Written by David Chalmers, former Professor & SDSU Extension Turfgrass Associate.
Lawn care certainly is a seasonal activity in South Dakota with our six-month growing season. Spring is a time when we can’t wait to get the garden going or the lawn fertilized so it can develop that green color we have been missing all winter. Summer is left for keeping the lawn going with mowing and making the decisions on when and how much to irrigate. Yet, homeowners often don’t have the same focus and enthusiasm for late season lawn care. The late growing season period I want to emphasize is from August 15th to October 10th. It is part summer and part autumn on the calendar and it is the last best chance to improve our lawns before winter. It is the “prime time” to get some key lawn management practices in play when they will do the most good. Good late-season management will enhance lawn quality for the remainder of this year and set up the lawn to come out of the spring with improved density, color and fewer weed issues next year. So now is the time to get focused on late season lawn care! Your lawn care calendar should begin now!
Fall management needs depend on whether your lawn is maintained as a low, moderate or relatively high maintenance lawn. Yet all levels of lawn maintenance can benefit from some late season fertility, and if needed, irrigation, weed control, thatch control, seeding to repair small areas or overseeding a thin and worn out lawn. So let’s look at the late summer to early autumn best management practices for lawns.
Fertilizer Application
Late season is the best time to fertilize. The goal this time of year is to fertilize when there is a good chance to get the late season grass response. Timing is important. Yet, the lawn needs good soil moisture from rainfall or irrigation to make the most of the fertilizer. Late season nitrogen fertilizer applications allow for good fall to spring growth, increases in turf density and green color. With late season nitrogen fertilizer applications, the timing of the spring fertilizer application can often be delayed until after the normal spring growth surge. This can help reduce spring mowing that results from too much early spring nitrogen fertilizer.
- Low to moderate maintenance lawns: Fertilize once about Labor Day.
- Moderate to high maintenance lawns: Apply one or two applications. The first in late August to very early Sept along with a second application 4 weeks later, around October 1st.
Watering
Last year’s drought prevented non-irrigated lawns from recovering during the late season. Irrigation to supplement rainfall during this time may be needed for the turf to best take up the applied fertilizer. Fall watering will also help newly seeded turf to become better established before winter if moisture is not limiting.
Broadleaf Weeds
Broadleaf weed control is preferred in September on established cool-season turf. The temperatures are such that the weeds are actively growing to take up the herbicides and the grass is better able to fill in the voids left by the weeds with late season fertilization. This is also a good time to use herbicides because most of our garden vegetables, flowers and woody plants are beginning to go dormant or die so they will not be as adversely affected by spray drift as they might during spring. The most effective weed control comes from choosing products from the garden center that are labeled for the types of weeds in the lawn. Garden center weed control products for home consumers typically contain mixtures of 2 to 3 herbicides to provide more control across a diverse amount of weed types than products formulated with only one herbicide. Always read the product labels for weeds controlled, rates to apply and safety precautions. Follow all label directions when making any pesticide application.
Crabgrass and Annual Grassy Weeds
These weeds are very difficult to control this late in their annual life cycle. So we will live with them as they die off. They will lose vigor as temperatures begin to cool down and are killed off by the first frost. Encourage lawn grass growth with late season fertilizer and irrigation to try to fill in the voids as these annual weeds die out. If crabgrass was a problem this year it will return again next year. There are a number of pre-emergence herbicides that can be used in the spring (around May 1st) that will effectively control crabgrass in next year’s lawn.
Thatch and Soil Compaction
Late season is the best time to core cultivate (also called aerifying) to help relieve soil compaction if that is a problem. The soil cores brought up by coring will break up and mix into the thatch to also help its decomposition and keep it under control. De-thatching machines (vertical mower or power rake) are also used to physically remove thatch build-up if thatch is a problem. Late season treatment allows for 4 to 6 weeks of good growing conditions needed for the grass to recover, following these disruptive practices.. Use a shovel to pry back the turf to see if a thatch layer is building up above the soil. Thatch layers thicker than 1/2 inch or so in lawns can begin to cause problems and should be managed.
Planting and Overseeding Lawn
Get ready now to establish a new lawn or to overseed to renovate your existing lawn in mid to late August. The earlier you can get this done the better the grass will grow-in before winter. The choice will be to do it your self or have a landscaper do the work. If you plan to use a landscape contractor contact them as soon as possible to get on their schedule, as it is their busy time of year! This is absolutely the best time of the year to seed a lawn. It is also a great time to plant sod if it gets a bit late to seed. The cooler weather and more likely fall rains make establishment much easier in the fall. Also, some of the warm season annual weeds like crabgrass will not be as much of a problem compared to spring plantings.
The “take-home” message here is for homeowners to set their cool-season lawn management calendar to begin August 15th in South Dakota! To have a “lawn to your liking” focus on the amount of care needed based upon the kind of lawn you want. If your lawn needs some TLC don’t miss the mid-August to early October “window” of opportunity to set your lawn up with the basic management it needs.
