359 Tree Surrounds, Cardboard Mulch Pros-Cons. Winter Tomatoes

They’re known as tree rings, or tree surrounds. Basically, it’s a demilitarized zone for your trees, where the trunk and roots are safe from weed whackers and lawn mowers as well as competing plants (especially lawns). It might be a short term solution for a newly planted tree. But leave it in place longer than that, and problems can ensue. Debbie Flower, America’s Favorite Retired College Horticulture Professor, tells us about those issues.

Is using cardboard for mulch in a garden a good idea? We tackle that question today, as well.

And finally, we revisit the subject that many gardeners with a fairly new greenhouse might be thinking about right now. How to grow tomatoes during the winter. We get into the best varieties for growing in a greenhouse, and the problems that might pop up. (Originally aired in Episode 56). And be forewarned: the flavor might turn out to be  just a couple of notches above supermarket quality. But at least it’ll be freshly picked, and packed with more nutrition.

We’re podcasting from Barking Dog Studios here in the beautiful Abutilon Jungle in Suburban Purgatory. It’s the Garden Basics with Farmer Fred podcast, brought to you today by Smart Pots and Dave Wilson Nursery. Let’s go!

Previous episodes, show notes, links, product information, and transcripts at the home site for Garden Basics with Farmer Fred, GardenBasics.net. Audio, transcripts, and episode chapters also available at Buzzsprout.

Pictured: A protective tree ring

Links:
Farmer Fred’s Ride for the Kids. Donate Now!
Subscribe to the Beyond the Garden Basics Newsletter https://gardenbasics.substack.com
Smart Pots https://smartpots.com/fred/
Dave Wilson Nursery
HeirloomRoses.com (with the FRED discount link)

Other links mentioned in today’s podcast:
Sheet Mulching
Winter Greenhouse Tomato Growing Tips

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Chapters

• 1:51 Tree Rings, Tree Surrounds Pros and Cons
• 13:32 Smart Pots!
• 15:43 Q&A Cardboard Mulch
• 23:11 Dave Wilson Nursery
• 24:24 Want to Leave Us a Question?
• 25:26 Growing Greenhouse Tomatoes in the Winter

Transcript

359 TRANSCRIPT Tree Rings, Cardboard Mulch Pros and Cons. Winter Tomatoes.

Farmer Fred:

[0:00] Garden Basics with Farmer Fred is brought to you by SmartPots, the original, lightweight, long-lasting fabric plant container. It's made in the USA. Visit SmartPots.com slash Fred for more information and a special discount. That's SmartPots.com slash Fred.

Farmer Fred:

[0:20] 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.

Farmer Fred:

[0:31] They're known as tree rings or tree surrounds. Basically, it's a demilitarized zone for your trees where the trunk is safe from weed whackers and lawnmowers, as well as competing plants, especially lawns. It might be a short-term solution for a newly planted tree, but if you leave it in place any longer than that, problems can ensue. Debbie Flower, America's favorite retired college horticultural professor, tells us about those issues. Is using cardboard for mulch in a garden a good idea? We tackle that question today as well. And finally, we revisit the subject that many gardeners with a fairly new greenhouse might be thinking about right now. How to grow tomatoes during the winter. We get into the best varieties for growing in a greenhouse and the problems that might pop up. And be forewarned, the flavor just might turn out to be a couple of notches slightly above supermarket quality. But at least it'll be freshly picked and packed with more nutrition. We're podcasting from Barking Dog Studios here in the beautiful Abutilon Jungle in suburban Purgatory. It's the Garden Basics with Farmer Fred podcast, brought to you today by SmartPots and Dave Wilson Nursery. Let's go.

TREE RINGS/TREE SURROUNDS - THE PROS AND CONS

Farmer Fred:

[1:51] We like to answer your garden questions here on the Garden Basics podcast. Debbie Flower is here, America's favorite retired college horticultural professor. And Scott wants to know again, because he says, 

“You were kind enough to answer my question about livestock troughs for blueberries. I have three citrus trees and pots that I want to put into four foot tree surrounds. And I was wondering if it's a good time to do this and what type of soil should I put them in? Thanks for your time and have a great day.” 

Thanks, Scott. Ione California, by the way, is where Scott lives and is in Amador County, which would be about due east of Sacramento in the foothills. And their soil there would be foothill kind of soil, which is kind of iffy. Maybe. Now, you lived in the foothills.

Debbie Flower:

[2:41] I lived 20 minutes from here. Yeah.

Farmer Fred:

[2:44] Well, this is kind of the foothills, but you were higher up in the foothills.

Debbie Flower:

[2:48] Lots of rock. We had to buy, we had a pick and a digging stick. Anytime we dug a hole, when you start to rise up in elevation, you get less and less soil because unless you're in the mountains don't just go straight up and down. They go up and then they have low spots and go up and have low spots. If you're anywhere but in those low spots, you have no soil to speak of. And that makes it very difficult for plants to dig the hole and then for the plant to get established.

Farmer Fred:

[3:16] Yes, I know that well. The official garden trowel for Folsom, California is indeed a handheld pickaxe, because the ground is rock.

Debbie Flower:

[3:24] I learned how to use one. Yeah.

Farmer Fred:

[3:26] Soil goes downhill.

Debbie Flower:

[3:28] Yes. Soil goes downhill. So living in the low spot is beneficial for your garden. It's better soil.

Farmer Fred:

[3:34] However, having said that, there are a lot of citrus groves in the foothills here in Northern California. So, it must be possible.

Debbie Flower:

[3:42] Well, I think that location has to do with temperature, that cold air also goes downhill. And so, when there's a marginal, a period of marginally cold weather, you want the cold air to go downhill, drain away from those orchards, and they get more protection that way. 

Farmer Fred:

[4:00] So, that's why, if you have that ability, is to plant on a slope and on the high end of a slope.

Debbie Flower:

[4:06] Yes.

Farmer Fred:

[4:07] And probably not on the north side of a slope either.  Yes, you're looking for sunshine. But anyway, Scott, wants to know about tree surrounds. Well, I like the idea that you want to surround the tree with something that is four foot in diameter. A lot of things that are advertised as tree surrounds, which I guess we should define as being what? A metal ring, basically.  Or a wooden ring, or a plastic ring, or a mason stone ring.

Debbie Flower:

[4:31] A circle. A circle.

Farmer Fred:

[4:33] Yeah.

Debbie Flower:

[4:34] That... May just be a circle that's completely empty in the center or it may extend all the way to the trunk of the tree. There are a couple of different types of tree surrounds.

Farmer Fred:

[4:46] Yeah. In my mind, the benefit of a tree surround, it differentiates a lawn from the plant and it really ends the competition between a lawn and the tree's roots.

Debbie Flower:

[4:59] You can hope. But the tree's roots go so much further. It's really not the best place to plant a tree in the middle of the lawn. A tree should be in a bed that is handled differently than the lawn, watered differently than the lawn, fertilized differently than the lawn if you get into fertilization. But obviously, there are many trees already in lawns and somehow we have to take care of them. And one of the bad things about having them in lawns is the equipment we use to maintain the lawn, like the weed whacker or string trimmer and the mower which can be bump against that trunk. Yeah.

Farmer Fred:

[5:33] And it can also help you keep certain fertilizers that shouldn't be anywhere near that tree, away from the tree, especially the weed and feed product. Right.

Debbie Flower:

[5:43] But again, your roots, tree roots are going to go way far away. They go further away from the tree in all directions than the tree is tall. So there's no way you can protect all of that unless you get rid of all of that lawn.

Farmer Fred:

[5:57] Citrus trees, though, have a generally smaller root system, especially if it's more of a dwarf citrus tree. That's why...

Debbie Flower:

[6:03] Well, the smaller the tree, the smaller the root system. Right. Yeah.

Farmer Fred:

[6:06] And having a four-foot diameter tree surround, I would think would be the bare minimum for that citrus tree. Because like you say, for a lot of ornamental trees, their roots just keep on going. Right. And you've had some instances where you've seen these tree surrounds in action and to a tree, it just goes, ha, I can solve this one.

Debbie Flower:

[6:25] Right. Sometimes tree surrounds are used as root barriers to prevent the roots from extending beyond that circle and trees... That never works. Even if it goes down two feet, the tree roots will either go under it or over it, or they'll find the crack in it and go through it. There was one on a property, a commercial property that I used to show the students when we taught plant ID, and there was a white birch tree there, and the roots went right over the top of this tree surround.

Farmer Fred:

[7:02] As opposed to under.

Debbie Flower:

[7:03] I suppose they also went under, but I didn't dig a hole to find out because it wasn't my property.

Farmer Fred:

[7:09] Yeah. And in the research we've done about tree surrounds, and we better define the differences here because depending on what source you look at, a tree surround might mean a different thing to different people because sometimes tree surrounds are sold as tree rings. And if you look at what's available as tree rings, it could be like a flat carpet-like moat that goes around the trunk of a tree to protect an area that might be two feet wide and with a radius of two feet or maybe three feet, but they look pretty small. Some of them are made out of rubber. Some of them are made out of cocoa fiber. The long-term ramifications of that to me are just like, okay, you're just waiting for trouble to happen. Right.

Debbie Flower:

[7:54] They have very small holes in the center. So, they're right up against the tree trunk. And then they're rather thick, an inch or more. And so, they're going to impede the movement of air and water into that soil beneath.

Farmer Fred:

[8:11] And even if it does say that it's permeable to air and water, you've pointed out on this program many times the fact that weed cloth, which is also permeable to air and water, eventually clogs up.

Debbie Flower:

[8:23] Yes. So these would clog up too. Yes.

Farmer Fred:

[8:27] And that means you're just starving the tree roots that are under there. Right.

Debbie Flower:

[8:31] So, they're not a good idea.

Farmer Fred:

[8:32] Yeah. And Scott wants to know about, okay, what soil should I put in there? I think with a tree surround, the ones we've seen, which are only a few inches tall.

Debbie Flower:

[8:42] Yes.

Farmer Fred:

[8:43] You wouldn't put any soil in there. Right.

Debbie Flower:

[8:45] A little mulch, not touching the trunk of the tree, but a little mulch to cover the soil, three inches maybe, but not touching the trunk of the tree. And it makes a barrier then, as you mentioned, between the lawn and the tree trunk.

Farmer Fred:

[8:57] I could see using that tree surround as a temporary way to help protect a young tree, especially one with a thin trunk, a small trunk. So it won't get hit by mowers and weed whackers. But after a few years, I would remove it.

Debbie Flower:

[9:13] Yeah, I don't have a lawn that gets mowed. But I do put stakes around a newly planted plant. Or sometimes I just use a tomato cage so that I don't step on it, my husband doesn't back into it, the cats don't run through it, that kind of thing. So, yeah, some protection like that would work. But another kind of tree ring I've seen is when there's a mature tree and often the tree roots come to the surface on a mature tree because they expand over time in diameter and people don't like the looks of that. And so, they bring in some kind of soil, sometimes it's field soil, sometimes it's bagged media, and create a ring out of something plastic or metal, usually, and then plant things into that. And that is not a good idea.

Farmer Fred:

[10:03] For a lot of reasons. Yeah. Not the least of which is, okay, if that new soil is up against a tree trunk that never had soil around it before, say goodbye to that tree trunk.

Debbie Flower:

[10:14] You're going to suffocate. Yeah. The rule of thumb is it takes one year for every inch of trunk diameter to die. So, if the tree trunk is a foot across, then it's going to take 12 years. But the tree will just slowly not look so good. Yeah.

Farmer Fred:

[10:30] And if you had pulled away that dirt from that trunk, you would probably see the start of the damage. Yes. And by the way, if you do that, you might want to just keep pulling that dirt away from the trunk and create a chance.

Debbie Flower:

[10:43] I should say that rate of decline is going to vary depending on where you are. I was visiting my son in Minnesota and they've been having so much rain that every GPS thing I put in my phone directions to go somewhere said your route might be impacted by flooding. And there's a tree stump in his yard. The tree was cut down maybe three years ago. And it is, the stump is just full of all these interesting mushrooms and insects and it's totally crumbling apart. In our climate, that would not happen because we are not that wet. So, that rate of you're going to have both suffocation of the trunk of the tree and rot beginning from the outside due to trapped moisture. So, that rate will vary. Yeah.

Farmer Fred:

[11:27] And you've created an anaerobic environment too. So that there's all sorts of problems. So, Scott, I would say maybe as a temporary measure, and certainly you do want to plant it in the field soil that you have and not put any soil in that tree surround. But mulch, yeah, mulch would be fine. 

Debbie Flower:

[11:50] Not a lot of mulch, not deep mulch. Citrus is very sensitive to having the roots covered, the roots that are under the canopy.

Farmer Fred:

[11:58] Oh, tell that story, would you please? I've told this story before.

Debbie Flower:

[12:02] I did some consulting, horticultural consulting, and both Fred and I knew citrus growers, commercial citrus growers. And I'd spent time talking to them about what they did and what the trees need and that sort of thing. And so my number one call was a declining citrus tree. And I would get on my stomach and climb under this tree. And they were usually old, taller than I am, you know, maybe eight feet tall. And there was just a huge pile of mulch created by the leaves that had fallen off the tree. Citrus are evergreen, but all evergreen trees lose some leaves every year. They fall down, right? Right. So I went under and I pulled those leaves out. And over time, after I left, the tree got better. They are so sensitive to having, and I learned this from the commercial growers, that citrus are incredibly sensitive to having a layer of anything, soil or mulch, on their roots.

Farmer Fred:

[13:01] End of story?

Debbie Flower:

[13:02] End of story. 

Farmer Fred:

Oh, okay.

Debbie Flower:

[13:03] You weren't listening, were you? 

Farmer Fred:

I was listening, but your voice didn't go down at the end.

Debbie Flower:

[13:09] You were just listening for the sound of my voice.

Farmer Fred:

[13:11] Yes, the musicality. I was waiting for the denouement.

Debbie Flower:

[13:15] Tonality, yes.

Farmer Fred:

[13:16] All right, fine. So, Scott, proceed with caution with tree rings or tree surrounds or whatever you put around a tree, and maybe just think of it as a temporary solution. Debbie, hope we solved somebody's problem. 

Debbie Flower:

I hope so, too. 

Farmer Fred

Yeah, thank you.

SMART POTS!

Farmer Fred:

[13:33] I've been using the SmartPot compost sak for a few years now, and it is coming in very handy for amending and protecting the garden soil year-round. I like to amend my planting beds before putting in any of the seasonal crops or improving the bed before I plant any time. One of the ingredients that gets worked into the soil in my raised beds is compost, and making up the bottom half of my SmartPot compost sak right now is some of the richest-looking, finest compost I've ever seen made from last fall's oak leaf collection. Thank you. Yep, it's beautiful leaf mold. The design of the compost sak, with a little help from Mother Nature, turned those shredded leaves into beautiful, ready-to-use compost. And I use some of the existing leaves that haven't broken down near the top of the compost sak as a few inches of mulch, and I use that year-round. The SmartPot Compost Sak is a large 100-gallon fabric bag. It's lightweight, yet extremely durable, and lasts for years. Years, it can hold 12 cubic feet of pure compost. This rugged fabric is entirely porous, containing many micropores that allow for air circulation and drainage. The fitted cover is a flexible plastic top designed to increase heat and help manage moisture in the mix, accelerating the composting process.

SmartPots, they're proudly made 100% here in the USA. SmartPots are available at independent garden centers and select Ace and True Value hardware stores nationwide. You can find the nearest location of SmartPots at their website, smartpots.com slash fred. That's where you can get 10% off your SmartPot order by using the coupon code FRED, F-R-E-D. Do it at checkout from the SmartPot store. Visit smartpots.com slash fred for more information about the complete line of SmartPots lightweight,

colorful, award-winning fabric containers, as well as the SmartPot compost sak. SmartPots, the original award-winning fabric container. Go to smartpots.com slash fred.

CARDBOARD MULCH - PROS AND CONS

Wyoming Listener:

[15:46] “So I have a raised bed I made out of scrap, and you're not going to laugh. Dogs were getting into them. I fenced it off. But my question is, does this work? I lay down this on the grass everywhere. I lay down cardboard, and I'm putting my grass clippings over the cardboard. We're planning on doing that for the entire summer. In the winter, well, I'm from Wyoming, in Casper. I'm hoping to till up the grass and the cardboard. Would that be too much nitrogen if I put all my grass, my clippings, on it? They kind of dry out. I spread them. But thank you.” 

Farmer Fred:

Well, thank you, Garden Basics listener in Casper, Wyoming. Appreciate it. I don't think we need to worry about nitrogen at this point, Debbie Flower. 

Debbie Flower:

I agree. 

Farmer Fred

I think maybe we need to think more about his method of improving the soil by putting down cardboard and then the grass clippings. I'd almost want to do it the other way or do it both or do layers.

Debbie Flower:

[16:55] If you Google it, you can find out that grass clippings have about 4% nitrogen in them, which is really not much at all.

Farmer Fred:

[17:02] And it'll disappear soon.

Debbie Flower:

[17:04] Right, it'll disappear. Nitrogen moves in the environment quickly. It moves, it volatilizes, meaning it becomes a gas and it goes up into the air if it's not covered up with something. And if it's wet, it moves with water. So there's going to be almost nothing left by the time the tilling occurs. I'm guessing that the cardboard is on top of existing grass. He didn't, well, he talked about a raised bed. So I don't know if it's on top of existing grass or not. And I don't know about layering.

Farmer Fred:

[17:36] It's an idea to look at. If you do, we'll have some links in the show notes about sheet mulching. And in most instructions for sheet mulching, they talk about mowing the grass as low as possible. Right. Watering the soil thoroughly. Right. Putting down the cardboard, watering the cardboard.

Debbie Flower:

[17:51] Which is also wet, yes.

Farmer Fred:

[17:53] And then topping it with mulch. But I'm wondering if, I like the idea, was it your uncle used with his old grass clippings, you said? 

Debbie Flower:

[18:03] My dad. My dad would mow the lawn. My dad was a professor of solid waste management, of garbage dumps, basically, of garbage. And part of what he did on a grant with the Environmental Protection Agency was he went out to what then were just garbage dumps, and poked holes. We called it the pogo stick, a device that would poke holes into the soil about two feet deep or more. And then he would collect gases from there to find out what was moving out of the garbage dump horizontally in the soil, like methane, which is the primary problem. And he'd take temperatures and that sort of thing. So he had a long necked thermometer. They're called a compost thermometer. And he would cut the grass and put all of the grass in a metal garbage can and go in wash your hands or whatever and come out and take the temperature and it got very very very hot in there like 180 degrees. We're hoping in a compost pile for 140 degrees, and the reason we want to get that hot in the compost pile is to kill weed seeds and other problematic things that might be in the plant material that's in there. So a concern about the grass clippings is how many weed seeds are going to be in there and if the process of tilling is going to, plant those seeds into the bed where you're going to garden.

Debbie Flower:

[19:25] Composting, you could compost the grass clippings in a large container like a garbage can, but it would take possibly two garbage cans. So one, you put the grass clippings in and then the next day you pour them into the next different garbage can, take the temperature. If it gets up to 140, let it sit there for a couple of days, then pour it back into the first garbage can. The pouring is just what we would in composting would call turning, turning the pile so that the stuff that's hot on the inside gets moved to the outside. The stuff that's cold on the outside gets moved to the inside. Eventually it'll all break down and it won't look like grass anymore. And it'll decrease by about two thirds in size and you will have composted grass. It won't end up being very much.

Farmer Fred:

[20:08] Yeah. It shrinks dramatically. Did your dad in this composting system, did he take a shotgun to the can first to aerate it? 

Debbie Flower:

[20:17] No. No. This was just him playing. We had a cold compost pile in the back corner of the yard and he would take it out there and dump it. 

Farmer Fred:

[20:26] I would see using the grass clippings as part of a compost pile.

Debbie Flower:

[20:30] Yeah.

Farmer Fred:

[20:31] But I'd also add in other things to that compost pile, your kitchen scraps, your yard waste, things like that. And just make sure, like you were indicating, it's a hot compost pile. And then using that to put on your newly cleaned out raised bed or whatever you're doing to eliminate whatever is there, putting that compost on it, then wetting it, cardboard layer, wetting that, mulch on top,

Debbie Flower:

[20:55] Wetting that.

Farmer Fred:

[20:56] And then come back and plant, just plant right through it. You don't have to clear it and till it. 

Debbie Flower:

[21:02] Right. You can just punch holes. It'll decompose over time.

Farmer Fred:

[21:03] Cardboard will have to decompose. You can just plant.

Debbie Flower:

[21:05] It might not happen the first year, especially if you just put the cardboard on before the snow arrives. Cold will slow down the decomposition process. But yeah, eventually, yeah, either poke holes in it or it won't be there anymore. So, the only harm I see with putting the grass clippings on top of the cardboard is the introduction of seed. 

Farmer Fred:

[21:27] Yeah. You mean seed from the grass itself?

Debbie Flower:

[21:32] Seed from whatever is growing in the grass. Typically, this grass is not in bloom and is not bearing seed unless it's not been mowed for...

Farmer Fred:

[21:40] Depends on the lawn.

Debbie Flower:

[21:41] Yes, it does. It does. It could have grass seed in it. It could have other seed. It doesn't matter. It would be introducing new seed into an area where you don't really want any. The other thing that could be used would be composted cow manure, steer manure. And I imagine there's sources of that or there's sources of fresh that you can pile somewhere and throw your grass clippings in there too and enjoy the fragrance until it breaks down.

Farmer Fred:

[22:09] I think manure, well-aged manure, is a good start for that. And then put the cardboard on top of that. But again, water each layer.

Debbie Flower:

[22:20] Yes, that's very important for the compost.

Farmer Fred:

[22:22] So, Casper, in Wyoming, you might be working a little too hard on this. I don't think there would be any tilling necessary, but just layering those in, as we suggest. And we'll have more links in the show notes, too, that can help out. And just keeping it moist. Let it overwinter that way. the next spring, you can plant right in it.

Debbie Flower:

[22:40] Yeah.

Farmer Fred:

[22:40] With no addition needed to the soil.

Debbie Flower:

[22:43] Right. And you can put the grass clippings elsewhere and make them part of a compost pile.

Farmer Fred:

[22:47] And then maybe use that compost later on. Yeah. When you're growing the crops. Right. Or whatever you're planning on growing.

Debbie Flower:

[22:53] But don't worry about the nitrogen. Yeah. Even if you use some chicken manure that's been aged, then you won't have a nitrogen problem. All right.

Farmer Fred:

[23:01] Just enjoy the beauty of Wyoming.

Debbie Flower:

[23:03] Yeah. All right.

Farmer Fred:

[23:04] Thank you, Debbie.

Debbie Flower:

[23:04] You're welcome, Fred.

DAVE WILSON NURSERY

Farmer Fred:

[23:11] Fall is in the air, the perfect season for planting and planning. And if you're planning to buy and grow some fruit trees this fall and winter, you need to check out the home garden page at DaveWilson.com. That's Dave Wilson Nursery, the nation's largest grower of fruit trees for the backyard garden. At DaveWilson.com, you're going to find planting tips, taste test results, fruit variety recommendations, and links to nurseries in your area that carries Dave Wilson and fruit trees. Just go to DaveWilson.com, click on the Home Garden tab at the top of the page. There, you're going to be just a click away from their informative YouTube video series. Especially popular in that video lineup is Dave Wilson Nursery's Tom Spellman explaining Backyard Fruit Tree Basics. Viewers have raved about that episode, calling it absolutely the best single video for growing backyard fruit trees. Check it out before you plant. The Backyard Fruit Tree Basics video. It's on YouTube. Find a link to it after going to the Home Garden tab at DaveWilson.com. Click on the Getting Started link, and you're on your way to your best fruit garden ever. Your harvest to better health begins at DaveWilson.com.

WANT TO LEAVE US A GARDEN QUESTION?

Farmer Fred:

[24:22] Want to leave us a garden question? You'll find a link at GardenBasics.net. Also, when you click on any episode at GardenBasics.net, you're going to find a link to SpeakPipe. You'll find it in the show notes. And when you bring up SpeakPipe on your computer or smartphone, you can leave us an audio question without making a phone call. Or you can go to SpeakPipe directly. That's speakpipe.com slash gardenbasics. You want to call or text us? We have that number posted at gardenbasics.net. It's 916-292-8964. 916-292-8964. Email? Sure, we like email. Send it along with your pictures to fred at farmerfred.com. Or again, go to gardenbasics.net and get that link. And if you send us a question, be sure to tell us where you're gardening, because all gardening is local. Find it all at gardenbasics.net.

GROWING WINTER TOMATOES IN THE HOBBY GREENHOUSE

Farmer Fred:

[25:28] Want to demonstrate to your friends what a great investment your greenhouse is, well, here's a little trick. Serve them homegrown tomatoes on New Year's Day. Now, here's what you'll need to do to grow greenhouse tomatoes for the winter. First of all, you need to choose the right tomato. For the typical hobby greenhouse, it might be 8x5 or 8x10 or 8x12, the cool season determinate tomatoes are the varieties that do best. They tend to be fairly compact plants that are under 4 feet tall. They don't put on lots of growth after they set fruit.

Farmer Fred:

[26:03] Determinant tomatoes usually ripen at the same time, so choose several tomatoes that will ripen at different times, going from seed to fruit, in 50 to 70 days. And to minimize any disease problems, choose tomatoes that have built-in disease resistance. They'll have letters like V, F, N, T, and A. 

V is for verticillium wilt resistance, F for fusarium resistance, N for nematode resistance, T, tobacco mosaic virus, and A, alternaria fungus resistance. And here's the expensive part. You're going to need a warm greenhouse. So whether you warm your greenhouse via electricity or gas, you're going to need to keep that greenhouse warm, even at night. To grow tomatoes in a greenhouse, you need to maintain a nighttime temperature range of 55 to 70 degrees, preferably above 60 degrees for tomatoes. Daytime temperatures should be in the 75 to 85 degree range. Tomatoes need light. Now, there isn't that much sun in the wintertime. It's kind of low in the horizon. So if you haven't installed a greenhouse yet, think about where it should be to get the best advantage of a low angle sun during the cold months. Make sure the building isn't shaded by any evergreen trees or other structures. You will need artificial light to aid the process. There are many artificial lighting systems available. We've talked in the past about LED systems.

Farmer Fred:

[27:29] Fluorescent lights are probably the most economical. You can use four 40-watt, 48-inch-long fluorescent tubes side-by-side, keeping them about 8 to 12 inches above the plant. Although standard shop lights are okay,

Farmer Fred:

[27:41] Investing in GroLux wide-spectrum fluorescent tubes will give your tomatoes more of the light spectrum that they can use. And you're going to find that same light spectrum in LED lights as well. The choice is yours. And, of course, you're going to be planting in the greenhouse soil. But there are issues with that. If you plant directly in the soil that's at the bottom of the greenhouse, that soil needs to drain readily. Make sure it's been amended with organic matter and it isn't compacted. Building raised beds into the floor of your greenhouse works best.

Farmer Fred:

[28:11] Make the sides of the raised beds about 8 to 16 inches high, at least 18 inches wide. The bed can be framed by a number of things, including untreated wood, blocks, bricks, or whatever your imagination tells you. You can even grow tomatoes in plastic 5-gallon pots, but larger works better, such as half-barrels. And if you don't want to spend money on half-barrels, a 10-gallon or a 15-gallon plastic pot does wonders. And another great container choice, if you'll excuse the plug, are SmartPots. These flexible fabric containers can grow anything you want in a greenhouse in the wintertime. Summertime, too. But fill it with the best potting soil you can find. There's a lot of good potting mix brands on the market. Ask around, do your homework before you buy a lot of potting soil. The ideal time to get your winter tomatoes started, actually, from seed, is late September.  Keep the seed beds evenly moist. Although the cooler temperatures of the fall and winter will cut down on the amount of water that tomatoes need, a drip system connected to a timer will ensure that the plants get the moisture they need.

Farmer Fred:

[29:20] Four to eight gallons of water per week per plant should be plenty. And plants, too, also tend to slow down their growth in the colder months. So cut your dosage of your favorite tomato fertilizer by half and maybe apply it once a month.

Farmer Fred:

[29:33] So how do you pollinate your tomato plants? Well, in nature, bees and the wind do most of the tomato pollination. In the greenhouse, you can accomplish that same task by either gently shaking or holding an old electric toothbrush (or any battery operated or rechargeable vibrating device) next to the plant, or twirling a small brush inside a tomato flower to transfer the pollen. And having a running fan is a great idea, because not only will it help the plants pollinate, it will also help develop a sturdier plant. 

Now here's the part they don't like to tell you about. The pests. Yes. In a greenhouse, white flies can be the toughest challenge. Monitor populations with yellow sticky traps. When you catch a few, take action. Maybe insecticidal soap or narrow-range oils are effective, as is a blast of water applied on a regular basis on all the leaf surfaces. And frankly, if one of those tomato plants is heavily infested with white flies, just get rid of the plant. Put it in the trash. Don't compost it. Put it in the trash.

Farmer Fred:

[30:29] All right, and here's why you tuned in. Which greenhouse tomato varieties are best for the colder months? There are several. Now, all of these are determinate varieties. They ripen between 54 and 66 days, 68 days. And the plant themselves don't get that big, maybe three, four feet, maybe five feet at the most. So some of my favorites that I've used over the years include Bush Early Girl, Bush Beefsteak, Oregon Spring Five, Polar Baby, Prairie Fire, Red Robin, Siletz, Subarctic Maxi, Tumbler, and 506 Bush. 506 Bush only gets 18 inches tall and they're pretty drought tolerant too, and they actually produce medium-sized tomatoes. And by the way, the tomatoes we're talking about may be at most 6-ounce tomatoes. Some might get up to 8 ounces but generally speaking, four to six ounces is the usual size for many of these tomatoes. Cherry tomatoes, of course, do well in a greenhouse in the wintertime. But remember, most cherry tomato plants are indeterminate, which means they will just fill your greenhouse with an (overwhelming) nice green jungle. I'll have a link to this information in today's show notes.

Farmer Fred

[31:52] Garden Basics with Farmer Fred.

Comes out every Friday. It's brought to you by SmartPots and Dave Wilson Nursery. Garden Basics, it's available wherever podcasts are handed out. For more information about the podcast, as well as an accurate transcript, visit our website, GardenBasics.net. And there you can find out about our newsletter, “Beyond the Garden Basics”. And thank you so much for listening and your support.