Lawns languish in the heat of summer unless showered with the water they require to thrive. But not to worry, the grass isn’t dead.
Come fall when the rains start again, grass greens up quickly, said Alec Kowalewski, turf specialist for Oregon State University’s Extension Service.
While letting your lawn go dormant in summer isn’t a bad thing — especially with concern about water shortages — lack of irrigation does allow pesky weeds to gain a foothold, he said. And regular wear and tear can cause compaction within a lawn, which leads to brown or bare spots.
If irrigation doesn’t bring back healthy lawn, early September to late October is the optimal time to sow fresh grass seed or replace an existing lawn throughout the state.
If you wait until November, it’s too late – the next best bet to establish a new lawn comes around the following April to May.
“The problem is that when you get later into the year, annual bluegrass takes over,” Kowalewski said. “If your turfgrass seed germinates late in the fall, it will not out-compete annual bluegrass, a very problematic, profuse weed due to our wet climate.”
Don’t think you have to completely start over.
“You should always try renovation before putting in a new lawn because it’s difficult to get a stand of grass established,” Kowalewski said. “So if you have something to begin with, go with renovating.”
What you have to begin with can vary from addressing a few brown spots to a desert of weeds to hardpan soil. Assess your lawn’s level of neediness and then proceed with a regular renovation or a no-holds-barred one. Most often, a regular tune up is all that’s needed.
Whether you’re renovating or starting over, determine the type of lawn seed you need first.
Kowalewski recommends perennial ryegrass for a lawn in full sun in western Oregon. If your lawn lies in the shade or you don’t irrigate much, fine fescues are a great choice. Tall fescues are best if you don’t water much and your lawn gets full sun.
“Fescues are very drought-tolerant,” he said. “Tall fescue is the most drought-tolerant and fine fescue is both drought- and shade-tolerant.”
For eastern Oregon homeowners who deal with a significant amount of snowfall, use Kentucky bluegrass. But remember, it needs irrigation.
Science has not created a kind of turfgrass that stays green all year without any water – yet.
“Tall fescue is the closest thing to it,” Kowalewski said.
Once you’ve got your lawn established, adhere to Kowalewski’s three steps to a healthy lawn that will outcompete weeds: water, fertilize and mow properly.
Watering is a matter of 1 inch a week, but don’t do it all at once. Recommendations for watering have changed, according to Kowalewski. Research now shows that instead of 1 inch of water once a week, lawns should be irrigated several times a week for a total of 1 inch. Apply about 1/4 to 1/3 inch three to four times a week. During intense heat, water even more often — up to five times a week — but not any more than 1/4 inch in one application. Measure with a rain gauge, plastic cup or tuna can.
“If you look at the roots, the majority are in the top 1 inch of the soil,” he said. “The deeper you go the fewer roots there are so watering more than a quarter inch at a time is a waste. So irrigate more frequently with less amounts when it’s not raining.”
Fertilize four times a year. An easy way to remember is to apply on Memorial Day, Fourth of July, Labor Day and Thanksgiving.
When it comes to mowing, never remove more than one-third of the grass at one time. That means if the lawn is 3 inches long, cut only 1 inch. Cutting more than one-third weakens the lawn, leaving it vulnerable to weeds and diseases. For most grasses, 2 inches is about top range of what a homeowner will tolerate, but higher is even better.
“Increase the height of the grass as tall as you can stand it and mow once a week,” he said. “If you mow it to an inch, it’s horrible to the health of the plant because you’re decreasing rooting depth and stress tolerance. And you’ll have to water more often.”
Mow once a week in spring and fall, less often during summer and winter months. Instead of bagging up clippings, consider leaving them where they fall. They break down quickly and resupply much-needed nitrogen. The more often you mow, the easier this is to do. Don’t, however, leave clumps of clippings sitting on the lawn.
For tips on starting a new lawn, see Extension’s publication Practical Lawn Establishment and Renovation.
To renovate, follow Kowalewski’s recommendations:
For regular renovation:
- Do a pH test. Either take a sample with help from Extension’s Guide to Collecting Soil Samples for Farms and Gardens and send it to a soil lab, or buy a test kit at the nursery. Lawns grow well in a pH of 6 to 6.5.
- Remove weeds by hand or with a broad spectrum herbicide.
- Aerate lawn with a machine available at rental shops. Pay particular attention to bare spots or compacted areas. Rake off plugs of soil removed by aerator.
- If the pH is on the low side (below 6.0), add lime. It’s common in western Oregon for lawns to need lime every two to three years.
- Fertilize with a product that has plenty of nitrogen, low or no phosphorus and a medium level of potassium. Check the fertilizer label and choose something with a high first number (N), low second number (P) and medium third number (K) such as 20-2-6. You’ll get best results using a rotary spreader.
- Overseed at the recommended rate, going a little thicker on really bare spots. Use a drop seeder for even distribution.
- Water newly seeded turf daily unless it rains.
For major renovation, do the above steps and add the following:
- Mow lawn as short as possible before getting started.
- Before aerating, dethatch the lawn with a dethatching machine or power rake, which you can rent. The idea is to expose as much soil as possible. Run the machine across the lawn twice, in opposite directions. Remove loosened thatch before changing direction.
- After seeding, mulch with a thin layer of sawdust, bark dust or compost. A quarter inch is enough; don’t overdo it or seed will have a tough time germinating. To make the job easier, rent a wire drum roller.
Article written by Kym Pokorny, a garden writer with more than 20 years of experience writing for The Oregonian and other publications. She is currently a communications specialist with Oregon State University Extension Service. Kym can be reached at firstname.lastname@example.org.
This has been republished with permission from Ms. Pokorny and OSU Extension. To view more of the OSU garden tips, please visit their website here.