# Dactylis glomerata

**Orchardgrass**

**Poaceae**

*Dactylis glomerata* is a widespread perennial grass, originally from
Eurasia. It is a highly competitive species, and has occasionally been
grown with alfalfa in order to keep weeds out of the stand (e.g, Spandl
et al., 1997), or tree species out of electrical utility right-of-way
(Brown, 1995). Its ability to hybridize is thought to contribute to its
adaptative versatility (Volaire, 1995). Populations of orchardgrass from
the Mediterranean demonstrate different strategies in reponse to drought
conditions: they enter a summer semi-dormant state, whereby individuals
maintain relatively high tiller density and accumulate significant
levels of carbohydrates, which are then used for active growth in the
fall; or they remain active during the summer drought, and undergo high
levels of mortality (Volaire, 1995). These latter populations are
unadapted to Mediterranean dry environments. Invading orchardgrass in
California habitats with a similar climate regime, then, may have
originated from the more drought-adapted lineages of *Dactylis
glomerata*. In general, while *D. glomerata* tends to be most productive
on nutrient-rich sites, it persists across a wide range of ecological
conditions.

Short day lengths are satisfactory to induce flowering in *D.
glomerata*; at no stage of development is any cold needed for flowering
in this species (Heide, 1994).

The deeper in the soil profile *D. glomerata* seed is buried, the lower
the percent germination (Andrews et al., 1997). These authors also found
that the ability of *D. glomerata* to emerge from soil was not related
to its mesocotyl length. Generally, they found that *D. glomerata* tends
to have lower percent emergence than other range grasses (e.g., *Lolium
multiflorum*, *Bromus willdenowii*, and *Festuca arundinacea*).

*Dactylis glomerata* has a high relative growth rate compared to other
species of grasses with which it co-occurs in its native range (e.g.,
*Bromus erectus* and *Arrhenatherum elatius*), whether conditions are
high- or low-nutrient (Ryser and Notz, 1996). Although this ability
leads to competitive advantage in the short-term, it also means that
under low nutrient conditions this rapid growth and associated nutrient
losses may not be sustained. That is, rapidly growing plants with short
organ-life span experience high nutrient loss and must have high
resource availability to compensate for those losses. It may be more
efficient, then, to concentrate on control in those sites which are more
fertile, because competition with other grasses may constrain
populations of *D. glomerata* in the less fertile sites.

*Epichlor typhina*, the cause of choke disease, was first reported in
the US in Oregon in 1996. This disease is important in France, where it
reduces seed yields of orchardgrass (Alderman et al., 1997). Wild and
cultivated perennial grasses like orchardgrass are thought to be a large
and permanent source of the barley yellow drawf virus for cereal crops
(Kendall et al., 1996). Another disease in orchardgrass, cocksfoot
virus, causes chlorotic streaking in leaves and affects the growth habit
of plants grown singly and in swards (Torrance et al., 1994).

**Literature cited:**

Alderman, S. C., W. F. Pfender, and R. E. Welty. 1997. First report of
choke, caused by *Epichloe typhina*, on Orchardgrass in Oregon. Plant
Disease 81:1335.

Andrews, M., A. Douglas, A. V. Jones, C. E. Milburn, D. Porter, and B.
A. McKenzie. 1997. Emergence of temperate pasture grasses from different
sowing depths: importance of seed weight, coleoptile plus mesocotyl
length and shoot strength. Annals of Applied Biology 130:549-560.

Brown, D. 1995. The impact of species introduced to control tree
invasion on the vegetation of an electrical utility right-of-way.
Canadian Journal of Botany 73:1217-1228.

Heide, O. M. 1994. Control of flowering and reproduction in temperate
grasses. New Phytologist 128:347-362.

Kendall, D. A., S. George and B. D. Smith. 1996. Occurrence of barley
yellow dwarf viruses in some common grasses (Gramineae) in south west
England. Plant Pathology 45:29-37.

Ryser, P. and R. Notz. 1996. Competitive ability of three ecologically
contrasting grass species at low nutrient supply in relation to their
maximal relative growth rate and tissue density. Bulletin of the
Geobotanical Institute 62:3-12.

Spandl, E., J. J. Kells, and O. B. Hesterman. 1997. Weed invasion in
established alfalfa (*Medicago sativa*) seeded with perennial forage
grasses. Weed Technology 11:556-560.

Torrance, L., A. T. Jones, and G. H. Duncan. 1994. Properties of
cocksfoot streak and cocksfoot cryptic, two viruses infecting cocksfoot
(*Dactylis glomerata*) in Scotland. Annals of Applied Biology
124:267-281.

Volaire, F. 1995. Growth, carbohydrate reserves and drought survival
strategies of contrasting *Dactylis glomerata* populations in a
Mediterranean environment. Journal of Applied Ecology 32:56-66.