Fall Lawn Care Checklist for Boise

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pile of leaves spread across grass

In the City of Trees, there’s no shortage of gorgeous fall color. Boise’s harvest celebrations are hard to beat, but before you enjoy the potato- and pumpkin-filled fun, there are some important yard care to-do’s to prepare your lawn for cooler weather.

While our winters aren’t as extreme as higher-elevation towns to our north, Boise still experiences its fair share of freezing weather. Our fall lawn care checklist will get your lawn ready for winter and set to grow strong in spring.

1. Rake routinely

Boise is renowned for its lovely oak, maple, and ash trees, which means fantastic fall foliage and … a whole lot of leaves to rake. Rake your leaves every three to four days to prevent disease, mold, and soil compaction.

When dead leaves build up on your lawn, they block oxygen, sunlight, water, and nutrients from reaching your soil. That means your grass can’t photosynthesize to grow. 

Neglecting to rake can lead to:

  • Disease and fungal growth
  • Soil compaction
  • Pest infestations 
  • Suffocated, dead grass
  • Thatch buildup

Regular raking keeps your soil and grass healthy for spring growth and prevents the harmful buildup of thatch (the layer of dead organic material between the grass and the soil surface).

Pro Tip: Don’t bag and trash your leaves! Dead leaves are a secret treasure trove of nutrients. Either compost them to spread over your grass in spring, or mow them and leave them on your lawn to decompose.

2. Water until the ground freezes

Before you soak in the sights at the top of Table Rock, give your grass a good soaking. Fall days may be cool and crisp, but your grass needs to stay hydrated for strong growth before the winter freeze.

Stop watering after the first hard freeze, which typically occurs in mid- to late October in Boise. Once daytime temperatures consistently fall below 40 degrees Fahrenheit, your lawn won’t need to be watered. Doing so can cause a sheet of ice to form overnight, which can suffocate your grass.

How much water should I give my grass? Boise lawns typically require 1 to 2 inches of water per week. You can water once weekly or break waterings up into two sessions. Don’t water your lawn more than twice a week: Shallow, frequent waterings weaken grass roots and make your grass less drought-resistant. 

When should I water? Water in the early morning before 10 a.m. to minimize evaporation from the midday sun and prevent fungal diseases. Don’t water at night, as it will invite pests and diseases.

Pro Tip: Want to lower your water bill? You can reduce water use by up to 80% when you replace thirsty turfgrass with a drought-friendly xeriscape

3. Dethatch, if needed

illustration explaining thatch on grass

When your grass starts thinning and the ground feels spongy to the touch, it’s time to give your lawn a thorough dethatching.

Thatch is the layer of living and dead plant matter found between grass blades and the soil surface. A thin layer of thatch is healthy for your grass, but a thick layer prevents sunlight, water, and nutrients from reaching grass roots. Too much thatch causes poor root growth, diseased and thinning grass, and bare patches.

If your thatch layer is thicker than half an inch, it’s time to dethatch. Dethatching is the process of vigorously raking up excess thatch so nutrients can reach grass roots. 

How do I dethatch my lawn? Deeply rake your soil surface using a manual dethatcher, electric dethatcher, power rake, or verticutter. For small areas with a mild thatch problem, a manual dethatcher is sufficient. For large lawns with a serious thatch problem, a power rake or verticutter is the way to go.

When should I dethatch? Dethatch in early fall (mid- to late September) to give your grass time to recover before the first frost. Dethatching is temporarily stressful for your grass, so it’s important to dethatch while your grass is actively growing so it can heal. 

How often should I dethatch? You only need to dethatch when your thatch layer is over half an inch thick. With a healthy yard care routine, you may only need to dethatch once every few years. 

4. Aerate annually

illustration showing how aeration works and the benefits of aerating soil

If you’ve ever seen a lawn with a bunch of tiny holes in it, you’ve seen aeration at work. Aeration is the process of removing small cores of soil from your lawn to increase the flow of nutrients and give grass roots room to grow.

For Boise soil, it’s best to aerate in late September to early October. While you can aerate in spring, fall is preferable because weeds are less likely to sprout in the holes. 

Aeration: 

  • Gives grass roots space to spread
  • Encourages dense grass growth
  • Reduces soil compaction so roots can breathe
  • Reduces stormwater runoff
  • Increases your grass’s resistance to disease and drought
  • Reduces fertilizer needs
  • Invites earthworms and other beneficial soil organisms

What’s the difference between aeration and dethatching? 

Aeration and dethatching are similar practices, but they fix different problems. Dethatching removes thick thatch, while aeration alleviates soil compaction. Dethatching is done on an “as needed” basis, while aeration is an annual preventative practice. 

If you have both a thatch and compaction problem, always dethatch before you aerate. It’s much easier to aerate your soil once the thatch is gone. 

Pro Tip: Give your grass a growth boost by applying fertilizer one week before aerating. After aerating, overseed your lawn while the soil is still open. 

5. Overseed before the first frost 

After summer frisbee games and backyard barbeques, your lawn may be looking a little patchy. An easy fix? Spread seed over bare spots to get your grass growing densely and evenly again, so your lawn is set for spring. 

Fall is the season for robust grass growth in Boise, so it’s the perfect time to broadcast seed. For our cool, semi-arid climate, it’s best to overseed with tall or fine fescue, Kentucky bluegrass, or ryegrass, or a mixture of these varieties.

When should I overseed my lawn? Spread seeds in early September, at least 45 days before Boise’s first frost of the year, which typically occurs in mid-October. This gives grass time to germinate and grow deep roots before cold winter weather.  

6. Order a soil test, if needed

Soil is a treasure trove of different rocks, minerals, organic matter, and living organisms, so it’s no wonder that it’s constantly changing. Test your soil every three to five years to determine your soil quality and nutrient levels, so you can make the necessary soil amendments for healthy, green grass. 

For example, Boise soil is highly alkaline, so you may need to add sulfur or compost to soil if you’re planning to grow acid-loving plants like blueberries or daffodils.

A soil test shows:

  • Your soil’s nutrient levels and deficiencies
  • Salt levels (salinity)
  • pH level and imbalances (acidic, alkaline, or basic)
  • Soil factors that might be suppressing plant growth
  • The best fertilizers and soil amendments to balance your soil and increase nutrient levels for healthy grass growth

The University of Idaho’s Analytical Sciences Laboratory offers soil testing for a reasonable price, and you’ll receive a certified soil report within 15 business days.

Pro Tip: Always test your soil before starting a major landscaping project. You don’t want to build a gorgeous rock garden only to learn the plants you’ve chosen don’t grow in your soil!

7. Winterize your sprinklers

Idaho winters can be tough on your sprinkler system, and cracked pipes and damaged sprinkler heads aren’t exactly a welcome spring surprise. Protect your irrigation system by winterizing it in early October before Boise’s first hard freeze.

Winterizing your sprinklers means using compressed air to “blow out” all water from the system and equipment so water won’t freeze and expand in pipes over winter. Start by shutting off the system and draining it. Then, follow our step-by-step instructions to blow out the system. 

Pro Tip: Be sure to wear proper eye protection when winterizing your irrigation system. If you’re unfamiliar with your watering system, it’s a good idea to call in a Boise lawn care pro to prep your sprinklers for you. 

8. Fertilize for fresh growth

Think spring is the best time to fertilize your lawn? Think again! For cool-season lawns like ours, fall (mid- to late October) is the best time to apply fertilizer. It rejuvenates grass from stressful summers and gives it a healthy growth spurt before the long, cold winter.

Why apply fertilizer? Fertilizing offers a fantastic array of benefits:

  • Encourages fast recovery from damage and heat
  • Prevents weed encroachment
  • Keeps grass growing densely (unfertilized grass gradually loses its density)
  • Protects your grass’s lush green color
  • Improves your grass’s heat, drought, and cold tolerance
  • Increases disease and pest resistance
  • Encourages roots to store energy for winter
  • Reduces potential for snow mold

What is N-P-K? N-P-K is the ratio of nitrogen, phosphorus, and potassium (the three most essential soil nutrients) that a fertilizer contains. For example, a fertilizer with a ratio of 5-1-2 may be labeled as 25-5-10, which means it contains 25% nitrogen, 5% phosphorus, and 10% potassium.

What’s the best N-P-K ratio for my lawn? Check your soil test to see the ratio of nutrients your lawn needs so you can choose a fertilizer that addresses your lawn’s nutrient deficiencies. In general, Boise lawns do well with a 3-2-1 ratio (ex. A 24-12-6 fertilizer).

For ideal fall growth, choose a combination fertilizer that contains both slowly- and quickly- available nitrogen. The slow-release fertilizer will encourage root growth while the quick-release fertilizer will accelerate turf growth.

How often should I fertilize my lawn? It’s a good idea to fertilize your lawn on a regular schedule, two to four times per year (in spring, early summer, late summer, and fall).

How much fertilizer should I apply? In general, you should apply 0.5 to 3 pounds of nitrogen per 1,000 square feet per year. The amount of fertilizer you apply depends on your grass type and how satisfied you are with your grass’s growth. Never spread more than 1 pound of fertilizer in a single session, as this can cause fertilizer burn. 

9. Control weeds with post-emergent herbicide

Grab your gloves and attack those perennial weeds with a vengeance. Fall is the perfect time to kill pesky weeds that seem to have superhuman powers of survival.

In fall, weeds begin moving carbohydrates from their leaves to their roots. So, when you spray herbicide, they absorb it and transport it all the way to their roots. The result? The whole plant is poisoned and dies.

Spray actively growing weeds with post-emergent herbicide between Aug. 15 and Oct. 15, after the first light freeze.

Post-emergent herbicides will kill Boise weeds like: 

  • Dandelions
  • Field bindweed
  • Broadleaf and buckhorn plantain
  • Prostrate knotweed

Dicamba, 2,4-D, and triclopyr are selective herbicides that control broadleaf weeds. Alternatively, you can spot spray weeds with heavy-duty, non-selective glyphosate. Just make sure you don’t let it touch your favorite plants! 

Want to go all-natural? Opt for an organic herbicide instead. 

Pro Tip: Herbicide can be tough on young grass. If you plan to overseed your lawn this fall, hold off on the herbicide until spring.

10. Mow until your grass stops growing

Don’t stop mowing ’til your grass stops growing! Our cool-season grass will keep growing until daytime temperatures fall below 50 degrees Fahrenheit, generally in early November. Once you notice your grass isn’t getting longer, it’s time to haul out the mower for one final cut. 

How long should I mow my grass? In general, Boise lawns should be mowed to a height of 2.5 to 3 inches during the growing season, depending on the grass type. However, for the final mow, you can set your blade height a notch lower: A shorter cut will prevent matting and snow mold. 

Don’t go too wild with your mowing! You don’t want to damage (scalp) your grass as harsh winter weather approaches. Always keep your grass at least 2 inches tall. 

Follow the one-third rule. Never cut more than one-third of your grass height in a single mowing. For example, if your grass is 3 inches tall, do not cut more than 1 inch off the top. Otherwise, you could damage your grass and leave it vulnerable to pests and diseases.

illustration explaining the one-third rule for mowing grass

Pro Tip: Don’t toss out your grass clippings. Instead, mow with a mulching mower and let grass clippings lie on your lawn and decompose. They’ll act as a natural mulch and return nutrients to your soil.

11. Put gardens to bed

It’s time for your veggies and flowers to take a long winter’s nap. They’ll need you to tuck them in securely so they can grow strong in spring. Winterizing your garden insulates your soil and protects your plants from pests, weeds, and disease.

How to winterize your garden:

  • Clean out dead weeds and annuals to prevent disease and pests. (Leave annual roots in the ground: They’ll break down and improve the soil.)
  • Trim perennials, shrubs, and trees. Wait to cut back flower stalks and seed heads until spring, as they provide food and protection for birds and bees.
  • Bring tropical and semi-tropical potted plants indoors for the season.
  • Divide overgrown perennials so they don’t compete for nutrients and space in spring.
  • Mix in a thick layer of nutrient-rich compost. It will decompose over the winter so you’ll have healthy, loamy soil in spring.
  • Prevent snow damage by tying trees, shrubs, and large perennials with jute or twine.
  • Insulate the soil bed with a 1- to 4-inch layer of mulch (like straw or decomposing leaves). Mulch regulates soil temperature so garden plants don’t green up too early when there are a few warm days in winter.
  • Deeply water plants one last time before daily temperatures fall below 40 degrees Fahrenheit.

Check off your fall lawn care list

Sure, we’re famous for our spuds, but potatoes aren’t the only plants that flourish in Boise. With the proper fall lawn care, your grass will be the talk of the neighborhood come spring. 

If you’re an old hat at aeration and know your way around a sprinkler system, you can make fall lawn care prep a DIY project. Start planning in late August so you don’t get spooked by a long to-do list later in fall. (You can get your jump scares at the Idaho Horror Film Fest, instead.) 

Don’t know the front from the back end of a dethatcher? We’ve got you covered. Lawn Love’s Boise lawn care team will tackle your fall lawn care chores while you kick up your heels at the Old Boise Oktoberfest.

Main Photo Credit: Linus Lorentzen | Unsplash

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