New tetraploid ryegrass mixtures look set to take the chill out of winter overseeding

In virtually every sphere, groundsmanship has transformed out of all recognition in just a generation. Not only have technical and scientific demands reached unprecedented heights, but also pressures on groundstaff have been placed into even sharper relief given the boom in televised sports: turf quality and performance have to be better than ever and to be seen to be so.

Likewise, ever-evolving turf science brings the possibility of creating more manageable groundcare year-round and making sustained high standards more attainable, especially through winter.

Once upon a time, turfcare professionals knew which grass seed was suitable for the particular time of year, and worked accordingly within seasonal constraints to attain optimum results from it.

Ryegrass has long been a species that has undergone vast swathes of research and development in a bid to harness its hardy virtues for year-round application.

After thirty years of trialing ryegrass cultivars, the industry is entering a truly revolutionary era - one where the culmination of so much research into ryegrass has created a reliable species for utilising in any overseeding programme, in any season.

New turf type tetraploid cultivars (4Turf) have been trialled at UK sites and are about to be unveiled in early 2012 in a move, it is believed, will bring a wholesale shift in the effectiveness of overseeding, whatever the season. In particular, these ryegrass cultivars are expected to address many of the issues groundstaff face when trying to overseed in winter.

Winter overseeding poses one of the toughest challenges for groundstaff, who have limited hours to work, diseases to contend with, competition from unwanted species and poor conditions for germination due to low temperatures and light levels - all issues further exacerbated by modern stadia, which often allow little natural light to fall on the grass through the winter months.

Despite the pitfalls, overseeding at this stage of the year is beneficial to maintain surface quality and ensure a denser sward to withstand the rigours of winter play.

Good winter overseeding also helps maintain a diverse and balanced sward, repairs worn and damaged surfaces and, importantly, fights to outcompete weed species, especially Poa annua - the scourge of countless grounds professionals.

Late autumn, into winter and early spring represent some of the least productive times for growth, leading to periods where poor plant coverage and appearance can persist.

The tetraploid overseeding mixtures being introduced are set to transform winter maintenance programmes. In trials, they have produced specifically better low temperature establishment, improved winter disease resistance, improved shade tolerance and increased winter wear tolerance.

It is the combination of the annual rye for the very fastest establishment, the low temperature germinating high wear diploids for outright long term wear tolerance, and the new tetraploid (disease resistance and fast establishment) that deliver the high level of wear tolerance, not the tetraploids on their own.

The science behind the improvements in winter stress tolerance characteristics is simply explained. Traditional turf type perennial ryegrasses (diploids) have two sets of chromosomes - tetraploids have four sets, and 4Turf seeds are one and a half times larger than regular turf type ryegrass. Because of that characteristic, they can produce seedlings quicker, and generate a thicker sward, so turf is no longer resigned to poor growth and the characteristically thin, patchy appearance.

The biggest benefit of the tetraploid is the winter disease resistance. The picture above, from a breeding plot last winter, shows a range of diploids that were all badly hit with snowmould, yet all of the tetraploids remain virtually untouched. The increased seed size also gives them the ability to establish quickly and at lower temps than regular diploids.

What is new and unique is that this new grass, with its specific features combined with traditional grasses, has created a new range of seasonaly specific overseeding mixtures that are designed to work best when utilised as an overseeding programme.

The company leading the way in these developments is DLF, which has funded the research and trials into these cultivars. In particular, field trials conducted in January 2011 in The Netherlands have demonstrated just how successful these types were in winter overseeding programmes, with almost double the wear tolerance and faster establishment time.

The new ryegrasses have been combined with Poa trivialis for increased winter shade tolerance, and with low temperature germinating diploid perennial rye for outright wear tolerance. Each mixture is designed to maximise overseeding results in a specific season.

Perhaps the most dramatic effects are that they allow groundsmen to extend the traditional sowing season by as much as four months.

The benefits of this better protection in cold temperatures was realised earlier this year when Martin Knight, Head Groundsman at Worcester Warriors Rugby Club applied one of the new mixes, Johnsons J Rescue, at the back end of 2010, in what was one of the UK's coldest winters. The results that Martin found allowed play to progress with few cancellations through, what was, an intensively fought campaign in bitter winter weather.

For further information on the new tetraploid mixture, visit www.dlf.co.uk

Axcella - annual ryegrass
Low minimum germination temperature
Fastest establishment and growth

4Turf - New turf type tetraploid perennial ryegrass
Disease resistance
Stress tolerance
Speed of establishment

Diploid perennial ryegrasses
Highest level of wear tolerance
High density
Germination in low temperatures (specific cultivars)

Rough-stalked meadowgrass
Fast establishment
Excellent shade tolerance
Especially for damp conditions

New Mixtures

J Premier Pitch
Premier quality football and rugby pitches
40% Bizet Perennial Ryegrass
25% Eurodiamond Perennial Ryegrass
25% Churchill Perennial Ryegrass
10% Columbine Perennial Ryegrass New

J Rescue Autumn
Oct-Dec over seeding programme and rapid repairs. Football & rugby pitches, tees, polo fields and racecourses
30% Axcella Annual Ryegrass New
25% Double Tetraploid Perennial Ryegrass New
25% Berlioz Perennial Ryegrass
20% Solo Rough Stalked Meadow Grass

J Rescue Spring
Jan-March over seeding programme and rapid repairs. Football & rugby pitches, tees, polo fields and racecourses
50% Axcella Annual Ryegrass New
25% Double Tetraploid Perennial Ryegrass New
25% Berlioz Perennial Ryegrass