Zane Raudenbush, turf and herbicide specialist within the Davey Institute, talks about invasive lawn grasses, the importance of soil testing and pH with grasses.
In this episode we cover:
To find your local Davey office, check out our find a local office page to search by zip code.
To learn more about lawn care, read our blog, First-Time, New Homeowner’s Guide to Lawn Care.
Connect with Davey Tree on social media:
Twitter: @DaveyTree
Facebook: @DaveyTree
Instagram: @daveytree
YouTube: The Davey Tree Expert Company
LinkedIn: The Davey Tree Expert Company
Connect with Doug Oster at www.dougoster.com.
Have topics you'd like us to cover on the podcast? Email us at podcasts@davey.com. We want to hear from you!
Zane Raudenbush, turf and herbicide specialist within the Davey Institute, talks about invasive lawn grasses, the importance of soil testing and pH with grasses.
In this episode we cover:
To find your local Davey office, check out our find a local office page to search by zip code.
To learn more about lawn care, read our blog, First-Time, New Homeowner’s Guide to Lawn Care.
Connect with Davey Tree on social media:
Twitter: @DaveyTree
Facebook: @DaveyTree
Instagram: @daveytree
YouTube: The Davey Tree Expert Company
LinkedIn: The Davey Tree Expert Company
Connect with Doug Oster at www.dougoster.com.
Have topics you'd like us to cover on the podcast? Email us at podcasts@davey.com. We want to hear from you!
Doug Oster: 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. Welcome back to The Talking Trees podcast, and we have an old friend coming on the show. Zane Raudenbush is the turfgrass and herbicide specialist for the Davey Tree Expert Company in Kent, Ohio.
Every time that Zane and I talk, we're only supposed to talk for about 20 minutes Zane, but it ends up being about 40 minutes, and it makes me have to put two episodes out, but that's okay.
Zane Raudenbush: No, man. I appreciate you having me back. I love riffing with you on all this stuff, so yes, we'll see where it takes us today.
Doug: Well, so we're getting into the time where things are warming up. We're getting to spring and we're thinking about that turf on our own properties. When you get to this point in the season, what are some of the first questions you get from homeowners about their lawn? What should they be doing now to get ready for when we're going to start mowing?
Zane: I'm going to take that one in two parts Doug, because there's definitely a cadence to the type of questions that I receive as a technical expert from our field, from our customers, and then also the samples that our lab receives, so our in-house diagnostic lab that does about 2,300 samples a year, they get a lot of turf samples. You start to see the same stuff over and over and over again at certain times of the year. The beginning of the year, the two biggies that we get coming into the lab are two weedy grass species. We have one known as annual bluegrass, or poa annua, you might hear it called, and then roughstalk bluegrass, which is Poa trivialis.
They're both in the bluegrass family, and generally we consider them to be weeds. A lot of times they're almost in every lawn. I could go to most lawns and probably find both of those species, and most people don't know that they have them, but in the spring those species green up. They have a really light lime green color, and they start growing sooner than the desirable species do. Like the rye grasses and Kentucky bluegrasses and tall fescue. You'll see you're like, "What are these light green patchy plants in my yard that seem to be growing a lot faster than everything else?"
Yes, I get a lot of questions about those two weedy species that are really difficult to control, Doug. The annual bluegrass is probably the most troublesome weed in turfgrass systems in the world and so that's a real challenge. It produces a lot of seed at low mowing heights. That's one thing that's different about turfgrass systems is that, if you want to be a successful weed in a turfgrass system, you have to tolerate mowing. A lot of weeds don't tolerate mowing. Annual bluegrass tolerates mowing, and then it's also able to just produce hundreds of seeds below the mower deck.
Some plants produce seed, but we mow off all the reproductive structures not annual bluegrass. It's really well adapted producing lots of seeds, so that's a challenge. Then Poa trivialis is a stoloniferous grass. For the listeners out there, grasses really have three growth habits. They can be bunch type grasses like ryegrasses and tall fescues where basically you have a single plant and it can produce new shoots, but it really can't spread laterally. It can't fill pockets and voids from dog urine stains or foot traffic. The stand will just thin and you'll end up with bare spots once the stand begins to thin.
Then you have rhizomes like Kentucky bluegrass. Those are below ground stems. These are stems that are produced from a plant that grow out laterally under the soil, and they can produce new shoots at the nodes and begin to put offshoots from the parent plant. That has really good recuperative ability, but stoloniferous plants like creeping bentgrass and Poa trivialis, they produce these lateral stems that grow on the soil surface. They're growing above the surface. They have these lateral shoots, and they allow the plant to start creeping throughout the lawn, and you get this really patch like behavior.
Poa trivialis is one that's creeping along the surface and amongst your desirable plants and in the spring, because it grows so vigorously, people notice these light green patches in their lawn, and they really key in on that. It's good to notice because it has really poor heat tolerance. Poa trivialis or rough stock bluegrass as it's called, is a weedy species, because in the summer months it will die. It has no heat tolerance. It's a grass that has two main uses, wet heavily shaded sites, and then it's really primarily used to oversee putting greens in the south.
Bermuda grass putting greens that would go dormant, they use Poa trivialis, they seed it into those greens and they play on it in the winter, and then when it gets warm, it just naturally dies and the Bermuda grass takes over. I start to receive a lot of questions about that in the lab.
Doug: If I had both of those things in my lawn, what would I want to do? How do I get rid of it and do I care? I guess I do care because it might look okay to me now, but when it gets hot and dry, that's going to be a bare spot, is that right?
Zane: It will, yes. Particularly with Poa trivialis it will cenaze and die, but it often comes back. Doug, that's a million-dollar question. If I knew the answer to that one, I would be-- many smarter people than me have tried really hard to manage both of those plants and it's just difficult. There are things that you can do I think to decrease the prevalence of it in a turfgrass system, but they're incredible invaders. I tell people sometimes you're picking a battle that you might not win. If it really gets to a point where it's becoming a major component of the stand, like it starts to reach that 20%, 30% of the stand, that's where sometimes we just recommend a renovation. Start over, get those plants out of there either with non-selective herbicides or mechanical removal.
If they're just small patches, sometimes we can go in there and apply a non-selective herbicide and kill those areas and re-seed them. They could be mechanically removed. There are some options, but it's one Doug, that professionals, people with all the resources it's a challenge. In sports fields, if you look in a professional field, they mechanically remove it. They have people that walk every inch of those fields and mechanically cut it out and re-plug it in. It's a very, very challenging weed, like where you are there in the Pittsburgh area, people embrace it. When you look at many of those great golf courses, the Oakmont's of the world, they just manage annual bluegrass. They embrace it because it's just so prolific in that area.
Doug: Well, I'm going to embrace it because I don't want to go out there and mechanically move it out of there. If it's green for a while, it's good for me. I have what I call a quilted lawn. It has a little bit of everything.
Zane: I understand. I would say too, for the listeners, if you're someone that's in that space like, "Oh no, I see what Zane's talking about, I have it." As the other grasses, the desirable species come out of dormancy really start growing, the color differences begin to weave together. They're not nearly as noticeable once you get into the growing season, but the Poa trivialis is one that it will die in the summer months. That's one that you may want to try to get controlled, and there are options. Talk to a professional. There are some selective tools, but it's a long-haul process, a couple seasons, Doug. It's not a one and done type deal.
Doug: How important is it to have a soil test when you're in this part of the season spring like this and you are wondering how to make your lawn the best it can be?
Zane: Soil testing is an underutilized tool in my opinion. I use soil testing for a couple different reasons. One, I often use it to see if there's any smoking gun. You don't know if you don't test. I always tell people don't guess test. What I mean by a smoking gun is sometimes there can be really funky things going on in the soil. Odd chemistry pieces, super low pHs that can result in aluminum toxicity. You can have really high pHs above 8.5 if you maybe have a potential irrigation source that has lots of salts in it. Then you can sometimes find just nutrient deficiencies.
Nutrients that are just completely deficient in the soil that if you're not applying those nutrients with your fertilization program, you're missing an opportunity to improve the turfgrass quality. I use it in two ways primarily. One, I use it to determine is there a deficiency somewhere. Something about the soil that is deficient, but then I also use it to determine, “What do I not need to apply?” Because soils are amazing reservoirs of nutrients, and so sometimes I find that they have plenty of phosphorus, plenty of potassium in the soil. We don't actually need to apply those nutrients in any large quantities and so for me, that can reduce the amount of the cost of the fertilizer. That's the two primary ways that I use it. Then I also, depending on the scenario, can tell me a little bit about the health of the soil. Soil tests will tell you the percentage of organic matter. They will tell you the cat-iron exchange capacity. You can also get them to tell you the soil texture. For me, Doug, for what they cost for your listeners that are in Pennsylvania there, I'm sure Penn State does a lot of testing or whoever your land-grant institution would be. This is usually a $15 to $20 test that can reveal a ton of information, particularly if it gives you that smoke and gun where it's like, "Wow, I didn't realize I had a major magnesium deficiency or whatever it might be."
Doug: If I get my pH right and my nutrients right and maybe a couple of other things, when I get that soil test, is it going to tell me what to do once I see all this information?
Zane: It depends on, like our lab, we do then provide the recommendations. You'll get their results. Then there's recommendations that accompany that about whether you need to lime and if you're going to lime, do you need a calcitic lime source or a dolomitic lime source? Then what are some of the sources of fertilizer that would deliver the nutrients that you need? Yes, most soil tests will give some basic recommendation about what to apply, but they don't always tell you the right time, so on and so forth. That's where work with a local extension specialist to try to hone in a little bit more on what would the timing be, so on and so forth.
Doug: Getting the pH and the nutrients right is definitely going to be a bonus for me when I'm trying to grow grass, right?
Zane: Yes, for sure. For me, I have a little bit different perspective on pH. If you really scour the literature, there isn't always a ton of evidence to support that changing the pH results in major differences in turfgrass quality. You see that for agronomic crops, where we can measure the yield that you can see that changing the pH has a measurable difference. In turfgrass systems, turfgrasses are plants that are not all that sensitive to pH. They can grow over a wide range of pHs. They're not like a blueberry plant that needs a really acidic soil.
There are definitely examples of plants that thrive at certain pHs. In general, turfgrasses, they're pretty receptive to a wide range of pHs. For me, I definitely get concerned when I see the pH dropping below 5.5. You can have concerns of aluminum toxicity as you start to solubilize more of that acidic pHs. Then again, when I start to see it climbing up above 8, that's when I start to get concerned that is there a potential of sodium getting onto the site. If that's the case, it's usually coming along in the irrigation water dug. That's not one that I see a lot in our area.
I see that more of the soil tests that I deal with from other parts of the country within our company. The pH thing for adding lime, there are a lot of other benefits to lime. It can help with soil aggregation. Aggregation is this idea that the little small soil particles will start to create colloids where they ball together. As you do that, you create soil structure. Really soil structure is a major part of creating a good system. That's what creates the little pockets and holes for water and air and roots to go through. Liming, yes, it's used as a way to try to change the pH. There are other benefits to liming that people don't always realize.
Doug: That's interesting because I always tell the story about when I was a kid growing up in Ohio, how my dad would send the boys out, “Boys, we're going to lime the yard.” I've always thought that looking at it from my perspective now was like, "How did he know how much lime to put on there?" What you're saying is at least if you put some lime on there, it's going to help. Is that right?
Zane: It definitely depends on the scenario. If you have a pH that is neutral or alkaline, so you start to get a pH above-- anything above 6.8, I don't recommend liming those soils. If you get a soil test back and has a pH of 7.2, there won't be a liming requirement there. We're not going to recommend that you would apply lime to that soil. You could use a product called gypsum, which also has calcium in it that does those things like I was talking about of giving a place for the little clay particles to attach to and start to create some structure. Yes, back to the question, liming, you can put a lot of it down.
I often recommend that it be put down in the fall. It's not very soluble. It takes a long time to break down in the soil. It's not something that you apply and immediately see a response. It takes time. If you put it down in the fall, you give it time to break down and to get into the soil. Liming is definitely something I think that people see is often recommended in agriculture and agricultural cropping systems. It does make a difference. In turfgrass systems in general, like if you look at a lot of the worst turfgrass diseases, like the soil borne pathogens like take-all patch, summer patch, a lot of evidence to suggest that they are much worse at higher soil pHs.
For me if the soil is on the acidic side, I typically don't mess with it. I leave it there. I focus my efforts, Doug, on the other parts of that soil test like, what is the organic matter? Does this soil have much organic matter in it? Does it have a nutrient deficiency? I'll use the resources that someone might spend online to maybe amend that soil with organic matter or a nutrient that you wouldn't apply before you had a soil test. Again, you look through the literature. It's funny. We see a lot of liming recommended, but there is not a ton of literature to suggest that in turfgrass systems, it makes a major difference.
In fact, there are some experiments out there like part grass experiments that show as the pH goes up, you actually can potentially start to get more weeds. I mean, these are long-term studies that they did for many, many years that as the pH begins to increase above 7, 8, that you start to get more weeds and the weeds are thriving and potentially in those systems. I could talk for an hour, Doug, on soil pH and what we do and don't know. It's a challenge because there's a lot of facets. There are soil type, turfgrass species. It's just not always so straightforward. I think the turfgrass community in general, there is a real focus right now, Doug, on soils.
I think the turfgrass community in general, there's a feeling of we really need to look hard and get a better understanding because most of the recommendations for turfgrass systems, as it relates to soil tests and fertilizer recommendations, have been adopted from field crops, grassy field crops like wheat and rye, and forage crops, and so they take those recommendations and apply them to turfgrass systems, but they're different. The objectives are often different. The soils are different. We're often growing these plants in urban environments where the soil has often been disturbed within the last 10 or 20 years as they constructed a home or put in a sidewalk. It's a little bit different. Yes, I think you're going to see a lot more research in that space, and it wouldn't surprise me if the recommendations change over the next decade.
Doug: Zane, we're already at a time for our first episode, but we're going to continue recording and break this up into two episodes. Great stuff. I can't wait to continue our conversation. Thanks so much.
Zane: Yes, thank you, Doug.
Doug: Tune in every Thursday to The Talking Trees Podcast from the Davey Tree Expert Company. I am your host, Doug Oster, and do me a big favor. Subscribe to the podcast so you'll never miss an episode. Do you have an idea for a show or a comment? Send me an email at podcasts, that's plural, @davey.com. That's P-O-D-C-A-S-T-S@D-A-V-E-Y.com. As always, I'd like to remind you on The Talking Trees Podcast, trees are the answer.
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