Plant of the Month – May, 2010
Thryallis – Galphimia gracilis
AT A GLANCE
Latin name: Galphimia gracilis
Common name: Thryallis or Shower of Gold
Flowers: Large clusters of golden-yellow, star-shaped flowers
Mature size: 4 ft. tall by 5 ft. wide
Hardiness: Persistent shrub in Zone 9 south; summer annual in all areas north
Soil: Not particular
Exposure: Full sun to light shade
Water usage: Low, once established
Sources: Local retail or Internet
Thryallis (Galphimia gracilis). All photos by Jimmy Turner.
Why this shrub/summer annual isn’t used more in Texas landscapes baffles me. Golden-yellow clusters of flowers cover the plant from early summer until the first frost, and the hotter it gets, the more it blooms! What more could you ask for?
Depending on where you live in Texas, this plant can be anything from an annual to a deciduous shrub. Texas gardeners in Zone 9 can enjoy this plant as a deciduous shrub that will drop its leaves in cooler weather. In Zone 8 gardens, it may freeze to the roots and return in spring, depending on the severity of the winter. In my Dallas garden, I’ve never managed to over-winter one, but thryallis still blooms so heavily that it is valuable in any garden, even as an annual.
This fast-growing native of eastern Mexico will quickly grow from a 1-gallon-sized plant to more than 3 feet tall in one season. Large spikes of golden-yellow flowers will cover the bluish-green foliage from early summer until the first frost. Thryallis is also very drought-tolerant once established, and actually seems to flower more if allowed to dry out between waterings. I’ve found that this plant isn’t choosy about soil, as long as it is well-drained; do not let this plant become water-logged. Full sun is preferred for best flowering, but it will tolerate light afternoon shade. I haven’t found any pest or disease problems.
Thryallis is great as a backdrop in summer color beds or as a centerpiece in containers. I like it mixed with Pennisetum ‘Princess’ or Pennisetum setaceum ‘Rubrum’ (purple fountain grass). The soft-textured burgundy foliage contrasts with the yellow flowers and echoes the red-tinged stems and flower centers of the thryallis. For an added bonus, butterflies constantly flock to the flowers of this plant.
No matter where you live in Texas, you should go on the hunt for this plant. With its ease of care, heat- and drought-tolerance, and constant flowering, it is sure to be a hit in any garden. I can guarantee you it will grace my personal garden and the gardens of the Dallas Arboretum for years to come!
About the author: Jimmy Turner is the senior director of gardens at the Dallas Arboretum. Visit www.dallasplanttrials.org for more information on his trials.