Depending on the condition of your lawn and your goals going forward, I may recommend one of several renovation options and seed mixtures. Ideally, this work would be carried out from mid-August to mid-September. Renovation strategies can be grouped into four categories:
Lawn improvement- conducted when less than 20% weeds or bare soil are present. The goal is to utilize existing grass species and determine the factors leading to poor lawn quality and correct these. Often, recommended practices for improvement will include aeration, fertility, seeding, and weed control.
Partial renovation- conducted when 20-40% weeds or bare soil are present. This process requires stressing the existing vegetation to reduce the competitive advantage of existing species, while overseeding with new (possibly different) turf species. Depending on the weeds present, herbicides may or may not be recommended.
Species conversion- conducted when greater than 40% weeds or bare soil are present, but there are no major soil issues. This process requires killing the existing vegetation by the use of non-selective herbicides or solarization (plastic sheet) and overseeding with new turf species. The species conversion process allows you to change the function of the lawn (ex: low input, no mow, high traffic tolerance) by establishing new species in a short period of time.
Complete renovation- conducted when greater than 40% weeds or bare soil are present, and soil remediation is required. This process is essentially the same as the species conversion except soils will be tilled, graded, and possibly amended with organic matter or nutrients.
For more detailed information about all of these renovation strategies and in-depth detail on how to conduct the species conversion, view this webinar: Lawn Renovation
No matter which renovation strategy you choose, selection of the proper seed will be critical to the long term success of your lawn. I would generally suggest utilizing a mixture of several turfgrass species to overseed with, but let’s discuss the species individually and next week we’ll look at some mixtures that are available to you.
Mixtures vs. Blends
Mixtures are different from blends. Blends of grass seed include only one species, for example Kentucky bluegrass, and most blends would have 3-4 different varieties of that species. Mixtures of grass seed include two or more species and greater genetic diversity. Mixtures are often utilized for lawns that have differing microclimates (ex: sun and shade).
Cool Season Species for Minnesota Lawns
|Leaf texture differences between tall fescue (left), Kentucky bluegrass (center),|
and fine fescue (right)
Kentucky bluegrass is the most widely used species in Minnesota lawns due to its high aesthetic quality, adaptation and stress tolerance. If you have an existing lawn, chances are that a good majority of it is Kentucky bluegrass. Additional benefits of Kentucky bluegrass include its cold tolerance, drought survival through dormancy and high recuperative ability. However, downfalls with this species include a high water requirement, frequent mowing and high fertility needs. There is a wide range of genetic diversity in Kentucky bluegrass and Seed Research of Oregon has put together this great classification of the different varieties: Kentucky Bluegrass Classification.
Perennial ryegrass can also be a high quality species, although its poor tolerance to winter and summer stresses make it undesirable in many cases. Perennial ryegrass is included in many of our Midwest mixtures due to its incredible germination and establishment rate. If quick establishment is desired, perennial ryegrass can be used, but I would suggest not using more than 25% perennial ryegrass in your seeding mixture.
Fine fescues have been receiving a lot of attention recently because of their ability to survive low maintenance environments. Fine fescue is a category of about five different species that are often mixed together. These species include hard fescue, slender and strong creeping red fescue, Chewings fescue, and sheep fescue. Like perennial ryegrass, the fine fescues germinate very quickly. Fine fescues are often the best performing species in drought trials and no-mow turf situations. They are also adapted to shade or full sun. For more information on fine fescues for lawns have a look at this short video: Fine fescue.
Tall fescue is a coarse fescue species that has been gaining popularity due to its shade and traffic tolerance, as well as its ability to avoid drought through an extensive root system. I find myself recommending tall fescue more and more. Tall fescue is a bunch type grass and it can be unsightly when overseeded into existing lawns, so I generally recommend using it for new seedings or utility turf areas. When tall fescue is greater than 75% of a stand it looks very comparable to a Kentucky bluegrass lawn, and it will require less inputs of water and fertilizer. Tall fescue is also very shade adapted. For more information on tall fescue have a look at this short video: Tall fescue.
For a more detailed explanation of the turf species visit this short video: Grasses for Minnesota Lawns.
Next week we will look at the various seed mixtures that are available on the consumer marketplace. Stay tuned.