On The Rocks Part 2; Flowers walled and jeweled.

Must-have mustards:

One of the plants I chose to try on my rock outcrop was Western wallflower, Erysimum capitatum (v. capitatum), a lovely biennial species frequently seen on rocky banks, ledges, road cuts, openings in woodland and chaparral, etc.  Often, after fires or other disturbances that open up and expose rock or soil, this plant can appear prolifically, sometimes by the hundreds.

Western wallflower just starting to flower in February.  Eventually the primary spike elongates, often to 3'.  In most situations the side branches will also elongate and flower, though in stressful sites usually only the primary spike flowers.

I had been wanting to try this native wildflower for several years, but I also wanted to grow the race that naturally occurs in the Garnett Creek drainage, this is the creek that drains through our property here in Calistoga CA.  But I had only seen it occurring naturally in one spot and only one plant, on a rock bluff about a half mile up the canyon.  Last spring I explored another nearby rock outcrop and found a few more and made a point of returning to collect 3 siliques (seed capsules); each plant might have 20 - 50 siliques if medium-sized.

A loose grouping of wallflowers on my rock outcrop in March.  They provided a wonderful bright wand of color during the damp and often dreary days of "winter" here.  The bluish lilac heads in the picture are the native blue-dicks, Dichelostemma capitatum, pre-existing at this site.

Knowing that this species is biennial, that is, it takes two years to flower and then die - and, not wanting to wait for two years before "seeing" it, I decided to try a trick that I had used years ago while at the UC Botanical Garden at Berkeley.  I waited until the last week of August to sow the seeds, even though it was during a heat wave and hardly the conditions you wanted tender seedlings to endure.  I made sure the seed pot stayed watered, and within eight days, there were dozens of tiny seedlings.  During September and October I carefully made sure that they didn't dry out and gave them small doses of fertilizer every few weeks.

Grown off of rock, in "regular" soil - here being a heavy clay - Western wallflower typically produces a bushier plant with many side branches, thus creating a mound of flowers.  This can also be induced by pinching the primary "leader" during its vegetative phase.  Sometimes browsing rabbits may do this for you..

We were fortunate last fall to have a substantial rainfall in mid October which thoroughly moistened the ground including my rock outcrop.  I used this opportunity to plant out the rather small seedling plants into various crevices, niches, ledges, etc. on the outcrop.  Although we didn't have follow up rains for several weeks after that, I watered down the areas with new seedlings regularly so that they did not dry out - as young seedlings are wont to do if not watered, usually with tragic results.

By the time the rains returned in November, the seedlings were already quite well established, and subsequent rains kept them growing quickly.  A little fertilizer around each rosette helped them turn into small plants by December.  Being mustards, wallflowers thrive during the cool season, getting bigger as the days got colder and shorter.

Early flowering wallflowers and juvenile rosettes (rosette above right of big flower head).  The rosettes of wallflowers are formed from many long narrow leaves, each leaf having shallow drawn-out lobes on the sides - these scattered teeth and lobes give an extra visual appeal to the foliage mound .

In nature, wallflowers germinate soon after the first rains and grow through the winter/spring into rosettes, which then sit out the long dry season until the next seasons' rains revives them and prompts them to flower the second spring.  By starting them early and getting them to grow before the New Year into little rosettes, when the days lengthened, they "thought" that they were already a year old.  Thus during January I was thrilled to see most starting to elongate into flowering stems - the "trick" had worked.  Of the nearly 75 seedlings planted out, nearly 68 flowered (5 had died), thus the biennial had been turned into an annual.


Apart from growing them in your garden which is quite easy since they are readily available (Annies Annuals, etc.), our Western wallflower is always an attractive plant to come across in the wild.  This species, Erysimum capitatum, is the most widespread in the state, occurring in many sites at many elevations.  The color too varies considerably, and previously some of the color variants were considered species or subspecies but are now lumped together.  The most widespread color is a deep golden orange, but some are more pure orange, others more yellow, others even cream.  For example, the plants native to the Calistoga area are slightly more golden than those at The Cedars 40 miles to the W, where they are more orange.

Western wallflower at The Cedars in Sonoma Co. in March.  Wallflowers are excellent at attracting butterflies to the springtime garden.

Evalyn's Touch.

If you want to add an annual to your garden that no-one has ever seen before, one that will amaze you every time you see it, try the Farnsworth jewelflower, Streptanthus farnsworthianus.  Native to the southern Sierra Nevada foothills it is named for a 20th century rancher and amateur botanist/naturalist, the late Evalyn Farnsworth of Porterville, Tulare Co.  Like most jewelflowers it grows on sterile, stony or rocky places, especially "balds" and ledges.

I was first given a 4" pot of this annual (actually two separate friends gave me one each - I guess my penchant for weird plants is well known) about 4 years ago; it was being grown - and still is - again by Annies Annuals of Richmond CA, a source for many unusual plants in our area (she ships too).

While the wallflowers were flowering in Feb. through April, the seedlings of the Farnsworth jewelfower were growing discretely, having self-sown for 4 years now on this rock face.  By May, they were producing their curious "flowers", actually spikes of flowers set off by huge purplish/metallic blue bracts.  While hard to see in this overall view, there are many in the central area of this picture.

Having moved to Calistoga the previous year, I immediately thought that I should  try this native treasure on my new rock outcrop.  They did excellently, and when they went to seed, I crushed it up and sprinkled around to a wider area.  The next season they returned in good numbers, and I've enjoyed this plant ever since.

Sometimes called Evalyn's jewelfower, this remarkable annual displays its bright white true flowers against a very unusual expanded bract of rose purple overlaid with a strange bluish color that reflects the light.

Our native jewelflowers (genus Streptanthus) are numerous and all seem to have developed odd features - growth form (branching), foliage modifications, flowers and even seed capsules (siliques).  But Evalyn Farnsworth really hit upon one of the weirdest.  But it isn't simply weird, it is quite lovely, Dr. Seuss would have loved it.

Those who have followed my "ramblings" for some time know that jewelflowers have been an interest of mine for nearly 30 years.  Here in Calistoga, we have the bristly jewelflower, Streptanthus glandulosus (ssp. glandulosus) on a rock outcrop across the canyon.  At our property at The Cedars N of Cazadero in Sonoma Co. we have two other subspecies (ssp.) of bristly jewelflower, the ssp. sonomensis (Sonoma jewelflower) and the ssp. hoffmanii (Hoffman's jewelflower).  We also have another annual, the bearded jewelflower, S. barbiger, and the odd biennial, Morrison's jewelflower, S. morrisonii.  The last four entities only occur on serpentine soil or rock - another interest of mine.

While the stems and true flowers are small, it is the purple-blue bracts that stand out from a distance, creating a wonderful color accent in the garden.

I have over the last 30 years tried to grow many of California's fascinating jewelflowers, but most have been very difficult and frustrating in cultivation; especially if you want to keep them for more than one season.  Last winter I tried growing seed of the bristly jewelflower from across the canyon, but it - while germinating quickly and easily - grew stunted and distorted as the plants enlarged.

What you see is not what you get.  Similar to some other jewelflowers, the juvenile plants give no indication of its future.  As a young plant the leaves are finely divided, with almost thread-like divisions.  In mid-life, it has a "crisis" and changes its appearance entirely, the ferny foliage of youth becomes large clasping heart-shaped leaves which then produce the even larger purple colored bracts below the flowers.  This plant is in transitions showing the two types of foliage.

Thus it is surprising to me that the Farnsworth jewelflower does so well.  I'm sure the rock outcrop helps, but it doesn't seem to be bothered by disease, mildew or aphids like some of my other attempts with other species.

Mass of Evalyn's jewelflower on rock face.  These have self-sown into the rock crevices - a hard place for any plant to grow.  The colored bracts provide an excellent accent to the silver and grays of Dudleya, Santolina chamaecyparissus, Senecio talinoides 'Jolly Gray', and trailing Salvia sonomensis. Below, Athanasia acerosa, a shrub with yarrow-like flower heads and lilac-pink rose.

Autumn in June.  As the plants matures and begins to dry out the clasping foliage turns soft colors of lilac, bronze, peach, salmon, yellow and chartreuse. The purple bracts look even more interesting at this phase.

Not your ordinary garden annual, both the form and color of this jewelfower creates exceptional interest.  I have not tried this, but if it could be dried with these colors, it would make a unique dried "flower" arrangement.

A cloak of many colors giving its farewell to spring, time to segue to another season.

On the Rocks; gardening on a rock outcrop. Part 1

The rocky bank as I first saw it before we purchased the property.  Here it is covered in dry weedy grasses, thistles, etc.  There are two separate terraces above the stone-inlaid concrete walls, with garage, small house (roof) and water tanks behind them.

A habitat that has always fascinated me is the rock outcrop.  Rock plants are frequently different than the prevailing plant community, thus represent a sort of island of unusual beings.  The conditions of growing on rocks often creates plants of atypical form or expressions, odd appearances and features.  And plants growing on rocks tend to display themselves dramatically and with flair.

Part natural, part exposed rock bank along driveway just after moving in.  A few pots, ceramic pig, pipes and metal sculptures temporarily set against hillside awaiting decision on future placement. The lower of two concrete retaining walls can be seen at top.

Because of my attraction to rock outcrops, I have often envied yards that had exposed rock. One could construct a rock outcrop, but that is a lot of work. And unless you are very good with rocks, it is often unsatisfactory, especially compared with nature.

So I was rather thrilled when we bought our property in Calistoga 5 years ago and it had considerable rock around the houses. I speculate that originally the site was probably an impressive rock outcrop that mostly got leveled to build the two houses, garage and two driveways.  However fragments persisted and some areas were actually created by excavation, which exposed the subsurface rock.

The rock bank after first rains showing new growth. predominantly weeds.  Two Yucca and a 'Santa Rita' opuntia (cactus w pinkish pads) and the pre-existing purple fountain grass (Pennisetum) are the only plantings in Nov 05. (The little shed is a pump house).

While the horticulturist may crave rocks, rocks don't crave horticulture; the simple truth is that it is really hard to grow plants on rocks.  On this bank the top had something like soil in spots, a colluvium of clay and rock rubble, but other sections are mostly rock and rubble.  The four native blue oak - Quercus douglasii - were obviously going to have priority of resources, especially water once the heat arrives.  There were three other native plants growing there; the perennial Phacelia heterophylla, the summer dormant bulb, soap plant, Chlorogalum pomeridianum, and another bulb (corm) called blue dicks, Dichelostemma capitatum.

 By the spring of 2006 more planting had taken place, especially at the base of the bank where good soil had been brought in to grow a more traditional mix of horticultural material such as roses, Cape reed, Chondropetalum tectorum, shrub milkwort, Polygala dalmasiana, 'Purple Haze' honeyplant, woodland beschorneria, etc. etc. etc.  The idea was to make the approach to the main house more exuberant, but not to hide the rock face.  Most of the growth on top of the rock are the pre-existing natives; phacelia and soap plant.

The rock outcrop here was always intended to be naturalistic with an overlay of horticultural experimentation.  Seen mostly in passing while driving or walking along the driveway, it was not intended to be a precious "rock garden" of choice alpine treasures or minute bun plants.  That is another form of horticulture altogether,  generally more suited to a place where the exquisite details of those types of plants can be more fully appreciated.

 By the spring of 2008 both the bottom "mixed border" planting as well as the rock planting itself had grown in a bit, although the plants on the rocks were quite slow.  Thus there is not much that stands out in this picture except the Yucca 'Blue Boy' below the wall and the Yucca aloeifolia 'Marginata' above the wall.  However all the native-to-site plants were thriving, and the diversity of plants was much greater than might appear.  On the rocks were shrubby Senecio, many Agave species and cultivars, Dudleya and Echeveria, Pachyveria, Salvia sonomensis and S. brandegei, Aloe species, Trachycarpus wagnerianus, Eriogonum umbellatum, Xanthorrhoea preissii, Watsonia X's, Amaryllis belladonna, Amarcrinum, Aeonium, Puya, etc.  Also another native annual, Phacelia distans had moved in on its own.

The summer months were very hard on the rock plantings as they received very little water, some none, and they are subjected to many hours of intense sun and heat almost every day for 6 months.  The plantings at the bottom did receive more regular irrigation, thus were able to "cover" for the drier background planting.  While many gardeners consider the winter as the "off season", here it is the opposite, with summer being the dormant time of year.  In spite of this, some plants did retain good appearance, particularly the Yucca, Opuntia and the shrub Senecio - which are particularly impressive in their drought tolerance (there are two green plume-like small  Senecio shrubs below the wall, one on the left and one in the middle, both near oak trunks.)

By November most of the plants are in full re-hydration and starting to grow again.  This is the same pattern as one would find in nature in this area.  However a "trick" I developed while taking care of the CA native collection when I was at the UC Botanical Garden (1978 - 2002) was to extend the season by starting to water in October if the rains didn't appear on their own - this activates the new growth so when the rains do materialize, the plants are set up to utilize the moisture more rapidly.  (While the philosophy of "celebrating dormancy" is valid in a dry climate, after 6 months, the celebration gets kind of tiring. Time to celebrate rejuvenation.)

 

This is a close up detail of the center of the rock area showing several Agave, Dudleya, Pachyveria, and the trailing Opuntia compressa. (Opuntia compressa, native to the central and eastern North American continent especially on sand dunes along the coast and Great Lakes, is a lovely cactus of great hardiness.  It is best displayed cascading down a slope.  However, while its lack of large spines makes it look "friendly" for a cactus, the tiny and numerous glochid spines - barely visible - can be insidious and irritating if handled without good gloves).

By late January the rock plants are in full growth, with an Aloe arborescens Variegata in flower.  The two green shrub Senecio, mentioned above, are especially attractive in the winter light.  The low gray ground cover on the top center of the bank is the native sage, Salvia sonomensis, native to the volcanic ridges not far from the property. It, and the native bulb called blue dicks, while not obvious in this picture, are already in flower. 

 

 View of rocky bank planting in April 2010.  Spring is definitely the peak season here, though some of these will look good into the early summer; particularly the mixed shrub plantings at the base which get routine irrigation.  The numerous yellow flowered scapes projecting from the upper rocks are the native wallflower, Erysimum capitatum, grown from seed obtained in the canyon.  Blue dicks, Dichelostemma capitatum, are numerous on the upper slopes, but not as visible in this picture - yet are showy in real life.

Part II will feature more detailed portraits of a few select plants from this rocky site.