At this time of year, it seems that yellow flowers are especially prominent in the garden. It’s as if the sun, which is suddenly more visible in the sky, has an ally in the color of so many spring blooms.
I was reminded of yellow’s vaunted horticultural status in the current moment upon recently encountering a plant I had never seen before. Known as yellow forest lily (Veltheimia bracteata var. Yellow Comet), it displays a mini-forest of luminous yellow tubular flowers whose arrangement at the top of a 1-2 foot stalk will remind you of torch lily (Kniphofia spp.). What makes yellow forest lily special is its unusually wavy and lush green foliage and its preference for a partial sun to somewhat shady exposure. Moreover, it grows from a bulb, a highly unusual circumstance for a nearly evergreen species. In terms of leaf lushness and flower color, it is kin to yellow clivia (Clivia miniatata), whose flowers are typically seen in orange but whose yellow cultivar is also available. When it comes to exposure, clivias are even more shade tolerant than forest lilies.
Before leaving forest lilies, I should mention that they are also available in dark pink and a variety (Pastel Series) with tubular flowers that are pink at their base, transitioning to peach and yellow toward their tips. These and a cornucopia of other exotic flora are available through San Marcos Growers (smgrowrs.com), a Santa Barbara nursery that will be closing at the end of this year. In my humble opinion, every plant lover should spend a day or two going through the catalogue found on their website. More than 2,000 different plants are there; many of them you have never seen before and, once the nursery closes, will be challenging to find again. Moreover, the nursery has stopped propagating most of its collection.
Getting back to the flowers of spring, legumes take the most prominent place in the pantheon of this season’s yellow bloomers. All of the species that follow are leguminous plants. Woody perennials that bloom this time of year are dominated by a family of plants (Fabaceae) and the color of the flowers are nearly always yello. Acacias occur in tree, shrub, and ground cover forms. They grow wild in Australia and East Africa where summers are similar to our own, if not hotter, and so they bloom now before the heat arrives that would make their flowers wilt before pollination, preventing seed development and perpetuation of their species. Acacia trees put forth golden yellow flower puffs at this time each year. They grow quickly, even in compacted soil, and require little water; at maturity, they are no more than 25 or 30 feet tall.
A good example is Acacia baileyana, the golden mimosa. Its blue-gray feathery leaves impart an unparalleled softness to the tree’s canopy. Acacia baileyana purpurea is a variety with distinctive violet-tinted foliage. Knife acacia (Acacia cultriformis) has fascinating triangle-shaped leaves, and Sydney golden wattle (Acacia longiflora) produces scads of flowers in butter-yellow chains.
Weeping acacia (Acacia pendula) is a highly ornamental small tree that grows around 20 feet tall and displays tiny spherical yellow flowers. Foliage is silver to blue-gray to green, depending on sun exposure; the more sun it gets, the more silvery it becomes. Like many other acacias and leguminous trees in general, a weeping acacia may experience branch dieback within its first decade or two of life. Still, it will pleasantly persist for some years, showing off fresh cascades of leafy shoots.
Prostrate acacia (Acacia redolens ‘Low Boy’) is one of the toughest flowering ground covers available. Plants grow one foot tall and spread out to a diameter of 15 feet. Make sure to specify ‘Low Boy’ if you ask for them, since the common Acacia redolens species, although sometimes classified as a ground cover and commonly seen in Caltrans freeway landscaping, may grow up to six feet tall.
In the case of yellow pride of Barbados (Caesalpinia pulcherrima flava), large plumes of golden flowers are perched on feathery, fern-like shoots of bipinnate leaves. In my garden, this plant has been blooming since February and will continue to do so, on and off, until summer’s end. Flava is the subspecies name of yellow pride of Barbados since “flava” means yellow in Latin. The reason for the subspecies name is to distinguish it from its more familiar and widely planted cousin, red bird of paradise (Caesalpinia pulcherrima), whose brilliant red stamens emerging from red or orange flowers make it a garden standout too.
Canary bird bush (Crotalaria agatiflora), a gangly species that can grow up to 12 feet tall, is one of my favorite plants, and my absolute favorite plant with yellow flowers. Leaves are trifoliate and a lovely blue-green in color, presenting a perfect contrast to the brilliant yellow pigmentation of its flowers, a color that has been described as startling, electric, phosphorescent and high voltage. In the minds of some, the flowers have the appearance of miniature canaries perched on a branch.
Popcorn Senna (Senna didymobotrya) has leaves that smell like buttered popcorn. Flowers are golden torches, born on a shrub-like tree that may grow up to eight feet tall. Flower buds are black and present a stunning contrast to the golden blooms that emerge from them during summer and fall. Feathery cassia (Senna artemisioides) has delicate silvery blue pins for leaves and an abundance of dark yellow flowers. It is suitable for either full or partial sun exposures. This is another leguminous shrub whose principal maintenance requirement involves being left alone.
Golden shower tree (Cassia fistula) shows off long chains of blooms, so profuse that they completely obscure the tree’s foliage. This species is well-suited to our climate, so it is a mystery why you seldom see it here. And there is another stunning leguminous tree in gold, also strangely absent from our gardens. It is called copperpod (Peltophorum pterocarpum) due to the color of its pods, while its overall form, foliage, and flowering season correspond to those of the jacaranda. Both golden shower and copperpod are medium-sized trees, 30-40 feet tall, and hardy to 25 degrees. You can locate seeds of both golden shower tree and copperpod through online vendors.
The procedure for germination of seeds from leguminous trees is the same for all species. They generally have hard seed coats on account of their drought tolerance, giving them the ability to survive many years of drought without loss of vitality until rain finally comes.
Leguminous tree seeds may also contain chemicals that prevent germination until – when seeds are finally submerged in water after a soaking rain – these chemicals are diluted or leached out. Therefore, you should first soften the coats and remove these chemicals by plunging the seeds in water that has just been boiled. Keep the seeds in the cooling water for 24 hours.
Tomorrow, April 6, from 9 am – 5:30 pm, the South Coast Chapter of the California Native Plant Society is highlighting nine gardens in the South Bay featuring California native plants, demonstrating their water-saving qualities, low-maintenance needs, and ability to attract local birds, butterflies, and bees. Homeowners will be present to answer questions. There will be an ending talk with landscaper Mike Garcia at the Gardena Willows Wetland Preserve at 4 pm, with light refreshments. Each attendee will receive a free California poppy plant while supplies last. Tickets may be purchased at southcoast@cnps.org, upon which they will be emailed to you together with an itinerary of the garden tour.
California native of the week: Western five-fingered maidenhair fern (Adiantum aleuticum) is a cousin of classic maidenhair ferns of the multitudinous tiny leaflets studded along the stem. All maidenhair ferns are shade and moisture-loving, making them ideal subjects for a sun-protected front entrance or patio setting. In truth, fronds of the five-fingered variety, which open up like fingers on a hand, resemble those on sword ferns. This fern is deciduous to semi-evergreen, in the manner of certain other maidenhair fern species. I learned about this fern in the best book on California natives. It’s titled “California Native Plants for the Garden” (11th printing, 2022) by Bornstein, Cross, and O’Brien. I ordered a pristine copy from cnpsslo.org.
Do you have any spring bloomers with yellow flowers you would like to crow about? If so, send your testimonial to joshua@perfectplants.com. Your questions and comments, as well as gardening conundrums and successes, are always welcome.