Thryallis (Rain of Gold)

On last weekend’s GardenLine shows, I was reminded by my two guests about the hardiness and natural beauty of thryallis, or Rain of Gold. So, I’ve decided to highlight it in this week’s Friday Profile.

Thryallis is not hard to pronounce (THRY-al-is) as are some Latin-sounding plant names, but I don’t understand why the pseudonym “Rain of Gold” isn’t more popular. I mean, we seldom call Angel’s Trumpet by its technical name, datura. And, while plumeria is a cool-sounding name, technically it should be called frangipani. See what I mean?

The actual scientific name for thryallis is Galphimia glauca (gal-FEM-ee-uh GLOCK-uh). I guess that makes the name thryallis a bit more inviting.

Anyway, thryallis is a compact, upright, rounded evergreen shrub that is covered most of the year with small, very showy, yellow flowers - a Rain of Gold! I love its loose, open, and natural growth habit, which I feel is ideal for informal plantings. But whether you plant it informally or use it in a hedge row, it will need some pruning to keep from becoming too leggy. If, however, it seems that your pruning produces a thinned-out look at the bottom of the plant, leave the bottom slightly wider than the top to allow sunlight to reach to the lower foliage.

Full sun is normally required for best growth, but thryallis can tolerate some shade. Still, flowering may be sparser without a full day of sun. They are not freeze tolerant, so they will die back to the ground in most winters if temperatures dip below 25 degrees. But like another yellow-flowering plant that loves sun – esperanza – every thryallis I’ve ever planted regrows quickly from the roots in the spring.

Any slow- or controlled-release blooming plant food I endorse, such as Nelson’s Color Star or Nitro-Phos’s Color X-Press, will keep a thryallis blooming all summer and fall. But you can use just about anything, including rose or hibiscus food, to keep the thryallis thriving.

And while it’s not a true native plant, it features the two best attributes for planting in Texas: They are technically pest-free, and deer will not eat them. For those who don’t live in Southeast Texas but try to follow my advice, I should warn you that thryallis is considered a plant for zone 9-10-11. That means if your soil can freeze, your thryallis will likely not rebound from the roots every spring as they do along the Texas Gulf Coast.

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