Monday, June 3, 2013

Visiting Northern California: A Garden of Succulents

cactus in bloom, and a variety of other succulents
Cactus in bloom, and a variety of other succulents,
Ruth Bancroft Garden, Walnut Creek, CA
small succulent, flowering
small succulent, flowering
   Succulents are plants with fat fleshy leaves or stems in which they store water. All over the world, different plants have become succulent, so there is no particular relationship between succulents, although some groups, for example the cacti, are particularly rich in succulents.

     The Ruth Bancroft Garden in Walnut Creek, California showcases the diversity of succulents. 

   For hundreds of years, people have enjoyed growing succulents.  Most succulents are from dry areas around the world and evolved to tolerate dry conditions. Most deserts around the earth occur at 30o North and South, so the winters are mild. A few succulents can survive really cold conditions, but those are exceptional. That means in northern Colorado where I live, the array of succulents I can find is limited, and in the East Bay of northern California, where I visited, a much greater variety of succulents can be grown.

   In general, succulents are easy to grow, requiring very little care if planted in favorable locations. And mostly their idea of a favorable location is some rocky spot in full sunlight, which is often a place where other plants grow poorly.

ice plant at Point Reyes
Fat succulent leaves on
Caprobrotus edulis, ice plant,
at Point Reyes
 In cacti,
the stems are succulent

    Almost all cacti are succulents but so are agaves (Asparagaceae, yucca family), many bromeliads (Bromeliaceae, pineapple family), ice plants (Aizoaceae, ice plant family), sedums (Crassulaceae, hens-and-chickens family), portulacas (Portulaceae, moss-rose family) and some euphorbias (Euphorbiaceae, poinsettia family) to name a few. Often these plants have taken different paths to the water-storage traits that we see as being succulent. Many of them store water in their leaves, which swell when full of water. Cacti, on the other hand, often have small, normal-looking leaves that drop off when conditions get dry, and it is the stem which is succulent (and the important organ for photosynthesis, usually the function of leaves).

   In the northern California's East Bay, about an hour east of San Francisco, the summers are hot and the winters mild and wet. Here, succulents thrive. In the 1950s, Ruth Bancroft, married to the grandson of California historian and publisher Henry Howe Bancroft, and living on the family farm in Walnut Creek, planted her first succulent and by the 1970s when what is now called the Ruth Bancroft Garden was established at its present site, she had thousands of succulent plants.

Diverse succuents, Ruth Bancroft Garden
Diverse succuents, Ruth Bancroft Garden
    The color and diversity of shape of succulents are obvious.
Colored succulent leaves
The leaves can be brightly colored
succulents at Ruth Bancroft Garden
More different succulents! 
a group of succulents
a group of succulent rosettes
    Succulents are not so drought resistant that they can go for months without water. What the succulent leaves or stems do is let the plants endure to the next rain. In a garden, frequent watering makes them look and grow a lot better. Ruth Bancroft gardener Walker Young told me that they regularly flood the garden, soaking the ground.
Barrel cacti, Ruth Bancroft Garden
A row of cacti bigger than basketballs,
Ruth Bancroft Garden

   But succulents perish if they are waterlogged for very long, sooner than most plants. Consequently the Ruth Bancroft Garden puts its plants on mounds so that the plants can reach the water but are not immersed in it. Having or creating good drainage is one of the keys to successfully growing succulents.

    Another attraction of succulents is their flowers. Plants that seem plain can become dramatic in flower: 
Agave flowering stalk.
Agave flowering stalk,
Ruth Bancroft Garden.
Yes, those are phone lines
in the background
non-flowering Agave
Non-flowering Agave beside tree, Ruth Bancroft Garden

Flowering Opuntia, Ruth Bancroft Garden
Flowering prickly-pear cactus,
Opuntia, Ruth Bancroft Garden

Big prickly-pear cactus, 
Opuntia with no open flowers

So many flowers on the succulent
So many flowers you can't
see the succulent leaves 
      (The many succulents that are monocarpic, waiting for years to flower and then die immediately after the seeds mature, make a particularly dramatic flowering display.  See last week's post about flowering in agaves  Visiting Northern California: Flowering Agaves! )

      Columnar cacti and agaves are conspicuous succulents of very arid environments. But many succulents simply slip into spots that, for the region, are relatively dry due to a shallow soil or position on the top of a sunny slope. There, they are not conspicious but can be surprisingly common if you know where to look.
Opuntia macrorhiza in grassland
Opuntia macrorhiza in grassland
Phemeranthus parviflorus in grassland

    Comments and questions welcomed.

    For explanation of my use of plant families (Bromeliaceae, pineapple family for example) see previous post: Botany Rules 3: Why do Botanists Always Tell You the Plant Family?
    For more on agaves and monocarpy, see previous post: Visiting Northern California: Flowering Agaves!

Kathy Keeler, A Wandering Botanist
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