Word of the Month: Botanical Definitions

Chapter member Margaret Chatham contributes these definitions in conjunction with plants being featured in our Potowmack Newsletter. You can click on the dates provided to see the relevant issue. All photographs are by Margaret Chatham unless otherwise noted.

Androgynous: see Gynecandrous.

Culm: a hollow or pithy stem, especially in the grass (Poaceae), sedges (Cyperaceae), or rushes (Juncaceae). Shown below: mixed fertile culms and leaves of Eastern Star Sedge (Carex radiata), at Fraser Preserve, 5/23/14. Culms don’t always stay upright. (Mar 2017)

culm

Dextrorse
Dextrorse/Sinistrorse: twining by the right hand rule: a vine that twines in the direction your right hand fingers curl while growing in the direction your right thumb points. Sinistrorse: same idea using your left hand. This young Beech tree (Fagus grandifolia) at Fraser Preserve has been shaped by a dextrorse twining *Japanese Honeysuckle vine (Lonicera japonica). This distinction can be diagnostic. *Chinese Wisteria (Wisteria sinensis) is dextrorse, while *Japanese Wisteria (Wisteria floribunda) is sinistrorse. Native Wild Yam (Dioscorea villosa) is sinistrorse, while *Chinese Yam (Dioscorea polystachya) is dextrorse. (Jan 2017)

Endozoochory: plant dispersal by seeds traveling through the gut of a bird or animal, like all those lovely berries you see waiting to be eaten in the winter. This includes natives such as dogwoods, spicebush, magnolias, and Mayapples (spread by box turtles), but also many invasive exotics, like Autumn olive, English ivy, and burning bush. (Jan 2015)

Forb: a seed-producing, non-grass plant that has no woody stems and so dies back to the ground at the end of the growing season. May be annual, biennial or perennial. (Jan 2016)

Guttation: the exudation of liquid from an uninjured plant surface, most often seen as droplets at the tips of leaf veins on moist mornings. Check your unmown grass tips or strawberry leaves. (Aug 2014)

Gynecandrous/Androgynous: description of the arrangement of flower parts on sedge spikes that contain both staminate and pistilate flowers. Gynecandrous spikes have the pistilate flowers grouped above the staminate, while androgynous spikes have the staminate flowers grouped above the pistilate. Pictured below left: the gynecandrous terminal spike Short’s sedge (Carex shortina) along with lower completely pistillate spikes. Pictured below right: the androgynous terminal spike of Wildenow’s sedge (Carex wildenowii). Photos by Gaylen Meyer. (Sep 2016)

Gynecandrous3

Imbricate
Imbricate: overlapping like roof tiles or shingles, derived from Latin from Greek meaning rain. The imbricate flower bud of Rhododendron catawbiense is shown. (Mar 2016)

Marcescent: withering but hanging on, like the leaves of some (especially young) oak and beech trees. (Apr 2014)

Mycoheterotrophic: parasitic on chlorophyllic plants by means of a mycorhizal fungus. (Aug 2015)

Myrmecochory: seed dispersal by ants. Plants like bloodroot, trilliums, and wild ginger grow a fatty attachment to their seeds called an elaiosome. Ants carry home the seeds, eat the elaiosomes, then discard the seeds in places well apart from the parent plant. This is why spring beauties may need your help to cross a road. (Jun 2014)

Noctodorous: releasing fragrance only at night. One example of a noctodorous flower is the Cranefly Orchid (Tipularia discolor), which blooms in July and August, long after its leaves have disappeared for the summer. (Jun 2016)

Peltate: shield-shaped, like a leaf with the stem attached to the middle of the underside rather than an edge. Examples: Mayapples (Podophyllum peltatum), American Lotus (Nelumbo luteum) and Whorled Marsh-pennywort (Hydrocotyle verticillata). (Mar 2015)

Ruderal: of a plant growing in disturbed habitats, or of a habitat subject to frequent disturbance. (Nov 2014)

Sinistrorse: See Dextrorse.