Plant Answers

Weekly Express-News Article
By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist
Saturday, August 18, 2007

“Color on the Way”

Many of our summer blooming plants bloom until cold temperatures arrive but there are also some special fall blooming plants that can make a major impact in the fall landscape.

Fall asters (also called michaelmas daisies) are inconspicuous right now but come October, they become a focal point in many area landscapes. They grow to mounds 2.5 feet tall and six feet around that are covered with lavender blooms for about three weeks. The best spot for a fall aster is a hot sunny corner of the boulevard or other location in full view. The soil does not have to be very good and once they are established fall aster does not require supplemental water. They will soon be available in area nurseries with limited blooms but the real show will be in future years when the tough plant gains some size.

Fall asters are pest-free. They die back to the roots every winter and grow from late spring until early fall. They can be pruned lightly to control size until mid-August and then allowed to grow unfettered until they complete their bloom period.

Cape honeysuckle has tubular orange-red one inch flowers. The foliage and flowers resemble trumpet creeper in miniature. Beginning in September, they are blooming machines until the first freeze. In addition to the color, the blooms are a favorite nectar source for the waves of hummingbirds that visit San Antonio every autumn.

Cape honeysuckle die back every winter but can grow to 10 or 12 feet tall by September 1st. They can be used on an arbor as a leaning vine or can be trained as an upright shrub. Cape honeysuckle is drought-tolerant and pest-free. Grow them in full sun.

Firespike grows and blooms in deep shade. It makes an excellent container plant or can be grown in the shrub border where it dies back to the roots every winter. The plant is so shade tolerant that container grown firespike can be taken into the house during the winter where it makes a decorative foliage plant. As attractive as the shiny green leaves are, the major show in the fall comes from the spike of red blooms that arise a foot or more above the foliage. Firespike is a favorite hummingbird plant for shady patios and gardens. They are in bloom at area nurseries right now. Firespike is not a xeriscape plant. It does best with regular irrigation.

Salvia coccinea is another fall blooming plant that can tolerate the shade. It is very drought-tolerant and grows in the sun in addition to the shade. The common red and a bicolor (pink and white) version are available as container grown stock. The bicolor is called tropical salvia. The red flowered salvia coccinea will reseed itself in the garden or even a weedy field. It is an excellent xeriscape plant that the deer do not eat, and is a favorite hummingbird food source.

Purple coneflower will also naturalize for fall blooms. It prefers full sun but is just as drought-tolerant and pest-free as salvia coccinea. In addition to attracting hummingbirds, purple coneflower is a favorite butterfly food source and provides seed for the finches and cardinals. Coneflower is a part of every wildflower seed mix or they can be purchased as large plants in containers at area nurseries. Deer do not seem to eat purple coneflower.

Blackeyed Susan is a Rudbeckia just like purple coneflower. The flowers resemble sunflowers with richer colored, lusher petals and can be quite spectacular in the autumn garden, but they do not over winter or reseed as well as purple coneflower. The “Indian Summer” variety is just one of many showy selections. Use blackeyed Susan for yellow fall blooms that attract butterflies. Grow them in morning or full sun.

Mexican mint marigold makes a mound of golden yellow flowers up to three feet tall. They are pest-free and very drought-tolerant, but require well drained soil to prosper. Mexican mint marigold is like fall aster in its ability to become a visual center of the autumn landscape. Like fall aster, they require full sun to bloom to their full potential. Mexican mint marigold has a longer bloom period than fall aster, but they look great together. I am not sure why they have mint in their name. They should be called Mexican licorice marigold because they have a pleasant anise fragrance.

Autumn sage or salvia greggii is another fall blooming plant. It also has a bloom flush in spring and has a few blooms even in the hottest summer. Autumn sage is available in many bloom colors including red, pink, salmon, and white. The flowers are small and dispersed along the stem so the impact is not as great as some of the other autumn bloomers, but they are attractive and reliable. Autumn sage has some shade tolerance, is very drought-tolerant, and is pest-free. It is best to cut this evergreen perennial back to the ground every few years to prevent it from becoming too leggy. It looks best at about 2.5 feet tall with new herbaceous growth. Deer do not eat autumn sage.