When to fertilise your lawn in Australia and New Zealand

First: warm-season or cool-season?

The feeding calendar follows the grass, so identify it first. Overseas lawn advice often uses different names for the same grasses, which matters when you read it:

Warm-season grasses grow hard in heat and go dormant or slow right down in winter over most of southern Australia. Cool-season grasses do the opposite: they grow best in spring and autumn and slow in summer heat.

The feeding calendar

In the tropical and subtropical north, warm-season lawns grow for most of the year. Spread the feeds across the growing season and avoid the heaviest wet-season rain, which washes fertiliser away.

How much per feed

The label rate comes first, and for most granular lawn foods it is 20–35 g/m². What does the work is the nitrogen, and that depends on the product's analysis:

• Per feed: university turf research puts the ceiling for a single application at about 4.9 g N/m² (1 lb per 1,000 ft²), and a little less for quick-release forms. Most lawn foods at label rate land at 3–5 g N/m².
• Per year: needs vary by grass. Zoysia is one of the least hungry, performing best on about 5–10 g N/m² a year; vigorous couch and kikuyu use more.
• Phosphorus: established lawns need little. Many lawn foods are low in P for that reason, and phosphorus that washes into waterways feeds algae.

The fertiliser calculator turns any label into kilograms for your lawn and shows the grams of N, P and K per square metre.

How to feed without burning the lawn

1. Mow a day or two before. Granules then reach the soil instead of sitting in long leaves.
2. Feed a growing lawn. Never feed a lawn that is drought-stressed or dormant. Water a dry lawn first and wait for it to recover.
3. Spread in two directions. Half the product walking one way and half across. A spreader gives the most even result.
4. Water it in the same day. This moves the nutrients into the soil and stops granules scorching leaves. In hot weather, feed in the cool of the morning or evening.
5. Sweep the paths. Fertiliser on concrete ends up in stormwater drains. Do not feed just before a heavy storm.

Liquid lawn foods are easier to apply evenly but act for a shorter time, so they are used more often, typically every few weeks through the growing season. Organic fertilisers such as pelletised manures are slower and much lower in nitrogen by weight, so their rates per square metre are higher.

Worked example: a year of feeding

An 80 m² buffalo lawn in Melbourne, fed with a granular lawn food labelled 15-1.5-6 at 25 g/m²:

1. Each feed: 80 × 25 g = 2 kg of product, supplying 3.75 g N/m², inside the per-feed ceiling.
2. Three feeds (October, late January, April): 6 kg a year, one 10 kg bag lasting well into the next season.
3. Annual nitrogen: about 11 g N/m², a moderate programme for a buffalo lawn.

Questions