A poet is said to be someone who sees the world each day as if for the first time.
I can vouch for this poetic feeling whenever I see certain plants, no matter how familiar they might be. At this time of year, perennials robed in purple make it easy to compose an ode to that royal color. If I had to choose flowers of perennial plants with which to surround myself at this time of year, I would choose purple, and my next preference would not even be close.
Purple and green are appealing together because they are analogous colors. On the color wheel, analogous colors are separated by another color, which, in this case, is blue. Color experts regard the combination of analogous hues, whether expressed in green and purple interior design or purple flowers emerging from green foliage, as highly desirable both aesthetically and emotionally, creating a feeling of irresistible calm.
Mexican sage (Salvia leucantha) leads the purple parade each fall. This robust perennial will persist in the garden for up to a decade. Flowers are woolly purple wands, nicely complemented by gray-green foliage that has a delightfully honeyed fragrance. Give Mexican sage full to partial sun.
You can propagate when days shorten at this time of year by detaching four to six-inch shoot terminals, referred to as shoot tip cuttings. Make each cut below a node (where leaves meet stem), remove cuttings’ bottom leaves, and then insert the leafless portion directly into well-drained garden soil; you do not need to root the cuttings in pots to transplant later, although you could, of course, insert cuttings in containers for permanent growth on your porch or patio. By next spring, your cuttings will already have begun to send out roots and new leaf growth will be visible. Even in the hottest weather, Mexican sage should require no more than a single soaking per week. When Mexican sage starts to look shabby, as it will on an annual basis, cut it back to a height of eight inches.
Another fragrant fall bloomer is Heliotrope (Heliotropium arborescens); its olfactory delight is provided by its powerfully redolent blooms. Yet, while nearly all plants with fragrant flowers demand most of the day’s sun, heliotrope is uncomfortable with more than half a day’s sun exposure. Bringing fragrance into a semi-sunny to shade garden is a rare treat, yet heliotrope provides it. Since its roots are shallow, it can be kept in a container for years, eventually reaching a height of four feet.
Blue lace or throatwort (Trachelium caeruleum) is a third fragrant perennial for the fall garden. Generous clusters of aromatic flowers in lavender-blue, violet and purple grow on clumping plants to a height and girth of three feet. Flower clusters are four- to eight-inches wide and are a magnet to birds and butterflies, persisting for months in dry flower arrangements.
Blue potato bush (Lycianthes rantonnettii) is more purple than blue, especially the Royal Robe cultivar. Famous for being trained into a lollipop as a container plant, it is highly uncomfortable when confined to that limited form. It is grown that way because it is almost impossible to resist in the nursery when you see it covered with violet blue flowers in that form. However, it is a chore, based on my experience, to keep it looking like that for long. However, when left to its own devices, blue potato bush expands to something much more than a bush, growing into a ten-foot-tall by ten-foot-wide wall of flowers. You can train it to grow up a trellis or, planted as a screen or along a property line, it can serve as a spectacularly flowering hedge.
Blue hibiscus (Alyogyne huegelii) is also more purple than blue. This is a plant that needs full sun and a weekly soaking, but it’s laden with silky purplish-lavender flowers that begin to bloom in the fall and will continue to do so throughout the winter. The decorative leaves of blue hibiscus are palmate, deeply lobed and appear to be the hybrid offspring of an oak leaf and a snowflake. Blue hibiscus has a tendency to put out lanky shoots, which, if nipped before they grow too long, will gladly stay within the confines of a pleasing, nearly spherical form.
Gazing upon a blue hibiscus in full bloom is a horticultural high like none other, except perhaps for that of the Frikart daisy. Depending on the cultivar, Frikart daisy (Aster frikartii) blooms in lavender to purple and its flowers completely cover its foliage at precisely this moment of the year. Texas Ranger (Leucophyllum frutescens) belongs to that group of plants that thrive on being ignored. The reason you do not see more Texas Rangers, despite their spectacular autumn bloom, is because they are typically coddled to death. After their first year in the ground, they require minimal water, no fertilizer and no pruning. No insect pests bother them. The main reason for their virtual absence from our gardens is due to overwatering or poor soil drainage.
Mature Texas Rangers should never be watered more than twice a month. But even before watering comes into play, it is essential that Texas Rangers be planted in perfectly drained soil. Test your soil by digging a planting hole and filling it with water. After the water drains through, fill the hole again. If, after filling the hole a second time, the water is still standing after an hour, it is too heavy and must be amended with compost or other additives to assure that water drainage is adequate. There are more than a dozen Texas Ranger shrubs in the Leucophyllum genus, including eight-foot-tall giants and a three-foot compact type. You can regularly shear the larger varieties and keep them as hedges, but this will diminish their flowering and shorten their garden life expectancy.
Rose of Sharon (Hibiscus syriacus) flowers may be purple, rose, or white, although purple is most widely planted. At this moment, hundreds of blooms are visible on the plants, which grow into an eight-foot-tall, five-foot-wide, vase-shaped shrubs. For dramatic effect, each shrub should be given a separate domain in the garden. I once saw a stunning rose of Sharon collection in which each of half a dozen specimens occupied its own distinct area of a front yard. Grown against a building or in a hedge, with restricted air flow on any side, it is highly susceptible to mildew and mealy bugs. Cold hardiness is a major virtue of the rose of Sharon. It can grow in the chilliest desert and mountain regions, from Lake Los Angeles to Lake Arrowhead.
A vine of similar cold hardiness is Hardenbergia, sometimes referred to as lilac vine, although its color is typically deep purple. Varieties in pink or white are also available but not as durable. A member of the legume family, Hardenbergia manufactures its own nitrogen fertilizer and is thus suitable for desert soils of low fertility.
Last but not least, Salvia x Amistad is worth special mention. It is a shrub that blooms in purple from spring until frost. Amistad means friendship in Spanish. The botanist who discovered this plant in Argentina, instead of exploiting its commercial potential, decided to distribute its seeds indiscriminately, desiring only that everyone should share in its beauty.
California native of the week: Columbian monkshood (Aconitum columbium) is a highly toxic perennial whose flower shape is indicated by its common name. It is found throughout California in moist environments, whether meadow or woodland. It grows from tubers and is easy to cultivate as long as soil stays somewhat moist. Deep purple flowers, in addition to intricately cut leaves, are born on stems that grow up to six feet tall, making monkshood a highly desirable ornamental. Handle it with gloves since skin contact is likely to produce a rash. Columbian monkshood is widely available, both its seeds and as starter plants, through Internet vendors.
Do you have a plant that blooms in purple this time of year? If so, please send your experience with it to joshua@perfectplants.com. The questions and comments of all readers, as well as their gardening conundrums and successes, are always welcome.