Species, Cultivars and Diverse Grass Mixtures

The species and cultivars of grasses that are appropriate for lawns depend on the region (e.g., Maritimes), site (shady, sunny etc.) and management (intensive use of fertilizers and pesticides, organic, low maintenance).

The grass species that are best adapted for lawns in Atlantic Canada are:

• Kentucky bluegrass (Poa pratensis),
• perennial ryegrass (Lolium perenne),
• fine fescues (Festuca spp.) including creeping red fescue (F. rubra) chewings fescue (F. rubra ssp Fallax) and hard fescue (F.brevipula).

Kentucky bluegrass has two major benefits which make it a very important grass for lawns in temperate regions: (i) it is very winter hardy; (ii) it has underground stems (rhizomes) which enable it to grow into bare patches quickly and fill them in. Kentucky bluegrasses have been intensively selected over a long period for use in temperate region lawns, and in the turf industry it is generally considered to be the most desirable species. Most or all sod that is sold locally is 80 to 100% Kentucky bluegrass. A few drawbacks of straight or predominantly Kentucky bluegrass turf:

• It does very poorly in shady situations.
• The relatively sparse tillering (formation of multiple shoots at the crown) make pure stands of this species very susceptible to invasion by weeds. ^[L6]
• It tends to develop excess thatch.
• Generally, a high level of management and inputs is required to maintain a pure or mostly pure stand of Kentucky bluegrass

Ryegrasses germinate quickly, which is an important benefit for lawns established from seed, and for overseeding. The early germinating ryegrass acts as a 'nurse crop', meaning that it quickly provides a canopy that helps to maintain a favorable environment for later germinating species. The ryegrasses have a 'bunch' habit, forming dense clusters of tillers (shoots) at the crown, and develops in clumps. They do not form underground rhizomes as in Kentucky bluegrass, so they must invade new areas via seed. The ryegrasses are not as winter hardy as Kentucky bluegrass, but newer cultivars are more persistent, and in Atlantic Canada this species generally does well.

Fine fescues have finer blades than Kentucky bluegrass and ryegrass. Creeping red fescue produces short rhizomes and spreads in the same way as Kentucky bluegrass, but not as quickly. The chewings and hard fescues are bunch types. Two important features: (i) generally they have much lower nitrogen requirements than Kentucky bluegrass and ryegrasses; (ii) they have good shade tolerance. Mixes designed for lower input systems usually have high proportions of the fine fescues, and mixes for shady areas are predominantly fine fescues. (However, no grass mix does very well in constantly shaded areas in eastern Canada; groundcovers such as periwinkle are better options for those areas, subject to the restriction that they do tolerate much or any wear.)

In general, to maximize site adaptation, persistence of grasses, resistance to weed invasion, resistance to diseases etc., diverse grass mixes (varietal blends with several species) are recommended for ecologically (organically) managed lawns^{[L6, L16]}. Diverse mixes have also proved to have better persistence in pastures and hayfields than mixtures of only 1 or 2 species.^[L27]

In general, the fescues tend to become more abundant and Kentucky bluegrass less abundant with age of the lawn under low input management.^[L23]

A Diverse Grass Mixture for the Maritimes

Following is a suggested diverse grass seed mix for sunny and partially shaded areas in the Maritimes and the northeastern U.S.A. It is based on recommendations of Michael Talbot ^[L16] and local experiments with mixtures under organic management.^[L6]

Kentucky bluegrass 20-30% by weight of seed (2+ cultivars)

Perennial Ryegrass (2+ cultivars), 20-30%

Fine fescues 40-60% (including hard, chewing and creeping red fescues; more than one cultivar of each as possible)

Be sure that the ryegrass is the perennial type, NOT the annual type.^[L28] (Also don't confuse ryegrass with rye which is a cereal crop).

A mix of this sort is unlikely to be available on the shelf. Some options:

1. Select a general purpose mix containing Kentucky bluegrass, ryegrass and fescues (e.g. Halifax Seed's Greenfast).


2. Obtain a custom blend at specialty stores that provide individual species and cultivars (e.g., at Halifax Seed).


3. Use a general purpose mix as a base, and add species and cultivars to bring the composition closer to that above — usually that means adding ryegrass and fescues.
   
   For example, a seed mix that is 40% Kentucky bluegrass, 40% perennial ryegrass and 20% fescues might be mixed 10 parts of original seed mix with 5 parts fescues by weight to give approximately 27% Kentucky bluegrass, 27%% perennial ryegrass and 46% fescues. The seeding rate would then be a compromise between the seeding rates for the individual seed type (given in the table above); in this case, approx. 2.2 kilograms of the mix per 100 m² would be appropriate.

For overseeding Kentucky bluegrass sod, a mixture of 1 part fescue and 1 part perennial ryegrass would be appropriate for sunny areas, straight fescues on shadier areas. Overseed sod at the same rate as for new turf.