In my introductory turfgrass
management course I always stress the importance of establishing cool season
turfgrasses in the fall of the year. Seeding turfgrasses, such as tall fescue,
in September or early October offers the advantages of near optimal soil
temperature for seed germination, less weed and disease problems and greater
retention of soil moisture during early seeding growth due to declining temperatures
and day length. Implicit in my discussion of this topic is that one has a
choice of when they will establish their lawn. Nothing could be further than the
truth for a Home Builder. Lawn
establishment in new residential developments usually occurs in a relatively
narrow window between the time the finished grade is created on a lot and the
sale of the home. Lawn establishment has to occur during this window because sediment
and erosion control plans almost always stipulate that soil stabilization on
the lot needs to occur before transfer of the property to the new owner can
take place.
In northern climates it is usually
permissible to stabilize the soil for late fall to early spring property
closings by placing straw or another type of erosion control material over the
seed. For the remainder of the year though vegetative stabilization of the soil
needs to occur in advance of transfer of the property. This means that cool
season turfgrasses are sometimes seeded at the worst possible times of the
year. This was clearly the case for the two residential lots that were seeded
at the project showcase site. One lot was seeded on May 29, 2012 and the other
on July 3 2012. Since neither lot
possessed in ground irrigation, lawn establishment was completely dependent on
natural rainfall. Rainfall during this time of year typically comes in form of
thunderstorms and the summer of 2012 was no exception to this type of
precipitation pattern.
The contractor placed down what I thought was
an unusually thick layer of straw ( 3 inches uncompressed) over the 95% tall fescue 5% microclover seed
mixture that was broadcast in May . I was concerned that this much straw would
inhibit the growth of microclover seedlings so I had the contractor cut the
amount of straw blown over the seedbed by about a third in the July seeded
lot. After a couple of severe thunderstorms had passed through the area it
became apparent why the contractor had placed so much straw down in May. Three
inches uncompressed straw did a good job minimizing erosive losses and seed
washout. Putting down two inches of straw was much less effective at minimizing
washout, especially in areas where runoff tended to be limited to sheet flow
only. Neither of two depths of straw was effective stopping erosive losses in
areas of two yards where flow became channelized.
By October, the
lawn seeded in May looked great. The July seeded lawn was still
struggling to achieve full soil surface coverage due to the seed wash out that
occurred over the summer. Did straw
thickness affect the establishment of the microclover? There was a fair amount
of microclover present in the May seeded lawn by the end of summer. However, because
of the seed washout that occurred in the July seeded lot, it was difficult to
determine if microclover establishment was influenced by amount of straw placed
in the seedbed. To get a better handled on the effect of straw cover on microclover
establishment we will be conducting a study at the University of Maryland Paint
Branch Turfgrass Research Facility this fall to see how the amount of straw
cover affects the establishment of a tall fescue+ microclover lawn seed
mixture. This study is one of the several microclover management studies that
will be discussed at the 2013 University of Maryland Landscape Contractor Field
Day. For those interesting in attending this field day, it will take place on
Wednesday October 23, at the University of Maryland Paint Branch Turfgrass
Research Facility, in College Park, Maryland.
Lawn composition ten weeks after a 29 May seeding of a 95% tall fescue, 5% microclover lawn seed mixture.
