Farm advice: Choose the right ryegrass for your farm

By: Jeremy Klingender, Ravensdown seed product manager

Choosing the right perennial ryegrass can be a daunting task, so here are some options you should look at when choosing the right perennial ryegrass

There are four main points you have to consider when choosing the right perennial ryegrass:

  1. Endophyte strain (relative to insect pressure)
  2. Flowering/heading date
  3. Ploidy (tetraploid or diploid) 
  4. Lineage/breeding

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Endophyte strains

Insect pressure is one of the main reasons perennial ryegrasses don’t persist. The higher up in the country you are, the more protection your ryegrass will need from insects. Black beetle, porina, Argentine stem weevil, grass grub, and field crickets all have a huge effect, stripping valuable dry matter and can even kill ryegrass pastures.

Choosing and understanding the correct endophyte strain is important for the longevity of your pastures. AR1, AR37, and NEA2 are all novel endophytes and have been developed by plant breeders to help protect grasses from insect attack.

Flowering/heading date

A heading date is when 50% percent of the plants have emerged seed heads. It is an important consideration as seed head development reduces feed quality in late spring and the heading date determines when this occurs. Heading dates are defined relative to the cultivar Nui (approximately 22 October) heading at day zero.

Heading/flowering time is important here, as it controls the extent of early spring production and late spring quality.

The standard heading/flowering ryegrasses are good for late August–early spring growth, as this is when the quality is best and will carry the farm through the typical spring feed pinch. By mid-spring (October), growth rates are often high and the feed supply often changes to a surplus. Pasture quality may deteriorate here if grazing management is not precise.

At this point, late flowering ryegrasses, such as Ultra and Matrix (+20 – +23 days after Nui) come into their own as the earlier flowering ryegrasses lose their quality.


Ploidy is a term referring to the number of chromosomes per cell. The two main ploidies are tetraploid and diploid.

"Diploids are the most common, normally found on sheep and beef farms, due to ease of management, and have two sets of chromosomes per cell.

"Tetraploids have four sets of chromosomes per cell, which are larger, and generally grow bigger, darker leaves with larger but fewer tillers. They have a higher ratio of water-soluble carbohydrate (cell contents) to fibre (cell wall), e.g. higher ME, and are preferred by livestock. However, tetraploids take greater management as they are easily overgrazed by stock, and therefore, persistence can be an issue.


Like top-quality breeding stock, it is important to understand the bloodlines or parentage of your grasses. It’s pointless trying to grow a plant that doesn’t belong in your environment.

Most of the breeding lines of grasses in New Zealand come from North Western Spain, as the conditions there are similar to ours. The difference is that the germ plasm is millions of years old, so the perennial ryegrass has evolved over centuries to be able to survive those conditions.

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