Monocarpic Plants

dinner plate (Aeonium urbicum) inflorescence

Aeonium ‘Blushing Beauty’

For those of you who are into botanical trivia, see if you can answer the following existential (having to do with life and death) question: What do carrots, radishes, lettuce, agaves, fishtail palms, aeoniums, annual flowers, bananas, zinnias, sunflowers, tillandsias, bromeliads, bamboo, wheat and rice have in common?

Hint: When a certain event occurs in the life of any of these plants, it’s a signal that another event is sure to come in the not too distant future.

Well, in case you have not figured out the answer by now, it will probably not surprise you, nevertheless, to learn that once the plants on this list have flowered (and produced seeds), they die. In botanical jargon, these plants are referred to as monocarpic.

The literal meaning of monocarpic is single (mono) fruit (carpic). Single-fruit plants fruit once and then they die. The fact that they produce a fruit is actually secondary to the formation of seeds that occupy the fruit. No physiological process in plants requires more resource expenditure than seed formation, so much so that certain plants literally exhaust themselves to death in order to make seeds.

Seeds are the ultimate insurance policy for a bright future regardless of prevailing conditions. Seeds can survive many years of drought just fine whereas whole plants may wither and die for lack of water. That’s why monocarpic plants invest everything they’ve got and go “all in” when it comes to seed production.

When horticulturists or gardeners describe a plant as monocarpic, they are referring to the fact that it flowers just once and then dies even though, strictly speaking, if you quickly remove the flower of a monocarpic plant before it can produce seeds, you may see it flower again, sometimes many more times, before its death.

The horticultural procedure known as dead heading addresses this issue. You will get a lot more flowers out of any plant — from pansies to roses — by removing faded flowers before they go to seed. Your pansies may bloom until June and your roses may flower until winter.

Interestingly enough, leafy vegetable crops — from lettuce to spinach — will delay going to seed when they are continually harvested since, in this manner, they are kept in a continuously juvenile or vegetative state. Flowering and going to seed occur when a plant matures and enters its adult or reproductive state and, even if you should see a flower stem start to grow from your lettuce, cutting this stem back immediately will help your lettuce persist in its vegetative state a while longer.

I got to thinking about monocarpic plants recently when considering the magnificent inflorescences that adorn the aeonium plants growing on the hillside behind Paul Weinberger’s home in Woodland Hills. Aeoniums, native to the Canary Islands, an archipelago located not far off the coast of northwest Africa, are magnificent monocarps, to say the least. Their gaudy and conical floral scepters, often more than a foot long and consisting of tightly clustered golden florets, bring gasps of disbelief when first encountered. They simply do not seem real.

When you look at aeonium roots, or the lack of them, it is easy to understand the insecure, monocarpic status of this genus. Although the plants are succulent, they will quickly shrivel when grown in full sun unless given regular moisture.

Aeonium roots are thin, sparse and pathetically shallow. For this reason, aeoniums do much better in half-sun locations where water economy is a consideration. On their island habitat, aeoniums cling to cliffs facing the ocean so that a regular wind blown mist keeps them hydrated yet, even so, their continued existence is sufficiently perilous that death itself is a reasonable price to pay for assurance that a new generation will be born once the aeonium’s monocarpic swan song has been sung.

Although an aeonium plant will die after flowering, it may form offsets or pups along the way, depending on the species, so that there will be plenty of young clones to take its place. A similar phenomenon is observed among many species of bromeliads. In addition to pups, agaves often produce bulbils or miniature plants on their flower stalks, increasing the number of offspring to take the place of the dying mother plant.

Although Weinberger has done a commendable job of bringing in a variety of water-wise and heavily flowering plants, it is his Jupiter’s beard (Centranthus ruber) that grabs the lion’s share of your attention when it comes to outstanding bloomers on site. There is irony here since Jupiter’s beard is virtually absent from the nursery trade. The only way you can bring this plant into your garden is by planting its seeds, available through online vendors, or by being gifted a seedling or two from a fellow gardener.

Weinberger plants nothing but water-saving plants on his hillside, including California natives. One of his outstanding selections is variegated Carmel creeper (Ceanothus griseus horizontalis ‘Diamond Heights’). In general, Carmel creeper grows best in the Valley and other inland locations in what is known as bright shade, meaning there is plenty of ambient light but protection from hot afternoon sun.

Tip of the week

Many weeds are edible and one of the most famous, in this regard, is miner’s lettuce (Claytonia perfoliata).

More often seen in Northern than in Southern California, its appearance on Weinberger’s hillside was a pleasant surprise.

The taste of miner’s lettuce is similar to that of spinach and, in the manner of that vegetable, is most flavorful when boiled. Miner’s lettuce got its name during the California Gold Rush when it was often the only source of vitamin C available and, without its consumption, those seeking to get rich quick were likely to get scurvy instead.

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