Colorado Lawn Fertilization: A 4-Step Annual Schedule

Four Applications, Four Jobs

A healthy Front Range lawn needs four targeted fertilizer applications per year. Miss any of them — especially the fall application — and you'll spend the following year trying to recover density and color that a $40 bag of fertilizer would have maintained.

Application 1: Early Spring — Green-Up (March–April)

What it does: Kick-starts growth after dormancy.

What to use: Balanced slow-release fertilizer, 29-0-4 or similar. Light on phosphorus since established lawns don't need much.

Rate: 0.5 lbs nitrogen per 1,000 sq ft

Timing: When soil temperature reaches 50°F consistently — usually late March to mid-April along the Front Range.

Don't push high nitrogen in early spring. Fast top growth before root systems have fully activated leads to thatch buildup and disease susceptibility.

Application 2: Late Spring — Feed (May–June)

What it does: Sustains strong growth during the most active growing period.

What to use: Slow-release nitrogen, 32-0-10 or similar with potassium for stress tolerance.

Rate: 0.75 lbs nitrogen per 1,000 sq ft

Timing: Memorial Day, give or take two weeks.

This is the application most homeowners do correctly. The rest of the schedule is where they fall off.

Pro Tip: Skip fertilizing in July and August. Heat + nitrogen = burned turf and increased disease pressure. Let the lawn coast through summer.

Application 3: Early Fall — Recovery (August–September)

What it does: Rebuilds density after summer stress, supports new seed germination if overseeding.

What to use: Starter fertilizer if overseeding (18-24-12). Otherwise balanced slow-release.

Rate: 0.75 lbs nitrogen per 1,000 sq ft

Timing: Late August to mid-September, same window as aeration/overseeding.

Application 4: Late Fall — Winterizer (October–November)

What it does: Builds carbohydrate reserves in the root system for winter survival and early spring green-up.

What to use: High-potassium formulation, 13-2-13 or 0-0-50 (straight potassium) in very poor-soil lawns.

Rate: 1 lb nitrogen per 1,000 sq ft

Timing: After the lawn has gone mostly dormant but before hard freeze — typically late October along the Front Range.

This is the most important application most homeowners skip. The nitrogen stays in the root system over winter and fuels green-up weeks earlier than unfertilized lawns in spring.

Updated on: 29/04/2026