Zane Raudenbush, turf and herbicide specialist within the Davey Institute, answers a listener's question and talks about fertilization, soil testing, weeds and grass cutting tips.
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, answers a listener's question and talks about fertilization, soil testing, weeds and grass cutting tips.
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. This week it's part two of our lawn discussion with Zane Raudenbush. He's the turf grass and herbicide specialist for the Davy Tree Expert Company. Zane, I wanted to start off with a question I received from a listener and see what you would do in this situation.
He has a very small backyard, 7,500 square feet, and it's all clay, and they're struggling to grow grass. Thinking of adding organic matter or maybe gypsum, what would you do?
Zane: One, I would take a soil test. I would start there and make sure that you're not missing anything. Again, is there an odd PH piece on one of those extreme ends really high or low? Is there a potential deficiency piece? I'd be looking for is there any organic matter at the surface. If you take a knife and cut into the soil, we want to see the upper parts of that surface being dark. Rich in organic matter should be a really dark color.
Then typically like where we are in Cleveland, a few inches down, we start to get into that really heavy clay. If that clay is right at the surface that there is no nice organic matter layer, that might be where we really start to lean into amending the soil with organic matter. You mentioned gypsum, definitely, gypsum is a great soil amendment for heavy clay soil. Gypsum is calcium sulfate. If you look at lime, calcite lime would be calcium carbonate. Both are adding calcium to the soil.
That calcium being a positively-charged ion, the negatively-charged clay particles are attracted to it, and that's what begins to get the soil balling together, creating colloids, which creates structure. The challenge with lime is because it's not that soluble, that takes a long time to happen. It doesn't break down right away versus gypsum is much more soluble, and you can get that process to happen a lot faster. Yes, gypsum would definitely be a recommendation that I probably would make in that particular scenario of adding gypsum, seeing if you can lightly incorporate it right at the soil surface with a York rake or something to scarify the surface, get it lightly incorporated into there.
You can certainly look at other amendments, things that are compost, biochar. You have to be careful. I think sometimes people, and I have made this mistake, too, of you can create layers in the soil if you just go out there and just dump a bunch of different material on top of the soil. You'll just create two distinct soil layers. Whenever you create layers in the soil, in general, good things do not happen. You can have issues with water retention, water infiltration. It's always nice to find a way to get those two interfaces to be mixed a little bit.
That's a challenging one, Doug. Heavy clay soils, there's no easy answer there, for sure. Gypsum would definitely be a great recommendation in that particular instance. Gypsum is going to help create a little bit more structure, a little bit more porosity of the soil. You can put it on very heavy [chuckles]. You can add a lot of gypsum.
Doug: Well, that question actually came from a friend in Ohio [chuckles].
Zane: Well, yes, up here, where I live in the Worcester, Cleveland area, we see really heavy clay soil, some of them what they call that blue clay, which I wasn't that familiar with before I moved here. Blue clay is something that they actually mine and they use it to line the bottom of irrigation ponds. They'll take that blue clay and they'll put it on the bottom of an irrigation pond because it literally does not let water pass through it. Imagine trying to grow turf in an area where water won't move through the soil profile. Then also it can set up like concrete, and it's just hard to get good brooding. It is a challenge, clay soils.
Doug: Well, let's talk a little bit about fertilization because that's something we see a lot of in all sorts of different applications for the lawn. First off, you don't want to overdo it, right? The lawn can only take so much fertilizer, and what it can't take, it's going in the storm sewer, right?
Zane: Absolutely, Doug. Couldn't have said it better. In terms of going in the storm sewer, that part is where turf grass shines. If you put fertilizer on a turf grass system, one of the best things that grasses do is they really reduce the surface movement of water. There's been a lot of studies that show you put the fertilizer on the turf grass, it does not leave there in surface water. The challenge is you get people without proper training that apply it to impervious surfaces and don't blow them off. That most certainly does, unfortunately, reach the stormwater system.
You had a good point there about, and you're getting at it, is to match the fertilizer demands of the plant. Ideally, in a perfect world, we would only apply the amount of fertilizer of what the plant can use and what it needs. Apply more is wasteful. Certainly, you can overdo it. I see that done a lot in the spring that plants don't need a lot of help to get going in the spring.
If you're someone that takes care of your lawn, you're into your property, and you fertilize multiple times per year, you know that in the spring, those plants will jump out of the ground, and you could mow every three or four days. Sometimes I see people, they overdo it in the spring months with nitrogen. That can have some negative effects. The plant focuses all its energy into producing lots of shoot growth and can have an underdeveloped root system.
For me, as a fertilization standpoint, in the spring, a little bit of nitrogen in the spring can help to promote early spring green up, but you don't need to put it on super heavy. Oppositely, though, Doug, if you're a new-- Maybe you just purchased a lawn, or purchased a new home and the lawn is in really poor shape, really thin, has never been fertilized. That's where you could put a little bit more down in the spring months to try to promote more growth, more density. Yes, as it relates to turf grass fertilization, more is not always better. In fact, more can often have detrimental effects, particularly in the spring months when the plants are already putting lots of resources into growing shoots.
Doug: High nitrogen, balanced fertilizer, what are you thinking when we get to the right time? When would you recommend the heavier fertilization of a lawn? What should you be fertilizing it with?
Zane: Most of the fertilization for a cool-season lawn should be happening in the fall. Believe it or not, that is a beautiful time to fertilize because the plant is putting all its energy into survival, which is in the root system. They're putting a lot more energy in the fall to developing that root system. Not all that energy is put into new shoots. When you apply fertilizer, ideally, what you're trying to do is promote some density and to grow a really nice, vigorous root system. In the fall, we see that that happens.
In the spring months, it's all about trying to crowd out the people around you. You're trying to develop a canopy to reduce competition from weeds. In the spring months, we see that you can apply less nitrogen. I typically don't recommend more than a half a pound, sometimes three-quarters of a pound of nitrogen per thousand square feet. In the fall months, that could be closer to a pound of nitrogen per thousand square feet. In terms of the seasons, Doug, we think about spring, summer, fall. Most of the fertilization should be happening there in the fall months.
In the spring, one thing about fertilization is often we use fertilizers that are impregnated with our crabgrass preemergent. That we are applying a fertilizer that has the material that prevents the germination of crabgrass on it. Sometimes that material dictates the timing a little bit more. For me, I don't like to fertilize when the grass isn't going to use it. Right now, things are not growing where we are in Worcester, Ohio. I'm not going to go out and fertilize my lawn right now. I'm going to wait until I see things really begin to start growing. We've got a little ways to go yet. I, in the spring, I like to wait until things begin to grow. I'm just going to apply a little bit about a half pound of nitrogen per thousand square feet. Then in the summer months, I wish I had a chart to show this, but in the summer months, the grass really begins to slow down its growth rate because of the air temperature. You all know this if you mow your own lawn that sometimes in the summer months you could go weeks or even a month, really, if you wanted to, without mowing.
Applying a bunch of fertilizer at a time when the plant isn't growing results in what you were talking about, potential where it could get tied up in the soil or leach down past the root zone. Most of the roots of a turf grass system are hanging right there in the upper three inches. If you apply a bunch of fertilizer that can move down past that, the plants can't take it up. The summer months is a time where if you're going to fertilize, you don't need to apply a lot because the plants aren't growing a lot. They're not going to extract a lot of nutrients from the soil.
That's a great time to use some of your organic sources or really slow-release nutrient sources like poultry litter sources. These would be low-analysis fertilizers, Doug. They could be like a 822, a 824, versus you might see more synthetic sources could be like a 1905 where you're having higher nutrient analysis. You asked about what would the proper analysis look like. This is where you really cannot answer that question without a soil test. People want me to do it all the time. The one that doesn't change, Doug, is nitrogen.
I have a pretty good idea of what the nitrogen demand is going to be for the turf grass system based on the year, but the phosphorous and potassium, that's where a soil test could reveal how much of those you need, and if you need to apply them at all. I get a lot of soil tests, Doug, where very adequate amounts of phosphorous and potassium, we can just get away from using those at all in that fertilization program, save the customers some money. Let them take that money and invest it in other parts of the landscape.
Doug: If I'm thinking about overseeding or I need to seed, what should those soil temperatures be at? When in Ohio or when in the East here is the best time to do that? If I'm putting any seed down, I'm always looking at the weather and I want that to be followed by three days of rain. That's my idea. Is that right or wrong, or what are you thinking?
Zane: 50 degrees is a pretty cardinal temperature for seeing things happen from a germination standpoint for turf. I'm always watching the soil temperatures like you. If you're going to seed, you want to get some water on it right away, but what I always tell people in the spring is that the challenge for spring seedings is that the soils are cool. We have the rainfall, but if you think about plants germinating and growing vigorously, developing a canopy, the soil temperature is what actually drives a lot of that.
That's why really always recommend seeding in the late summer, early fall because you still have the elevated soil temperatures, but you get the cooler nights, the reduced air temperature so you're able to get things to germinate fast. They grow more rapidly, but you don't have all the disease pressure of the high temperatures. Oppositely, in the spring, we have the rainfall component. That's nice like you're talking about, but the soils are cold. They're cool. Instead of plants germinating in 5 or 6 days, it might take 10 to 14 days. Even when they do germinate, they're going to grow more slowly. I'm not telling people not to overseed in the spring. It's just to recognize that your timeline is going to have to be longer. For me, I'm watching the soil temperatures. If you're going to do seedings in the spring, definitely for me I would use perennial ryegrass is a species that germinates quickly. It can establish quickly. There are definitely issues with perennial ryegrass but in the spring months, it's a go-to because it germinates and establishes so much more quickly.
If you're going to go out there and do that kind of work, if you are on any kind of a lawn care program, really important that you communicate with your provider that they don't go out there apply pre-emergent to your lawn before you've had an opportunity to put down this seed. If you put down a pre-emergent it's going to inhibit the germination of your turf grass seeds. If you're somebody that's in that position, you're teeing this up, Doug, is that once the weather begins to break for us, that's where you right away want to get out there, prep a seed bed, get the seed down.
I'm a big fan of putting some kind of a cover on it, whether it would be potentially straw or a compost or me, and the professionals, we sometimes use grow blankets as a way to keep the moisture. I like compost a lot of times. It's real dark in color so it's going to help to warm the soils up, hold some moisture. Just recognize that if you do this, don't get frustrated, after seven days, you're like, "Where's the seed? Why is it not germinated?" It's going to be more around that 10 to 14-day range for a spring seeding.
Now is the time, Doug. Don't wait. If you're somebody who's yard is thin, you have patches. Maybe you had a tree removed and stump work, whatever it might be. If you have seeding to be done, get on that right away because what you don't want to do is all of a sudden, you wait until maybe let's say it's mid-May and you want to go out and do that seeding work. Those young plants are going to germinate and get thrown into the dog days of summer, and that's a recipe to have to redo it again in the fall.
If you're going to do this work, you want to get on it early so that those plants have as much opportunity to mature before they're thrown into the fire of summer.
Doug: I have a three-part question here. Importance of a sharp blade, how high should I cut my grass, and what should I do with what's left over after I'm done cutting?
Zane: Okay. These are great topics, Doug. More blade sharpness, key. You definitely want to start the season with a sharp mower blade because again, we're going to get all this flush of growth. Your mower is going to mow more grass in the next two months than it might mow the rest of the season. Particularly for someone that has a mulching mower where it's going to grind those clippings up a bunch of times. It's not just as simple as they're cut once and injected from the mower. Those mowers are grinding those clippings up many many times and so you need the blade to be really sharp to get a good quality of cut.
Really, I like to see people sharpen their blades twice per year. I like to see them do that second one believe it or not, right after all that surge growth is done in the spring. Start your season off with a sharp blade and this is where it's going to mow a majority of its grass and then get it freshened up right there before summer because in the summer months, we don't mow as much turf. The summer months is such a stressful time that what you don't want to do is take a blade that was good in the spring, have it mow all this flush growth in the spring months, and then run that same blade through the summer.
You'll see that summer months is when it's stressful. That's where we want the highest quality cut. Also to make sure your mower deck is really clean. That's an important piece. We always focus on the blade but these decks are designed in a way that they create a vacuum. They actually create some vacuum to stand the leaf blades up as the mower rides across it. If your deck is full of leaf clippings, you don't get the proper vacuum and you often get really poor mulching. If you have a mulching mower and then deck is not clean, you're going to see it's going to struggle. That's where the mower is really struggling. It wants to stall.
Sharp blade is paramount. Get a sharp balanced blade. If you're new to this, you want to make sure that your blade is balanced. You don't want to remove a bunch of material off one side of the blade and not remove the same amount of material from the other side. A real simple way to balance your blade is just to hang it on a nail and you'll see the heavy side will drop to the bottom. If you take it to a professional, they'll do all this for you, but if you're a DIY-er and you're sharpening your blade, make sure you balance it afterwards. Make sure you install it the right way. You'll be surprised, Doug, how many people I see put blades on backwards. [chuckles]
They put it on upside down and then it's going to be spinning with the dull side hitting the turf. Sharp blade to start with, and then this is a really key piece, Doug, is that the mowing frequency should match the growth rate. In the spring, when turf is growing really vigorously, you're going to have to tighten the mowing interval. You shouldn't be someone that just says, "You know what, I'm going to mow once per week. I mow on Tuesdays because that's when I mow and that's when I want to do it." If you're someone that does it that way, you're missing an opportunity to really have the best-looking turf you possibly could have because in the spring, the moving frequency often has to get tighter.
Maybe every four or five days believe it or not. If you have the ability to do that, you'll see you get much better texture, a little finer texture, and you get better density by being able to increase the mowing frequency in the spring months. In the summer, when the grass slows down, then we can extend sometimes the mowing frequency out to 10 or 14. That's where if you're someone that says, I still mow on Tuesdays, you could be actually potentially doing some damage in the summer months there where the plants are drought stressed and heat stressed by going out there and excessively mowing them.
The last one is the mowing height. This is paramount. This is something I hammer with our customers and with our sales folks is that in general, I see Doug that we can't get our customers to mow the lawns high enough. There's an appetite to want that really manicured look and people just start to mow too short. I train out people to use what I call the credit card tool, the credit card trick where if you have a credit card, which most of us all do, a credit card is about 3 1/4 inches in height. This is a really great way.
Take your credit card, stick it down in the turf grass canopy, and see after you've mowed, how much of that card is sticking out of the turf. In general, I like to see people mowing above two and a half, closer to three inches. After you mow the turf and you stick this credit card down in, you should see that there's only a little bit of the cards protruding above the canopy. If you see half of the credit card sticking out of the turf canopy after you've mowed, you're mowing too short. Increasing the mowing height is a really great way to improve turf grass quality.
There's a direct relationship, Doug, between the mowing height and the rooting depth. The higher you're able to mow the turf, generally, the deeper the root system is going to be. People who scalp the yard or mow two close, they have poorly developed roots, and I see a lot more weedy issues in those lawns. Lots of creeping weeds. This is where you can have issues with nimblewill, bentgrass, annual bluegrass. There's a lot of weeds that really thrive. Bentgrass is the one I see most often. Bentgrass gets into people's lawns, and it just loves being mowed at those.
It's not a very good competitor for higher mowing heights. People that mow too low have a lot of issues with bentgrass. It's just able to creep across the lawn. You get these really well-defined patches of it. As it relates to mowing sharp blade, make sure that your frequency changes with the growth rate of the turf. If the turf is growing really vigorously, then you need to mow more frequently, and as the growth slows down in the summer months, you can begin to decrease the mowing frequency. This is something professionals do.
Sports field managers, golf course superintendents that mowing frequency changes with the seasons. Then, to get the height dialed in, that's the most common frequent offense I see with our customers is that they're typically mowing too low, very seldom. In fact, I don't think I've ever seen it, Doug. I've been to one of our customer's lawns, I'm like, "Wow, you're mowing too high. We need to reduce the mowing height." I've never seen that. It's only the opposite. Too low, too low.
Doug: What about the grass clippings? Let's say you don't have a mulching mower. What am I supposed to do about those?
Zane: In general, we want to return those clippings back to the lawn. In those clippings, there's a bunch of nutrients. There's a bunch of nitrogen and phosphorus, and potassium. If you're removing those clippings by bagging 'em, that lawn is going to have a higher nutrient requirement. It's going to have a higher fertilization requirement than a lawn where the clippings are getting returned and returning those clippings is adding that organic matter. That's a key piece to soil health. It's food for all the microbes. If you are bagging those clippings off, you're going to see that you have a higher fertilization requirement.
You potentially may have a lower organic matter, but I understand there are times where it is nice to remove the clippings, particularly in the spring where you could end up with a lot of clippings sitting on the surface. That's definitely a big no, no. What you don't want to do is windrow a bunch of clippings and leave them sit on the surface. It's going to shade out the plants under it, they'll begin to rot. If you're someone that has a side ejection mower, you really have to be careful about windrowing where you're going to get a really dense amount of clippings that shade out the canopy under, that can sometimes be helped by the way that you mow.
One thing, if you're someone that likes to stripe the turf and you have a side ejection mower deck, at some point, you're going to be mowing over the clippings that you just discharged, if that makes sense. You can picture you going back and forth. Eventually, you're going to have to mow back over the clippings that you discharged, and that's where you start to get that windrowing effect. Versus, if you're constantly mowing in a--, Wouldn't be a circular pattern, but you're always mowing a fresh pass that doesn't have clippings discharged in it. That can be a way to help disperse the clippings a little bit better.
For me, if I would think about that, I'd be going down. I'd move over and come back, and you create a rectangular pattern. If you are someone that wants to stripe your yard and you do end up windrowing, if you have a backpack blower, that's a great way to disperse the clippings quickly. Just blow 'em and fan them out a little bit. If you want to rake them, that is an option, but I'm all about returning the clippings back to the yard. I typically don't like to take that resource, remove it, and send it to a landfill. You're removing a really precious and valuable resource from the turfgrass canopy. If you have the ability, I like to return the clippings back to the canopy.
Doug: I have one more question before I let you go. I think the weed is called nutgrass, is that right?
Zane: Nutsedge?
Doug: Yes. How is that to be dealt with because I think it's absolutely impossible.
Zane: That's a great question, Doug. Nutsedge is definitely if I had to think of the top three most troublesome weeds in turf grass systems, I think nutsedge would be in there every time. The thing that is challenging about nutsedge is the way that it reproduces. Nutsedge does produce seeds, and for the listeners out there, identifying nutsedge, this is a plant that will emerge typically in mid-May to late May, and your neck of the woods, Doug, and sedges have triangular stems. If you like, "What is that plant?" If you pick it up and look at it and you roll out your fingers, you'll feel that the stems are triangular.
That's a good way to help ID this plant, but the way that it reproduces is why it's so troublesome because it does produce seeds, but that's not how this plant really survives in the landscape. It produces these underground tubers or what we call nutlets. That's the real troublesome part. Here's a scenario for you. You bring in a bunch of soil to establish a yard. That soil is contaminated with nutsedge. Has a bunch of these nutlet tubers in them. This is very common. I see this a lot. When you bring soil in, you bring in these nutlets with it. You see that that first year, wow, I have a lot of nutsedge issues, and you let those plants mature, maybe you try to treat them, do something about them, but recognize when those plants get big, they've already produced many, many nutlets in the soil. The next year's crop has already been established in the soil. It's there already when those plants are mature. This is where I sometimes hear people say, "Hey, pulling nutsedge actually makes it worse." Not true. The thing about pulling nutsedge is if it's big enough to probably pull, it's already dispersed those nutlets in the soil. When you pull the plants out, you don't get the nutlets, and so it's already there.
The thing about nutsedge, Doug, is that there are some really good selective herbicides that you could apply that will control the nutsedge and not the grasses. The key is that you have to control it. You have to apply these products when the nutsedge is small. When you have young plants that have not had an opportunity to produce those nutlets, if you let them get big and mature, and you treat them, yes, you'll burn down the leaf tissue and you'd be like, "Yes, I got control," but the whole nutlet bank in the soil's already been established, and you'll have to deal with those plants next year.
Unfortunately, Doug, the thing about nutsedges is it's a multiple-season thing because if you're someone that inherits this problem, there's probably a good amount of them in the soil that you'll have to deal with for a couple of years. If you're someone that gets to it late, you take control when the plants are big. They've already put nutlets in the soil. The key to nutsedge control is two things. Get control early when they're first emerging, which will be in that mid to late May timeframe. Then, make sure culturally that you're not doing anything to sabotage it.
I see nutsedge thrive in over-irrigated lawns. That's often another common thread that I find, Doug, is people who just over-irrigate have a lot of nutsedge problems on their properties. There are selective control tools if you're going to use them, though timing is everything and you need to get timing early, and you probably have to be prepared to do that for two seasons.
Doug: Zane, we're out of time. I could seriously, and we say this almost every time you and I talk, I could talk another hour. We've got so much more to cover, but I want to bring you back in the fall. I realized from talking to you that we need to talk about this in the fall because so many of the jobs that we've talked about today are best at that time. You know you're talking to a great turf expert when you look in the background and you see two microscopes.
Zane: Yes. They haven't been used much lately, but in the summer months, looking at a lot of samples, Doug, I'd love to come back, and I think timing-wise, I'd love to do it in the middle of summer because some of these things that we're talking about, take some time to plan. It takes time to take soil samples and get results back, and get the supplies. Ideally, that might be something that we tee up there and mid-late July gives people some time if they want to do some of these practices to get their ducks in a row and execute them at that right time.
Doug: We'll make it happen, Zane. That's a great idea. We'll do it this summer. As always, thanks for all this great information. It was just wonderful.
Zane: Yes. Awesome. Great to see you, buddy.
Doug: It's always great to catch up with Zane. Now, tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I'm your host, Doug Oster. Do me a favor, subscribe to the podcast so you'll never miss an episode. Do you have an idea for our show or maybe a comment? Send me an email to podcasts that's plural@davey.com. That's P-O-D-C-A-S-T-S@D-A-V-E-Y.com. As always, we like to remind you on the Talking Trees podcast, trees are the answer.
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