The Polyculture Garden has been a fascinating garden to grow in, especially compared to the
other 5 family scale gardens which form a key part of this RED Gardens Project.
It is the garden with the least amount of advice that I can follow,
as not a lot of people have tried growing in this way, especially in this climate.
So there is a lot to learn and explore and many opportunities to fail.
This Polyculture Garden is the one that I’ve struggled the most with, though we are becoming
more successful in the past two years since we switched to a clustered form of planting.
And a big part of this planning and management strategy is to determine
the number of plants of each type of vegetable that is appropriate to grow within a cluster.
As there are so many potential complex interactions within a polycrop bed,
as well as staggered timing of growth, seasonal variations,
and changes in the size of the plants we might want to harvest, figuring out appropriate
plant densities for each of the different clusters is not a straightforward task.
This Polyculture Garden has aspects of intercropping and companion planting,
in that it tries to take advantage of potential benefits to plant health,
pest control and increased yield, by integrating different crops rather than segregating them.
It is trying to be the opposite of monocropping, and the method I had originally tried for this
garden had involved the broadcast sowing of a wide range of different crops in a bed.
This required a lot of harvesting to clear space for other plants to be transplanted in,
which I struggled to keep up with, and often ended up with too many plants competing for the soil
fertility and the space below and above ground. A lot of this was because I was not able to
give this garden the amount of attention that it needed.
In many ways this random polyculture planting was at odds with my brain’s
preference for order and control, and it also made it difficult to compare with the other gardens.
So I decided to divide each bed up into sections, or overlaying a grid in ways
that are similar to a square foot garden. And in each grid I would plant a single
larger plant, or a cluster of smaller plants of the same type,
and to arrange all of the clusters in a bed so that similar plants were not in adjacent clusters.
This has been a very useful way to apply a beneficial amount of structure and order,
while still hopefully getting a lot of the potential benefits of
the more complex intercropping, as well as some of the problems.
When switching to a grid based planting structure, the first main decision was what
size to make each grid, and I felt that the square foot size would be too small for some
of the main plants that I wanted to grow. I use a variety of different spacings for
the larger brassica plants in the other gardens, but they generally translate
to 5 plants per square meter or less, or at least 2 square feet per plant.
The beds in this garden are about 1.2m wide by 10m long, and I decided to divide
the beds in 3 across the width and 20 along the length, this would give a grid or space
size of about 40 by 50 centimetres or 16 by 20 inches, or about 2 square foot each.
This would produce 60 grid spaces on each of the 6 beds, with 5 spaces per square meter,
which roughly matches the minimum spacing I would want to give a lot of the larger brassica plants.
I have found that transplanting one cabbage, a kale, cauliflower or a broccoli plant into each
cluster has worked out quite well, but this depended on timing and the varieties we grew.
With early season calabrese broccoli and cauliflower plants, the large leaves tended
to squeeze out or overshadow the plants in some of the neighbouring clusters,
but after the brassica plants were harvested the other plants had a lot more space to grow into.
Some of the longer season brassicas plants often ended up growing quite big,
and occasionally leaning over too far if they were not supported, making it difficult to grow
anything in the adjacent overshadowed clusters. Potatoes are the other key crop, and in the other
gardens we would generally plant potatoes at a spacing that translates to between 3.5 and
7.5 plants per square meter, so an equivalent of 5 plants per square meter theoretically works well.
And depending on the types of plants in the adjacent clusters,
and when they were planted and harvested, a lot of the potato plants in the Polyculture Garden
produced a larger crop of bigger potatoes than the same plants in the other gardens.
The squash and the courgette or zucchini plants are the only two crops that we grow
that need a lot more space than one cluster. We have been transplanting these plants into
the middle of one cluster, with the aim of leaving 4 of the adjacent clusters clear
of other crops so that these these large and vining plants had space to grow into.
But I also want to grow fast growing early season crops in these neighbouring clusters,
as a type of relay intercropping, and this hasn’t work so well for the courgette or squash plants,
partially because we didn’t harvest and clear these early crops out in time.
I also think there was an issue with the roots of the newly transplanted courgette and squash
plants having to compete with the roots of the established plants, and it took longer for these
transplants to start growing well compared to the same plants in the other gardens.
Digging to cut back the roots of some of these established plants would probably give the
transplants a better chance, and providing more fertility would probably help as well.
The courgette plants eventually started to become more established,
but the squash plants still had to compete with the strong kale and purple sprouting broccoli
plants that we had planted in the same bed. We probably should have planted fewer of these
heavy feeding and overshadowing plants in the bed with the squash, or even transplanting them later
to give the squash plants a better start. And the runner beans that were also growing
in the same bed would have also caused a lot of overshadowing, even if they
weren’t competing as much for fertility. And with the cool summers that we get
here in Ireland, these heat loving squash plants need as much sun as they can get.
Because of the overshadowing, and the competition, each squash plant in the
polyculture bed produced less than one third of what the same plants in the other gardens
were able to produce in the same season. Perhaps I need to accept that squash
is never going to grow well in this kind of Polyculture Garden, at least here in Ireland,
and accept it is just a small additional crop that we can get from the bed.
But if we really want to get a larger squash crop we probably need to set aside more clusters for
each squash plant, to reduce the density of plants in the bed, include fewer aggressive companions,
or clear the surrounding clusters a lot earlier, perhaps all three.
With most of the other types of vegetable plants, we sowed or transplanted several plants into each
cluster, ranging from two or three chard plants, up to too many direct sown radishes to count.
To determine an appropriate number per cluster for each type of plant, I figured out the typical
density or number of the same plants per square meter in the other gardens, and divided this by
5 to figure out how many plants I should grow in each grid or cluster of the Polyculture Garden
that are 1/5th of a square meter each. For example we would grow garlic in the
Intensive Garden at a close spacing of 15cm apart in rows 20cm, apart producing a density
of about 33 plants per square meter of bed, which translates to between 6 and 7 plants per cluster.
In the No-Dig Garden and in the Polytunnel Garden we spaced the plants or rows a bit
farther apart for a plant density of about 27 to 30 plants per square meter, which translates
to between 5 and 6 plants per cluster. And the Extensive Garden has a significantly
lower density of about 18 plants per square meter, which would limit it to between 3 and
4 plants per cluster in the Polytunnel Garden if we used a similar density.
We ended up growing 5 plants per cluster, but I think 6 would also be appropriate,
especially as many of the adjacent clusters ended up being empty for a lot of the winter.
With the lack of competition for these overwintering garlic, we could grow
more garlic plants, or the smaller number would generally grow bigger, which is also beneficial.
With many of the other crops I did the same kind of calculation, figuring out a typical
number of plants per square meter that we grow these types of vegetables in the other gardens,
and dividing it by five, to get a rough number of plants for each Polyculture cluster.
So we generally plant 2 chard plants in a cluster, grow 3 broad bean or kohlrabi plants,
5 bush bean or leak plants, and six beetroot, onions or lettuce plants in a cluster.
But this often depends on how big we want the plants to grow,
or if we plan to harvest some of the plants from a cluster when they are partially mature,
to make more space for the remaining plants.
This method of figuring out how many plants to grow in a cluster is useful
for the medium size plants, especially for the ones that are transplanted into the garden bed.
For a range of other crops that we generally direct sow at higher densities
we tend to use even more approximate figures. Crops like carrots are generally direct sown in
rows in the other gardens, where it is relatively easy to sow the seeds at an appropriate spacing,
or to thin the seedlings to get a suitable spacing between the plants.
And it is relatively easy to translate this to approximate plant densities.
For example, if carrots are thinned so that they are about 2.5cm apart, in rows 30cm apart,
this would translate to about 130 plants in a square meter, and divided by five, would equate
to approximately 25 plants in a cluster. We could sow a couple of short rows in
each cluster of the Polyculture Garden and thin the carrot seedlings in the same way,
but I prefer to sprinkle the seeds over the central section of the cluster.
But then when thinning I don’t really want to be counting out 25 seedlings in each cluster,
so generally I just estimate and clear enough plants so that there are
between 20 and 30 plants in a cluster, roughly evenly spaced from each other.
When we direct sow crops like pak choi, we often sow considerably more
seeds than would grow to full size. When the seedlings grow big enough
to cover most of the soil, we cut out some of the seedlings as an edible early crop,
and leave between 8 and 12 plants, depending on how crowded the adjacent clusters are.
And then when the plants fill out the cluster again, we would harvest a second thinning,
leaving 5 or 6 plants to grow if there is the space around that cluster.
Or at least that is the plan, and we often don’t get around to thinning in time, and the plants can
get too crowded, and can end up struggling and even impacting the plants in adjacent clusters.
With a lot of the fast growing salad leaves that we usually grow as a cut-and-come-again
crop, the strategy is similar, where we broadcast sow the seeds in each cluster.
Depending on how many seeds we sowed, and the success of germination, there could be too many
plants or not enough, with large gaps in the cluster, which isn’t necessarily a problem,
but we try to adjust the timing of the first cut depending on the density of what germinates.
If there seems to be too many plants in the cluster or if it is crowded by
crops in adjacent clusters, we try to cut the first harvest when the leaves are quite small.
And after cutting it is easier to thin out some of the more congested areas of the plants,
so that there can be more rapid growth for the next cutting.
Or if germination was lower and there is more space around the cluster,
we will get a better yield if we leave the plants to grow larger leaves before harvesting.
This also depends on how quickly we want to clear the cluster to plant another crop,
or to make space for the squash or courgette plants to grow into.
If these types of fast growing crops are growing before another main crop, it should
be possible to adjust the number of seeds sown in each cluster so that we can we can get a
cutting or two of smaller or larger leaves, depending on how many days are available.
But this also changes depending on the season, and how quickly everything is growing,
and planning around these types of variables is more difficult than the usual strategy
in the other gardens of planting a crop at a particular time of the year at standard densities.
We can adjust the density of a lot of the crops in order to impact the size that the plants will
grow to, depending on what we want to harvest. Part of this is the amount of space that the
plants actually take up above ground, which of course is fairly easy to see,
but it also depends on the availability of water and fertility, as well as the amount
of space for the root system underground. The more plants there are in a garden bed,
and the bigger they are, the more water they will pull out of the soil.
I have noticed the soil of this polyculture garden drying out faster than in the other gardens,
even when the soil surface was covered enough to drastically reduce evaporation.
The higher density of plants increased the risk of all the plants suffering when we
were not keeping up with enough watering, and it is essentially the same with fertility.
If there is a higher level of nutrients available to the plant roots in the soil,
then more plants can be supported, providing that the fertility can last the full growing
cycle, or we regularly top it up. All of this is common to all of the
gardens, but I think it’s probably more important in the Polyculture Garden.
The recommended spacing or densities of a crop are generally based on monocropping,
with each plant only needing to compete with similar plants.
But in a polycrop planting, or in a small garden where different crops are growing close together,
some plants will likely also have to compete with the roots of other plants
that might be more aggressive, or better at extracting soil moisture and fertility.
And many of the root systems can occupy an area or volume of the soil that is much bigger than
the size of the plant above ground, potentially impacting other crops in quite a few clusters.
So it is not just the density of the plants in a particular cluster that we need to consider,
but the density of the full bed and the different
requirements of different plants at different times of the year.
In ways this Polyculture Garden probably works better for those of us who want a more informal
or relaxed approach, where we are content with simply growing a wide range of things
and harvesting whatever grows well enough. For those of us who are trying to get more out
of a garden, or to get certain quality of crops or a reliable harvest, a polyculture approach
can make it harder, even if the overall yields from the same area can be bigger.
I think it really depends on the amount of resources we can provide, including water,
nutrients and our attention. And I think this was one of the
big mistakes that I’ve made with this garden. Looking back, I should have started with fewer
plants overall, and then only gradually increased the density as I became more confident about
being able to provide the amount nutrients, water and attention that would be needed.
As we gradually improve the soil fertility, including getting better at providing additional
feeding during the growing season, and we are using better watering infrastructure to maintain
appropriate soil moisture, the denser plantings in this garden are becoming more successful.
This also applies to all the gardens, but in the Polyculture Garden there is
the added complexities of the interactions of all the different crops that share the bed.
And it’s a lot more than just how crowded the beds looks above ground.
In the other gardens it is easier to rely on numbers or data to determine
the appropriate plant densities. In the Polyculture Garden,
the numbers and data help, but with so many other things going on, figuring out
appropriate plant densities for a particular cluster is much more of an intuitive process.
And that is taking a while to accept and to understand how to work with.