Scotts vs Milorganite vs Jonathan Green vs PRO-MIX vs Safer's — which lawn fertilizer works best on GTA clay soil? Timing guide, NPK explained, Ontario phosphorus rules.
Yes, but use a starter fertilizer with phosphorus for new seed only — this is the one exception to the zero-phosphorus rule. A 12-24-12 or similar starter formula applied at seeding time supports root development on new seedlings. Once the new grass reaches 3 inches and has been mowed twice, transition to a standard zero-phosphorus maintenance formula.
Wait 24 to 48 hours after fertilizing before mowing — give the fertilizer time to water in and begin absorbing. Mowing immediately after application, particularly with fast-release granular products, can scatter granules unevenly and increase the risk of scalping stressed areas.
The two easiest-to-find organic or organic-enriched options for GTA homeowners are Golfgreen Organic Lawn Food at Canadian Tire and PRO-MIX Heal and Feed at Home Depot Canada. Both are Canadian-made products genuinely available at big-box stores across Toronto, Mississauga, Vaughan, and Scarborough.
After. Core aeration creates channels directly into the soil that allow fertilizer granules to reach deeper root zones. Applying fertilizer immediately after aeration — within 24 to 48 hours — is the most efficient application timing of the year. The combination of aeration plus overseeding plus fertilizer in fall is the single most impactful annual lawn treatment you can do on a GTA clay-soil lawn.