Our Blog | Learning Centre | Yard Dawgs Lawn Care

How to Plant Grass Seed for Thicker Lawn

Written by Clare Ottenbreit | Oct 8, 2025 7:32:46 AM

When your lawn starts looking thin, patchy, or tired, there’s no need to start over from scratch. Planting new grass seed directly into an existing lawn, also known as overseeding, is a proven way to bring density, vibrancy, and resilience back to your turf. 

But here’s the catch: the success of overseeding depends on when, how, and with what kind of care you plant your lawn grass seed. Timing, prep, and follow-through are everything. So if you’re wondering how to plant grass seed on an existing lawn the right way, this guide will walk you through it step-by-step.

Why Overseeding Matters More Than You Think

Grass naturally thins out over time due to foot traffic, weather extremes, and pests like chinch bugs. Overseeding isn’t just about fixing bald patches; it’s also a smart preventative strategy that:

  • Thickens turf to naturally crowd out weeds
  • Enhances resistance to insects and disease
  • Improves overall lawn colour and uniformity
  • Helps your grass recover faster after summer stress

At Yard Dawgs, we know the climate challenges homeowners face in Western Canada. That’s why we offer Slit-Seeding & Lawn Seeding Services designed to ensure every seed gets the soil contact and protection it needs to thrive.

Step-by-Step: How to Plant Grass Seed on an Existing Lawn

Let’s break down the process so you can start seeing visible results in a matter of weeks.

1. Pick the Right Time of Year

Late summer to early fall is the ideal time to overseed in Alberta and Saskatchewan. The soil is still warm enough for quick germination, while cooler air temperatures reduce stress on tender new grass. Spring can also work, just be prepared to stay on top of watering as summer heat arrives.

2. Choose the Right Grass Seed

Select a high-quality lawn grass seed blend suited for your region and sunlight exposure. Cool-season grasses like Kentucky bluegrass, fescues, and ryegrass perform well in Calgary and surrounding areas. Avoid cheap mixes with fillers or weed seed, your lawn deserves better.

3. Prep Your Lawn Properly

This is where many people go wrong. You need to create the ideal environment for seed-to-soil contact.

  • Mow Low – Cut your existing grass shorter than usual (1.5–2 inches). This gives the new seed more light and room to grow.
  • Bag the Clippings – Don’t leave anything behind that could block the seed from reaching the soil.
  • Rake or Dethatch – Remove debris, dead grass, and thatch buildup with a stiff rake.
  • Aerate – If your soil is compacted, mechanical or liquid aeration is essential. It opens up the soil, improving airflow, nutrient absorption, and seed integration.

4. Apply the Grass Seed Evenly

Spread the grass seed across your lawn using a broadcast or drop spreader. Aim for even distribution, no heavy clumps or bare gaps.

Pro Tip: Apply half the seed in one direction, then go over it again at a right angle. This cross-pattern ensures consistent coverage.

5. Boost with the Right Nutrients

Support your new grass with the nutrients it needs to establish strong roots.

  • Consider a natural feeding boost like Sea Kelp or Super Juice, which promote rapid root development and stress resilience.
  • Avoid synthetic fertilizers right after seeding. Wait until the grass is mowed a few times before feeding with stronger products.

6. Water Consistently

Watering is critical for germination and early growth.

  • First 2 weeks: Lightly water daily (or even twice a day during heat) to keep the top inch of soil moist.
  • Weeks 3–4: Reduce to every other day, but water deeper.
  • After establishment: Transition to deeper, less frequent watering to encourage long root systems.

Avoid overwatering, which can rot seeds or invite fungal issues.

7. Skip the Mulch Or Choose Carefully

Unlike seeding a bare area, overseeding doesn’t typically require a mulch cover. However, if you want added protection, a thin layer of compost can help retain moisture and improve soil quality. Just don’t smother the seed, you still need good airflow and light penetration.

What to Expect After Planting Grass Seed

Grass seed germination time varies:

  • Ryegrass: 5–7 days
  • Fescues: 7–10 days
  • Kentucky Bluegrass: Up to 21 days

Be patient and keep watering on schedule. Once the new grass reaches about 3 inches tall, mow it gently with sharp blades set high (around 3 inches). Continue mowing regularly, but don’t scalp it, tall grass shades out weeds and promotes deep roots.

Keep It Thriving with Professional Lawn Care

Overseeding is a great start, but keeping your lawn thick, green, and weed-free all season long takes year-round attention. That’s where Yard Dawgs comes in. We offer personalized care plans that include:

  • Routine fertilizer treatments to maintain soil health
  • Effective weed control backed by our Weed-Free Guarantee
  • Season-long monitoring for chinch bugs and other pests
  • Aeration and slit-seeding options for stubborn areas

Learning how to plant grass seed on an existing lawn gives you the power to transform your yard without starting from scratch. But if you’d rather skip the mess and guarantee success, our local pros are ready to help. With Yard Dawgs, your dream lawn is just a few treatments away. Let’s grow something great together!