plumeria tree in Sherman Oaks, California

Question: What should I do, if anything, to protect my plumerias from severe cold and/or freezing? Can you provide any suggestions? I would hate to lose them due to what could be extremely cold temperatures this winter season.
– Bill Moak
Simi Valley
Answer: Plumerias are cold-sensitive, especially when young, and require protection when freezing temperatures are forecast. Older, more robust specimens should survive a freeze, as long as it’s not too severe, even if they suffer some damage.
With younger, smaller plants, the safest course of action is to wrap them in burlap – potato sacks are perfect – toward evening and unwrap them in the morning. You can also simply drape an old bedsheet or blanket over your plumeria.
Another idea is to decorate plumeria or any other cold-sensitive plant with Christmas lights to provide an extra measure of heat, although wrapping or draping with an insulating material is the more thorough way to go.
Alternatively, you can make a box out of wood and plastic, open on one end, and then place the box over your plumeria before nightfall. Again, make sure to remove the box when morning comes.
You might also consider planting the ‘Celadine’ plumeria variety, available through Internet vendors, which is moderately cold-tolerant.
The most successful Valley plumeria I have seen is a 15-foot-tall, umbrella- shaped tree growing near the corner of Moorpark Street and Sunnyslope Avenue in Sherman Oaks. It faces west and grows flush against the facade of a two-story building. It is in peak bloom at the moment, displaying dense clusters of fragrant pink flowers.
Mandevilla surprise
Plants never cease to amaze me. Just when I think I have a particular species figured out, it surprises me. In more than 25 years of Valley plant watching, I had never seen a truly lush Mandevilla vine.
Mandevilla is that gorgeous vine with the large pink pinwheel flowers and ribbed foliage. It is in the dogbane family, a relative not only of plumeria, but of oleander and star jasmine as well.
Nothing looks more glorious in a container at the nursery than Mandevilla but, once planted, it nearly always goes into a sparsely flowering, chlorotic, yellow-leafed funk from which it never recovers. It attracts insect pests, too.
But then, just the other day, near the corner of Haskell Avenue and Dickens Street in Encino, I saw a near perfect Mandevilla that stopped me in my tracks. It was a dense carnival of pink pinwheels against a background of unblemished sea-green foliage.
Of course, growing conditions help to explain this, or any other, horticultural success.
The bottom half of the vine disappears into a shrub. This means that the vine’s roots have to be losing the battle for growing room waged against the more aggressive shrub roots that surrounded it. But then I recalled hearing, and learning from personal experience, that the only way to produce a significant flowering display with Mandevilla was to keep it container bound.
Now, confronted by a Mandevilla whose roots were obviously constricted by a competing shrub, I understood. Flowering is often a response to stress. When a plant senses that its survival is in doubt, it throws out a mass of flowers in an effort to set seeds before it dies. This is commonly seen in agaves, whose majestic, towering flower spikes are their swan song, produced immediately before death of the mother plant.
It’s not that this Mandevilla was about to die, but the stress exerted on its roots must have created an impression that its days were numbered. Also, the fact that its roots were completely sheltered from the elements may have helped it flower, in the manner of clematis and other plants either tropical in origin or possessing a delicate root system.
The Mandevilla vine was also growing against a brick wall, giving it the luxury of radiant nighttime heat in fall and winter, to keep it from slipping into cool-season doldrums from which it would probably never recover.
In response to the flowering woes of the traditional or old-fashioned Mandevilla, hybrids that flower with more ease have been developed. These are sometimes called dipladenia but they are really Mandevilla hybrids.
Some years ago, ‘Red Riding Hood’ came on the market, with smaller but more numerous flowers than old-fashioned big pink Mandevilla. ‘Red Riding Hood’ was not quite as finicky as the original type.
Now there is an even more floriferous Mandevilla called ‘Sun Parasol Crimson Red.’ Its deep cardinal flowers are the most powerful red you will see anywhere. ‘Crimson Red’ is more floriferous and cold-tolerant than all other types and makes it through a mild freeze just fine.
Different view of cycads
You may think of cycads as tough plants from the age of dinosaurs, with leathery foliage that is sometimes barbed, but definitely not soft and asking to be touched.
Ceratozamia cycads, however, would be an exception and, even more so, the singular Debao cycad (Cycas debaoensis.)
Debao cycad is sometimes referred to as the multipinnate cycad (pinnate comes from the Latin word for feathers) because of its ultra-lacy foliage. Veteran garden designers call it the ultimate species as far as ornamental foliage is concerned.
Discovered in Debao County, China, in 1997, this is an extremely endangered species, having been heavily poached in the wild over the last 15 years. Its fernlike arching fronds emerge from an underground caudex, or thick stem, and reach up to 10 feet in length. Leaflets resemble silk oak (Grevillea robusta) foliage.
With the holidays approaching, you may consider procurement of a Debao cycad for the plant lover who has everything. Be prepared to spend over $100 for a good-sized plant, a bit less for smaller specimens.
One local cycad nursery you may wish to visit is Maurice Levin’s Jurassic Garden in North Hollywood. Levin grows Debaos and many other cycads and unusual succulents. You can arrange a visit by calling him at 818-759-0600.
A wealth of cycad information may be found on his website: www.cycadpalm.com.
Tip of the week
Not long ago, you could not find lettuce plants growing at the nursery, but now this has changed.
Lettuce (Lactuca serriola) is one of the easiest vegetables to grow. It sprouts reliably and quickly from seed but is difficult to transplant when small and, thus, it made no sense to grow it in the six-pack containers in which winter vegetables have traditionally been offered for nursery purchase.
Suddenly, though, nearly full-grown lettuce and other winter vegetable plants are being offered in 4-inch or larger containers.
You may wonder, “What’s the point? Why not just go to the supermarket and buy them?”
Well, there is something called edible landscaping. You can edge the side of a flower bed with lettuce, for example. It’s an attractive lush green annual and, plucking off a leaf or two from each head to make a salad, keep your lettuces nice and trim throughout the winter season since, like any pruned plant, they will sprout new leaves after trimming. This will continue until weather warms in the spring, when lettuce goes to seed and dies.
Keep in mind that root and leaf crops – carrot, radish, beet, lettuce, arugula and cabbage – are well-suited to fall and winter growing.
Lots of vegetables are now being offered in larger nursery containers than previously. If you know how to nurture them for continual harvest, it might save you money to purchase these vegetable plants and keep them growing in pots or in the ground, as opposed to buying them at the store.