Ontario lawn maintenance schedule: what to do each month

This lawn maintenance schedule for Ontario covers the cool-season grasses in the usual lawn mix: Kentucky bluegrass, fine fescues and perennial ryegrass. A GTA lawn needs very little from December to March and a lot from April to November. Most of the work that decides how it looks next year happens in two short windows: late May into June, and mid-August into September.

Miss the fall window and thin spots tend to fill in with weeds instead of grass.

If you’d rather hand the weekly cutting to someone else, that’s what our lawn mowing and lawn care service covers.

What is the recommended lawn maintenance schedule for Ontario?

Rake in April, mow at 7.5 cm from May on, feed in late May or early June and again in late summer or fall, and overseed and aerate from mid-August to mid-September.

Here’s the full lawn care calendar for Markham and the rest of the GTA. Dates shift a week or two with the weather, so go by what the grass is doing.

Scroll sideways to see the whole table.

When should you fertilize your lawn in Ontario?

Feed in late May or early June and again in late summer or fall, and leave midsummer alone. Landscape Ontario, Health Canada and OMAFRA all agree on that much. Where they differ is how late in fall to feed.

Scroll sideways to see the whole table.

OMAFRA’s turf manual is the most cautious of the four. It caps each feeding at 0.5 kg of nitrogen per 100 m².

Use a slow-release lawn fertilizer and follow the bag. OMAFRA and Landscape Ontario’s lawn care members both recommend a phosphorus-free fertilizer on established lawns, unless a soil test shows the soil is short on it.

When is the best time to overseed and aerate in the GTA?

Mid-August to mid-September. OMAFRA calls this the preferred time to seed cool-season grass in Ontario, because soil moisture and temperature suit germination and fewer weeds sprout to compete.

The Nursery Sod Growers Association adds that seed should go down at least 45 days before the first frost. That’s another reason not to leave it until October.

Health Canada suggests doing it in this order in late summer:

1. Aerate the lawn.
2. Topdress.
3. Overseed, so the seed lands in the holes and touches soil.

Spring seeding (mid-April to early June) works too, but the young grass then has to get through July. Our fall lawn care guide covers overseeding and repair step by step.

Check thatch while you’re at it. Landscape Ontario says a healthy lawn has about 1 cm of thatch, and more than 2.5 cm is too much.

How much should you water in summer, and what does Markham allow?

Once a week, in one deep watering of about 2.0 to 2.5 cm, when rain falls short. That’s OMAFRA’s figure. Health Canada says at least 2.5 cm per watering, no more than once a week.

Frequent light watering grows shallow roots and favours crabgrass.

You can also let a healthy lawn go brown. OMAFRA says turf can sit dormant for four to six weeks in a dry spell without lasting harm, and it greens up within one to two weeks after the rain returns.

The catch is that a dormant lawn lets more weeds in, and OMAFRA warns against heavy foot traffic on it. Plan to overseed thin spots in late August.

In Markham, the water use by-law sets these rules:

Scroll sideways to see the whole table.

Our guide on watering new sod explains how much new sod needs.

When do grubs and chinch bugs show up?

Chinch bugs in July and August, grubs in late summer and fall.

OMAFRA describes hairy chinch bug damage as small, sunken, irregular brown patches that start in mid to late July and spread fastest in sunny parts of the lawn. The worst of it runs from mid-July to mid-August.

It often gets mistaken for drought, and it’s worst on lawns with heavy thatch that don’t get watered.

European chafer beetles fly from late June to mid-July, and their grubs do most of their damage feeding on roots in early fall. Damaged turf lifts like a carpet. Skunks and birds digging up the lawn are often the first sign.

Ontario’s cosmetic pesticide ban limits homeowners to products whose active ingredients are on the province’s Allowable List, which is mostly biopesticides and lower-risk products. TRCA suggests beneficial nematodes for grubs.

OMAFRA’s cultural controls for grubs are habits already in this calendar: deep watering, aeration, balanced feeding and a higher cut. For chinch bugs, Landscape Ontario suggests overseeding with a perennial ryegrass mix, which the bugs tend to avoid.

Common mistakes on GTA lawns

• Cutting short to stretch the time between mowings. TRCA’s 7.5 cm height shades out weeds and keeps the soil cool and moist. Short grass dries out first when July turns hot.
• Taking off more than a third of the blade after a missed week or two. OMAFRA and Landscape Ontario both give this one-third rule, so a lawn kept at 7.5 cm should be cut before it passes about 11 cm.
• Feeding in July heat, which Health Canada specifically advises against.
• Light sprinkling every evening instead of one deep watering a week.
• Seeding in October. OMAFRA’s seeding windows end in late September, and the sod growers’ rule of 45 days before the first frost rules out most of October.
• Letting grass get away in June. Markham’s property standards cap grass at 15 cm.
• Leaving a thick mat of leaves on the lawn into November.
• Bagging clippings. TRCA says they can boost soil fertility by up to 30 per cent, and Markham’s curbside yard pickup doesn’t take them anyway.

When it makes sense to call someone

Most of this calendar is weekend-sized work if you have a sharp mower and an hour a week. Mowing is the part people struggle to keep up with.

Missed weeks do the most damage, because the catch-up cut always takes off too much. So that’s the job most worth handing off, and it’s what our lawn care service is for.

Bigger problems are a different job. If grubs, dogs, shade or a dry summer have killed whole sections, new sod gives you a full lawn right away instead of waiting on seed. See our sod installation and lawn repair service.

For the leaf and debris side of spring and fall, the spring cleanup checklist and fall cleanup guide walk through what to do, or we can handle it as a seasonal cleanup.

We work across Markham and nearby, including Richmond Hill and Stouffville. Call (437) 684-2535 or text us a couple of photos of your lawn and we’ll come by for a free quote.