Our ‘A’ to ‘Z’ of Gardening Terms

Terms that begin with “R”

racemeA flower stalk on which the florets start blooming from the bottom of the stem and progress toward the top.
radial spacingThe horizontal spacing of branches around a trunk.
radicleThe first part of a seedling to emerge from the seed. Grows downward and develops into the primary root.
raphideA needle-shaped crystal of calcium oxalate in certain species’ cells that deter herbivores.
ray flowerOne of several small flowers often forming a ring around the disc flowers in a composite head.
receptacleThe enlarged end of a flower stalk to which the flower parts are attached.
recessive traitA genetic characteristic that is masked by a dominant gene.
relative humidityThe ratio of water vapor in the air to the amount of water vapor the air could hold at the current temperature and pressure.
resinA viscous, protective secretion of many conifers that is insoluble in water and hardens in contact with air.
resistantA plant having qualities that make it retard the activities of a pathogen or insect pest. See immune, tolerant.
respirationThe process within plants where sugars and starches are converted into energy.
reticulate venationA net-like vein pattern in some leaves.
reversion growthA stem that originates from, and has the characteristics of, the plant’s rootstock. See sucker.
Rhizobia bacteriaBacteria that live in association with the roots of legumes and convert atmospheric nitrogen to plant-available forms, a process known as nitrogen fixation.
rhizomeA thickened underground stem that grows horizontally with bud eyes on top and roots below. Bearded iris is an example of a plant that produces rhizomes.
rhizosphereThe thin layer of soil immediately surrounding plant roots.
ribosomeA celluar organelle which is the site of protein synthesis.
ripeness-to-flowerThe minimum vegetative size a plant must achieve before it is capable of flowering.
rootGenerally, the underground portion of a plant. It anchors the plant and absorbs water and nutrients.
root capA protective cover over a root tip.
root cuttingA section of root prepared for the purpose of vegetative propagation.
root hairA delicate, elongated epidermal cell that occurs just behind a root’s growing tip. Root hairs increase the root’s surface area and absorptive capacity.
root noduleA small swelling on a root resulting from invasion of nitrogen-fixing bacteria.
root pressureThe pressure developed by living cells in the root pushing water up the xylem.
root pruningThe cutting or removal of some of a plant’s roots.
root tuberAn enlarged, food-storage root bearing adventitious shoots.
root-boundA condition in which a plant’s roots have completely filled its container. Typically, the roots begin to encircle the pot’s outer edge. Further growth is prevented until the plant is removed from the container.
rootstockThe root or stem onto which a scion or interstock is grafted.
rosetteA small cluster of leaves radially arranged in an overlapping pattern.
rotDecomposition and destruction of tissue.
rotationThe practice of growing different plants in different locations each year to prevent the buildup of soil-borne diseases and insect pests, or the depletion of specific nutrients.
row coverA sheet of synthetic material used to cover plants in order to retain heat and exclude insect pests.
runnerSee stolon.
russetYellowish-brown or reddish-brown scar tissue on a fruit’s surface.