I talk to a lot of people about the 7 different family sized gardens that I’m trialing as
part of this RED Gardens Project. And I'm often asked which one is my favourite,
or which one I’ve had the most success with, and I always answer the Polytunnel Garden.
Each of the 7 gardens has a different fundamental approach, a main idea or philosophy upon which
everything else hangs. In the case of the Polytunnel Garden this
is simply to cover the entire 100m2 garden with a sheet of plastic stretched over a metal frame.
The main reason for doing this is to create
a warmer micro climate with more suitable growing conditions throughout the year.
This can be especially useful in Ireland as it keeps in the heat, but also keeps out the wind.
By doing this I can more successfully grow tomatoes, cucumbers, peppers, and other crops
that prefer more heat than is normally available in Ireland.
In this cool and windy maritime climate it is very difficult to reliably grow these crops outside,
even with the hardiest varieties.
But they are much more successful growing under a sheet of plastic.
If I was only growing vegetables for myself, I would fill a polytunnel full of heat loving
crops, and grow everything else outside. But within the context of this RED Gardens Project
I'm exploring the question: what if a family only had a polytunnel to grow in?
This means that I’m trying to grow a much
wider range of crops all year round. This includes the usual tomatoes, peppers,
cucumbers as well as all the crops that I grow in the outside gardens, including carrot,
parsnip, leeks, cauliflower, potatoes, lettuce and all of the rest.
I'm also trying to be able to harvest abundant crops from the garden over the winter months.
For this I have taken a lot of inspiration from Eliot Coleman, particularly from his
book Four-Season Harvest. He has pioneered a lot of simple methods for
producing crops throughout the winter in North Eastern United States.
Some of these methods work quite well here, but others don’t seem to be as appropriate,
with the warmer but less sunny winters that we have in Ireland.
In addition to a wider range of crops, covering the garden leads to higher yields.
This is partially because the warm season fruiting crops tend to be really high yielding,
but most of the other crops produce better as well.
It seems that all plants grow faster with more heat, within limits of course.
There is also less wind damage, and less damage by some pests, so more of the crop tends to be useable.
The extended season and faster maturing plants
means that more crops can be grown one after another on the same piece of ground.
I’m usually able to grow at least 3 crops in succession each season and sometimes 4.
It would be hard to grow more that two crops in the outside gardens
without some form of similar protection.
Given the cost and the environmental impact of the plastic and metal frame, as well as
all the effort it takes to put up and maintain this structure, it makes sense to try to get
as much out of this garden as I can. This naturally leads to a more intensive approach,
and in many ways the Polytunnel Garden is similar to the Intensive Garden,
though perhaps more extreme.
But, in trying to get more out as I can,
I have learned, often the hard way, that there's a few things that I need to manage really
well or things can go very badly.
Keeping the plants adequately fed has been one of my main struggles over the past few
seasons, especially with hungry crops like tomatoes that are in the ground for a long
period of time. The sandy loam soil in the gardens can’t
hold enough nutrients to feed so many plants for the full season.
I now add a fresh layer of compost before every crop, as well as extra fertility including
chicken manure, seaweed and soft rock phosphate. I have also started liquid feeding the growing
plants as well as foliar feeding on a regular basis.
It’s taken me a while to figure out how much fertility is enough, and how frequently
I need to top up, and I’ m still learning.
The issues of fertility seem to be compounded whenever there isn’t enough soil moisture,
as water stress seems to lead to nutrient stress.
Because of the higher temperatures and faster growth, this Polytunnel garden needs much
more soil moisture than the outside gardens do, but paradoxically, it can't benefit from
the abundance of rain that we get throughout the year.
The full garden under the plastic needs to be watered.
There are lots of methods that I could use for automated watering, but for the last few
years I have stuck with watering by hand. I fill up a few large tanks, which allows
the water to warm up, then use watering cans to water all of the beds.
I do this several times a week in the main part of the growing season.
This definitely increases the work load, but it does give me a chance to investigate all
of the crops within this enclosed garden.
Ventilation is another key issue, which involves balancing the desire to increase the heat
in the tunnel, while preventing it from getting too hot.
Dealing with high humidity is part of this, especially with the diverse range of crops
that I'm growing. I have come to prefer more ventilation rather
than more heat, especially with the ever changing weather in Ireland.
This means that the inside of the tunnel is often cooler than the heat loving crops would
prefer, but it does reduce the risk of the other crops suffering.
The plastic enclosing the polytunnel can both exacerbate and reduce pest issues.
On the one hand it makes it easier to keep out some animals and birds that can cause
damage in the vegetable garden. It also makes it easier to clear the garden
of slugs, which are by far the most damaging pests in Ireland.
But the enclosed space can be an ideal environment for greenflies and other aphids.
They have been big problem in the past, and I've been quite successful in attracting native
ladybird populations to help deal with them. But, I am intrigued that there haven’t been
many aphids or ladybirds in the polytunnel this season.
I'm not sure if this is just seasonal variation, or weather conditions compounded by some other
factor, or if it’s just simply that the plants are generally healthier.
But what is the result of all of this? More heat, lots of fertility, faster maturing
crops, and less wind damage, all of this leads to a much higher yields.
Last season I harvested almost 800kg of a wide range of vegetable out of this Polytunnel
Garden, and it looks like it could increase to 1000kg this season.
That is a lot of food. It's more than enough to supply most families
with vegetables throughout the year, and about double what I’ve been able to get from the
gardens outside. In my opinion, this more than justifies the
financial and ecological cost of the plastic and metal frame especially because it has
been up for 7 years, and counting. But it is a lot of work, it takes about twice
the amount of time to manage as it does to manage the outside gardens.
A fair amount of this is simply because of the hand watering, but most of it is due to
the fact that there is a lot more to plant, care for and harvest.
I am very pleased with how this garden is developing, but there are a few key things
that I would probably change. I'm planning to take what I have learned from
the Intensive Garden and start double digging the beds in the Polytunnel, incorporating
more compost deeper into the soil. I think it is also time to use a different
method for watering, probably a combination of drip line and sprinkler systems.
This could include catching rainwater off of the polytunnel, for use in addition to
the municipal supply. I’m also going to explore covering the entrances
with mesh or netting, to keep out some birds and insects that have become pests.
All of these should help to make the garden more resilient, and probably save some time,
but hopefully without making things more complicated.
So, the Polytunnel Garden produces a lot more than the other gardens, and generally better
quality vegetables, in appearance at least. I also get crops like cucumbers and tomatoes
which are difficult to grow outside, and it's much easier to produce fresh vegetables all year round.
These are the main reasons why the Polytunnel Garden
is my favourite garden, despite the extra work.
But, if I'm honest, it's also the garden that I enjoy spending the most time in.
I like the heat in the summer, and I appreciate the shelter from the wind and rain through
most of the year. I like being here, and I think that makes
a big difference in how successful a garden will be.
This Polytunnel Garden is one part of the RED Gardens Project, which is focused on helping
people grow more food for themselves and others. This project has been unfunded up until now,
apart from the sale of surplus vegetables to neighbours.
I’ve now started a Patreon account to help fund the production of these videos, and all
of my work in the gardens. If you would like to see a lot more videos like this and to
support the further development of this project, please consider becoming a patron.
You can do this by pledging a small amount for each video that I make in the future.
If you would like to support me, please follow the link here or in the description below.
I want to thank those generous people who have already taken the leap to become patrons,
and thank everyone for watching.