Wonders of Wigandia

For years, it had baffled me. I caught a glimpse of it every time I traveled north on Beverly Glen Boulevard, just as I began the ascent that ended at Mulholland Drive. At the base of the steep embankment on either side of the road was a plant unlike any other I had ever seen. It had dark green tobacco-like leaves that were easily 12 inches across, and large, bright, violet, vertical clusters of flowers. I thought it might be a California native since it was clearly growing without supervision and in extremely challenging circumstances. It also sprang up here and there, from seeds that it dropped, in a haphazard fashion, indicating a high degree of self-sustainability.
Over the years, the numbers of this mystery plant declined. This was an inevitable consequence of carving into the embankments for construction purposes. Last weekend, as I searched for this horticultural landmark, I realized that it had vanished from the west embankment but still had a few representatives on the east side of the road. I had to get out of the car and take a picture, not knowing how much longer it might still be there. Still, its identity eluded me.
Luckily, there is a website called Dave’s Garden (davesgarden.com) that allows you to e-mail pictures of plants for identification. I had visited the site many times but had never noticed this feature.
Within two hours of posting the picture, it had been identified by a gardener in north central Texas.
The plant is Wigandia urens, the absence of a common name indicative of its exotic status. Native to Mexico and South America, it has a tropical look but is as drought tolerant as any California native. This is a plant with a protean growth habit, developing into a ramrod straight sentry soldier where space is limited, yet growing into the biggest funnel-shaped shrub you have ever seen, up to 20-feet tall, when given room to expand on all sides.
In my opinion, Dave’s Garden is the premier gardening website. Registration is free and there is abundant information on thousands of plants, including testimonials from gardeners around the country as to the growth requirements of just about any plant you have ever seen, including both positive and negative experiences with any particular species.
I was pleasantly surprised to encounter a luxurious expanse of dwarf bottlebrush growing in a long median strip on Whites Canyon Road, in Canyon Country, in the Santa Clarita Valley. For some reason, bottlebrush trees are seldom seen in the Santa Clarita area, whether it is due to their poor wind resistance or to the fact that they struggle in alkaline soil or both. However, the dwarf bottlebrush (Callistemon viminalis “Little John”), which flowers most of the year, has really taken off, continual exposure to car exhaust notwithstanding.
Its foliage is bluish green and its deep scarlet trademark flowers are even more densely arrayed than you find on any bottlebrush tree.
Q. Several years ago, I went to my home for a visit, on the Big Island of Hawaii, and brought back a bag of macadamia nuts. I planted one in the yard, it grew to about 12 feet, has yellowish leaves, and has stopped growing.
I have also planted citrus and avocado trees but they did not do well at all even though I would add compost before planting. Do you know why these trees have struggled?
-Maku Cuizon,
Thousand Oaks
A. I know that Thousand Oaks has areas of intractable, poorly drained soil. Yet, the Conejo Valley Botanical Garden does boast a large collection of tropical fruit trees so it is possible to grow them in your area.
I would suggest amending the soil in a radical way, digging a planting hole 2-3 feet wide and deep before filling it with fast-draining top soil, available by the bag in most nurseries, and amendments.
That being said, growing macadamia trees is its own unique science. The macadamia, named for chemist John Macadam, is indigenous to Australia and belongs to the Protea family of plants. Macadmia trees demand mineral-rich, fast-draining soil. Once established, however, since they are slow-growing, they should only be fertilized lightly twice a year with citrus food or fish emulsion.
If you can wait until they mature, you will see that macadamias make excellent shade trees, growing to around 30 or 40 feet, so that, even if your nut harvest is minimal, you can still have a picnic in their shadow. As in the case of most fruit and nut trees, single macadamia trees will produce a crop, but planting two different varieties side by side will yield more nuts than planting two of the same variety together.
As stated, macadamias are in the Protea family, which includes popular ornamental genera such as Grevillea, Hakea, and Leucospermum. These plants show off fascinating flowers, from spidery combs to pin cushions, and require little water once established. They may be harmed by any fertilizer that contains phosphorus so, as a rule, it is a wise practice to refrain from using any fertilizer other than fish emulsion.

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