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Sunday, March 18, 2012

Plant of the Month: Arroyo (Succulent) Lupine - Lupinus succulentus

Arroyo (Succulent) lupine (Lupinus succulentus)

This was the first post we wrote in the 'Plant of the Month' series in 2012.  The garden has matured a lot since then.   The seeds from the original lupines have spread, giving us a bright show every year about this time.  We've added a few photographs to inspire you to grow this delightful annual in your own garden.

            Arroyo Lupine is an annual wildflower in much of western California, parts of Arizona and Baja California.  It’s a lowland plant, usually growing in open places, coastal prairies and grasslands below 2000 ft. elevation.   It used to grow extensively in the Gardena area and still can be found in the Preserve.   Like many annual wildflowers, Arroyo Lupine was not seen every year.  But in years with the right  rainfall, our roadsides, fields and open areas were once covered with native lupines.

Arroyo (Succulent) lupine (Lupinus succulentus)

            Arroyo Lupine is the largest of our native annual lupines.  Like all annuals, it completes its entire life cycle in less than a year.  In most years, Arroyo Lupine will sprout from seed in winter (December to February) and then grow rapidly into a fleshy plant that is 1-2 ft. tall and wide.   The plants normally flower for about a month, usually in March or April in our area.  Once the seeds mature (in May or June) the plant dies and the cycle is complete.

The bright green leaves of Arroyo Lupine are ‘compound’,  composed of several leaflets.  The leaf shape is called ‘palmate’ because the leaf looks like an open hand.  This leaf shape is shared with other lupines and, along  with the flowers, is a distinguishing characteristic of the lupines.  The leaves are designed to trap water and channel it down to the soil.  On a foggy day you will notice  water droplets gathering on the leaves.  These droplets run down the leaves and into the ground, providing water to the roots.  The leaves are eaten by the caterpillars of several butterflies such as the Painted Lady, West Coast Lady  and Common Sulfur, so Arroyo Lupines attract butterflies to the garden.

Note pink color of pollinated flowers.

Arroyo Lupine, like all lupines, is a member of the Pea Family.  The flowers are densely spaced on flowering stalks that grow above the foliage to attract pollinators.  The flowers are a bright blue-purple with a white dot.  If you look at the individual flowers, you will see the similarity  to Sweet Peas and garden peas – all of which are in the Pea Family.  Arroyo Lupine flowers are pollinated by bees (often the larger bees) and occasionally by hummingbirds.  You can tell if a flower has been pollinated because it changes from blue-purple to a pink-purple color. 

Lupines improve the fertility of the soils in which they grow.  Many members of the pea family have a unique relationship with special soil bacteria.  These bacteria live within nodules in the roots and convert nitrogen into a form that can be used by plants.  When the plant dies, the converted nitrogen is released into the soil, improving the soil fertility.

            Native annual wildflowers like Lupinus succulentus grow best if they are seeded directly into the ground.          Because we planted our garden in late February, we raised our plants in pots before we planted them in the ground.  Most wildflowers have delicate roots and don’t like being replanted.  So next year, we’ll plant our seeds directly in the ground.  

Arroyo lupine seedlings
            Growing annual lupines is quite easy.  Spread the seeds on prepared ground in early winter (right before a good rain storm) and rake the seeds in lightly.   Then watch for the seedlings to emerge in the next few weeks (see photo).     If the weather turns hot and dry, you may need to water the seedlings to keep them alive.   Plants need regular rain/watering until they have flowered.  In most years, rainwater will supply all the water needed, since the  roots can reach down as much as 3 ft.   Once flowering is done, the soil needs to dry out.  This allows the seeds to mature – including the last stage of drying out.   If you continue to water, you’ll not get a good seed crop.

Seed pods at the bottom of the stalk are
becoming ripe - note brown color
Lupine seeds grow in seed pods along the stalk.  When the pods are dry, they twist open with a ‘pop’ showering the seeds across an area several feet wide.   These seeds will become next year’s plants, if they aren’t eaten by doves and other ground-dwelling creatures.  If you want to save Arroyo Lupine seeds, you’ll need to collect the pods when they are almost dry (they will start to turn brown & look dry).  Place the pods in a paper bag and seal it securely;  then place the bag in a cool, dry place.  Don’t be surprised if you hear the pods ‘explode’ within the bag.   

Lupinus succulentus can be grown in containers

            Arroyo Lupines can be grown in the ground or in large pots.  In fact, we suggest growing your first lupines in pots.  This allows you to understand the plant’s stages better and to collect seeds easily.  A pot of lupines blooming on a sunny deck or patio is a heart-warming sight!
Arroyo Lupine (Lupinus succulentus) - Mother Nature's Backyard garden

Arroyo (Succulent) lupine (Lupinus succulentus) has naturalized
 throughout Mother Nature's Backyard garden.


            The only drawback to growing lupines is that all parts of the plant are toxic (poisonous).  People and pets should  never eat the leaves, stems, seeds or roots.   It should be noted that many common plants whose parts are poisonous are routinely grown in home gardens.  These include daffodils, Iris, Angel’s Trumpet, Azaleas, Calla Lily, Columbines, Foxgloves, Plumeria, Privet and common ivy.

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