Cassia’s long season brings bountiful blooms

Winter cassia is one of the sunniest shrubs you can put in your garden. In late summer when other plants are beginning to think of cutting flower production for the year, Cassia bicapsularis begins unfurling lavish racemes of bright butter-yellow flowers with curling petals and pronounced stamens at the tips of its branches. These generous sprays of orchid-like flowers are a wonderful addition to autumn bouquets. Their season is long. On the coast cassia can be relied on to bloom all through winter and into spring when other flowers begin providing welcome spots of color in the garden.
     The foliage of this shrubby legume is a deep-emerald green that looks fluffy and deceptively lush as if it gulped gallons of water every day. While cassia appreciates and flourishes best with fertilizer, neutral pH soil, ample water and sunlight it will grow reliably in shade with stingy water and near neglect. Absorbent mulch or organic material worked into the soil at planting time will act to hold water and help it survive during prolonged dry periods.
     Native to South America, Cassia bicapsularis is now pan-tropical and common across the southern United States. It is cold tender and requires warmth. In case of frost, prune the plant back severely and allow it to regrow from the roots. Cassia self-seeds readily, but is not a pest in our dry area. Yank seedlings if they appear or repot them to use as new plants. Cassia is easily propagated from softwood cuttings or seed. Cylindrical six-inch pods form on the branches at the end of the bloom season and slowly turn brown. Allow seeds to dry in the pods. Scarify or scald them in hot water and soak overnight as you would pea seeds and plant in the ground or pots.
     Cassias make showy specimen plants when trimmed and staked as small trees. They are subject to breakage, but are very amenable to pruning and shaping. Their root system is shallow, making them a suitable choice for parking strips and walkways. They topple over easily and benefit from support. One stratagem is to plant them in a hedge between sturdy plants that will hold them upright, allowing the cassias to peek through and provide a punctuation of color. They can be grown as a mounded shrub or encouraged to spill down a hillside in a cascade of cheerful gold and green. To achieve low shapes, stake flexible young trunks down early in the growing season so that they are horizontal to the ground. Continue to pinch the ends of naturally vertical new branches back during the year to encourage bushy lateral growth.
     Cassia and Senna are host plants to the larvae of species of yellow sulfur butterflies. In San Diego, all through the warm months, until they hibernate in their pupas for winter, beautiful two-inch cloudless sulfur butterflies (Phoebis sennae) can be seen fluttering restlessly through the air above cassia plants like fragments of detached sunshine. If you search for the well-camouflaged caterpillars you’ll find that they are green when they feed on foliage and turn yellow when they begin to dine on flowers. This plant is an absolute must for butterfly gardens. Insects, birds, bees and butterflies all frequent it for food.
     ‘California Gold’ is the commonly seen cultivar. ‘Worley’s Butter Cream’ reaches six to eight feet and its fragrant flowers are a paler shade of yellow.