When it comes to having a great lawn, what is most important?

Is it the lawn care applications?
Is it mowing practices?
Is it environmental conditions?

All three are keys to a great lawn - Lawn Care Applications, Maintenance, and Environmental Conditions.

Great lawns are not a result of getting one, or even two, of the three correct. Great lawns are equally the result of all three.

In April, we covered Lawn Care Applications.

In May. we discussed Maintenance.

Today we are covering the last key - Environmental Conditions.

Environmental Conditions are all the things that are outside of our control:

Rainfall & Soil Moisture
Air Temperatures & Soil Temperatures
Sunshine & Wind

Oh, don’t you wish you could control environmental conditions!?

Our role when it comes to environmental conditions is to monitor, supplement, and adjust our practices based on the conditions.

A good source for monitoring all weather data is mesonet.org.

The Oklahoma Mesonet is a world-class network of environmental monitoring stations. The network was designed and implemented by scientists at the University of Oklahoma (OU) and at Oklahoma State University (OSU).

The Oklahoma Mesonet was commissioned on January 1, 1994 and consists of 120 automated stations covering Oklahoma. There is at least one Mesonet station in each of Oklahoma's 77 counties.

At each site, the environment is measured by a set of instruments located on or near a 10-meter-tall tower. The measurements are packaged into "observations" every 5 minutes, then the observations are transmitted to a central facility every 5 minutes, 24 hours per day year-round.

The Oklahoma Climatological Survey (OCS) at OU receives the observations, verifies the quality of the data and provides the data to Mesonet customers. It only takes 5 to 10 minutes from the time the measurements are acquired until they become available to the public.

How do environmental conditions impact our lawns and what we can do?

Rainfall & Soil Moisture

The amount of rainfall in the last 7 days is an important starting point for watering decisions. But, knowing the soil moisture is even more important.

The best rainfalls are slow soakers vs downpours. A slow soaker will increase soil moisture and provide your lawn’s root system with life sustaining moisture. A downpour will help the lawn in the short term but has little benefit when it comes to increasing soil moisture. It is important to not only know rainfall amounts but also to know the soil moisture.

Through the month of May, Oklahoma City enjoyed frequent rainfall in varying amounts around the metro. But, the tap has been shut off for the last 12 days. Halfway through the month and June is not living up to its billing as our wettest month.

Based on this map, May’s soil moisture is fading quickly in our 90-degree temperatures.

These two maps combined guide my watering decisions. During the summer months, when the 7-day rainfall map reports less than 1” and soil index is less .7 or less, it is time to start watering. Early this week I started regular watering, early in the morning, every other day for the first time this year.

Fescue, when watered with deep soakings every other day, will stand up to 90+ temperatures.

Best Watering Practices -

Deep soakings are always best. Short, shallow watering is detrimental to your lawn and landscape in the heat. The healthiest lawns are watered to the point of runoff and then allowed to dry for a day. Daily watering, except for newly planted lawns, is not beneficial, even in 90+ degree heat.

Only water in the early morning. This is typically the least windy time of day and always the time of the least evaporation. Avoid watering in the evening. Wet grass, especially wet fescue, is prone to disease when it stays wet for more than 5 hours at a time and temperatures are in the 90s.

Lawns need 1” to 1.5” of water per week during the summer months to stay green and active.

How long should you water? Every irrigation system is different – different head types, different size nozzles, different head spacing, different areas, etc. The best way to know how long you should water is to place a few cans around your lawn in a random pattern. Run your sprinklers through a cycle and measure the amount of water in the cans. If the sprinklers ran for 15 minutes and you had .25” of water, you need 60 to 90 minutes per week. Next determine how long you can run your irrigation before you there is excessive runoff. This will tell you how many times per week you need to water. If you can get away with watering every 4th day, you will have a healthier, stronger landscape. Unfortunately, with our tight soils, watering every other day on the required ODD/EVEN system during the hottest times is needed to get the correct amount of water on the lawn without excessive runoff.

If you don’t have the time to audit the amount of water your system puts out, start with these settings, monitor, and adjust: Fixed spray pattern heads with 10-15’ spacings – 15 mins per time. Larger rotor type heads on 10-30’ spacings – 40 mins per time.

After watering a normal cycle, the Hall | Stewart water gauge is showing just over 1/2” of moisture. In this situation watering 2-3 times per week will give your lawn the correct amount to remain healthy and green.

Set your controller to water with back-to-back run times to reduce the amount of runoff. Moist soil absorbs more water than dry soil. Split the amount of time each zone runs in half and set your controller to come on twice on your water days. Example: Set controller to come on at 4:00 AM and 5:00 AM. When the first cycle is complete, the controller will start the second cycle.

I started the practice of setting irrigation controller to run back-to-back run times a few years ago, on slopes and gradually have incorporated the concept to all lawns. It really makes a difference in water efficiency.

Aeration improves moisture absorption. You can’t beat aeration for improving your soil structure and a benefit of improved soil structure is better water absorption. Lawns that are aerated every year (or at least every other year) do not experience as much runoff.

Watch for uneven water patterns. If you notice areas where the lawn is fading, check your system for a broken head, clogged nozzle, or a head that is out of adjustment.

Even if you don’t have an irrigation system, the concepts of good watering apply. There are several brands of inexpensive hose type timers that make it easy for you to control the timing and frequency.

Too much water can be a problem. You can cause damage to your lawn and landscape quicker by overwatering than you will by underwatering. Waterlogged soil reduces the amount of oxygen. Roots need both moisture and oxygen to survive. Many plants struggle when they do not have a chance to dry out between waterings, such as fescue. Fescue’s biggest problem is brown patch. Brown patch will develop when nighttime temperatures are in the 70’s and the leaf blades stay wet too long. Don’t create your own microclimate that promotes disease by overwatering, watering too often, or watering at night.

The Kansas State Turf and Landscape Blog (Link: https://blogs.k-state.edu/turf/) this week led with “Wet Spring Will Likely Lead To Quick Drought Response As Summer Approaches.” Interesting… wet spring could lead to quick drought? You would think a wet spring would lessen drought stress.

K-State’s point is frequent rains through the spring reduced the need for grass to develop deeper roots. As summer approaches, rainfall decreases, and heat increases the lack of deep root development this spring will result in quicker signs of drought stress on lawns.

Oklahoma City experienced similar moisture patterns in May. Now that we have gone 12 days without rainfall combined with several days of above normal temperatures, we are seeing lawns that are showing signs of drought stress much sooner than expected due to shallower root development.

*If you notice areas where your lawn is fading start with an irrigation check to make sure heads are functioning correctly.*

Air Temperatures & Soil Temperatures

Air temperatures get all the attention. But the driving factor for lawns is the soil temperature.

Soil temperatures are a key factor in determining when weeds germinate, when lawns start to turn green, and when they are actively growing.

Soil temperature of 55 degrees in the spring is when most summer annual weeds begin to germinate. For the best weed prevention each summer a pre-emergent herbicide must be applied before the soil temperature reaches 55 degrees for three consecutive days. This year summer annual weed germination began the first week of March, earlier than normal.

Soil temperature of 55 degrees is when fescue starts to absorb nutrients, regains a rich green color, and begins prolific growth. Most years in central Oklahoma, March is the month to start fertilizing Fescue.

Soil temperature of 65 degrees is when warm season grasses (bermuda and zoysia) become active. Then once soil temperatures consistently reach 70 degrees bermuda grows its best. In a typical spring, we expect bermuda lawns to green up gradually during April and be active growing by early May. Inconsistent soil temperatures in April and May are the biggest reason for slow warm season turf growth.

Bermuda performs best when soil temperatures are consistently in the 70s.

*Brown patch disease in fescue appears as irregular areas that lead you to believe the lawn may not be getting enough water.*

Other environmental factors that will impact spring green-up: Shady areas and turf on the north side of homes will come out of dormancy slower because the soil temperature will lag. Low moisture levels during the transition period will slow green-up. Turf grass that must compete with weeds for nutrients and moisture will also be slower. And, compacted soil will slow the process by restricting air, nutrient and water movement to the roots.

Soil temperature below 70 degrees in the fall is when winter annual weeds start to germinate. This typically occurs in mid to late September. For the best weed free lawn during winter dormancy, the first fall pre-emergent herbicide needs to be applied between mid-August and the end of September.

Once soil temperatures begin to cool in September it is important to apply little to no nitrogen fertilizer to warm season turf. Pushing the turf to stay green deep into the fall is the most common cause for Bermuda problems such as spring dead spot.

When soil temperatures begin to cool in September and into October it is the best time to establish fescue from seed.

Soil temperature is the critical measurement for pre-emergent herbicides, fertilizer applications and seeding.

Applications of high nitrogen fertilizer on bermuda lawns after mid-September increases the probability of having spring dead spot the following spring.

There is one important thing you can do to help when temperatures are high – adjust mowing height. Mowing at the maximum mowing height for your turf type provides a canopy that cools the soil and promotes a deep root system. Maintain fescue at 3” to 3.5” and Bermuda at 2.5” during the summer heat. If you mow frequently enough don’t bag your clippings. A light sprinkling of grass clippings will act as mulch for the lawn helping to hold moisture in the soil. The key is mowing often. Leaving clumps of clippings on the lawn is not helpful.

Sunshine & Wind

Turf grass moisture loss is much higher on windy, sunny days. This is a fact we often overlook and fail to adjust for.

Evapotranspiration (ET) is the loss of moisture through evaporation from the soil and transpiration from the leaves. Turf grass leaf blades are usually 75% water. The highest ET rates occur on hot, sunny days with lower humidity and moderate winds. This past week, high ET rates have started taking a toll on many lawns.

Another way sunshine and wind impact lawns are in areas of low air circulation and heavy shade. Areas with thicker plant materials, privacy fences, and structures are more prone to diseases due to low air circulation. Be aware of these areas and make sure you are not keeping these areas too moist.

The last of three things that impacts the quality of your lawn, environmental conditions, is something that you have no control over.

But just because you have no control doesn’t give you an excuse.

Your role, and our role, when it comes to the impact of environmental conditions on your lawn is to be aware, monitor and adjust our practices based on the conditions.

Our goal, no matter the current conditions, is to help you have the best lawn possible.

Lorne Hall

Hall | Stewart Lawn + Landscape

(405)367-3873