Maybe the only sunny area you have for a garden is currently a lawn. How about reducing the size of that lawn and converting it to a food and flower producing garden? Or, maybe you’re trying to get rid of persistent weeds in a current garden. Or maybe your soil has pests or diseases such as nematodes or verticillium wilt. This is the time of year to tackle all those tasks…with soil solarization.
Were going to tell you how to heat up the soil to kill off an unwanted lawn, do away with bermudagrass, and thwart soil borne pests and diseases, resulting in some of the best soil you’ve ever had, using clear plastic. Soils expert Steve Zien has the tips. Here's what we did in our own yard.
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Don’t be in a hurry to pick apples from your backyard trees. In many cases, the longer you wait, the better they taste, and that is especially true for one particular very popular apple variety that is probably harvested two months too soon.
And as you stroll through the garden, maybe you’re noticing some wilting plants, browning leaves or lack of growth. Our favorite retired college horticulture professor, Debbie Flower, has a quick tip on solving a very common problem in yards and gardens: ignored irrigation systems. Make sure your drip irrigation on-off valves are open!
It’s all part of Episode 24 of Garden Basics with Farmer Fred. Get comfortable on the clear plastic sheeting and give us a listen.
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Garden Basics with Farmer Fred is brought to you by smart pots the original lightweight, long lasting fabric plant container. It's made in the USA visit smart pots.com slash Fred for more information and a special discount, that's smart pots.com slash Fred. Welcome to the Garden Basics with Farmer Fred podcast. If you're just a beginning gardener or you want good gardening information, well you've come to the right spot. Maybe the only sunny area you have for a garden is currently a lawn. Well, how about reducing the size of that lawn and converting it to a food and flower producing garden. Or maybe you're trying to get rid of persistent weeds in a current garden, or maybe your soil has pests or diseases, nematodes, verticillium wilt and more. This is the time of year to tackle all those tasks with soil solarization. We're going to tell you How to heat up the soil to kill off an unwanted lawn, do away with Bermuda grass, and thwart soil borne pests and diseases, resulting in some of the best soil you've ever had, using clear plastic. Soils experts Steve Zien has the tips. Hey, don't be in a hurry to pick those apples from your backyard trees. In many cases, the longer you wait, the better they taste. And that's especially true for one particular very popular apple variety, that's probably harvested two months too soon. And as you stroll through your garden, maybe you're noticing some wilting plants or browning leaves or lack of growth. Our favorite retired college horticulture Professor Debbie Flower has a quick tip on solving a very common problem in yards and gardens: ignored irrigation systems. It's all part of Episode 24 of Garden Basics with Farmer Fred, get comfortable on that clear plastic sheeting and give us a listen. We'll do it all in under 30 minutes. Let's go. Soil solarization is an excellent method for reducing some weed seeds and soil borne diseases. And what exactly is solarizing? Well, it involves leaving a clear plastic tarp on the soil surface for four to six weeks during the hottest part of the year. Now it works great when you're in a warm growing area. But if you live in a foggy or low light or low temperature area, there are options for you as well to kill weed seeds and nematodes and maybe even verticillium wilt, which are all pathogens that are adversely affected when you solarize the soil. And you may even have success removing Bermuda grass with soil solarization if you live in an area where Bermuda grass is more of a weed than a turf. We're talking with Steve Zien of living resources company. He's a pedologist, 45 years in the soils business. Steve, how long have you known about soil solarization?Steve Zien :
Oh Boy, I don't know, my guess is 20-30 years. The the folks that actually did the research just down the road at UC Davis, and they did the research on it. They have they had a student organic farm. And they were looking for alternatives to the fumigants that they that the farmers use and in crops like strawberries, and they found that you can use these this clear plastic, and if you do it right, it will actually basically act like a greenhouse. If you have a greenhouse out there this time of year when you go out and the greenhouse is at 100 degrees outside, it's probably about 180 in the in the greenhouse. If you don't have it cooled or vented, it basically cooks the soil. They could they call it solarization because it's not quite sterilization, but it's it, it gets in, you know, kind of in that direction. I mean, for example, If you do it properly, you're going to get your soil to really really heat up at a depth of two inches, it can get anywhere from 108 to 140 degrees. And what you really want to do if you're really trying to manage weeds and diseases and insect pests, your goal is to maintain the soil temperature for pretty much close to six to eight weeks at anywhere from 110 to 125 degrees. And you can actually determine whether that's happening because you're going to be using clear plastic, you can get a soil thermometer and put that soil thermometer down in there and usually the probe is about six inches long and it'll have a little dial on the top and you can go out there and see how warm that soil is getting.Farmer Fred :
So obviously the best time of year to do soil solarization is during the summer, the months of June, July and August for much of the country. Not all the country but for much of The countrySteve Zien :
and for our country, the United States of America if you live in the southern hemisphere not going to work so well. Well, okay it has to be in this in the heat of the summer starting, roughly you know, a month before the summer solsticeFarmer Fred :
in this timeframe where daytime highs maybe in the 80s or 90s. It is remarkable that soil temperatures can get up to 140 but the key as you pointed out, and it bears repeating, the key is to be using clear plastic,Steve Zien :
very much clear plastic and and the thinner the better. Actually, what you want if you if you can deal with it and have it be successful, is one mil thick plastic clear plastic and you want it to be as clear as possible. If it's kind of smoky or cloudy, that's going to cut down the light transmission through the through the plastic. The issue with the one mil plastic if it's a windy area, or you've got critters like cats and dogs that might be walking on it. It's Not going to probably hold up. And if you want to do it for more than six or eight weeks, the sun will probably start breaking that plastic down. And so then you're going to want something thicker. Like if you're in a windy area to one and a half to two mils thick, would be probably more advisable.Farmer Fred :
And if you go to a big box store like Home Depot or Lowe's and you go to the paint aisle, they usually have rolls of plastic or painters that they put down on carpets. And that Yeah, and that is enough to solarize your yard many times over because usually fairly big rolls and like you mentioned, if the wind does rip it well it's not that difficult to replace it with another piece.Steve Zien :
Well a lot of times if it's if you can replace it with a little piece but you want to go out there probably every day especially if it's you're in a windy area, or there's you know skunks and raccoons. or any kind of critter that could be walking on there, because even a small little hole will you'll lose heat from that. And so you got to go out there and and monitor it on a regular basis. If you find like your cat walked over it and didn't like do that and put her claws through it, you know if it's just a small little area you can get like duct tape or something. plug those holes.Farmer Fred :
Alright, so we're gonna be killing weeds. We're going to be killing nematodes. We might even be able to thwart verticillium wilt if it's in your soil. And let's go let's go step by step through the whole soil solarization process. So we're going to be doing this at the hottest time of the year. So June, July, August, it'll be about a four to six week process.Steve Zien :
I would like to say six to eight weeks. Okay. All right. So the longer you've got a cooking the better chances of you killing the nasties.Farmer Fred :
The first thing I would think you would have to do is clear the area if it's a lawn that you You want to convert to a garden area, you'd want to mow it as short as possible. If it's a weedy rocky area, you'd want to at least weed whack the weeds back to soil level and remove the rocks rake off the rock so you have a fairly smooth surface.Steve Zien :
Yeah, you want to do you want to be flat and you want to basically remove as much vegetation as possible and the soil should be flat because when you lay that plastic down, you really don't want any air packets, you want that plastic to basically hug the soil.Farmer Fred :
And one way to get it to hug the soil is in that process while you're leveling the soil and getting all the weeds knocked down or the lawn knocked down is to dig a trench along the outer perimeter. It doesn't have to be that deep of a trench just a few inches, but that's where you can anchor down that clear plastic with bricks or rocks.Steve Zien :
We are actually you know, we like to lay the plastic down and then I know where the where the where the trench should be okay. Or you but you can you can measure it, you know, you know how big of a piece of sheeting that you have. But yeah, you want to, you know dig a trench and then bury the edges too so that it forms a tight seal but before you put the plasticFarmer Fred :
Yes, yes what do you do before you have toSteve Zien :
realize that that what actually transmits the heat through the soil is moisture and so you need to irrigate that area really, really well. And in this case, drip systems might not work very well because you want that moisture to be starting at the soil surface. So you want to water that area, typically from above the ground. And then you need to be you need to use a soil probe or or some sort of device to make sure that that water goes down 18 inches because you want that heat to move down 18 inches. If you've only got that water going down four inches. That's all the soil solarization you're going to get, is four inches.Farmer Fred :
So this is going to be a process that might take a few days because you're going to be cycling the water on and off just to avoid runoff. Yeah. And basically what like you say what you're trying to do is get that water as deep as possible. So you might plan on spending at least a couple of days, running that sprinkler in order to get the soil moisture to percolate downward.Steve Zien :
Yeah, and at this time of year, you really, you know, normally I tell people don't water at night. But, you know, with it being so hot a watering in the evening. You're not worried about diseases of foliage because you're going to be killing the foliage anyway. You will be you won't need to use quite so much water if you do it during the evening or early morning hours when you're going to lose less to evaporation.Farmer Fred :
And I imagine to that right before you lay down that clear plastic, you probably should just wet the soil. Again,Steve Zien :
yeah, that would be advisable.Farmer Fred :
And again what this moisture what this moisture is doing is helping move that heat downward.Steve Zien :
Yeah, if the soil is dry, the heats not going to move through it, you're, you're basically heating the moisture in the soil. And you know if you can get it, you know, get that soil up to 110 to 125 degrees for a long period of time for those six to eight weeks, you're going to be able to kill a lot of the weed seeds and the disease spores and insect eggs. And another thing that's kind of cool is that it also makes some of those pests that might not be killed. it weakens them to the point where they're, they're going to be more susceptible to biological controls.Farmer Fred :
It's not uncommon for tomato gardeners to get some rather interesting surprises this time of year. Now they're pleasant surprises, usually In the form of a volunteer tomato plant, if you're a curious gardener such as myself, you just might want to grow it out to see what sort of tomato develops. However, that tomato plant may be popping up in an area where you don't want it to grow. And maybe all your garden area this time of year is filled with other vegetables and fruits. There is a solution. dig it up carefully, and transplant it to a large smart pot using a good quality potting soil. Place it in a sunny area, prune it back a bit, keep the soil moist, and voila you've got mystery tomatoes later in the summer. Smart pots are the original lightweight, long lasting fabric plant container made in the USA. They're sturdy, easy draining containers that will last for years. Smart pots are made with an easy breathing fabric. It keeps them cooler than plastic pots. You're going to have a more successful tomato growing experiment or whatever you're growing in the hot summer months. If you want more information, well, visit smart pots.com slash Fred. And be sure to include that slash Fred part that can get you a nice discount when you buy a smart pot. Smart pots are available at many Ace and true value hardware stores, local independent nurseries and online at amazon.com. Again, visit smart pots.com slash Fred and get yourself a smart pot, or two, or three. Hey, how would you like to win your own smart pot? from June 16 through June 30, one lucky winner can qualify to receive smart pots six foot long bed...a fabric container large enough to hold over 10 cubic feet of soil. It's 16 inches tall and 16 inches wide by about six feet long. That's enough room for a couple of tomato plants and a couple of pepper plants or maybe one fantastic display of summer flowers. We're going to award the smart pot long bed to the best comment or review about Garden Basics with Farmer Fred, that you post at the podcast service where you're listening to this show. And by best comment, I don't necessarily mean the kindest comment, just the most creative comment. So when you're done listening to the show, leave a comment wherever you're listening. And you just might get yourself the smart pot six foot long bed. We will announce the winner on the July 3 edition of the Garden Basics with Farmer Fred podcast. Thank you. We're talking about what soil solarization can do for your soil. You do it during the summer you put down clear plastic and voila, weeds are gone. weed seeds are gone. nematodes are gone. verticillium wilt just might be gone. But what happens to the garden good guys, all that beneficial bacteria and fungi that might be in the soil, Steve Zien, are they harmed in this process?Steve Zien :
Some of them are but in some cases, they can move out of the way area worms for example, but very, very quickly, they will you know, because the the surrounding area is not affected the area farther down is not affected. So, tests have shown that the beneficial critters move back in very, very quickly. You can also to improve that, add things when you're done. Top dress with things like organic fertilizers that have microbes. There are products that you can buy that have microbes. Probably two of the better things are good quality compost, and my personal favorite worm castings. worm castings that have all sorts of organisms. Now the key here though, is when you're done and you've removed that plastic, do not till that soil.Farmer Fred :
don't roto till the soilSteve Zien :
because you know, soil especially you know, the higher you are in the soil profile if you're only like two inches deep, three inches deep. You've probably killed just about everything there. But the farther you go down, the better the chances are that weed seeds, disease spores and insect eggs have survived. And so killing them would bring those critters that have survived up to the top. So when you're adding the worm castings or the compost, just put it right on top. And typically what happens is after you've tarped this area for six to eight weeks, that soil will really be nice and loose and friable.Farmer Fred :
Where did the earthworms go during all thisSteve Zien :
They'll go to the surrounding area, they're go farther down.Farmer Fred :
I am very impressed about how it does such a fine job on weed seeds, but we shouldn't shortchange the fact that solarization controls so many soil-borne fungal and bacterial problems including verticillium wilt. Fusarium wilt, phytophera, southern blight, damping off, crown gall, tomato canker, potato scab, and many others.Steve Zien :
Yeah, I mean It works really, really well. Like I said, You see, when they did the research, they were looking for alternatives to, you know, the fumigants. Some of the fumigants that the farmers used on a regular basis were being outlawed because they were so dangerous and so toxic. And they found that this really does a wonderful job, they get good. I mean, they're maybe they do a good job on controlling nematodes as well. If you've got if you've ever had a plant that didn't perform well, in particular, your vegetable garden, your vegetable garden and like tomatoes, for example. And your tomatoes not doing well you pull it up, and normally I don't tell people to pull, pull the roots out because those roots will decompose and add organic matter. But if a plant's not doing well, there's might be something wrong with the roots and if you pull those roots out, you might see little nodules. And that's fine to see little nodules on your peas and beans because those are that those are beneficial bacteria. Providing nitrogen to your plant. But on tomatoes, those are nematode called nematodes and they damage the plant roots and that's one of the causes for your plants not surviving. And this soil solarization will control the bad nematodes as well.Farmer Fred :
We mentioned this is best in warm area. So if you live in an area where the air temperature is in the Upper 80s 90s, or higher, such as the Central Valley of California, the deserts or other inland areas of California, or wherever you may happen to be summertime is the best time to do this. If you live in the cooler coastal areas of many parts of California, they have what they call the San Francisco summer, which is usually the month of September where it's not so much it gets hot, but at least it's not foggy, and that would be their best opportunity along the coast to try some solarizationSteve Zien :
Yeah, I mean we air temperature is not quite as critical as the sun being high. So most of the sunlight goes right in through the plastic instead of bouncing off, and then it'd be sunny.Farmer Fred :
Now, one thing I did not know, and I'd be willing to try it sometime is solarizing soil in containers that it's been shown to be effective for disinfesting small amounts of moist containerized soil, such as in cold frames, but you could do it in buckets too.Steve Zien :
Yeah. I mean, you know, buckets, it would probably work as well. Yeah, I'm thinking. And yeah, I think we raised beds, I think it would work really well. Again, you would, you would want to dig a trench around the outside of that raised bed soil so that you can bury that into the edges so that you cover the entire area and just rake it level first, and give it some good irrigation and it'll do the job.Farmer Fred :
All right. soil solarization works in many many climates. Could you use soil solarization in your home state of Wisconsin?Steve Zien :
I think so. Because we have a lot of our we had when I lived there, and I assume the climates relatively similar, most of the days are partly cloudy. And so there's, you know, cloudy or cloud there, but there's sun in between. and that it's not like the winters here where the whole sky is gray. And yeah, it would work. Would I think it would work well, in most areas where there is sun,Farmer Fred :
and again, it's in the summertime and again, it's with clear plastic.Steve Zien :
Yes,Farmer Fred :
why doesn't black plastic workSteve Zien :
black plastic? Well, it's not going to transmit the heat. The sunlight can't get through with a black plastic, but I found and i and i have used it for years, excluding light and that you can use tarps you can use black plastic, anything that's going to exclude light. it will not sterilize or solarize soil but it will kill any existing vegetation it's not going to do the weed seeds or the disease spores or the insect eggs. But if you you know, if you put a cover that will exclude the light, it will remove the existing vegetation. And then what I typically suggest is that after that's done you can then water the area let the weed seeds that are there grow and then control them either with a garden hoe or a flame weeder or something like that. And do that a couple times. And then you will basically have a weed free bed to put in your garden and you can do that anytime of the year.Farmer Fred :
how long would you leave that black plastic on to do that?Steve Zien :
Typically a month to two months go on again the longer the better. But you know a couple of months is is more more than sufficient. When I lived back in Wisconsin, I moved around a lot. And in many cases, it was not during the heat of the summer. And at that point we didn't know of soil solarization. And so that's what I did is, you know, by often I said, you know, for the landlord, well, I'm going to be moving here in a month or two. Can I and I would like to have a garden, is that acceptable? And then if they said, Yes, I said, Can I come out now to a month or two before I move in and cover with black plastic or some sort of tarp to exclude the light and then by the time I moved in, it was ready to plantFarmer Fred :
did he call you a damn hippie under his breath as you walked away?Steve Zien :
Well, he was a hippie too. So it all worked out. I lived in those kind of neighborhoods,Farmer Fred :
soil solarization for gardens and landscapes, it works. It's a non chemical method for controlling soil borne pests using high temperatures produced by Capturing radiant energy from the sun in the summertime with water and clear plastic. Steve Zien living resources company 45 years soils expert. Thanks for heating up the soil for us today.Steve Zien :
It was fun. Thanks, Fred.Farmer Fred :
One of the nice things about growing apples, they last a long time on the tree. In fact, you might be picking your apples a little too soon, especially when it comes to a very popular variety called Granny Smith. Granny Smiths do well in a wide variety of climates. here in California. We tend to start harvesting them in October. Phil Purcell is with Dave Wilson nursery based in Central California. They're a wholesale grower of fruit and nut trees for the entire country. And he says when it comes to harvesting Granny Smith, you ought to wait a while and wait for the apple to change color.Phil Pursel :
In our harvest chart we say that you know the Granny Smith really should be picked you know November or such and that's when you kind of see the granny smith start showing up in the grocery stores right the fresh the new season Granny Smiths come in and it's about that time well, Granny Smith should actually be almost like a Golden Delicious when it's picked. So when we're picking our Granny Smith off our mother trees at the nursery, we're picking them at the end of December. Oh in the flavor that you get off that Granny Smith is unbelievable. The tartness is taken out but you get that great Granny Smith flavor. You get that great crunch, getting you know, and it takes all the tartness off and at that point, I realized that for all these years, I've been eating unripe Granny Smith apples in the grocery store because Granny Smith should look almost like a Golden Delicious when it's picked off the tree the light greenish yellow color.Farmer Fred :
Debbie, time a quick tip now we were walking through my yard before we started the interview here and you notice that the pepper plants were looking a little droopy.Debbie Flower :
Yes, they wereFarmer Fred :
and I had that happen. The last time we had 100 degree days so I gave them a drink of water and as I'm pouring water on each of the plants, I happen to see the valve each of my raised beds has an on off valve and this particular valve was in the off positionDebbie Flower :
sure wasFarmer Fred :
sure was was I was accusing the dogs of having done it. Yeah, good for you. All right. You noticed how defensive my wife got when I mentioned this that she doesn't touch it. Yes.Debbie Flower :
My husband would be the same way.Farmer Fred :
But I turned it on and then I turn the system on to give them a good drink of water. Quick Tip of the Day. Check your watering irrigation systems regularly. Yes, especially in during heat waves. You may have to check it once a week. Every other week is Better or is good every other week is good once a month is minimal requirement, we do that if your sprinklers for your lawn come on at a certain time, if you have sprinklers on a lawn, get up early, go watch them work, make sure that they're all working correctly.Debbie Flower :
And if you're using a hose and some sort of hose-end sprayer that you put down or whatever, turn it on and see that that the spray is going where you want it to go that this sprayer is doing its job of spreading the water. There can be dry spots there can be over wet spots. And if you're not there to see it, you don't know thatFarmer Fred :
and this time of year, it's not uncommon for shrubs to grow quickly and if you have a sprinkler system it's not uncommon for shrubs to be blocking the spray right of those sprinklers so you may want to walk around with your pruners too.Debbie Flower :
Yes, yes.Farmer Fred :
So check your irrigation systems. Thank you very much. Don't forget you can get your garden questions into the Garden Basics with Farmer Fred podcast through a myriad of ways including leaving it via telephone 916-292-8964 you can also text your question there 916-292-8964. dot comemail it in to Fred at farmer Fred dot com. And you can leave it on a number of social media outlets including the get growing with farmer Fred Facebook page or on Twitter at farmer Fred and Instagram farmer Fred Hoffman. Debbie Flower we learned a lot. Thanks for your time.Debbie Flower :
It was great to see the studio. I'm happy to be here.Farmer Fred :
All right, we'll do it again.Unknown Speaker :
All right.Farmer Fred :
Thanks for listening to Garden Basics with Farmer Fred brought to you by smart pots. garden basics comes out every Tuesday and Friday. It's available on many podcast platforms, including Apple, Spotify, Google, iheart, Stitcher and many more. And if you're listening on Apple, please leave a comment or a rating that helps us decide which garden topics you'd like to see addressed. And again, thank you.