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Tuesday, July 8, 2014

Plant of the Month (July) : Guadalupe Island rock daisy - Perityle incana

Guadalupe Island rock daisy (Perityle incana; yellow)
in Mother Nature's Backyard

The between-season periods can be a challenge for those who love color.  That’s why season spanners like Perityle incana, with their long bloom period, are so appreciated by local native plant gardeners.  While Perityle incana technically doesn’t hail from California, it’s a water-wise sunflower (family Asteraceae) that’s often included among the California natives.

Guadalupe Island rock daisy is endemic to Isla Guadalupe, an island off the northern coast of Baja California.  The Baja Channel Islands (including Isla Guadalupe) have an interesting relationship with California.  In fact, they share a complex geologic history, full of movement, volcanic eruptions and more.  To learn about the geology of the California coast we recommend: http://www.nps.gov/chis/photosmultimedia/models-of-change-geology.htm

Northern Baja California (including the northern Baja Channel Islands) represents the southernmost extent of the California Floristic Province, an important biodiversity hotspot.  The coastal islands themselves are home to many unique species and sub-species, in large part due to their long separation from the mainland.    For more on the California Floristic Province see: http://en.wikipedia.org/wiki/California_Floristic_Province and http://www.calacademy.org/exhibits/california_hotspot/overview.htm.

Guadalupe Island rock daisy grows in the washes, canyons and bluffs of Guadalupe Island.   Guadalupe is a 100 square mile volcanic island located approximately 150 miles from the Baja coast.  It’s home to 34 unique plant species as well as endemic birds and invertebrates.  Among the plants are unique pines, cypress and oak in addition to smaller plants.  Severely degraded by goats, Isla Guadalupe is the current focus of conservation efforts by several organizations.  For more see: http://iws.org/CISProceedings/6th_CIS_Proceedings/Oberbauer.pdf

Growth form: Guadalupe Island rock daisy (Perityle incana)

Guadalupe Island rock daisy is a shrubby perennial or half-woody sub-shrub.  It grows to 2-3 ft. (< 1 m) tall and 3-5 ft wide, making it an excellent size for the garden. Mature plants are irregularly mounded in shape (see above).  The plant is adaptable, filling in around other shrubs.  

Like another island endemic, the Catalina Silverlace (Constancea (Eriophyllum) nevinii from California’s Santa Catalina Island), Perityle incana is probably best known for its light colored foliage.  While Catalina Silverlace is truly white, Perityle incana is more often a silvery green in the garden setting. 

The two species share several other characteristics, making them confusing to the beginning gardener.  They both have a mounded shape (though the Silverlace is more spreading) and have superficially similar leaves.  As shown in the photo below,  Perityle incana is best described as ‘feathery’ (deeply incised), while Constancea foliage is truly ‘fern-like’ or ‘lacy’ (bipinnately divided).  Once you see the two together, the differences become more apparent.

Foliage of Perityle incana (left) and Catalina Silverlace (Constancea/Eriophyllum nevinii) (right)

The flowers of Guadalupe Island rock daisy brighten any garden.  Blooming off and on throughout the year, the main bloom season is spring-summer.  We’ve seen blooms as early as April and as late as the end of July in Mother Nature’s Backyard.  The flowers are clustered in sunflower ‘heads’ that lack conspicuous ray flowers (the ‘petals’ of sunflower heads).  In fact, the flower heads are similar to the male Mulefat (Baccharis salicifolia), but a bright golden yellow.  The flowering heads occur in clusters above the foliage – very decorative indeed!

Flowers: Guadalupe Island rock daisy (Perityle incana)

Guadalupe Island rock daisy tolerates full sun along the coast.  But give it some afternoon shade further inland – it’s adapted to slightly cooler temperatures.  It naturally grows in well-drained rocky/sandy soils, but will tolerate clay-loams or even clay with judicious watering.  

Along the immediate coast, Perityle incana may get by with no summer irrigation. But remember that its native climate is more humid than the S. California mainland.  In most areas it will need occasional summer water.  In Mother Nature’s Backyard (summer temperatures in the 80’s and 90’s F.; clay soil) we treat it as Water Zone 1-2, watering every 4-6 weeks in summer.

Frost damage to Perityle incana. Note new growth after ~ 5 weeks.

In local gardens, Perityle incana is sometimes exposed to moderately low temperatures.  The species is frost-tender, affected by temperatures in the mid- to low 30’s F.; this is not a plant for areas with regular winter frosts.  If frost is predicted, you can water the day before and/or cover the plant with an old sheet to protect it.  If frost damage occurs, resist the urge to prune immediately.   For more on frost damage see: http://mother-natures-backyard.blogspot.com/2013/02/frost-damage-dont-prune-yet.html.
Other than the frost sensitively, Guadalupe Island rock daisy is easy to garden with.  It’s best neglected except for removing unsightly spent flower stalks (after the birds have eaten the seeds) and pruning back by 1/3 in the fall to keep it youthful and shapely.   Given the right sun and water conditions this is a dependable garden plant that blooms like clockwork in spring.

Use Perityle incana where its light foliage contrasts with other shrubs; it’s a great substitute for the non-native ‘Dusty Miller’ (Senecio cineraria).   Guadalupe Island rock daisy is often grown with native sages (Salvia species) and buckwheats (Eriogonum species) which have similar cultural requirements; it is particularly lovely with the Red Buckwheat (for more see: http://mother-natures-backyard.blogspot.com/2012/07/plant-of-month-july-red-buckwheat.html).   

Perityle incana (yellow flowers) with Red buckwheat (Eriogonum grade var. rubescens)
 in Mother Nature's Backyard

Guadalupe Island rock daisy would also look nice paired with evergreen Toyon, Lemonadeberry, Ceanothus species, manzanitas and other water-wise green shrubs.  Its yellow flowers work well with many color schemes: yellow-blue; warm colors (red, oranges, yellows); pastels.  We grow annual spring wildflowers around it to provide off-season color.

Guadalupe Island rock daisy (Perityle incana): mature plant

Some gardeners grow Perityle incana in a rock garden or dry stone wall – or at least next to a decorative garden boulder.  This is similar to conditions in the wild.  It is recommended for dry slopes. The plants also do fine in large pots/containers.  In fact, gardeners in colder climates have been known to bring containerized plants indoors during cold periods. 

Another good reason to plant Perityle incana is for its habitat value.  Many pollinators, including butterflies and hummingbirds, visit this plant for pollen and nectar. In the fall, songbirds eat the seeds.   So you get a long season of wildlife viewing.   If you enjoy watching/photographing wildlife you’ll want to place this plant in a convenient viewing location.   Your summer vegetable garden will also benefit from the additional pollinators.

In summary, Perityle incana is a lovely and interesting plant that almost disappeared in the wilds.  Its light foliage adds interest to the garden; and the yellow flowers provide welcome color from spring into summer.   We hope you’ll consider adding this plant to your water-wise – and life-friendly – S. California garden.

For plant information sheets on other native plants see: http://nativeplantscsudh.blogspot.com/p/gallery-of-native-plants_17.html



We welcome your comments (below).  You can also send your questions to: mothernaturesbackyard10@gmail.com


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