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Island alum root is the largest California native species among the coral bells, mounding to 12-18 in. high and 24 in. across. This species has large evergreen leaves, often to 5 in. wide, and produces white with pink flowers on 30 in. stalks.

The Island alum root is native to coastal islands of California and has been a popular garden plant for many years throughout the Inland Empire. Easy to grow, it is an excellent understory choice in shady areas along walkways, in mass plantings, pots and patio planters. It grows best in loamy soils and with regular moisture; it can endure short periods of moisture stress during summer.

Water Needs

Island alum root grows well throughout the Inland Empire in partial shade and with normal winter rainfall and moderate amounts of summer water. The chart shown below provides a recommended baseline guide to the monthly irrigation schedule and volume of supplemental water needed to maintain healthy growth throughout the average year. It should be noted there are several winter months marked by an asterisk (*) when rains can provide sufficient moisture and irrigation is not needed. The high and low range of moisture indicates Island alum root can grow with varying amounts of water; higher amounts of water will result in stronger springtime flowering performance and summer foliage character.

Irrigation Schedule and Graph

Moderate Water Use Plants

Irrigation Schedule 3

  Jan* Feb* Mar* Apr May Jun Jul Aug Sep Oct Nov* Dec*
Runs per Month 0x to 3x 0x to 3x 0x to 3x 2x to 3x 1x to 2x 1x to 2x 1x to 2x 1x to 2x 1x to 2x 2x to 3x 0x to 3x 0x to 3x
Inches per Run 1" 1" 1" 1" 1" 1" 1" 1" 1" 1" 1" 1"
Inches per Month 0" to 3" 0" to 3" 0" to 3" 2" to 3" 1" to 2" 1" to 2" 1" to 2" 1" to 2" 1" to 2" 2" to 3" 0" to 3" 0" to 3"

Range of supplemental summer water: 9"-16"
Range of supplemental winter water: 0"-15"

  Jan* Feb* Mar* Apr May Jun Jul Aug Sep Oct Nov* Dec*
For more information on how to use this Irrigation Schedule and Graph, follow this link.

For information how to calculate your irrigation system’s schedule and precipitation rate, please follow this link.

Plant Properties

Plant Type: Perennial, Native
Foliage Character: Evergreen
Habit: Mounding, Clumping
Growth Rate: Moderate
Height: 12 in. - 18 in.
Width: 12 in. - 18 in.
Water Needs: Moderate 3
Foliage Color: Dark green
Flower Color: Pink, White
Flower Season: Spring
Soil Adaptations: Loam
Exposure Adaptations: Moderate shade
Function: Rock gardens, Residential spaces, Near pools and water features, Hummingbird plant, Flowering accent plant, Container plant, Borders, Small spaces


In small gardens, spent blooms can be removed periodically to extend the bloom season (1). Heucheras can be divided to thin and replant elsewhere in the garden (or give away) by digging up and separating in November. Dividing every few years can also help reinvigorate plants (2).



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