petunia is a petite plant that can combine well with other annuals, and its bicolor flowers present an opportunity for creative compositions.

Judges described the eight-inch-tall-and-wide Shake Raspberry as “super compact” and “contained.” They admired the unique colors of the abundant flowers; each flower shows a mix of pink and yellow shades in varied ratios, from nearly solid to tie-dye. This petunia was also complimented for its heat tolerance.

Shake Raspberry petunia needs full to part sun and moderate watering. Apply a slow-release fertilizer at planting time, and then use a water-soluble fertilizer once a month on potted petunias. This variety was trialed in both containers and beds, performing equally well in each, but its tiny size really recommends it to pots.

Related: How to Garden With Multicolored Flowers

This plant is a cultivar of the species Catharanthus roseus, an annual that shares the common name “vinca” with Vinca minor, a vining perennial known for its aggressive growth. Catharanthus is also sometimes called Madagascar periwinkle, but that doesn’t help the confusion, as in some regions, true vinca is itself known as periwinkle!

In any case, rest assured that AAS winner Sphere Polkadot will not take over your garden or surrounding landscapes. Forming a foot-tall mound, this annual blooms profusely all summer, with clean white petals surrounding a magenta eye.

Judges were most impressed by Sphere Polkadot’s ability to persevere through harsh summer weather, including heat, drought and heavy downpours. One judge attributed its strength in rainstorms to the size of its flowers—smaller than the comparable cultivars—calling it the “vinca of the future” as weather events turn more severe.

Judges also felt that Sphere Polkadot vinca offers an eco-friendly option among annuals thanks to its lower water needs, which is particularly convenient in containers. If you choose to plant it in the ground instead of pots, it can serve as a (non-spreading) groundcover or edging when planted in multiples. In either situation, it likes full sun.

Related: Drought-Tolerant Annuals for Garden Containers

All images courtesy of All-America Selections, all-americaselections.org