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Johnson County

Research-based Information You Can Trust — Localized for your needs

Johnson County
11811 S. Sunset Drive
Suite 1500
Olathe, KS 66061

(913) 715-7000
(913) 715-7005 fax
jo@listserv.ksu.edu

Map to our office

Frequently Asked Lawn and Garden Questions

Lawns

Crabgrass control:

When should I apply crabgrass preventer to my lawn?

Answer:

The ideal time range for application of a crabgrass preventer or pre-emergent is from late March until mid April. It is best to apply just prior to the germination of the crabgrass seed to achieve the best control. There is really no benefit to apply treatment any earlier in the season because the weed seed does not normally germinate until late April. Another guideline is to time the application with the flowering of redbud trees. The redbud flowers when soil conditions are near the temperature needed for crabgrass germination. Most products should be watered into the soil for best results. Follow label instructions.

Fertilizing fescue lawns:

I have looked at several brands of lawn fertilizer that are called "winterizers." Some have high phosphorus levels while others have lower levels. What type of fertilizer should be applied to my tall fescue lawn and when should it be applied?

Answer:

The term ”winterizer” is very confusing. In the past, low nitrogen, higher phosphorus fertilizers were recommended for fescue lawns. Current recommendations call for high nitrogen and lower phosphorus applied in November. Lawn fertilizers such as 27-3-3 or 25-5-5 with a quick release form of nitrogen are recommended. It is the nitrogen fertilizer that stimulates the grass plants’ growth. High nitrogen in November is converted to stored food reserve that gives quick, spring green-up without excess top growth.

Fertilizing turf:

Because of the milder winter, my lawn is still very green. Is there any advantage to fertilizing in the early spring?

Answer:

Do not let “mother nature” fool you. It is still winter. Even though the grass is fairly green, it is still dormant and not actively growing. It is best to fertilize the grass when it is actively growing. September and mid-November are the most important times for fertilization of bluegrass and tall fescue. County Extension does not normally recommended late winter or early spring applications because the nutrients are converted to top growth, not root system development. Resist the temptation.

Fertilizing and weed control on lawns:

Tending the lawn can be confusing because of much conflicting information. I am most confused about spring fertilization and broadleaf weed control. I hear commercials for dandelion control and an application of fertilizer in the late spring. County Extension recommends fall dandelion control and very little or no spring fertilizer. When should fertilizer and weed control be applied to lawns?

Answer:

That is not an easy question to answer. Research-based findings on this subject are available, but not everyone reads, believes or follows research findings. Many homeowners are still fertilizing in the spring and summer, which can increase disease and insect problems and reduce drought tolerance. Spring fertilization also results in the need to mow frequently while providing little benefit in developing a strong root system. September and November are the optimum months for fertilizing a tall fescue or bluegrass lawn. These grasses should be fertilized in the spring or summer only if they will be watered and mowed regularly throughout the summer.

Dandelions are best controlled in the fall from mid-October through early November when the weeds are small seedlings and easier to control. Unfortunately, many homeowners do not think about controlling dandelions until they see them in the spring. This is the same time when retailers are promoting herbicide sales. Control in the spring is more difficult once the plants reach the flowering stage. There is also more risk to non-target plants with spring applications of herbicides.

Mowing newly planted lawns:

In the fall, I over seeded my lawn. I hear conflicting information about whether or not to mow the new lawn and when. What is the correct mowing practice for new grass?

Answer:

The recommendation is to mow new seedling grass when it reaches the same height as established grass. For bluegrass and tall fescue, that would be when the new grass reaches a height of between two and three inches. There is no benefit for letting it grow taller. Leggy leaf blades will fall over, shading out the turf. As a result, the grass plants do not fill in or spread as quickly. The grass seedlings are more durable than given credit for, so go ahead and mow.

Nutgrass (watergrass, nutsedge) - Control of:

My lawn has come back stronger than I thought it would after the heat and drought of last summer. However, I am noticing more nutgrass then ever. What is the best way to eradicate this pesky weed?

Answer: There are many names for nutgrass including watergrass and nutsedge. This weed is a sedge and is completely different from our more common grassy and broadleaf weeds. The products that control grassy and broadleaf weeds are not effective on nutgrass. The best chemical control of sedges is a product named Sedge Hammer. Read and follow label instructions for best results. Small patches of nutsedge can be controlled by hand removal. It will take several years of pulling, but eventually the plants will become weakened and die out.

Powdery Mildew on grass:

In the spring my lawn developed several areas where the grass was covered with a white growth. I am sure it is some type of disease. What is it and how do I get rid of it?

Answer:

The white growth or powdery-like substance on your grass is a disease called Powdery Mildew. This disease tends to be worse in the spring and fall under cool, moist conditions. It usually occurs on bluegrass in areas that are shaded or have poor air movement.

The good news is that the disease looks worse than it really is. The mildew attacks the leaf blades, so the affected area will not be as thick. It does not harm the crowns of the plants. When growing conditions become favorable again and with good culture practices, the lawn should recover completely. The general advice is to let the disease run its course and apply no fungicide treatment.

Ryegrass and bluegrass seed blends:

Is it a good idea to mix perennial ryegrass in a seed mix with bluegrass?

Answer: The answer to this question is debated in the world of horticulture. Some horticulturists recommend adding about 10% ryegrass to the mix; others do not. Johnson County Extension’s recommendation is that you plant the grass that most appeals to you and would be best for the growing conditions of your lawn. Ryegrass has low drought tolerance and requires more moisture than bluegrass. It often dies out with the stress of summer resulting in bare patches in your turf. Ryegrass should be added to the mix only if seeding late in the season for quick cover, or on a slope where the quicker germinating rye may help with soil retention.

Seeding bare areas in the lawn:

I have a couple of small bare areas in my lawn that I did not get seeded last fall. When is the best time in the spring to plant the grass seed?

Answer:

September is by far the ideal time to seed bluegrass or tall fescue lawns. Spring is acceptable, but more problems can arise with weeds and summer stress. Mid-March through early April would be the best time for establishment. Be sure to prepare the soil to ensure a good stand. Small areas can be hand raked while larger areas may require mechanical verticutting or core aeration. The use of crabgrass preventers should be avoided in the areas that have been recently seeded. Tupersan, a pre-emergent herbicide, will provide some relief from the crabgrass competing with the new stand of grass.

Zoysia lawns:

My zoysia lawn has not been very lush the last year or so. What I should do in the spring to revive the grass?

Answer:

Many homeowners’ Zoysia lawns have been suffering from a number of different problems over the past few years. Because zoysia is a warm season turf, it is best not to hurry spring care. Zoysia lawns should be fertilized in May. Fertilizing earlier while the grass is dormant will provide little benefit.

When mowing for the first time in the spring, lower the blade one notch, just enough to remove the debris. It is important not to scalp the turf back to clean up the brown debris. This is stressful to the turf. A setting that is too low causes crown damage and opens up the soil for more weed growth.
It is important to keep the thatch layer in check by either verticutting or by core aeration. A thatch layer over one-half inch is damaging for the lawn.

Return to Frequently Asked Lawn and Garden Questions

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Have questions? The Garden Hotline is staffed by trained EMG volunteers and Extension staff who will assist you with questions.

Phone: (913) 715-7050

Email: garden.help@jocogov.org