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- Greenhouse or polytunnel, which one's worth going for?
I'm giving you some ideas here in my garden.
There's both structures and we can compare
what they're doing now.
And I can give you a bit of history
and explain the different advantages
and benefits, or maybe disadvantages.
So in the greenhouse, for example,
you have a little bit more warmth at night.
We just had a run this spring of many frosty nights.
It's been frosty outside this morning.
And in here, the plants are not frozen.
It's just enough temperature difference to keep them going.
And that makes an impressive difference, actually.
We're just about to pick these salad plants.
We'll be picking them weekly now
for, this is about the 14th pick since late November.
This is late April to give you an idea.
You know, the value of that amount of protection to plants
can really keep them going for a long time
and give you a lot of return for your investment.
And the greenhouse is a big investment.
So this structure,
which is roughly three and a half metres wide,
eight metres long, because it's quite large,
it needed a concrete wall or concrete foundation for a wall.
So there is a wall here,
which the frame is sitting on, screwed down.
And it does make me a bit nervous actually in high wind,
it little moves around a little bit,
but the wall is very solid.
The concrete though does not go under the floor.
So we've got soil in here which is fantastic.
This is no dig with compost mulch,
and I just keep cropping.
So in the winter it's salad plants.
In the summer, it's tomatoes, aubergines and so on.
And the difference between the polytunnel
is that that you wouldn't have that permanent structure
and you wouldn't have the cost.
So just to get that wall built cost me over 2000 pounds
and then the structure itself here
costs just over 6,000 pounds.
And obviously you can get them a lot cheaper,
but I'm just giving you examples and ideas.
Whether you have wood or aluminium, for example.
I chose wood, partly because it looks really nice.
Aesthetics does make a difference,
but I do notice that the wood actually
keeps a bit of light out compared to aluminium,
which is why most commercial greenhouses are aluminium
and also aluminium doesn't rot or degrade,
it just lasts forever, I think.
Which kind of glass?
So this is toughened glass actually,
which I didn't necessarily want,
but the manufacturers advised it
and I'm really glad they did
because having that strength in the glass
helps to give the structure certain solidity
when it's moving a little bit in the wind.
Sometimes I wonder if it isn't the glass
that's kind of stopping it all falling apart.
So strong glass is good.
Are you going to heat it?
I think space heating is not really worthwhile
because you've only got one pane of glass
and then the heat is gone.
It's not double-glazed or anything.
That really doesn't seem to be worth it,
it'd be a big investment.
And you can get polycarbonate greenhouses
with sort of like bubble wrap effect.
And that works, it's really effective.
However, it's quite expensive as well.
So there's always that cost benefit analysis
you need to look at.
And here, I don't heat the space,
but what I do is I make a hotbed.
I'm off grid in here so I haven't got electricity.
That's another factor.
Are you going to have electric or not?
I mean, this video is more addressing for amateur gardeners
and electric though, I would say is worthwhile
in a propagating space if you want to raise plants
because you can provide that bit of extra warmth.
And it's very efficient way of using heat
because you can heat hundreds, thousands
of little seedlings with a small heated space
with bottom heat so that that heat is trapped
before it rises away.
So that's what my hot bed there is for.
And in the greenhouse it's also got
that little bit of added benefit
of nighttime temperature being a little bit higher.
Having said that I've got a thermometer there,
just on the doorframe and it was close to zero
last night and it was minus one outside.
So, you know, we're not talking huge differences
in temperature and in the winter here, it will freeze.
So, you know, I wouldn't try and grow tomatoes over winter,
so, in a structure like this in our climate.
You're mitigating the weather rather than
totally solving all weather problems.
One of the best things about structures like this,
both of them, is keeping off the wind and the lashing rain.
Wind in particular, actually, it can make
a huge difference, just having shelter from it.
So it's not all about temperature.
Then there's ventilation.
So I have these side windows,
which obviously increase the flow quite a bit.
They were optional in this greenhouse.
I could've had the greenhouse without them,
I'm really glad it did actually,
cause in warm weather, even now,
you know, generally ventilation is,
you need a decent amount of ventilation for plants.
And I've got the overhead roof vents,
which are on an automatic system.
So they open when the temperature goes above 25 centigrade
and that stops it getting too hot in the summer.
They don't open so much, even as, you know,
they're shot at the moment,
but we're warming up fast in here.
It was icy on the glass this morning
and already that's melted.
And it's just an hour since the sun rose.
So by comparison, we could now go and have a look
at the polytunnel and see what's going on in there.
(gentle music)
This polytunnel is five and a half metres wide,
13 metres long.
That's quite big for any structure in a garden.
This is a market garden,
so you can get much smaller polytunnels.
There's fantastic range of possibilities of size.
Have a browse through any catalogue or on online
and choose whatever is most suitable for you.
And maybe one thing to bear in mind
is if you go really long, like this is 42 feet,
you could get pockets of dead air in the middle.
And that's one big difference between polytunnel
and greenhouse, where you can't have the roof ventilation.
So that's where it would be worth considering side netting.
This one is polythene right to the base.
And I like that because in this climate it's quite windy
and particularly, this is actually
a higher value crop for me in the winter.
The winter salads than the tomatoes are in the summer,
for example, so it's two crops a year.
Make the most of your winters.
Both polytunnels and greenhouses give you fantastic options.
This does not keep the frost out.
So these salads freeze,
but they've been cropping since November.
Not much in winter, but plenty now.
And then it's very interesting to observe the differences
now compared to the greenhouse.
So we got lettuce for example, which Grenoble Red variety.
In spring I found quite noticeably stronger in colour here.
And that can be two things.
One is the cooler nights accentuates the colour
and also the extra light compared to the greenhouse.
More light makes more colour.
And in the greenhouse by contrast,
the paler leaves normally not quite so good growth
in the spring compared to the polytunnel.
But this year actually it's stronger in the greenhouse
'cause we've had so many frosty nights
and the panes of glass, the glass compared
to polythene keeping out the frost,
keeping the warmth in more has made more difference.
So there's all this slight differences
happening all the time.
These plants will come out in a month's time
we then will start cropping for summer.
So frost factor.
Don't transplant the summer crops too early in here
because it can freeze in here
even as late as middle of May
because of how the polythene in particular
doesn't keep the frost out very much.
Does a little bit in the spring
because the soil warms up more.
We got higher light levels.
And so the soil can hold warmth overnight.
It's like the radiator, long-term heat storage overnight.
And that effect you don't have in the winter
because you haven't got much sunlight.
So in the winter, actually,
it can be colder in here than outside
because you haven't got any air movement
and it's air movement outside that can stop
frost being too severe sometimes
because slightly warmer air above colder air
sinking to the ground, little bit of wind
or breeze can just mix the two
and stop it getting too cold.
Whereas in here you haven't got any air movement,
so don't be under any illusion, in the winter
it can get really cold overnight in a polytunnel.
In terms of ventilation,
there's no sense in which closing the doors
can keep the heat in.
It just doesn't work like that because the heat's
flying out all the time through polythene.
And like on a sunny day in the spring,
even this time of year, it's really warm,
the sun's out and the big black cloud comes over
and you lose that heat very quickly.
So it's, you know, it's come and go all the time.
It's better to have ventilation.
So with the doors, like the doors here,
I keep them open all winter actually.
I've hardly shut them this winter
because I want airflow for these salads.
I don't want them being blown around though.
So that's why I've got the bottom panels in.
It's one thing, actually, that surprises me
that manufacturers don't supply.
We've made them ourselves.
Because I find that you just don't want fast airflow
ground level over these little plants,
but you do want mix of air as much as possible.
With the polytunnel you haven't got
the possibility of roof ventilation.
That's one big difference, but you can, you know,
most of the time there is a bit of breeze.
And so for here, I find it works best
to keep the doors open even in winter,
unless it's blowing a really strong gale
and then I would shut them.
So keep your ventilation going.
Watering.
There are many options.
We have got automatic watering here.
I'm not convinced by it though, because, I mean,
this is sort of laws of physics really.
You got these circular patterns,
which is what, the only thing the water can,
that the system can generate
that needs to go into a rectangular space.
And that means wherever you got overlaps of circles,
you've got little bits in the middle
where there's maybe too much water.
And then you've got the bits around the corner
of each circle where there's not enough.
So whenever we use this,
which actually isn't very much,
we need to top up afterwards
with watering cans or the hose.
I actually prefer hand watering. I know it takes longer.
But you get benefits of just being there,
seeing what's going on
and more even and thorough final result.
But do consider that as an option
because, you know, in terms of saving time.
Drip irrigation. For these salads,
you need a lot of drip points for it quite close spacing.
So yeah, that's something to really think about.
With any structure like this,
whether greenhouse or polytunnel,
you're going to need to spend some time
and a bit of investment in watering.
The simplest is two watering cans.
And we do that a lot actually.
And in terms of heating.
In here, as I said, for the greenhouse
it's definitely not worth it.
It's about making the most of the sunshine.
And one way you can do that,
it's actually quite simple to get more sunlight in here.
Want light, is clean the polythene.
And last October we did that.
And so at least two people and we tied
two double sheets together, bed sheets.
And it was raining,
That's brilliant weather for doing it.
So you get out there in the rain
and one of you either side, you just pulling on the sheet,
it's up and down and you're walking slowly along.
And it was amazing difference.
It was quite a lot of green sort of algal mossy stuff.
You know, how does it stick to polythene?
I don't know, but it was.
And most of that came off
and then we finished off by hand.
And in here, actually we just use floor brooms, brushes.
Again, the polythene, see how now
there's condensation inside, there often is.
In October, between cropping the tomatoes
and planting the winter salads,
we just whizzed over the polythene with these brushes.
So combination of getting outside and inside,
you can see how clean it is now,
and that really makes a difference to light.
You know, light is so much a factor as well as temperature.
With greenhouse it's obviously just normal glass cleaning
actually is not as quick as doing this.
And I reckon to do that every autumn.
So particularly in winter, we really need that light.
In terms of cost difference.
This structure costs, to give you an idea, 2000 pounds
and the professional erection of it costs 2000 pounds.
So that's 4,000 pounds compared to the,
just over 9,000 for the greenhouse.
In my case, I'm just using these examples.
And the floor area, the space in here
is twice what's in the greenhouse.
So twice the area for half the price,
that's a four times difference.
Really, you know, if you're just looking
at it financially, that's so worthwhile.
But an option could be, for the greenhouse,
to reduce the cost, find a second hand one.
And they quite often are, they're knocking around
on the internet or wherever.
So have a look and you might get one that's suitable.
These, I think secondhand,
maybe not quite so worthwhile
because all the time design is improving.
And this one compared to the one I had before
is such an improvement.
It's got the lovely straight sides.
That's definitely something
to look out for in a polytunnel.
It used to be they were curving
right the way from the ground.
So you were losing height in your side bed
and convenience of access as well
when you're harvesting and that kind of thing.
And shape, strengths of structure.
These hoops are definitely stronger than my previous one.
And the thing about getting professionals to put it up
is that you will get a much stronger product in the end.
Because, I don't know, it's just what they do.
They will do it better.
This is the first time I've had a polytunnel erected for me.
Prior to that I'd done 30 years or more
of putting them up myself
and burying the polythene in trenches,
but getting as tight as I could.
I never got it as tight as this though.
You know, these guys know what they're doing.
And they reckon that this polythene
could last as long as 15 years.
We'll see. Surprised me, but you know, it's possible.
Whereas when you got the homemade more
and the polythene's a bit looser
and flipping around in wind
that slowly damages it and causes it to split.
You only need one reasonable size split
in a polythene sheet, and then it all blows out
and you've lost all that polythene, you've got to recover.
But I'll take 15 years for this.
And generally speaking, I would say,
if you're looking at value,
ease of construction and possibilities,
polytunnels hard to beat compared to the greenhouse.
But if you want,
perhaps just that extra difference in temperature.
Like for example, in here, in our climate,
I've struggled to grow such good aubergines
as I do in the greenhouse,
where that little bit of extra warmth by night,
makes such a difference.
So have fun weighing up all those factors.
And I've given you some ideas here
and good luck on your journey of growing under cover.
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