perennial, evergreen, hardy

From an exchange on Facebook a few days ago, in which (at least) two of the participants use the term perennial to refer to plants that are green all year round, that don’t lose their leaves for a dormant season. The discussion was set off by DA (not knowing the privacy wishes of the participants, I refer to them by their initials), posting about a practice that puzzles him:

DA: I never understood why [people] bother to plant [fruit] trees that don’t bear fruit.

To which DS replied with a number of reasons for the practice, but along the way introducing perennial in the sense ‘green all year long’ (relevant materal boldfaced):

DS: They provide many other benefits, for birds, shade, soil augmentation … they hold together hills so they don’t wash away .. and much more. Besides, they can be lovely. As far as I know, there are no perennial fruit trees so they can’t be used for privacy.

DA to DS: Citrus? [a point of fact: citrus trees are green all year long, unlike, say, peach trees; they don’t lose their leaves during a dormant season]

… MC to DA: mulberries are trees that don’t lose their leaves. That makes them perennials.

DA to MC: I have several of them and they all lose their leaves. [a challenge to MC on whether mulberries lose their leaves, rather than on the appropriateness of the term perennial; in any case, mulberries do in fact lose their leaves once a year and then grow new ones]

I then intervened in response to the DS/MC usage of perennial:

AZ: There’s a deep terminological confusion here, resulting from the non-technical senses of “perennial”.

Which I will now discuss. Then I’ll move on to the historical senses of perennial in reference to plants: there are two, one of them (now long obsolete) the DS/MC usage, now covered by the botanical term evergreen (as opposed to deciduous); the other referring to length of life, with the botanical term perennial used of plants that live on indefinitely (as opposed to annuals, which die after one season, and biennials, which bloom in their second season and then die).

But wait! There’s more! Perennials, in botanical usage, have lives not limited by a calendar program; they live on until they die of weakening due to old age. But… some of them — like avocado trees, which botanically are evergreen perennials — will die in a serious frost (a killing frost, as we say), no matter what. Fir trees are also evergreen perennials botanically, but they flourish through long heavy-freezing weather. In botanical terms, fir trees are said to be frost-hardy (sometimes just hardy for short), while avocado trees are frost-tender (or just tender).

All of this terminology was devised as technical usage by botanists, but quickly spread to everyday usage by gardeners, since the distinctions coded in them are crucial for gardeners. Back in Ohio, I couldn’t plant either citrus trees or silk oaks (grevilleas) in my garden; though they’re evergreen perennials, they’re tender. (I did grow them there, but in pots that I had to bring indoors during the winter.)

Similarly, if I want trees that will serve as visual screens all year long, I’ll stick to evergreen trees (ones that are suitable for my climate) and avoid the deciduous ones.

And if you want plants that will bear edible produce year after year, you’ll go for the perennials: strawberries, raspberries, and blackberries, for example. (They’re deciduous, but they are long-lived perennials. And hardy too.) The fact is that most vegetable plants (producing culinary vegetables) are annuals — lettuce, spinach, beans, cabbage-family plants, etc. (though there are perennial species of some of these) — so you have to be prepared to grow them fresh from seed every year (or buy already-sprouted plants every year). And a few — artichokes (tender) and parsley (hardy), in particular — are biennials. For artichokes, that means you don’t get the edible flower buds until the second year; while for parsley, that means you only get the leaves for herbs the first year, since the leaves get bitter the second year, as the plants go to seed.

Everyday (non-botanical) usages for perennial and evergreen. From NOAD, with the botanical senses omitted:

adj. perennial: [a] lasting or existing for a long or apparently infinite time; enduring or continually recurring: his perennial distrust of the media | perennial manifestations of urban crisis. … [c] [attributive](of a person) apparently permanently engaged in a specified role or way of life: he’s a perennial student

adj. evergreen: …[b] having an enduring freshness, success, or popularity: in Hollywood parlance, Star Trek is an evergreen asset.

They share the component of enduring or lasting long, exploited, for example, in the song “Evergreen”. From Wikipedia:

(#1) Like a rose under the April snow / I was always certain love would grow / Love ageless and evergreen

“Evergreen” … is the theme song from the 1976 film A Star Is Born. It was composed and performed by Barbra Streisand with lyrics by Paul Williams, and arranged by Ian Freebairn-Smith. [Streisand in #1 above]

The sense of evergreen here is pretty straightforwardly a metaphorical extension of ‘ever green’, and the botanical usage is simply a specialization of ‘ever green’ to a use for plants.

Many botanical and zoological terms are specializations — technicalizations — of everyday vocabulary, and some of these (evergreen among them) are felicitous, but (I have maintained on this blog), some are unfortunate. It’s distressing to have to explain to perfectly intelligent people that a strawberry is not, technically, a berry, while a watermelon is — a terminological choice that makes scientists look just silly.

For the term opposed to evergreen, botanists chose to take a different tack, coining a learnèd term based on Latin or Greek: here deciduous, based on a Latin verb meaning ‘fall down, fall off’.

Perennial is a more complex matter. OED3 (Sept. 2005) gives us this:

Etymology: < classical Latin perennis lasting through the year or years ( < per per prep. + annus year) + –al suffix.

It’s important here that the stem ann-/enn- ‘year’ is, semantically, neither singular nor plural, but is consistent with either understanding of the stem: ‘lasting through the year’ (i.e., ‘ever green’) or ‘lasting through the years’ (i.e., ‘long-lived’). In fact, with reference to plants, according to OED3, both senses are attested, at about the same time: one early sense, now obsolete, was ‘evergreen’ (1st cite c1660); and the other is the surviving ‘remaining alive for a number of years’ sense (1st cite 1669).

Now, more of my response on Facebook (edited for this blog), with some specific examples.

To start with, all trees are perennial, in the botanical sense. Many perennial plants, however, are deciduous, losing their leaves — going dormant — in one season of the year and regrowing new ones in a later season; while others are evergreen. Among the evergreen trees are (in general) the conifers, but also citrus trees, live oaks, trees in the laurel family (among them bay trees, and avocados), and more. Trees in the rose family — peaches, pears, apples, almonds, etc. — are all deciduous, and so are trees in the walnut family, and so are mulberry trees. The so-called live oaks are evergreen; all the rest in the genus Quercus are deciduous.

Then there’s hardy vs. tender. Frost-tender trees are tropical or semi-tropical trees — citrus, avocados, jacarandas, mango(e)s, grevilleas, peppertrees, etc. — that won’t survive in cold climates, but they’re perennials in warm climates. Similarly for tree ferns and for palms, both of which are (evergreen) perennials, but frost-tender.

Mulberries and their cousins. A fascinating genus of deciduous trees that somehow came up in the Facebook conversation above. From Wikipedia:


Morus, a genus of flowering plants in the family Moraceae, comprises 10–16 species of deciduous trees commonly known as mulberries, growing wild and under cultivation in many temperate world regions.

… The mulberry fruit is a multiple fruit, approximately 2–3 cm (3⁄4–1 1⁄4 in) long. Immature fruits are white, green, or pale yellow. In most species the fruits turn pink and then red while ripening, then dark purple or black, and have a sweet flavor when fully ripe.

… The ripe fruit is edible and is widely used in pies, tarts, wines, cordials, and herbal teas. The fruit of the black mulberry (native to southwest Asia) and the red mulberry (native to eastern North America) have the strongest flavor, which has been likened to ‘fireworks in the mouth’.

The fruits of most species contain an intense pigment, which stains hands and mouths and sidewalks. Common species are small, tough trees that tolerate city conditions and often grown as ornamentals; alas, the male trees produce highly allergenic pollen. Other species are grown for their leaves as silkworm food, and still others for their bark as a source of paper.

Morus is the type genus of the Moraceae (a family that’s come up a fair number of times on this blog, but without getting counted in my inventory of plant families — so now it’s #98). From Wikipedia:

The Moraceae — often called the mulberry family or fig family — are a family of flowering plants comprising about 38 genera and over 1100 species. Most are widespread in tropical and subtropical regions, less so in temperate climates; however, there is a cosmopolitan distribution overall. … The family includes well-known plants such as the fig, banyan, breadfruit, [jackfruit], mulberry, and Osage orange.

All about figs in my 5/20/15 posting “Fig time”, including this familiar plant:

(#3) Ficus carica

And then the Osage orange. From Wikipedia:

(#4) Maclura pomifera

Maclura pomifera, commonly known as the Osage orange, hedge, or hedge apple tree is a small deciduous tree or large shrub, typically growing to 8 to 15 metres (30–50 ft) tall. The distinctive fruit … is roughly spherical, bumpy, 8 to 15 centimetres (3–6 in) in diameter, and turns bright yellow-green in the fall. The fruits secrete a sticky white latex when cut or damaged. Despite the name “Osage orange”, it is only distantly related to the orange, but rather is a member of the mulberry family, Moraceae. Due to its latex secretions and woody pulp, the fruit is typically not eaten by humans and rarely by foraging animals …

Maclura pomifera has been known by a variety of common names in addition to Osage orange, including hedge apple, horse apple, bois d’arc, bodark, monkey ball, bow-wood, yellow-wood and mock orange.

… The trees acquired the name bois d’arc, or “bow-wood”, from early French settlers who observed the wood being used for war clubs and bow-making by Native Americans.

… The Osage orange is commonly used as a tree row windbreak in prairie states, which gives it one of its colloquial names, “hedge apple”.

The fruit is hard and aromatic. It is also excellent as a childhood missile.

5 Responses to “perennial, evergreen, hardy”

  1. chryss Says:

    Nice. Where I am (one degree south of the Arctic Circle), unsurprisingly, the limitation for perennials is winter hardiness. Many species and varieties that are perennials in temperate climates are “grown as annuals” here, for example just about all high-producing strawberry varieties. (There are two or three hard-to-find perennial cultivars, and a few cultivars that are marginal, such as Fort Laramie.) Reliable non-shrubby ornamental perennials include (at least some of) Bergenia, native irises, Veronica, Columbine, Lupine (also native), Delphinium, globe flower, Gentium, Allium, day lilies, bleeding heart, lily-of-the-valley. Some think of pansies as perennials, but AFAIK they’re annual or biennial, but just reseed themselves reliably. As for kitchen plants, chives are great, rhubarb is ok with well-amended soil, asparagus somewhat marginal, and I know one gardener who overwinters lovage outdoors. I’d really like to get some mint or maybe a rosemary bush through the winter.

  2. arnold zwicky Says:

    Nice report. Hardiness comes in degrees, of course. I’m not surprised that the fancy strawberry hybrids can’t take your winters; some varieties of wild strawberries are Arctic-Circle-tough, but they’re not the same thing.

    Rosemary is something else. We had trouble finding a variety of rosemary that would survive *Columbus OH*, and they were said not to work up in Cleveland. But that was decades ago, and everything’s been warming.

  3. Robert Coren Says:

    My memory says that years ago here in Gloucester, MA, we managed to get a rosemary plant through a winter or two, but when that stopped happening we took to potting our rosemary and bringing it to Cambridge to spend the winter indoors under a grow-light; sometimes they survive, mostly they don’t.

    It was only pretty recently that one of the many seed catalogs I get every year admitted that rosemary is only perennial from Zone 7 south (we’re at the northern edge of Zone 6).

    A lot of our supposedly perennial herbs didn’t make it through the most recent winter, including several ornamental thymes that had survived for at least 20 years.

  4. Robert Coren Says:

    Years ago, I started a new job out in the suburbs, and because I was never an early arriver, I sometimes had difficulty finding parking anywhere near the entrance I used. One day about a month after I started there, I was surprised and pleased to find a very convenient spot, the only one free for a considerable distance. It was only that evening when I came back to my car that I realized the reason the spot had been free: people who had been working there longer knew better than to park under a mulberry tree in June.

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