Spring Landscaping Checklist for the Denver Metro

In the Denver metro, spring landscaping season starts in late March to early April, as soon as the snow is gone and the ground isn't frozen or muddy. That's when you clean up, rake, aerate, and feed the lawn. But you hold off on planting frost-tender flowers and fully charging your sprinklers until after our average last frost around Mother's Day, because at a mile high a hard freeze can still hit into May. Get that timing right and the rest is a checklist. After waking up yards across Denver, Arvada, Westminster, Thornton, Golden, and Broomfield every spring since 2017, here's exactly what we do, and when.

When does spring landscaping season start in Denver?

Our high-plains climate makes timing the single most important thing in spring. Denver's average last hard freeze lands in the first half of May, and we usually treat Mother's Day as the line between "safe to plant tender stuff" and "still risky." The catch is that early spring here is a tease, we get 70-degree days in March followed by a foot of wet snow in April. So we split spring into two jobs:

• Early spring (late March to April): cleanup, lawn care, aeration, pruning, and bed prep, all the cold-tolerant work.
• Late spring (mid-May on): planting frost-tender annuals and vegetables, charging the full irrigation system, and laying sod.

Work the cold-hardy tasks early so you're not behind, but never rush the frost-tender ones. A single late freeze can wipe out a tray of annuals you put in two weeks too soon.

Your month-by-month spring checklist

Here's the cadence we run across the metro. Adjust by a week or two for elevation, foothills yards in Golden warm up later than lots out in Thornton.

Wake up your cool-season lawn

Denver lawns are cool-season grass, mostly Kentucky bluegrass, turf-type tall fescue, or a blend, and they green up early, which is why lawn care leads the spring list. Here's the order that works:

1. Rake and clear. Pull off leaves, sticks, and the matted "thatch" winter leaves behind so air and light reach the crowns.
2. Core-aerate. Our clay compacts hard. Pulling plugs opens the soil so water, air, and fertilizer get to the roots, this is the highest-value thing you can do for a Front Range lawn.
3. Overseed bare spots. Right after aeration, the open holes are the perfect seedbed for thin or worn areas.
4. Feed it. A spring fertilizer feeds the green-up. Don't overdo nitrogen, a steady feeding beats a heavy one that just forces soft, thirsty growth.
5. Mow high. Set the deck to about 3 inches and never cut more than a third of the blade at once. Taller grass shades the soil, holds moisture in our dry air, and crowds out weeds.

The single best move for a Denver lawn is spring core aeration. Our clay is so dense that everything else, water, seed, fertilizer, works better once you've opened the soil up.

Prep your beds and clay soil

Spring is the right time to get beds ready, while the soil is moist but workable. Cut back last year's perennials and ornamental grasses, pull early weeds before they seed, and clean up the edges so beds read crisp. Then feed the soil: our native clay is dense, alkaline, and low in organic matter, so work in 1 to 2 inches of quality compost as a top-dress, and refresh wood mulch to 2 to 3 inches to hold moisture and blunt the day-night temperature swings that crack clay. A quick warning that costs people every year: don't dig or till clay when it's wet from snowmelt, working saturated clay smears it into brick-hard clods. Wait until it's crumbly, not muddy.

What you can plant early vs. late

• Safe to plant in April: cold-hardy perennials, shrubs, trees, and cool-season veggies like peas, lettuce, and spinach, all fine through a light frost.
• Wait until after Mother's Day: annual flowers, tomatoes, peppers, and anything frost-tender, plus new sod, which needs warm soil and reliable watering to root.

Start your sprinklers the right way

This is where spring goes wrong for a lot of homeowners. Don't fully charge your irrigation system until the danger of a hard freeze has passed, usually mid-May. Water sitting in the lines can freeze on a late cold snap and crack pipes, valves, and backflow preventers, an expensive repair that's entirely avoidable. When you do start up:

• Open the main slowly to avoid a pressure surge, then walk every zone to check for broken heads, leaks, and bad spray patterns.
• Set early-morning cycles. Denver Water restricts summer watering to no more than three days a week and bans watering between 10 a.m. and 6 p.m., so program pre-dawn runs from day one. Watering early also cuts evaporation loss in our dry, sunny climate.
• Water deep and infrequent. Longer, less-frequent cycles drive roots down and build a tougher lawn than daily sprinkles.

If you'd rather skip the guesswork, a smart controller adjusts run times to the weather automatically, which pairs perfectly with our swingy spring.

Watch for late frost and spring hail

Two Front Range hazards round out the list. Late frost: keep old sheets or frost cloth handy through May to throw over tender new plants when a cold night sneaks in. Hail: Denver sits in the heart of hail alley, and a single May or June storm can shred tender foliage. You can't stop hail, but choosing tougher, more resilient plants and giving new plantings a week or two to harden off makes the difference between damage that bounces back and damage that doesn't. Build these checks into your routine and your yard comes out of spring strong, set up to cruise through summer instead of playing catch-up.