Zane Raudenbush, turf and herbicide specialist within the Davey Institute, talks about best practices for maintaining your lawn during the heat of the summer.
In this episode we cover:
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Doug: Welcome to the Davey Tree Expert Company's podcast, Talking Trees. I'm your host, Doug Oster. Each week, our expert arborists share advice on seasonal tree care, how to make your trees thrive, arborists' favorite trees, and much, much more. Tune in every Thursday to learn more, because here at the Talking Trees podcast, we know trees are the answer. This week, it's part one of a special two-part show covering everything you need to know about summer lawn care. Zane Raudenbush, turf and herbicide specialist with the Davey Institute in Kent, Ohio, is making a return engagement. Let's talk this week, Zane, about watering and reseeding. I'll tell you what, my lawn has been struggling this summer during the hot, dry weather.
Zane: The lawns look pretty toasty in my area in Wooster, Ohio, and I'm sure it sounds like the same for you in Pittsburgh. We just simply have not had the precipitation. As we discussed previous to the call since, in my area, June 15th, we've only received 1.6 inches of rainfall, and 0.6 of that actually came last night. It's like liquid gold, but we could use another inch or two. We really need one of those all-day soakers, these heavy precipitation events. A lot of that, unfortunately, just runs off and gets into the stormwater system. The soils are that crusty. They're just not getting good infiltration.
If we don't get some much-needed rainfall, you're going to see the effects of this long into the autumn months, unfortunately.
Doug: Tell me, what does the grass do when things dry out? Because I'm looking at the same thing in my area, doesn't look good.
Zane: That's a great question, Doug. The answer to that depends a little bit on the species. In our area, you're going to see lawns might be sodded Kentucky bluegrass, or they could be mixed stands of ryegrass and Kentucky bluegrass and the fine fescues. Kentucky bluegrass is an interesting grass where as the soil moisture starts to draw down in the soil, that grass actually will go dormant as a drought avoidance mechanism. It actually goes dormant, you'll see that it will turn off color. This is just a total strategy to avoid drought stress. Then when precipitation returns, you'll see the plants will begin to green back up and begin to grow again.
Kentucky bluegrass lawns, when they're in a full dormancy stage, you'll see they won't grow. They could go indefinitely without needing mowed, et cetera. What they're doing in terms of trying to conserve water is they close their stomata, and it's just a total drought avoidance mechanism. Then species like ryegrass and tall fescue, they don't go into this dormancy mechanism. They begin to close their stomata, and you'll see the effects of wilt starting to take place, but they are more adapted to withstanding high temperature stress, drought stress.
They are the plants that eventually, when the soil moisture gets so low, they can actually die. They don't go into that dormancy state. They will just actually turn completely necrotic. The crowns could begin to dehydrate, and those plants could actually die if they don't get some much-needed precipitation. Dichotomy is that Kentucky bluegrass maybe will throw in the towel early and go dormant, but when the precipitation returns, that plant will recover, versus you might see things like ryegrass and tall fescue, they maintain better color longer, but they may reach a point where if you don't get precipitation, they could receive irreversible damage. It is somewhat species-dependent.
Doug: Before I move on, explain that term to me, "Stomata." Did I say it right?
Zane: Yes, you did, stomata. Stomata are these small openings on the leaf blades. Plants are-- a lot of the water, they say up to 98% of the water that a turf grass plant absorbs will be used for this process in the summer months of transpirational cooling. The process of transpiration is basically the plants suck the water out of the soil from the roots, it goes up through the stems and the vascular tissue, and then out the leaves through these small openings called stomata. It's just like us as humans when we sweat. When we get hot, we perspire, and that helps to keep us cool.
Plants are doing the same thing. As you basically evaporate that water out of the leaf blades from the stomata, it's releasing energy in the form of heat and helps to keep the leaf blade temperature somewhat moderated. That's where, when the stomata close, those plants and the leaf blades begin to start, the temperature increases. They literally will start to cook. You need moisture in the soil, and you need the stomata open so you get this constant evaporation during the day of that water, and that helps to keep the plants cool.
Yes, so stomata, they have several functions. They help to let gases into the plant, but their primary purpose is to allow water to escape the leaf blades in the form of evaporation, and it keeps the leaf temperature moderated.
Doug: Is it realistic for a homeowner to put enough water on that lawn themselves to keep that grass going when you have 90 degrees and no rain?
Zane: Realistic, it can be done. You see professional sports field managers, golf course superintendents, that they can maintain an acceptable level of quality in temperatures like this. For a homeowner, and a lot of the irrigation systems I observe in many of these home lawns that maybe don't receive the maintenance that a professional turf grass manager might put, it is tough. I think a real goal, a realistic goal for a homeowner is to really prevent those plants from entering that dormancy, irreversible harm. You're just trying to supply some soil moisture to keep the plants actively growing.
I often see, Doug, people who, I don't want to say abuse those irrigation systems, but they can get themselves in actual more trouble from the effects of overwatering, which leads to a whole other slew of issues with diseases and can actually end up increasing soil compaction, et cetera. To answer your question, I think yes, it is possible to supply enough water to the lawn during these periods. In my experiences, it's not necessary. You're really just trying to supplement enough to keep the plants growing. Over-irrigating, in my opinion, is far worse than under-irrigating.
Doug: Let's talk a little bit about watering. Ideal condition for watering. Tell me if you could do it just the way you wanted to do it for a homeowner, what would be the best way just to keep that lawn alive until we do start getting rain?
Zane: Great question. That's a textbook answer, but the idea of deep and infrequent watering is just you get the most bang for your buck. What I mean by deep and infrequent, we sometimes go to customers' properties and I start looking at their irrigation timers, and during the months like this, they'll have the irrigation clock running every single day. Every day the irrigation system's coming on and it's watering for maybe 15 to 20 minutes. That's light infrequent watering. We're looking for the opposite, where maybe that system runs every four or five days and it might run for a one prolonged period of time if the slope or the topography is relatively level.
You'll see on steep slopes, we often do soak cycles where you run the system for some period of time, allow that water to infiltrate and come back and water it again. Maybe you actually have two run times, like four in the morning and seven in the morning for things of steep slopes. Deep and infrequent is the answer, Doug. Ideally, I like to see our customers watering sometime between the hours of 6:00 and 8:00 a.m. Ideally, I like them to water when they can do what's called putting eyes on the system.
What I don't want to see is a scenario where the homeowner never actually sees their irrigation system running, because that could be scenarios where heads aren't turning, zones aren't turning on, and the customer doesn't ever actually know that that's the case. If there's a time period in the early morning hours when you're awake and you can be drinking a cup of coffee or whatever it is that you do and take a peek outside, make sure that the zones are turning on, all the heads are turning properly, you're not watering the street, et cetera. Timing, getting it in that early morning hours, and then deep and infrequent.
In the summer months, it could be, if you're in a sandy soil, maybe every third day. Where we are, we have heavier soils that could be every four or five days. Really under no scenario should someone be watering every single day unless it's a recently established lawn or they're trying to establish turf. Watering every day just leads to a whole other slew of issues.
Doug: You bring up a good point there of having eyes on it, because the one thing that drives me crazy is seeing sprinklers run when it's raining. [laughs]
Zane: No doubt. Drives me nuts too. It gives people like myself and our profession a stigma and a bad name because those are easy things to fix. Many of these home irrigation systems can have rain sensors, rain tipping buckets. We're to the point now where it's pretty cost-effective to have a lot of these systems that have soil moisture sensors that are buried in your yard. They're communicating in real-time with your irrigation clock, and they simply won't allow the system to turn on if there's adequate soil moisture. Yes, that drives me crazy as well, Doug. I have a lot of pictures that I post up there and presentations of what not to do. [laughs]
Doug: Let's say that I get through this hot dry period, keeping it most of it alive, but I start to see spots where I didn't keep grass alive. When do I start to think about maybe throwing some seed down? Am I looking carefully at the weather? Do I have to wait? I certainly don't want to put any seed down if it going to be hot and dry. In that situation, I think I would have to run water every day or every other day. Is that right to keep that seed moist and get it to sprout? When do we want to do that?
Zane: That's a great question. I think it depends on what the objective is. If it's these little spot areas that you're trying to fill back in, you could do that all the way, starting as early as mid to late August all the way through. I, typically in our area, don't recommend doing seeding after October 1st. I have done seedings after October 1st, some of which you look like a rockstar, been really successful, and others that turned out really poor. The problem can be once we get that first frost, that will really slow things down. It can even injure the seedlings. The window starts there.
I would not seed anything before mid-August. Even if, like you said, you're looking into the forecast and you see the 10 days is hot and dry, I would wait until you start to see that you're going to get some precipitation. To answer your question, once you plant seed, in my mind, nothing is more paramount than keeping the soil moist. Really, irrigation is the most important tool that you have as someone who plants turf grass seed. To your point, if it's going to be hot and dry, it might actually be more than once a day.
If you're not going to use some type of cover, a straw or a mulch and you're just going to seed onto bare ground, you'll probably actually need to irrigate very light, but two to three times per day to keep that soil from drying out. The worst thing you can do for young seedlings is allow them to go from a moist state to really dried down that really decreases the uniformity of germination and you might actually begin to lose plants. If you're going to go through the process of prepping a little bit of a seed bed, putting the seed down, first thing you want to do is make sure you give it a good soaking. You want that seed to swell, absorb that water, and then from there you're just simply trying to keep the soil moist.
You're not trying to flood it, you're just trying to keep that soil moist. If you go back out and see that it's crusty, it's brittle and dry, it's time to irrigate again. Things like straw are a great way to help preserve some moisture and can allow you to maybe get away with irrigating just once a day.
Doug: Let me step back a little bit. What should that soil look like? Am I doing anything to that soil when I'm putting that seed in, or I'm just using the soil that's there and raking it or how am I preparing that to put the seed on? Is straw the thing that should go on there? Is that the number one thing I should put on top of that grass seed to keep it moist?
Zane: Doug, these are all great questions. Unfortunately, they're those answers where there's a little bit of caveats. If the areas that you're going to re-seed, you notice that the reason that you're re-seeding these is because the soil's poor. I observe this a lot when I go on lawns where maybe they had somebody come in and grind a stump and that person brought in really poor soil to backfill with and you're like, "Oh, I lose the grass and this place every year." It's like, "Well, I get my soil probe out and find that there's no top soil. This is cruddy sub-soil."
That instance, that's where you might want to amend the soil, bring in some organic matter and mixing that into that upper layer. If you've maybe lost turf because of something you did, maybe I sometimes see where people have cleaning solutions that they throw out into the lawn and kill all the turf. If the soil's good, what I like to do is I'll rake out all the dead leaf litter. If all those dead plants, I take a leaf rake and try to get all that out and then I'll loosen the soil as best I can. I sometimes often use what's called a Garden Weasel. It's that thing that has the tines on it and you can roll it back and forth and that helps to break up that upper layer.
Then I will put my seed down, and this is sometimes where I'll sprinkle some type of organic matter. It could be a garden soil, whatever it might be, but some rich dark soil on top and rake that lightly in. Then to your question, there are different schools of thought. I really don't use straw if I can get away with it. If I have the ability to irrigate, I can get away without using straw because I can control the water through manually turning it off or using little nine-volt timers on my hose bibs. If these are big areas that you've seeded that you simply cannot irrigate, mother nature's going to have to provide the irrigation for me.
Those are places where I really like to use straw because it will help, it makes a huge difference. I've done a lot of studies looking at different covers and compared to other mulches and things, straw really is superior. You do have to be careful. Straw can introduce undesirable species into the lawn if it's of low quality. You're playing with a little bit of a double-edged sword. To answer your question, areas that are big and open, you can't irrigate them. Straw will definitely help to get more uniform germination. If it's a small area in your yard where you have the ability to get the sprinkler out there and irrigate it, I don't think straw is necessary in those instances.
Doug: Just to be clear, man, as long as I could keep water on it, I don't have to have anything on top of it, whether it's compost or straw or anything, as long as that seed stays moist, I'm good?
Zane: Yes. Correct. You know what a cycle might look like. If you're going to go out there in mid-August like we're talking about and you see that the 10 day there really is no rain, there are hot warm days. I'm talking about running that system 3 to 4 times, and it might just be for 5 to 10 minutes each time. Again, we're not trying to totally soak, you shouldn't see standing water anywhere. You're just trying to keep the top of the soil moist.
This is where, if you're someone who's really into your lawn, these small nine-volt timers that go on your hose bib, they are incredible. They're perfect for things like this. You can off that hose bib, you can put a Y-adapter to where you maybe have two zones, two sprinklers running and it really can become hands-off. You can program them and you can step back and let that do the work for you. If you're anybody like me who has young kids running around and you're forgetful, it's pretty easy to forget to turn that sprinkler off and you realize like, "Oh boy, an hour later, I only want it to run it for five minutes." Use your smart devices, whatever it is to say, set a timer for 10 minutes so that you don't forget.
Yes, Doug, I'm all over the place here. I get excited about this stuff, but to your point, yes. If you have the ability to irrigate it, you don't necessarily need to put any type of straw or cover on. If you don't or you're someone who maybe isn't going to be as judicious as you need to be, then straw certainly will help to be an insurance policy that you'll preserve that soil moisture.
Doug: All right, Zane. If I am going to reseed or put some seeds in these areas, what kind of seeds should I be using? I never know what to do and I see some of these seeds have fillers and stuff in there. Is that good or bad? School me on that?
Zane: Yes. Lot of different schools of thought here. I'll give you what has been my experiences from my research and there's different scenarios. If you have a sodded, Kentucky bluegrass lawn, which in my opinion is the Cadillac, that might be one of the highest quality lawns that you can find, you have to be careful about what you put back in there. There are other species that are more coarse-textured, different colors, they're going to green up at different times of the year. Sodded Kentucky bluegrass is one of those where-- I really like to seed Kentucky bluegrass back in to straight stands of Kentucky bluegrass.
For areas that are in full sun that are mixed stands, Doug, I have really gravitated towards the turf-type tall fescue varieties. They are much lower input species particularly compared to Kentucky bluegrass. They produce an extensive root system, they really do well in the heat and drought and they establish relatively quick. Perennial ryegrass is the fastest establishing cool season grass. It germinates the quickest, it establishes really quick, and you'll see that many of the seed mixtures that you will buy at the store contain a significant amount of perennial ryegrass because it does fill in quickly.
From my experiences though, perennial ryegrass, if you're going to use it as the only species in the lawn, it's really susceptible to a lot of diseases leaf spots, red thread, dollar spot, pythium. I do not like it as a standalone grass, it would only be a component. Full sun, I'm a big fan of tall fescue. In the heavy -shaded environments, this is where I would use the fine fescue varieties. Mixtures that contain creeping red fescue, chewings fescue, and hard fescue. You'll see when you go to the store and you buy shade mixes, you'll see, I bet 30%, 40%, 50% of that bag might be perennial ryegrass. Perennial ryegrass has very little
if not any, shade tolerance. The only reason perennial ryegrass is put in that bag is so the customer looks and feels like they've got grass to grow. In time, you'll see that perennial ryegrass isn't going to survive. It'll be the other parts of that bag that stay in. For me, I'm all about putting the right plant in the right place. Heavy-shaded environments, I typically gravitate towards the fine fescues, full sun to moderate shade environments. I'm a big fan of the turf-type tall fescue varieties. If it's a straight Kentucky bluegrass lawn and full sun, I typically go back in with Kentucky bluegrass.
Doug: How do I find these seeds? Because a lot of times, it's just like you said, it's just a shade mixture. Over here in Pennsylvania, it would be Penn State Mix.
Zane: Penn State mix, yes.
Doug: Will I see four or five different types if I go to a good nursery and read on that bag and look for exactly what I want or am I mixing it myself? Where you're at in Wooster, Ohio, where would you go to get the seed that you wanted if you were just a regular homeowner?
Zane: That's a great question. I go to people that deal in grass. A lot of times your sod farms will also distribute seed. Those are places, high-end garden stores are going to have more of these specifically blended varieties. You go to a big box store, this is where you'll start to find a lot of these different species are thrown in one bag. That's often to help reach a price point, because they're able-- you'll see that these different varieties, most of them are grown out in Oregon, and they all have a different price tag. As a big box seller, you're trying to reach a price point for your seed, so they're able to go in and cherry-pick the different varieties to get the price where it needs to be.
It doesn't always agronomically mean that it will be the best blend for your lawn. For me, I typically turn people towards high-end garden stores where I know there's going to be a good variety of these different mixtures. Then if you go to someone that really deals in grass seed, they're certainly going to have everything you need. Again, that could be sod farms, from my experience, is typically also sell seed. Those can be places that can really help you out. They have some expertise there to help put the right plant in the right place.
Doug: I'm going to stop you right there, Zane. That's great information. Next week, I want to ask you about fertilizing and a problem I'm having with my own lawn. Thanks again.
Zane: All right. We'll see you, buddy.
Doug: Tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I'm your host, Doug Oster. Zane will be back next week to give us some more tips for summer lawn care. I can't wait to talk to him. Do me a favor, subscribe to the podcast so you'll never miss an episode. As always, we like to remind you on the Talking Trees podcast, trees are the answer.
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