Vegetative Reproduction - Two Types of Grasses
Multiple cadres of buds occur on Little Bluestem crowns ranging from 1-year-old (a) to 3-year-old (b) generations.
Bunchgrasses do not have stolons or rhizomes and instead develop dense clusters of tillers. Examples include Little Bluestem, Needleandthread and Prairie Junegrass.
Bunchgrasses repopulate primarily by tillering. New tillers develop in close proximity to current-year and previous-year tillers because buds primarily are located in the crown at the lower most nodes of parent tillers.
Multiple generations of buds often are discernible in bunchgrasses. Density, size and orientation of buds differ among species.
Buffalograss buds (a) originate at nodes where clusters of tillers develop on stolons (b).
Sod-forming grasses have stolons or rhizomes. Rhizomes are underground stems that produce roots at nodes. Stolons are above-ground horizontal stems that root at the tip or at nodes.
Buffalograss (see diagram, right) reproduces vegetatively by tillering from nodes on stolons. Buds on the crowns of buffalograss may differentiate into tillers or stolons.
In addition to producing buds for repopulation, nutrients are translocated through rhizomes from non-grazed to grazed tillers and from parent to daughter tillers for several years.
Western Wheatgrass rhizomes are composed of a relatively long series of nodes (a) and elongated internodes (d). Buds (b,c), roots (e), and rhizome scales (f) originate at nodes. Stage of development varies among buds on the same rhizome ranging from differentiated (b) to non-differentiated dormant (c) buds.
Continuous rhizomes produce aerial shoots from buds located at nodes, and the rhizome continues to grow underground (see Western Wheatgrass diagram, middle right).
In contrast, rhizomes that turn up and emerge as a green shoot are referred to as terminal rhizomes (see Prairie Sandreed diagram, lower right).
Growth of new rhizomes is seasonally most active in the boot stage of development, when tillers begin to elongate. Rhizome growth is dependent on the amount of current year herbage.
Therefore, grasses produce more rhizomes when precipitation is favorable compared to periods of drought, and vigorous grasses produce greater weight and length of rhizomes than overgrazed plants.
Management practices that periodically optimize growth of new rhizomes are likely to increase the spread and productivity of rhizomatous grasses.
Prairie Sandreed tillers (b) originate from extensive networks of scaly rhizomes (d). Buds occur at crowns of parent tillers (c) and at the end of rhizomes (a) with little or no tiller development from rhizome nodes in this species. Bud development ranges from differentiated (a) to dormant (c). Near the end of the growing season, differentiating prairie sandreed buds elongate to just below the soil surface (a). Tillers produced by these buds do not emerge until the following spring.