Introduction

Perennial bunchgrasses that are native to California can go a long way toward helping solve a series of problems associated with roadside maintenance. At the same time, they can improve the appearance of a part of rural landscapes that are typically weedy in one season or scraped bare in another.

Most road rights-of-way, whether county roads, state highways or interstate freeways, are covered with vegetation that consists primarily of noxious, invasive weeds. These weeds are considered to be a problem source of weed seeds that move into agricultural fields—resulting in herbicide treatments—and continue to reinfest the same roadsides. Efforts to clean up the roadsides usually involve multiple herbicide sprays and/or scrapings. These measures either contribute to pesticide runoff into waterways or leave soil stripped bare and subject to erosion during winter storms or heavy winds.

Bunchgrasses can be very effective competitors with these noxious weeds through shading and competition for nutrients. Their extensive root systems anchor soils during erosive rainstorms, keeping road shoulders more stable and firm, and provide pathways for surface water to percolate into the soil.

In addition to these benefits, native bunchgrasses also provide excellent wildlife habitat, encouraging greater biodiversity. Mature stands of these grasses can harbor a large variety of small mammals, reptiles, game birds, songbirds and insects - including important food crop pollinators.

Establishment

A roadside area can be categorized by the following cross-section of planting sites moving from roadside to field border: pavement edge, roadside berm and inner ditchbank, ditch bed, outer ditchbank  and fieldside berm, and finally, field edge. 

Roadside cross-section

Pavement edge: California barley (Hordeum californicum), Pine bluegrass (Poa secunda), Purple needlegrass (Nassella pulchra), Nodding needlegrass (Nassella cernua), California oniongrass (Melica californica).

Roadside berm and inner ditchbank: California barley, California oniongrass, Meadow barley (Hordeum brachyantherum), Nodding needlegrass, Pine bluegrass, Purple Needlegrass, and Squirreltail (Elymus elymoides).

Ditch bed: Meadow barley, Purple needlegrass, and sedges and rushes.

Outer ditchbank and fieldside berm:  Deep, Good Soils: Blue wildrye (Elymus glaucus), Purple needlegrass, Slender wheatgrass (Elymus trachycaulus ssp. trachycaulus), California barley, and Deergrass (Muhlenbergia rigens).  Poor Soils: Purple needlegrass, Nodding needlegrass, California barley, and Pine bluegrass.

Field edge: Creeping wildrye (Leymus triticoides).

Establishing native grasses requires using some standard farming practices for the first few years. Because of their slow germination, low seedling vigor and slower growth rates, they must be managed as many agricultural crops are with efforts made to reduce competition by more vigorous, non-native, annual weeds. Reduction of weed competition is so important that the process could be started up to a year in advance of the actual planting.

One way to begin site preparation is with a controlled burn in the summer or fall to destroy surface weed seeds and trash. Weeds that germinate later through the winter and spring can be disked under in March or April, before they set seed. The area should be left fallow throughout the growing season, but any additional weeds that germinate should be controlled either with herbicides sprays, tillage, or burning before seeds are mature. Final seedbed preparation in the fall, done by disking or other tillage equipment, may also serve to remove persistent weeds. If clods are large, a scraper or roller may be needed to provide seedbed uniformity and to close up air spaces so as to help conserve soil moisture.

The type of seed selected or the mixture of species will depend on location, soil type and moisture conditions expected throughout the season. Suppliers of native grass seed can provide good information on species to select for different situations. A mixture of varieties, with differing moisture adaptations, is often recommended for roadsides where a ditch or swale is present. Grasses suited to drier conditions will predominate on the higher ground, whereas those that tolerate occasional flowing water will thrive in the lower areas.

Seeding is usually done in the fall, to allow rains to provide the moisture needed for germination. Seed can be drilled directly into the seedbed, as prepared, or into soils managed under no-till situations. Where no-till management has been used, weed control before and shortly after planting can and should be accomplished with herbicides or burning.

Broadcasting is another means of planting native grass seed. After seeding by this method, a light harrowing and rolling is usually necessary in order to cover the seed and settle it well into the seedbed. Mulching lightly with native grass straw is often done to seeded areas to aid in erosion control as well as keeping the seedbed moist during dry periods.

Maintenance

Germination of native grass seeds usually occurs in about two weeks for early fall plantings when temperatures are warmer. Later plantings may take up to four weeks. Spraying of any non-selective herbicides for weed control must be done before the young seedlings emerge. Afterwards, weed control options include selective herbicides, rope-wick applications, or timed mowings that will affect taller annual weeds, reducing their canopy and allowing the shorter, less vigorous natives greater access to sunlight.

Long-term maintenance of native grass stands is mostly  weed control. This is needed for 2-6 years, depending on the grass species, conditions, and prior weed levels. However, after 3-4 years, when the perennials are well-established, maintenance needs should be minimal. Grazing, mowing and burning are effective, low-cost options for vegetation management.  An annual, well-timed treatment may be sufficient to maintain these grasses at a desired height or to reduce dry matter. This type of long-term management could ultimately cost less than the repeated sprays and cultivations traditionally used for roadside weed control.