How Lawn Seeding Rates Work
The seeding rate is the amount of grass seed applied per square metre, measured in grams per square metre (g/m2). Different grass species have different seed sizes and germination characteristics, so the recommended rate varies. Applying too little seed results in a thin, patchy lawn that weeds can invade. Applying too much wastes money and can actually cause competition between seedlings, reducing establishment.
Standard Seeding Rates for Common NZ Grasses
| Grass Type | New Lawn (g/m2) | Oversowing (g/m2) | Notes |
|---|
| Ryegrass / fescue mix | 35 | 17.5 | Most common NZ domestic lawn seed |
| Fine fescue | 20 | 10 | Small seed, ornamental or shaded lawns |
| Tall fescue | 40 | 20 | Robust, drought-tolerant, sports use |
| Kikuyu | 5 | 2.5 | Warm-season, spread by runners; seed is supplemental |
| Buffalo / St Augustine | 10 | 5 | Often established by runners or plugs rather than seed |
These rates reflect the midpoint of the ranges recommended by NZ seed suppliers such as PGG Wrightson Seeds. Rates at the lower end of the range suit good seedbed preparation in calm, warm conditions. Rates at the upper end are appropriate for exposed sites, poor soils, or when establishing a lawn quickly.
New Lawn vs Overseeding
Sowing a new lawn means preparing a bare soil surface, incorporating fertiliser, raking level, sowing seed, and keeping the surface moist until germination. The full seeding rate applies because there is no existing grass to supplement the new seedlings.
Overseeding (also called oversowing) thickens an existing lawn that has become thin, bare in patches, or worn out over winter. Because the existing sward provides ground cover and some competition for new seedlings, a lower rate is used, typically half the new-lawn rate. Before overseeding, mow the existing lawn short and scarify (rake) to expose soil for seed-to-soil contact.
Wastage Buffer
In practice, not every seed germinates. Some is eaten by birds (especially starlings), some blows off the prepared seedbed, and some fails to establish due to poor seed-to-soil contact or dry spells during germination. A 10 percent wastage buffer is standard for typical conditions with good seedbed preparation and some bird netting or deterrent in place. Increase to 15 to 20 percent for exposed sites, very light soils, or areas with heavy bird pressure.
Worked Example
A rectangular lawn 10 m x 10 m = 100 m2. Grass type: ryegrass/fescue mix. Sowing a new lawn at 35 g/m2. Total seed before wastage: 100 x 35 = 3,500 g = 3.5 kg. Adding a 10% wastage buffer: 3.5 x 1.10 = 3.85 kg. Buy one 5 kg bag to ensure you have enough.
Tips for Successful Lawn Establishment
- Sow ryegrass/fescue mixtures in autumn (March to May) or spring (September to October) when soil temperatures are between 10 and 20 degrees Celsius.
- Prepare a firm, fine seedbed by rotary-hoeing, levelling, and rolling before sowing.
- Apply a pre-sowing fertiliser (nitrogen, phosphorus, and potassium) and incorporate it into the top 50 mm of soil.
- Sow seed in two directions (half the seed in one pass, the other half at 90 degrees) for an even spread.
- Lightly rake the seed into the soil surface so seed is no deeper than 5 to 10 mm.
- Roll the seedbed after sowing to ensure good seed-to-soil contact.
- Keep the seedbed moist with light, frequent watering until seeds germinate (typically 7 to 14 days for ryegrass).
- Do not mow until grass reaches 75 mm; then mow to 50 mm.
Related Calculators
Sources and method: Seeding rates based on PGG Wrightson Seeds NZ sowing recommendations and DairyNZ pasture establishment guidelines. Oversowing rates are 50 percent of the full establishment rate as per standard agronomic practice. Wastage buffer applied as a simple percentage multiplier: Total seed = (Area x Rate x Method factor) x (1 + Wastage / 100).
Seeding rates are indicative based on standard NZ agronomic recommendations. Actual requirements vary with soil preparation quality, climate, seed germination rate, and whether a pre-germination seed treatment (such as coating or inoculation) is used. Always check the specific sowing rate on your seed bag, as rates can differ between seed blends and suppliers.
