Italian Ryegrass (Lolium multiflorum) — The High-Yielding Short-Term Silage Grass

Italian Ryegrass is a short-lived grass lasting up to two years, but what it lacks in persistence it more than makes up for in yield. On suitable soils it reliably delivers up to 18 t DM per hectare — making it one of the highest-yielding forage grasses available. It has a very open, upright growth habit with fewer tillers than other grasses, which makes it better suited to cutting than grazing. Italian ryegrass has been the subject of intensive plant breeding for many years, resulting in a wide range of commercially available varieties including both diploid and tetraploid types.

What It’s Used For

Silage, haylage, and high-quality stemmy hay crops. It is one of the most rapidly growing grasses and is commonly grown in mixes with red clover or vetch.

How Long Will It Last?

A short-term species — generally up to 2 years depending on conditions. Persistence can be further reduced by drought, particularly on light soils in low rainfall areas.

Key Strengths

• Very high yielding — up to 18 t DM/ha on suitable soils
• Responds well to artificial fertiliser applications
• Wide range of varieties commercially available
• Grows through winter — useful for early spring production
• Tetraploid varieties offer high palatability and voluntary intake

Frost Tolerance

Italian ryegrass will grow through winter, but frost tolerance is improved if surplus growth is removed in the autumn. Graze in mid to late autumn to prevent the crop going into winter in an upright leafy state where it is more vulnerable to hard frosts.

Yield

Up to 18 t dry matter per hectare on good ground.

Sowing Rate

• 14 kg/acre (35 kg/ha)

The upright, open growth habit means fewer tillers than other species — a robust sowing rate is needed to create a dense, productive crop.

When to Sow

Late March to September when adequate moisture is available. Autumn sowing will provide a full crop the following spring. Spring sowings can produce a lower-yielding, leafier crop — particularly challenging for hay making.

Management

Cutting timing for silage depends on the heading date — Italian ryegrass generally heads around the 2nd or 3rd week of May. As the plant matures and develops a seed head, forage quality (D-value) declines. A D-value of 67–70 represents good quality forage, equating to approximately 25–50% ear emergence.

When to cut depends on the stock being fed: dry cows can utilise a lower quality, stemmier silage, while growing young stock require higher quality forage. On good ground, Italian ryegrass typically provides 3 cuts plus aftermath grazing.

Italian ryegrass is susceptible to mildew and ryegrass mosaic virus. Modern varieties carry good disease resistance scores available on the Recommended List.

Diploid vs Tetraploid

Italian ryegrass is available in both diploid and tetraploid forms. Tetraploid varieties have double the chromosomes of standard diploids, making them highly palatable and increasing voluntary intake — of great value in seeds mixtures. However, tetraploids tiller less than diploids, leaving more soil showing and producing a less dense sward. Average seeds per kg: 500,000 (diploid) / 250,000 (tetraploid).

Identifying the Crop

Seed: One of the larger ryegrass seeds — long and thin, pale green to beige with a papery surface. 5–6 mm in length.

Mature plant: Pale green upright tufts. Leaves are finely pointed, green and hairless — younger leaves are rolled in the bud (unlike perennial ryegrass, which folds). The underside of the leaf is smooth and glossy; the upper surface can be minutely rough. Ligule 1–2 mm, membranous. Spikelets are awned — a key distinguishing feature from perennial ryegrass. Each spikelet is stalkless with alternate rows either side of the axis. A shallow-rooting species reaching 30–100 cm in height on fertile, moisture-retentive ground. Flowers May–September.

Works Well With

Italian ryegrass is one of the most rapidly growing grasses and combines well with aggressive companion species such as red clover or vetch, producing high-yielding, protein-rich silage leys.