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Common Name:

Thyrallis or Yellow Plumbago

Scientific Name:

Galphimia glauca (Thryrallis glauca)

Family Name:



Thyrallis is a handsome small to medium size evergreen shrub with season long interest that is native to Mexico and Guatemala. Plants have a rounded habit, blue-green leaves, and spring to fall terminal spikes of yellow flowers. Plants can serva as general purpose evergreen shrubs in warm climates and as summer annual accents in colder climates. They work well in shrub borders, hedges, masses, and large containers.

Plant Habit or Use:

Shrub, small shrub, medium shrub, topiary, tropical


sun, partial sun

Flower Color:

Bright yellow, small 0.5 inch flowers in dense 2 inch to 4 inch terminal spikes.

Blooming Period:

Spring, summer, fall

Fruit Characteristics:

Small brown 3-part capsules, not ornamental.


4 ft to 6 ft (9 ft)


3 ft to 4 ft (6 ft)

Earth–Kind® Index:

  • Heat Tolerance: High Heat Tolerance
  • Water Requirements: Medium Water Use
  • Soil Requirements: Medium Soil Requirements
  • Pest Tolerance: High Pest Resistance
  • Fertility Requirements: Medium Fertility Requirements
Explanation of the Earth–Kind® Index breakdown

Firewise Index

Explanation of the Firewise Index numerical value

USDA Hardiness Zones:

9, 10, 11

Regions that intersect these hardiness zones:
Region E - Upper Rio Grande Region F - Hill Country and Central Coast Region G - Southeast Texas Region H - Rio Grande Valley
Click image for enlarged map of USDA Hardiness Zones

Additional Comments:

This species should be more frequently grown where cold hardy, very marginal in USDA zone 8b. Few problems, sometimes reported to be difficult to root from cuttings.
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A Special Note about Cool Season Annuals

Cool season annuals typically are planted in the fall or early winter and flower in early spring under moderate temperatures. This group of plant materials includes: pansies, snapdragons, violas, dianthus, flowering cabbage/kale, etc. Because cool season annuals flower in the spring when conditions are mild, most have limited heat tolerance.

As a result cool season annuals do not receive a high Earth–Kind® index despite their outstanding landscape qualities.