At one of the California native plant sales we attended this fall we picked up a lovely ornamental brassica, Erysimum franciscanum var. crassifolium, commonly known as the Coarse-leaved Franciscan Wallflower. This plant, along with our other native plant purchases this fall, is destined to be transplanted in the orchard this next week, hopefully before the next rains arrive!
After tearing out hundreds of non-native mustard plants last spring, I admit it felt strange purchasing another plant in the mustard family to grow intentionally, but we selected this species for a reason.
Erysimum franciscanum is a biennial to short-lived perennial herb with a very limited geographic distribution, found along the coast of California from Sonoma to Santa Cruz county. Due to the limited range of this species, the California Native Plant Society considers this species as “fairly endangered in California”. This includes both the crassifolium subspecies, and its cousin, the San Francisco Wallflower (Erysimum franciscanum franciscanum). We love the look of the non-native mustard blooms in the spring, but dislike their invasive habit, so as this uncommon wallflower is similar in appearance, but endemic to Santa Cruz county, we decided to make room for it to grow here.
In its native habitat, Erysimum franciscanum is most often found growing on disintegrating serpentine soils, but the Coarse-leaved Wallflower isn’t particularly fussy about substrate, but does demand good drainage, and as such is expected to thrive well on our gravelly and sandy slopes.
That said, this plant does prefer to grow in an area with little competition from other species, so our plan is to plant it in the more wild and scraggy areas around the periphery of the orchard, where it can be allowed to grow and spread unhindered, rather than mixed in with the native wildflower seeds we’ll be direct-sowing in the central orchard area.
This rare local form of Erysimum grows between one to two feet in height. The fragrant flowers are a rich yellow color, and as is typical of flowers in the Brassicacea family, the flowers have four sepals and four petals.
Bloom period is from late winter to late spring, with peak bloom between March and June. However, the two specimens we acquired at the plant sale have been blooming steadily since mid-October.
The nectar from this species is particularly attractive to native bees…
and numerous species of butterflies, including this Mylitta Crescent (Phyciodes mylitta).
The leaves of Erysimum franciscanum var. crassifolium are 9-15 mm wide, and usually sharply toothed.
This plant may be in leaf all year, and although drought tolerant, like other California wildflower species, Erysimum is deciduous under significant drought stress, but flourishes with the return of the winter rains.
Seeds can be collected from Eryismums in late summer through mid-autumn. When we were selecting plants at the sale, we intentionally chose those that already had a number of maturing seed pods, in the hopes of collecting, and propagating seed.
Collected seed should be kept dry and stored in the refrigerator until ready to propagate.
To propagate this species from seed, the seeds should first be soaked for a few hours in fresh water, and then stratified in peat moss for 10-14 days until they germinate. Germinated seed can then be sown into flats or cell packs, and should be kept misted prior to transplanting. Reportedly, this species survives transplanting well, and will grow rapidly once it’s established. We’ll have to wait and see how well our plants do that are propagated from the seed we’ve collected this fall…