EP324 What To Fill My Raised Beds With & Lawn Care Advice Listener Question Answered.

You can spend a fortune on compost, seed, and clever gear and still end up with tired raised beds and a mossy lawn if you get the basics wrong at the start. We’re answering two listener questions that keep popping up because they sound simple, but the wrong advice can cost you seasons of progress.

First up, raised beds in a polytunnel or greenhouse. We dig into the big mistake of putting ground cover fabric or plastic membranes under your growing media. I explain why that layer cuts your beds off from native soil life, why that matters for long term soil health, and what to do instead. We keep it practical: cardboard, quality compost, steady moisture, and keeping beds planted or mulched so the soil food web stays alive. If you’ve already lined beds with plastic, we talk through realistic options to reopen access and start rebuilding.

Then we switch to a problem nearly everyone sees after a long wet winter: moss in lawns. We break down the most effective lawn care approach for heavy moss, including scarifying, debris removal, top dressing, and reseeding or overseeding. We also compare slower bacterial treatments, the quick blackening effect of iron sulphate, and why raking is essential. Finally, we touch on how robot mowers can help reduce moss by encouraging thicker grass growth.

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Transcript

Welcome And Spring Weather Check

SPEAKER_00 0:12

How's it going everybody and welcome to episode 324 of Master Regarden Podcast. Now, this week's episode is covering a couple of listeners' questions, and one of them is a question that keeps coming up time after time, and it's a surprising question, actually, that it keeps coming up. But it's one that seems to be seems to be stumping people. Um and they definitely seem to be getting wrong advice as well. So come to that one in a second. Um the weather has eventually started to warm up quite a bit here after a very, very cold start to the week. We've had some lovely warm and growthy days. And yeah, we're definitely looking for you know some sort of steady, warm weather as we move through April because growth growth has been slow so far. You know, you couldn't in most areas you wouldn't sow seeds outside yet. It's still too cold. Still, in a lot of cases, the ground is too wet. But we're definitely getting to the point where you know we can we can get going. It has been a kind of a stop-start spring in a lot of cold weather, a lot of wet weather, and ground is generally a little bit wet still. So, but when you get to this time of the year and you do get warmth, you get a little bit of sunshine, a little bit of wind, things dry up really, really quickly, and we can get going. I know a lot of people have you know potatoes in the ground and they have a good bit done, but generally speaking, outside it's cold, you know, there's not there's not any great warmth or kindness in the in the soil yet, so we're still waiting for that kind of prolonged, you know, that ten days that I talk about where you get you know kind of ten, twelve, fourteen degrees for ten days, then we kind of go. And hopefully we're gonna get that. Looking ahead, it's warm enough for the next few days, and then a smaller, a little bit of a small cold snap, but again, beyond that, it looks kind of warm again. So fingers crossed we're we're getting to the point where we can get up and running.

Raised Beds In Tunnels Question

SPEAKER_00 2:20

So listener's question, and this first question is a is a question that I answered I answered about a month ago um by a direct message on Instagram, but also there was a follow-on email to that and from the same listener. And on top of that, then over the course of the couple of Grow Your Own Food workshops this spring, it was a repeat question that came up on multiple occasions. So it's it's one that kind of people don't are a little bit unsure on. And it relates to raised beds, particularly raised beds in a polytunnel or a greenhouse. And the first listener basically what had happened was they had bought their polytunnel, they had gone to their local garden centre to get the growing media to fill the raised beds with, and they were advised to put down ground cover fabric and then put the put the growing media in on top of that. And the question was asked in relation to soil health and you know whether that was a good thing to do or the wrong thing to do. And definitely for me, it's the wrong thing to do. So in a raised bed, what you typically have, you know, depending on the level or the height that you're going to come up, but most people work with kind of lifts or boards of kind of nine nine inches uh or thereabouts, 20 20 centimetres or thereabouts. And you know, even with one one lift of 20 centimetres, let's say, you're going to

Why Plastic Fabric Hurts Soil

SPEAKER_00 4:10

you're going to have a good bit of of growing media on top of you know whatever is there, your grasses and so on. I would be using cardboard as opposed to as opposed to you know uh ground cover fabric. Um I don't I don't know what the thinking of. So this was a recommendation from a garden centre. I'm not sure what the thinking was in terms of using the ground cover fabric. Um, you know, in a in a position like that, it doesn't have a huge it doesn't have any any benefits really. So what what you do is you put down your your cardboard, and that cardboard blocks out any grasses or any weeds that are there. I would take out any noxious weeds initially, you know, if there's something like metals or something along those lines, I would dig those out, but out from that, I wouldn't be looking looking to put down something as heavy as a ground cover fabric. Number one, there's no need there's no need for it. Um but the biggest reason for me is that when and anyone that listens to the podcast for a long time, what we're trying to do as much as possible in raised beds is we're trying to replicate and introduce the native soil life that's there, improve the soil life that's there, improve the soil health that's there, because when that is improved, when that is you know working as it should, then everything up on top is much better. And when you put down a you know a heavy uh plastic-based ground cover underneath your growing media, you're basically isolating what's on top. Now it is difficult in a polytunnal situation or a greenhouse situation to maintain healthy soil life at times because obviously you get a lot of heat in there, you can get a lot of drying in there, and both of those things both of those things can be detrimental to soil life. So you're trying to always maintain moisture, maintain um maintain moisture particularly in that top layer, and that can be difficult. But the one thing we don't want to do is we don't want to start by isolating it from the native soil and with um you know plastic ground cover, that's what you're gonna do. So by putting that down, you don't really get the the soil life moving up and down, you don't really get now earthworms are not you don't get a lot of them in tunnels anyway. You certainly don't get them up high in tunnels uh because the the temperatures, the soil temperature tends to be a little bit too warm for them. They will be there, but they'll be maybe a little bit deeper, or they'll be sort of under under plants or under the the the shade of plants, so you get them in areas like that. But when you have raised beds particularly, it can take it can be difficult to get them up in it, and it can definitely be difficult to keep them in it. But having said that, if you have a layer of plastic, you're not getting them in there anyway. So definitely for that listener to now they had gone up a couple of boards, maybe two, possibly three, and you know the challenge then is the beds are already filled. Do you remove do you remove the all the growing media that you've put in there and then try and remove that you know that plastic membrane or that ground cover

What If Beds Are Already Lined

SPEAKER_00 7:45

membrane afterwards and then refill it, which is quite a lot of work. Um I think ideally you would try that. If you couldn't do that, I would certainly dig down and cut out squares, you know, so that you're able to open access at least at certain points. Um that would be helpful. The biggest thing going forward though is to make sure that the moisture in those in those raised beds always maintains, you know, at a reasonable level. Um I would continue to mulch down even with you know, even with live clippings, you know, with um grass clippings off the lawn, just small amounts to keep feeding once you get that side life in there to keep feeding it. And because what a lot of people find is they they get their growing media, they fill their raised bed, they get really successful for year one and year two, and then you start to see it deteriorating and the soil gets depleted, or the growing media gets depleted, and people often in year two, year three, year four will refer to things that are not growing nearly as well as the wearable. What's happened is the soil life has just died, and what you're looking to do is reinvigorate that and try and keep it alive, you know, mimic the outside as much as possible, and that's what you're trying to do. So if you're in that position where you have your polytunnel, your greenhouse, whatever the case may be, and you're setting it up as I know a lot of people are at the moment, you're putting in your raised beds, and you're wondering, you know, what should I do with you know under under these raised beds? Definitely the maximum you need to do is put cardboard down. So do not put you know ground cover, do not put plastic membranes. There is no need for it, number one, you're wasting your wasting your time, you're wasting your money, but also it's detrimental to the to the side life. You're not going to get that native side life up into the beds, which is what you want, because you want that soil life to create a healthy soil, which in turn creates the healthy plants up

Keeping Moisture And Soil Life

SPEAKER_00 9:55

on top. So you put down your cardboard, you put in your your growing media, typically you're talking about something like a good quality compost. Um you know, that's you know, that's what you're looking for. You're looking to keep that moisture, you're looking to keep plant cover on it as much as possible. So, you know, if you decide that you're putting in your potatoes into this raised bed, they'll be coming out, you know, within a polytiline situation in at this stage of your planting now, you know, kind of end of June, but you want to have something ready to go in there straight away. You want to always have plant cover on that bed and then ensure that it doesn't it doesn't dry out. It's something you know, something tricky because I've been guilty of that myself. You know, it does if you have you know certain crops in certain beds, you'll tend to tend to them. But if there's a couple of beds where you don't, you know, are not in use at that time, you do you do forget about them. And you just need to, but you do need to rejuvenate them. But if you have put a plastic layer there, it's very, very difficult to get them going again. Once that soil life is dead, once that soil itself is is dead, it's very, very difficult to reinvigorate it and to restart it. It is possible, but it's quite difficult. So to answer this listener's question and l yeah listen questions that have come up all over the spring, if you are putting raised beds inside inside in a polytunnel or a greenhouse, there is no need to put a ground cover fabric down initially. What you're looking for is you're looking for cardboard that would do the same purpose, which is to sub to to block out the sunlight to the block out the light to the grass or whatever it is that's there, and then you layer it down heavily in the first year with your growing media. And yeah, it it you the height then, how high do you go with those raised bed, that really depends on yourself. It's it's for me it's a it's a you're thinking so

Raised Bed Height And Alternatives

SPEAKER_00 12:00

if you are somebody who has potentially you know a bad back or mobility issues of any sort, then I would come up as high as possible with that raised bed because it will make your life easier, it'll make it easier to garden, you're not going to be stooped down as low. If you don't have, then I don't you know there's no great need for raised beds if you don't have, you know, if you don't have mobility issues, grow on the ground. It you'll have the exact same space, you can it's a lot easier to maintain them, they don't dry out as easily. So it's just depends on your situation, depends on you know where you're at. Um but raised beds are brilliant, they'll grow great crops, they just take a little bit more mining, and they're ideal if you do have a sore back or you have you know problems with your back or mobility issues or anything like that. Out from that, then ground beds are as good are as good, you know. There's no there's no downside to having ground beds, um, especially if you're fit and healthy and and uh able to work at that lower level. So that's that

Why Moss Takes Over Lawns

SPEAKER_00 13:05

question. The second question that has come in and it's one that I know huge amount of people will be will be looking at, will be struggling with, and it is moss in lawns. And yeah, it's after been as we've said a very, very, very wet sort of six months here in Ireland. And if you're maintaining a lawn and you have been keeping keeping it, you know, the grass cut short, inevitably with the level of wet that we've had, you will start to see uh moss building up. And there's a few a few ways you can deal with it. It's you know it's a much debated topic at the moment is the main maintenance of lawns and you know the application of of things to lawn. But there's some there's a lot of people that absolutely love their lawns they love the the stripy cuts, they love the the fresh, clean cut look on it. And you know, if that's what they love and that that's what they want to maintain, then you know that's that's their choice. Um what you can do, so number one depends on the level of moss that's in the lawn. That's that's kind of a critical point in terms of what you would do, or your level, your the the sort of method of approach. Um

Scarifying For A Fresh Lawn

SPEAKER_00 14:30

so number one option is to scarify. Scarifiers are basically a machine that is used to essentially ruffle up the the surface of the lawn, and they can be got in most higher centres. They're quite small in terms of width, so they might only be like 30 or 35 maximum 40 centimetres in width. So they're not going to be very wide, meaning that it will take a little bit of time to do this, but they're highly effective. So what they do is they go in and they scratch up the surface, they basically pull up all that moss, and that's dead grass that sits underneath the green that you see, and it kind of mats up, and when that mats up, it sort of prevents new grass coming up and encourages things like moss or weeds to push up. So the fresher and the the stronger your grass is grown, the less vulnerability to things like moss. So basically, this machine starts off, it ruffles up the surface, pulls up that moss, and it leaves it sitting. Now some of them come with a little bag. Um you probably won't use the bag because, to be honest, you won't get five metres down the lawn and you'll be emptying it again. So, what most people do is they will scarify, scratch up the surface, leave the bag off so that the this thatch and this moss just sit on the top of the ground. Then they'll come along with the right-on lawnmower at a higher setting, and they'll pick up all that grass or their ordinary lawnmower, whatever the case may be, and they'll pick up all that moss and they'll take it away to their compost heap or whatever. Um in that process it depends on so your next step kind of depends on the level of moss. But most lawns at the moment, or patches of lawns at the moment are have moss levels of 50%, where the grass is 50% and the moss is 50%. And in a scenario like that, you you if you want to maintain a really fresh, vibrant looking lawn, then you're going to have to do a little bit of reseeding. So the process is with in this method, you scarify, you take away that moss, then if you need to, you would apply a little bit of a compost or a or a soil, basically something that you just shake along the surface, a very, very light covering, and then you seed down on top of it and you roll it in and water it if it needs, you know, if it's not uh if there's not rain within the next day or two. And that process basically completely rejuvenates and you get a real fresh flush of growth, and now your your your green vibrant lawn is back. So that's

Bacterial Treatments And Temperature Limits

SPEAKER_00 17:20

process one for getting rid of moss. Other options include there are bacterial-based treatments out there, there you know there's several several names of them out there. They're they're a very good essentially they're a bacteria that will eat, thatch, and eat the moss that's that's there. Um it's a very, very slow process, so if you have moss in a lawn and you treat it, you won't notice any change within a week, even two weeks, and it's a very, very gradual reduction of the level of moss within the lawn. And that's something that you know that's something that you will you will notice, but it will take maybe three weeks, four weeks, five weeks to notice it. The the challenge with those is you need to start with a percentage moss that isn't greater than 30%. If it's more than 30%, then you either need to multiple apply it on multiple occasions or you need to do something like scarification first, because the level of bacteria in it is just not enough to take out a moss level that's above 30%. So they're brilliant products if you're starting with MOSS levels below 30%. Again, once you have, if you are starting below 30% and you have applied it and it has worked, again, another critical factor is is temperature. So temperatures will need to be 12-14 degrees. It the the bacteria in that just doesn't activate, doesn't work below that temperature. So if you apply it, it won't die, it but it will not activate, will not get going until the temperatures are higher. So that product, those products are really effective. But if you have 30% moss and you apply it, then in a in a couple of weeks' time you will need to you know do your reseeding or your overseeding

Iron Sulphate And The Raking Trap

SPEAKER_00 19:20

again, and and that's a really good way of reducing moss. Um another way is by using something like a sulfate of iron. Now, this is a different process again. So sulfate of iron is is essentially a product that's going to turn the moss black and turn the moss black very, very quickly. So you apply it, your moss will go black, your moss will die out, then you can rake out your moss, but you do have to rake it. That's the the beauty of the the bacterial system is that you don't have any raking, but with this one you'll have to rake or scarify. Um so it's another you know, it's another step that you will need to do. It in terms of effect though, you know, if you're starting at sort of 50% and you apply it, you will notice the very next day you will notice a blackening of the moss, you will notice the moss dying off, but it does have to be raked out. If you don't rake it out, what ends up happening is it actually comes back in another layer below the layer that you have just killed, and it'll come back much, much stronger. So yeah, for me, scarification is the best option. It's a little bit slow on one on the one day, but it does give you a much better it gives you a much better I suppose removal of the moss if that's your your aim, but it also gives you a very, very good sort of bed to bed in your new seed into, and very, very quickly you can end up with you know uh your lush looking lawn again.

Robot Mowers For Moss Prevention

SPEAKER_00 20:55

For anyone that is considering or looking at the likes of uh robot mowers, they're proven really effective at reducing the levels of moss in lawns, so this constant very, very light clipping of the lawn that is you know a major tool in in keeping the law healthy so it keeps growing vibrantly green. You are feeding it on a regular basis with that little little clipping of the lawn, but also keeping it tight makes the grass tiller, which is essentially means that the grass, instead of the grass pushing upwards, it pushes sideways, it tillers into the ground, and that blocks out any moss coming. So anyone that is using the robotic lawnmowers, they're finding very, very little you know, moss in their lawns and much healthier lawns generally. So that's another another option, you know, to go. But I know some people love their lawns. The person that asked me this question absolutely loves their lawn. They love going out and mowing it, they love the stripes on it and so on. But they have quite a lot of moss after a very, very wet period of time. So for me, scarification is the best option, but you do have other options as well. But scarification, while it takes a little bit of time on day one when you do it, it does it's bet more successful at removing it, and then it leaves a lovely bed for you to do a reseeding job or an over-seeding job onto that bed, onto that uh lawn. So that's probably the best option. So that's the two listeners' questions. Uh something else I just wanted

Medicinal Herb Workshop With Laura Darcy

SPEAKER_00 22:31

to talk about. There's only just five spaces left now in the workshop with Laura Darcy. So basically, this is a grow your own medicinal herb workshop. And it's sort of a different take on the workshops that I did in the springtime. So they're grow your own food, they're just myself. But now I'm bringing in the expertise of Laura Darcy, Yarlane Herbs, who's a community herbalist, so she does herbal commun um consultations, she's runs courses, so she teaches people how to firstly they're her initial one, how to basically become used to using medicinal herbs for everyday, you know, for everyday aches and pains, colds and flus and so on, all the normal ailments that you would have as a family. She has a sort of a beginner's course that takes you through those. Then she has an advanced one that is for people who kind of want to get into the world of herbal medicine or want to become, you know, a a herbalist themselves, and she has those courses coming up. But she is a fantastic she's a fantastic herbalist, she's very good plants person, loves talking about plants, um spotting plants, using plants in different ways, and you know it's a nice way to combine this workshop. So I'm going to look after the growing part of it. Laura's going to look after the the medicinal side of it. So we're talking about ten common herbs. We're going to create a garden with those, or a little herb garden with those. Um, but we're also going to look at all of the you know the the other plants that you would see in your garden. Some of these we gardeners consider weeds, but they're highly useful functional medicinal plants. And so on the on the list of ten, we're looking at things like chamomile, peppermint, lemon balm, canangela, thyme, sage, yarrow, uh, rosemary, echinacea, oregana. So we're looking at all of those type. So flowers, herbs, and we'll be looking at medicinal uses for those. So just five spaces left. It's on Saturday, the 18th of April, and it's from ten in the morning until three in the afternoon. And it's yeah, it's it's always tends to be a nice day, and yeah, it's an interesting one and a sort of a different a different sort of angle where we're bringing together my growing expertise and Laura's herbal expertise, and you know, it you'll be able to look at all these everyday herbs and know how to use them from a medicinal perspective to you know keep yourself um for for all the normal things like colds and flus and bumps and bruises and lip bams and whatever. So we'll make different things, things like cam mile tea. On the day, all those all those uh uses will be discussed, how to utilize these herbs. So five spaces, uh link is in the bio, or link is in the show notes, link is on my website, and all those usual places, but five only five spaces left. So if you're interested in

Final Notes And Sign Off

SPEAKER_00 25:55

going to that, uh get that book and done now. Uh, we'll be getting back in the next week or two to the open garden features and yes, some other interesting episodes coming up and guest interviews as well. But for now, that's been this week's episode. Thanks for listening, and I'll tell you next time. Happy gardening, I'm gonna go to the next one.