I have become more of a fan of the diverse range of different types of brassicas that we
can grow in the gardens here in Ireland. And the long season brassica plants,
including kale, Brussels sprouts and sprouting broccoli, have a prominent place within the
family scale gardens, especially at this time of year where there is very little else available
for harvesting or even still growing. I use to struggle with these plants,
which seemed to attract a lot of pests, and didn’t seem to produce a lot for the amount of space they
took up, and the length of time that we had to wait before we were able to harvest anything.
But, like a lot of other plants in the gardens, I am slowly getting better at growing these long
season brassicas, adopting simple techniques and purchasing supplies that help to make
these large plants more resilient and productive. And I am still learning how these closely related
plants, and the different varieties that we might select to grow, benefit from different spacing,
timing and methods, and there are still some key issues to figure out.
The kale plants might be one of the more striking things in the gardens
at the moment, and have been for a few months. We have been harvesting the larger leaves from
these plants quite regularly, and removing any side shoots as they develop, leaving a tall bare
stem topped with a cluster of leaves, looking more like a palm tree than a vegetable plant.
This method of regularly harvesting from the base of the plant upwards just as the leaves
are beginning to mature, has worked quite well for us in the past season.
One kale variety that we grew with long dark leaves seems to be more suitable for summer
and autumn production, which we sowed a bit earlier and started picking the
semi-mature leaves from the middle of July. By November and December the growth of the
plants really slowed down and many of them started to produce flower buds.
The other curly green hybrid variety is apparently able to handle winter conditions much better,
which we planted a bit later, but ended up started the main part of the harvesting of a
lot of the leaves as they developed from August. We intentionally delayed harvesting later in the
season, hoping to keep more of the leaves on the plants for harvesting during the winter when we
knew that the growth would slow down considerably. But this didn’t turn out to be a good idea,
as a lot of these older leaves that we left on the plants started to degrade,
and ended up being wasted, which surprised me. It is possible that the really cold weather we
had in December was part of the issue, but I suspect that it is more part of the process
of the plants abandoning leaves as they grow, to put more resources into the new growth, but
I would have thought that these plants would be able to support more leaves at this time of year.
The plants in the Intensive Garden were in better shape, but this might be because we
harvested more of the leaves, leaving fewer older leaves, rather than because
of the growing conditions in this garden. These same kale plants in one of the beds
of the Polyculture Garden hadn’t been harvested as recently, and they had a lot more degraded leaves,
so perhaps it is due to the weather, or fertility issues or simply a characteristic of this variety,
where they are bred for leaves to be harvested before they mature.
The dark leaved kale plants produced just over 1kg of leaves on average across all the gardens,
which is quite a bit lower than the other variety,
and quite a bit less than we got from the same variety last year, and I don’t really know why.
Apart from these leaves that were degraded in the winter, the plants of later season
curly kale were remarkably consistent, as I would expect from a hybrid variety.
In three of the gardens, each of the plants seemed to produce a very consistent yield, with close to
two kg of kale already harvested from each plant, not counting the degraded leaves, or anything we
pick from now until the end of the season. This is the first time I have grown this
particular curly leafed hybrid variety, but I think this is quite impressive, and with
the higher density of the plants in the Intensive garden, this translates into almost 9 kg/m2 with
still some more to harvest, which I think is the highest yield I have got from a batch of kale.
I think that this variety can be planted at a higher density than I typically plant kale, and
the widely spaced plants in the Extensive Garden didn’t seem to take advantage of the extra space,
likely because of how we managed them, though this could also be due to issues of fertility.
The plants of this variety in the Polyculture Garden produced a lot less, but only part of
this is due to the greater number of leaves that were left on the plants that degraded.
In one bed the plants were squeezed in with squash, runner beans, purple sprouting broccoli
and clusters of flowers, which caused the plants to grow quite a bit taller searching for light.
When the other plants were removed from the bed, the stems on most of the kale plants bent
over without any support and I am not sure how this would have affected or impacted the yield.
But the same plants in another bed of the Polyculture Garden were more productive,
but not as much as were produced in the other gardens.
I suspect that this variety is not very vigorous, with roots that don’t compete well with other
types of plants for the nutrients and water that they need during the growing season.
With most of the plants of this variety the little side shoots along the stem remained dormant,
but with a few of the plants in the Polyculture Garden garden these buds
have already started to grow into side shoots, that are large enough to harvest.
I think this is interesting, but I am not sure if it is because of the horizontal stem, or that the
competition from the other types of plants earlier in the season had been removed, leaving these
plants with less competition, or some other issue that may have prompted this additional growth.
The Brussels Sprouts plants are very closely related to the kale plants,
which have been bred so that these little side shoots above each leaf curl up into
tight little cabbages, which we typically harvest in the winter.
We grew one variety of Brussels Sprout plants this season, which are also long season plants
that were sown in late April or early May and only started to produce sprouts at the end of November.
So for 7 months the plants were growing, gathering energy, storing most of it in the thick stems,
and cycling through leaves as the plants grew. The plants pulled the nutrients out of the
older leaves, and allowed them to die and fall off the plants, putting the nutrients
into the newer growth of leaves or the developing sprouts later in the season.
This still seems strange to me, that plants would give up on the photosynthesis potential
of the older leaves, but apparently plants like this will only support so many leaves.
With the kale plants we were trying to harvest the leaves for eating before this
process of pulling the nutrients out of the older leaves started.
I wonder if the additional nutrients or some other form of feeding later in the season would
change things, or how the various moulds and other diseases may factor into all of this,
but removing the older dying leaves from these types of long season brassicas is a regular task.
This past season we also started using bamboo canes to support the Brussels Sprout plants, to
keep the tall, and top heavy plants from falling over, which was a regular occurrence in the past,
especially with the more densely planted beds. When the winds push over tall plants like this
it can damage the stem and snap some of the roots off at the base of the plant.
It also makes it harder to harvest, and often causes the plants to crowd out adjacent beds.
I was surprised how effective a few bamboo canes were when stuck
in the ground early enough in the season, without even tying the plants up a lot,
though as the season comes to an end, there are a few plants that could be supported better.
The Brussels sprout plants have not been as consistent in their growth as the kale plants,
even though it is also a hybrid variety. One of the plants in the Intensive Garden
started to decay earlier in the season and another one is really stunted, possibly
because the plants were too closely space, and we haven’t harvested anything from either plant.
One plant in the No-Dig garden produced quite small buds which we left without harvesting,
and a few of these buds have continued to grow into fairly large side stems.
And one of the plants in the Extensive Garden was significantly smaller, but
still produced a useable crop of smaller sprouts. And the amount harvested so far has been much less
consistent between the different gardens, even if we ignore the plants that have not produced well,
but it is hard to really compare the yields so far as we haven’t necessarily harvested
the same amount from each of the gardens. There are still quite a few sprouts growing
and they might produce for another few weeks or month, but I am not so sure with this variety.
And then the top of the plants can also be harvested, as a type of small cabbage,
and this final harvest can boost the yield a bit, but only if they remain in good condition.
In the Extensive Garden the tops of all four plants are in good condition, and the tops
of most of the plants in the Polyculture garden are looking good, but a few of them
have slightly damaged edges to the leaves. In the Intensive Garden more of the plants
have rotting tops leaves, and with some of the plants in the No-Dig Garden they are even worse.
I am not sure what is causing this, but I suspect it might be a fertility issue,
and possible lack of trace elements in the soil, and it is only in the Extensive garden that I
regularly supply trace elements with seaweed meals and other parts of the fertiliser mix that I use.
But it’s hard to tell with such a small sample size, and it could be an issue with the variety
that we grew, but this damage to the top of the plants is something that has happened in the past,
and is something that I want to try to figure out how to prevent.
Not so long ago I would have had additional problems with growing
Brussels sprouts and kale plants. Caterpillars were often a really
serious pest with both of these plants, and then in the winter the local wood pigeons
would land on the top of the plants, eat some of the leaves and damage the rest.
But since we have started covering the crops with a netting for the whole season,
we don’t have these issues any more, which has definitely increased the quality and quantity of
what we have been able to harvest, and saved a lot of time searching for caterpillars.
Because of the interplanting with the other crops, we were not able to cover some of the
kale and purple sprouting broccoli plants in the Polyculture garden,
and we did have some issues with caterpillars, but not as much as I would have expected.
Perhaps because all of the other usual plants that these white butterflies like
to lay their eggs on have been covered with a netting for the past few years,
there are a lot fewer of these butterflies around, or they have moved off to other areas.
And I am also surprised that the local wood pigeons have not found these unprotected plants,
but perhaps they have also given up on this area as a possible feeding ground.
We did lose a few of the young transplants to something early in the season,
and I suspect slug damage, but I wasn’t paying close enough attention to see what happened.
We have been generally better at keeping the slug population quite low in the gardens,
but we still get some slugs in the cabbages, but with the really cold weather this winter,
this has become less of an issue. But this year we have noticed a serious issue with
cabbage root fly larvae eating into the roots of a lot of the Japanese turnip that we were growing.
And we had a poor harvest of cauliflower, Calabrese broccoli and some cabbages in
the summer and autumn, and I suspect that it was because of the root damage from this pest as well,
but I didn’t investigate close enough to confirm that that was the issue.
It is possible that issues with some of the kale and Brussels sprout plants
could be due to the root damage from this pest,
but most of them seemed less affected that the other Brassicas plants in the adjacent beds
We need to do some work to prevent this type of damage next year,
and to try to reduce the population of this pest in the gardens, or at least to stop breeding them.
The other really long growing plants are the purple sprouting broccoli,
which are also really closely related to the kale plants, and to the Brussels sprouts.
These plants were sown at the beginning of June, a bit later than the other large brassica plants,
but they won’t start to produce a significant crop for another month or more.
This is probably one of the least productive crop that we grow,
especially for the amount of time that it occupies the bed, but they do provide really
useful and delicious immature flower buds at a time of year when not a lot of other vegetables
are available to harvest from the gardens. Most of these plants have become quite big,
and unlike the kale that are regularly harvested and controlled,
these plants probably need a lot more space. With the denser planting of the Intensive Garden,
the plants have dropped a lot of their lower leaves, similar to the Brussels sprouts plants,
leaving most of the growth at the top of a single thick stem, with only a few side shoots.
The plants in the No-Dig Garden seem to have lost even more of their leaves and
are relatively sparse plants on top of a tall single stems, and a flower
bud is already starting to grow on one plant. With the wider spacing in the Extensive Garden,
the purple sprouting broccoli plants have taken on a much different form, with multiple side shoots
growing from the full length of the stem. This has led to quite large plants,
and although there is still some leaf drop, they are many more leaves, and many more growing tips.
In the Polyculture garden, these plants were also interplanted with the runner beans,
squash and flowers, but they seemed to be able to compete with the other plants a lot
more successfully, and grow a lot better than the kale plants in the same bed, becoming some
of the biggest plants in all the gardens. They also have lots of side shoots growing
from the stem, though for some of the plants this side growth started farther up the plant,
likely because of overshadowing of the lower parts of the plant, and it is interesting to see how
this same plant changes its growth habit depending on the density and the proximity to other plants.
It will be interesting to see how this affects the cropping over the next few months,
and I expect many more broccoli shoots from these larger plants,
and a higher yield per plant, but I suspect the smaller plants in the other gardens will
produce a bigger central broccoli head on the top of the single main stem.
I find it interesting that this small selection of long season brassica
plants are not growing consistently better in any one of the 4 gardens.
The extra space of the Extensive Garden has benefited the purple sprouting broccoli but
has not improved the yield of the kales or Brussels sprout plants.
The kale has done well with the dense spacing in the Intensive Garden,
but the other plants have struggled, probably because they need a lot more space.
The No-Dig Garden has produced a lot of Brussels sprouts, but the tops of the plants are degrading,
indicating that the plants might not be getting what they need from the soil.
And the results of the Polyculture Garden vary so much depending on the differences
within the intercropping, but the less vigorous plants probably need more fertility and care.
These plant seem to do better in different growing conditions, with the plant density,
planting dates, method of harvesting, removing side shoots or not, and the
varieties we select, all having an impact. And these are all things that I want to
explore some more, to better understand the differences between the gardens and
the specific conditions and methods that benefit these closely related plants,
that we grow for harvesting different parts. But I am quite pleased with the difference
that simple bamboo canes have made to keep the tall plants under control and
preventing them from becoming damaged this year. The harvesting from these plants has been quite
successful this season, and the netting has kept some of the worst pests away,
we just need to figure out how best to prevent damage from the cabbage root fly larvae.
I also want to explore providing additional feeding to the plants later in the season,
which is something that I haven’t explored enough in any of the gardens, especially with the heavy
feeding plants that are in the ground for so long. It will be interesting to see what effect
additional feeding will have on yield, and the amount of leaves that the plants will be able
to keep growing later in the season, to see if we can improve the amount of kale that can
be harvested fresh during the relatively mild winters that we get here in Ireland.
This is all part of the continual refinement of knowledge, skills and methods of how to
grow crops like this, in a context that doesn’t always stay the same.