persistent [ per-SIS-tuhnt ] adjective: remaining attached beyond maturation after similar parts of the plant, such as flowers, seeds, or leaves, have normally dropped off or their function is completed
In human life, persistence is often considered a virtue, a tribute to endurance, to providing continuity. Or it can be a negative attribute, a lingering on, as of symptoms of disease. In botany, persistent also has an aspect of ambiguity. If plant parts persist after maturing, after their function is over, are they sapping the plant of nutrients that should go elsewhere? Or do they have some other use than the primary function?
Plants with Persistent Fruits
Left (top/bottom) to right: Ilex verticillata ‘Red Sprite,’ Oxydendrum arboreum, Clethra alnifolia ‘Hummingbird,’ Malus coronaria, Cephalanthus occidentalis.
Fruits that persist may provide the plant opportunities to reproduce by seed in more than one season, which would be an advantage if the year of fruiting was not a good one for seed germination. In the case of Clethra alnifolia (sweet pepperbush), for example, the fruits, small green capsules, turn brown over the summer season, and depending on the source, are described as brown or copper colored, dry, dehiscent, 3-valved, pubescent, 1/8 inch diameter, and persist “through winter,” or even “for a year or more.”
The word persistent is often married to the term deciduous, as in “deciduous-persistent” or “deciduous and persistent” for example in descriptors of the fruit of Clethra alnifolia. Some sources, for example the Utah State Forestry Extension’s “Tree and Botanical Glossary,” seem to refer to this meaning when they define the term. Their glossary says: “Persistent leaves: leaves that remain on the tree during winter.” In our view, those leaves would be described as marcescent. Older sources, such as the glossary of the Arnold Arboretum at Harvard (from 1940) defined persistent as “remaining attached, not falling off; opposite of deciduous.” Some sources say that evergreen trees have persistent leaves or needles.
Plants with Persistent Bud Scales, Styles, and Fronds
Left to right: Mahonia bealei, Clematis terniflora, Matteuccia struthiopteris, Onoclea sensibilis.
This whole question of the ambiguity of the term is explored in an article by Bob Harms of the University of Texas. He comments that the functional term “abscising adds a structural factor” to the falling off of plant parts, but it is not the whole story. Some plants lose a portion of their leaves or needles each year, usually at a particular season or time of year, but not all of them. On some plants, like Mahonia, bud scales persist long after their main function of protection of the bud is complete; in that case they are described as persistent. Plants like Clematis have a persistent style, which terminates the achene and plays a role in seed dispersal. When the aggregated achenes break apart, the long feathery style acts like a kite tail and helps each seed sail on the wind. Some ferns have fertile fronds that persist through winter. Unlike the sterile fronds that wither with the frost, fertile fronds of both natives Matteuccia struthiopteris (ostrich fern) and Onoclea sensibilis (sensitive or bead fern) remain through the winter, releasing their spores the following spring.
Plants with Persistent Calyxes
Left to right: Hamamelis virginiana (persistent calyxes and flowers with fruit), Rosa ‘Dr. W. Van Fleet,’ Datura inoxia, ‘Moneymaker’ tomato.
Missouri Botanical Garden’s glossary adds withered as another criterion to their definition of persistent: “remaining attached to the plant, albeit withered beyond the expected time of falling, e.g. of sepals not falling after flowering”
Such is the case with native Hamamelis virginiana (common witch hazel) whose fruits develop in the second season, maturing in fall when the plant flowers again. Depending on the year, the lightly scented yellow flowers appear either during the time when the deciduous leaves are in fall color, or as is often the case locally, after leaf drop. The flower sepals (calyxes) and pollinated ovaries persist over the course of the winter. After fertilization in spring, greenish seed capsules form and become woody and brown, and when ripe (often not until fall), split, exploding the black seeds distances of up to 30 feet. The plant’s genus name, hamamelis, comes from the plant’s relatively rare phenomenon of simultaneous flowering and fruit: hama means at the same time, while melis (melon) means apple or fruit. Other examples of plants with persistent calyxes are pomegranate, rose, and members of the Solanaceae (nighshade family) like Datura, eggplant, and tomatoes.
References
Clethra alnifolia. Plant Toolbox. North Carolina State Extension.
Clethra alnifolia. UConn Plant Database, University of Connecticut, College of Agriculture, Health and Natural Resources © Copyright Mark Brand, 1997-2015.
Hamamelis virginiana. (Witch Hazel). Minnesota Wildflowers.
Hamamelis virginiana. Plant Finder. Missouri Botanical Garden.
Harms B. Bud Scales in the Berberis/Mahonia Literature. A Phenological and Morphological Study of Berbis in Northern Hays County (Central Texas). Billie L. Turner Plant Resources Center. The Universitty of Texas at Austin (http://w3.biosci.utexas.edu/prc/DigFlora/BERB/bscale-lit.html, accessed December 5, 2021).
Harms B. Deciduous and Persistent. A Phenological and Morphological Study of Berbis in Northern Hays County (Central Texas). Billie L. Turner Plant Resources Center. The Universitty of Texas at Austin (http://w3.biosci.utexas.edu/prc/DigFlora/BERB/deciduous.html, accessed December 5, 2021).
Weakley AS, Ludwig JC, Townsend JF. 2012. Flora of Virginia. Botanical Research Institute of Texas.
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