Easy-to-grow rudbeckias liven up gardens

Each year the board of directors of the National Garden Bureau selects one flower and one vegetable to be showcased. They are chosen because they are easy to grow from seed, widely adaptable, genetically diverse and versatile.

The NGB flower selection for 2008 is the rudbeckia, commonly known as the black-eyed Susan. Native to North America, rudbeckias can be found growing as wildflowers in fields and along roadsides across the country. These reliable plants shine in the garden with an abundance of brightly colored flowers reflecting the brilliant yellows and oranges of the summer sun.

Maine gardeners interested in growing native wildflowers should focus on forms of Rudbeckia hirta, a short-lived perennial that is best grown as a self-sowing annual in Maine gardens. The cultivars described here all bloom from July until frost.

‘Indian Summer,’ an All-America Selections winner from 1995, produces stunning 5- to 9-inch flowers, double and semidouble, on plants that reach about 3 feet tall. The golden-yellow flowers, borne on sturdy stems with vigorous branching, are ideal for cutting.

Another AAS winner is ‘Cherokee Sunset,’ with semidouble and double 2- to 4-inch flowers in shades of yellow, orange, bronze and mahogany. Plants reach about 30 inches tall.

Several shorter varieties are available for growing in containers and in small gardens. ‘Becky’ produces dwarf 10- to 12-inch plants with large, 3-inch flowers in orange, yellow and cinnamon bicolor. ‘Toto’ is dwarf and compact with smaller flowers covering the 12- to 15-inch-tall plants. Several single colors are available as well as a mix. Other popular varieties are ‘Corona,’ ‘Cordoba,’ ‘Sonora’ and the fully double ‘Maya.’

Looking for something different? The 2003 AAS winner ‘Prairie Sun’ produces spectacular 5-inch blooms with golden-yellow petals tipped with a brush of lighter primrose yellow surrounding a striking, light-green center cone. The 3-foot-tall branching plants can be grown in gardens and large containers.

Experts at the NGB offer the following advice for growing rudbeckias:

. Soil – Rudbeckias tolerate a range of soil types but prefer a moist, well-drained soil that’s not too rich. Excess fertilizer can make plants weak and cause flower stems to flop. Water when the soil is dry to maintain even moisture.

. Sunlight – All rudbeckias thrive in full sun. They grow well in light shade, but flowers may be smaller and fewer in number.

. Spacing – The mature size of the plant determines the correct spacing. Allow 8-12 inches between rudbeckias being grown as annuals. Dwarf varieties can be planted closer together with 4- to 6-inch spacing between plants.

. Plant care – To promote blooming and extend the flowering period, remove or deadhead faded flowers by pinching off blooms at the base of the flower stem. Be aware that rudbeckias often self-seed, resulting in new seedlings sprouting up around the garden. Extra plants may need to be removed or transplanted to prevent crowding.

Rudbeckias are a must for the pollinator garden, attracting native bees and butterflies. If you want to attract birds to the garden, allow the old flowers on the plant to go to seed.

Look for plants of the newest Rudbeckia varieties at garden centers this spring. Or grow your own plants from seed. The Johnny’s Selected Seed catalog for 2008 lists both ‘Indian Summer’ and ‘Prairie Sun.’

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to rmanley@ptc-me.net. Include name, address and telephone number.