One of the favorite winter pastimes for Minnesota gardeners is looking through seed and nursery catalogs that in turn, fuel one's desire to plant and try new vegetables, flowers, trees or shrubs in the coming year. But, this is also a good time of year to plan ahead to repair or replace those lawn areas that may not be doing so well. If you are thinking about just trying to thicken up your lawn or perhaps even introduce some different types of grasses into an existing lawn to improve such things as drought tolerance, disease resistance, shade tolerance or lower the need for inputs of water and nutrients, this is also a good time of year to do some homework on the best grasses to use to achieve those goals.
A good planning exercise for the winter is to look out your windows and try to reflect on whether or not the lawn seems to be doing well in those areas. If not, make a note of what seemed to be the problem and try to determine why the grass may not be doing so well in those areas. For example, has the amount of shade increased due to the growth and canopy expansion of landscape trees? Or, has the shrub border grown and enlarged such that it has increased shading of the adjacent lawn area? Both of these conditions can cause a thinning and overall decline of the lawn. In this case, some tree and/or shrub pruning may be needed to provide some additional light and better air circulation to the area. Hence, with an improved growing environment for the grass plants, reestablishment success will be more likely.
As another example, an area may be thinning due to excessive play and use that has resulted in significantly compacted soils and consequent weed invasion. Making note of problem areas and possible causes for lawn decline will help determine appropriate turfgrass species and varieties to use as well as what other repair strategies may be needed. Spending some time making these assessments now will make the implementation of a repair plan during the busy spring gardening period much easier to carry out.
Now, on to our lawn grasses. In this part of the country, we are very fortunate to have several lawn grass species to choose from that can meet most anyone's lawn goals and expectations. Following is some brief information about the three primary lawn grasses used in Minnesota: Kentucky bluegrass, fine fescue and perennial ryegrass. If you would like a more comprehensive review of these (and other) species, see the home lawn care section chapter on selecting grasses in the Sustainable Urban Landscape Information Series website: www.sustland.umn.edu.
Kentucky bluegrass (Poa pratensis)
Kentucky bluegrass remains the most popular lawn grass planted in Minnesota and is almost exclusively used in the production of sod for this area. See Photo 2. It's widely used in home lawns, parks, athletic fields and golf courses. Varieties of Kentucky bluegrass range from medium to dark green in color. Most varieties require higher maintenance (water, nutrients, etc.) levels to remain healthy and vigorous and most will not perform well in shady conditions.
Kentucky bluegrass grows and spreads by producing underground stems known as rhizomes that send up shoots as they grow through the soil. This allows Kentucky bluegrass to more rapidly recover from injury and abuse than any of the other lawn grasses and be very competitive against weed invasion. This is also the primary reason why this species is so popular with sod producers.
The tip of an unmowed Kentucky bluegrass leaf is shaped like the front end of a typical fishing boat, hence the designation of having a 'boat-shaped' leaf tip. This is a very reliable identification characteristic for Kentucky bluegrass and can help to easily assess where and how much Kentucky bluegrass is growing in a home lawn.
Fine Fescues (Festuca spp.)The term "fine-leaved fescues" is generally applied to three similar species commonly used in our lawn mixes. They are strong creeping red fescue (Festuca rubra spp. rubra), chewings fescue (Festuca rubra var. commutata) and hard fescue (Festuca longifolia). Occasionally, sheep fescue (Festuca ovina) is utilized in mixes to be used in very low-maintenance areas and 'no-mow' mixes. Strong creeping red fescue does spread by rhizomes but is not nearly as aggressive as Kentucky bluegrass. Chewings fescue and hard fescue are considered bunch-type grasses as they lack rhizomes or stolons and spread primarily by tillering. They are both considered excellent choices for home lawns. Fine fescues are not normally available or grown as sod.
As their name implies the fine fescues are very fine textured grasses. See Photo 3 for comparison of fine fescue leaf texture with that of Kentucky bluegrass. They are also characterized by medium to slow growth rates and medium to dark green color. Fine fescues have lower maintenance needs (i.e., less water and nutrient inputs) including some that have reduced mowing requirements. They have good drought tolerance and adapt well to the shadier areas in the landscape, particularly dry shade. Their wear tolerance is not as good as that of Kentucky bluegrass or perennial ryegrass. Likewise, fine fescues will tend to do better in lawns receiving lower levels of lawn care inputs while Kentucky bluegrasses will perform better at moderate to higher lawn care inputs levels.
The fine fescues are frequently mixed with Kentucky bluegrass for average home lawn conditions. In a mixed landscape where there are some areas of full sun and some areas of partial shade, the fine fescues will usually tend to dominate in the shadier areas while the Kentucky bluegrasses will be more dominant in the sunnier areas. Fine fescues, particularly hard and sheep fescues, are usually major components of mixes sold as 'no-mow' mixes. See Photo 4 for example of a two year old no-mow mix growing out at UMORE Park in Rosemount, MN. These mixes have been increasingly popular choices where mowing is not able to be done on a regular basis or site conditions make mowing unsafe. No-mow mixes have also been used to create a transition zone from natural plantings such as prairie or woodland gardens to maintained lawn areas. Their slower growth rates and limited spreading ability help prevent them from aggressively invading into these natural areas.
Perennial ryegrass (Lolium perenne)
Perennial ryegrass is a cool season, medium-textured, bunch-type grass. It is a higher maintenance requiring grass that can withstand the higher amounts of wear and tear common to areas such as athletic fields or intensively used backyards. Its biggest drawback is its lack of cold hardiness. It is the least hardy of the three major lawn grasses used in this area.
Perennial ryegrass usually has a dark green color with a texture similar to that of Kentucky bluegrass. See Photo 5. Hence, perennial ryegrass makes a good seed mix component with Kentucky bluegrass when used for higher maintenance / higher use lawns and recreational areas.
Perennial ryegrass can usually be identified by its shiny green color on the underside of the leaf blade while the upper surface has a rather dull, flat green appearance. The mid-vein of the leaf is also visually quite prominent on the upper side of the leaf. The leaf tip comes to more of a point rather than the 'boat shaped tip' common to the bluegrasses. The lower portion of the perennial ryegrass shoot is usually dark red to purplish colored as opposed to Kentucky bluegrass which is a lighter green to nearly whitish at the base of the shoot.
Perennial ryegrass is well known for its quick germination and vigorous seedling growth. Those characteristics make it particularly valuable when rapid repair and establishment of a turfgrass cover is desired. A drawback of that characteristic is that it can quickly shade and overpower slower germinating Kentucky bluegrass and fine fescue seedlings when sown at the same time. Ultimately, this can result in very low populations of Kentucky bluegrass and fine fescue getting established in the lawn. With the hardiness problems associated with perennial ryegrass, severe winter injury could result in a very thin lawn the following spring with a consequent need for significant reseeding to be done. Nonetheless, small amounts (< 20%) of perennial ryegrass in a home lawn seed mix will help get some early establishment on the site and provide some protection of the slower germinating grasses.
More Next Month
That's it for now. Next month we'll explore a couple of other grass species occasionally encountered in seed mixes for this area. There will also be some information about specific turfgrass variety selection and what to do when you can't find them at your local garden center or other retail outlets. Until then, take some time to do a little lawn care reflection and planning along with enjoying the many seed and garden catalogs that all help, once again, create enthusiasm for this coming growing season.