Preparing your lawn for a Canterbury winter

1. Clear the leaves — and keep clearing them

Christchurch's big deciduous trees (planes, oaks, liquidambars, silver birches) drop from late March through May. A layer of wet leaves left on grass for a fortnight blocks light and traps moisture; underneath it the grass yellows and moss and fungal disease move in.

Rake or blow leaves off the lawn weekly through the drop, and clear them out of garden beds and gutters at the same time. Leaves can go on the compost or into green waste.

2. The final cut: lower, but not scalped

For the last regular cut in May, drop the mower one notch — to around 35–40 mm. Slightly shorter grass going into winter means less matting under snow or heavy frost and less leaf for disease to take hold on. Don't go below 30 mm; that exposes the crowns to frost.

After that, mow only when it's dry and thawed, roughly every three to four weeks, and put the height back up.

3. Aerate compacted areas

Autumn is the best time to core aerate in Canterbury, especially on clay and loess soils and anywhere that gets foot traffic (paths to the clothesline, under the trampoline). Aeration lets winter rain drain through instead of pooling, and gives roots air. A garden fork pushed in every 15 cm and rocked does the job on a small lawn; hire a corer for anything bigger.

4. Deal with moss now, not in spring

Moss thrives in exactly the conditions a Christchurch winter provides: cold, damp, low light, compacted soil. If you already have moss in shaded areas, treat it in autumn with an iron-based moss killer, rake out the dead material a fortnight later, and oversow the bare patches while the soil is still warm enough for germination (before mid-May).

Longer term, moss is a symptom: improve drainage, cut back overhanging branches to let light in, and don't mow that area too short.

5. Feed with an autumn fertiliser

An autumn-specific lawn fertiliser is low in nitrogen and higher in potassium, which hardens the grass against frost and disease rather than pushing soft growth. Apply in April on a day when rain is forecast, or water it in. Avoid high-nitrogen 'greening' products after March — the soft growth they produce is the first thing frost kills.

6. Stay off it when it's frozen or saturated

Walking on a frosted lawn breaks the frozen blades, leaving brown footprints that last for weeks. Walking or mowing on a waterlogged lawn compacts the soil. On the worst days, the best thing you can do for a Christchurch lawn is leave it alone.