Growing up in Canada sweetcorn season was always one of my favourite times of the year,
and we always used to eat lots of corn in the cob during that period of time in late summer
and early autumn, and this is something that I've really missed since I moved to Ireland. Sweetcorn,
as it's known over here, is just not really available except in frozen form and it's hard
to grow. I’ve always assumed that the summers here in Ireland are just not warm enough to
grow this heat loving crop, but last year we grew some sweetcorn in two of the polytunnels, and it
was more successful than I would have expected. This year we grew several batches of sweetcorn
undercover and we also grew some sweetcorn in the ground outside, and in containers outside,
and although there were definitely some issues we were able to produce a lot of sweetcorn.
Ireland has a cool maritime climate that is dominated by our position in the North Atlantic,
with lots of rain and a fair amount of wind, and without more extreme temperatures in both the
summer and the winter. Daytime high temperatures in the summer typically stay below 20° C and the
nighttime temperatures often drop below 10° C. We do get warmer spells most years often lasting
for several weeks but they're not so reliable and they often seem to happen earlier in the
summer. Sweetcorn generally prefers significantly warmer growing conditions, It would grow here but
it would grow very slowly and because it's also not very tolerant to frosts we don't necessarily
have a long enough frost-free growing season to be able to produce ripe cobs. I do grow other crops
that are similar to this, including squash and pumpkins which are marginal crops in this climate,
but I have to supply some extra protection in the spring, and generally have to grow very fast or
quick maturing varieties at least outside. In the polytunnel things are different, not only
because it generally extends a frost-free growing season, there's generally warmer conditions for
growing especially during the day, and usually a bit warmer at night. We grow a lot of tomatoes,
cucumbers, beans and other heat loving crops in the polytunnels usually selecting crops
that are both high value and high yielding, in order to justify taking up so much of this
relatively scarce growing space. And until recently I didn't think that sweetcorn was
high yielding enough for the amount of space that it would take up in the polytunnels.
Last year we extended the covered growing space by putting up another large polytunnel, so I felt we
finally had the space to try growing some sweet corn, and we grew a fair amount of it with two
batches of open pollinated varieties in two of the polytunnels. Corn is such a fascinating crop
and it's really interesting to see how different it is to all of the other crops that we grow. The
plants grew quickly and tall as expected with the tassels pressed up against the plastic at the top
of the polytunnel, even in the taller polytunnel, and this caused some overshadowing of adjacent
crops. We grew about 130 plants in the two spaces, and although not all the plants produced a cob we
still had a lot of cobs to eat fresh, and to freeze for later, which was great. We had sown
the seeds in mid April and transplanted them into the polytunnel bed in early May, and we're able to
harvest the first ripe cobs in early August and able to enjoy them fresh for almost 3 weeks. So
it took about 110 days from sowing the seeds until the first ripe cob was ready for harvest, which is
about 2 weeks longer than the days to mature that is specified with the varieties that we grew. So
it's definitely possible to grow sweet corn in a polytunnel like this, even if it is a bit cramped.
We grew a lot of sweet corn again this year, both in the polytunnels and outside,
but we ended up sowing the seeds a bit later in the spring, mainly to allow the other crops to
mature first, but I think that this was probably not a good idea. In the large polytunnel we grew
a hybrid variety, sewing two batches of seeds at the middle of May and the beginning of June,
which delayed the harvest until the end of August and well into September. A lot of the plants of
this variety produced more than one cob and although the second cob was a bit smaller,
we ended up with more cobs and a slightly higher yield than last year, in roughly the
same space. I didn't like waiting so long to be able to harvest the corn from this batch,
and the plants seemed to struggle a bit with the decreasing temperatures of August and the
shortening days. This might have contributed to the infestation of spider mites that the
plants got later in the season, which I didn't catch in time. But we still had a
decent crop with a lot of corn to eat though it could have been a bit better and earlier.
With the older and smaller polytunnel I decided to fill it with a trial of the Three Sisters
this year, which is a companion planting of corn, squash and beans, that was developed and used by
some of the indigenous peoples of North America. I haven't tried this type of companion planting
before, and it's hard to find details about plant density and how the three different crops relate
to each other, especially for a polytunnel here in Ireland. I ended up planting clusters of four
sweetcorn plants, spaced a reasonable distance apart, with the beans sown in a little bit later
at the base of these clusters, and the squash and the pumpkin plants transplanted into the edge of
the polytunnel, to allow the vines to grow in to cover the full ground. All the plants
grew well and they ended up growing so much that they overcrowded most of the poly tunnel space,
with the sweet corn plants losing out. The climbing beans eventually grew up all of the
corn plants and continued to grow to form a cluster of vines high up in the polytunnel,
overshadowing the plants, and some of the corn stocks were pulled over by the weight of the
developing pods. And some of the squash plants were really vigorous and ended up climbing up
and over the sweet corn plants, and I ended up cutting back a lot of the vines of the squash in
order to give the sweet corn a little bit more space. We did get a harvest of corn
cobs though some of them were hard to find, but with all of the plants being crowded out and the
overshadowing it was not a big crop. Most of the cobs were well-developed full of kernels of corn,
but there were some pollination issues with some gaps in kernels developing in some of the cobs, as
I think a lot of the pollen would have fallen into the space between the clusters of corn plants.
In the space beside this polytunnel, I decided to try a planting of the Three Sisters outside. As
expected this was not so successful in this climate, but at least the sweetcorn plants
were not overcrowded by the beans and squash plants, which didn't do so well in the cool
conditions. And the soil in this part of the ground was not so developed and probably could
have used a lot more fertility. There were also pollination issues, more than in the polytunnel,
with the wind blowing the pollen from the tops of the plants and missing a lot of the silks
that were developing at the ends of the cobs, leading to big gaps in the kernels of the cobs,
and a lot less to eat. The first batch of this open pollinated variety was sown at the beginning
of May, and transplanted 3 weeks later, but we had to wait until well into September to harvest the
first cobs. This was over 140 days from sowing to harvesting which is a lot longer than the 90 days
to maturity that people in warmer climates can apparently expect, when growing this variety.
In order to get a better crop I think I'd need to sow earlier and at a higher density of corn plants
than is probably useful in a companion planting of the Three Sisters. And better soil fertility
and a faster maturing variety would probably help as well. But we were able to eat sweetcorn growing
outside in Ireland in a summer that didn't have great weather, though the temperature on
average was a bit warmer than we would typically expect, except for the important month of July.
We also grew another batch of sweetcorn in in 16 large grow bags outside, transplanting
three plants in mid June into the large bags filled with a heavily fertilised growing medium,
using the same hybrid variety that we had growing in the larger polytunnel. I didn't
expect much from these plants, as I didn't know if sweet corn would even grow in containers,
or grow outside. But the plants grew well especially when I liquid fed them a few times,
and I was pleasantly surprised to see quite a few cobs developing which we were able to harvest from
mid-September through to the beginning of October. These plants seemed shorter, and the stand seemed
more dense than the same variety growing inside the polytunnel, and the cobs seemed smaller,
but there were more of them per plant, possibly because they were growing out in the open with
nothing else overshadowing them. We were able to harvest a few cobs from a lot of the plants,
and most of these cobs seem quite similar in size and reasonably well developed and full of kernels,
though there were a few instances of pollination issues. I think this might have been the most
successful crop of corn that we grew this year and it was relatively easy to manage,
and to water with the new dripper system that I had installed. And the plants seemed to be able
to get enough fertility despite the constrained root systems, and there was no obvious signs of
pest or disease issues. It took about 3 weeks longer for these cobs to ripen outside as
the same hybrid variety did growing inside the polytunnel, which is not as long as I expected,
and I wonder if the warmer growing medium in the grow bags would have helped to speed up
the growth of the plants. Looking at the numbers we were able to harvest about 74 well developed
cobs of sweetcorn from these 48 plants, growing in the 16 large grow bags, which took up about 8
square meters of space, which is more sweetcorn than I thought we would be able to harvest.
With all these different plantings and despite all the issues we were able to eat a lot of sweetcorn
and I learned a lot, but there are more questions and things that I want to learn, which is always
a really interesting part about learning how to grow a crop, especially one that doesn't grow so
well in this context. Selecting faster maturing varieties or more specifically varieties that
will mature faster in a cooler climate will make a lot of difference and is perhaps more important
than higher yielding varieties. There's also the difference between the varieties with a normal
sugar content and the super-sweet varieties, which is partially a personal preference,
but it also restricts the possibilities of doing variety trials because of cross-pollination
issues. Planting earlier in the season would definitely help, allowing the cobs to ripen
during the warmer part of the season. But it would also be good to explore succession planting, or to
plant varieties with different maturing times to stretch out the harvest over a longer part
of the summer and early autumn. I will definitely be growing sweetcorn outside again as I have a lot
more space available to dedicate to this crop, but I'll be planting earlier in the spring and
making sure that I use cover to protect from the frost, to either extend the growing season or to
get an earlier crop. It would also be interesting to explore growing in containers again, as this
was more successful than I thought it would be. I would like to grow sweetcorn as part of the Three
Sisters planting again next year especially to explore issues of spacing and timing but
I'm not sure if I have the space available with all of the other things that I want to explore.
I’m not sure about growing sweetcorn in the polytunnel again, even though I can get a
bigger and earlier crop as the more sweet corn that I grow in these tight spaces the less other
crops I can fit in, and the difference in yield is significant. From the batches of sweet corn
that we grew in the one polytunnel this year I calculated that we harvested about 11 cobs
per square meter, which weighed about 4 kg, but only about half of that is edible kernels. So the
edible yield is closer to 2 kg per square meter from a crop that occupies this valuable growing
space for the main part of the growing season. 2 kg is not a lot especially compared to the 15 kg
of tomatoes or 8 kg of beans or 30 kg of cucumbers that I could grow in the same amount of space. And
all of these heat loving tall crops don't grow nearly as well or at all outside here in Ireland,
and they're much easier to support by hanging from the polytunnel structure.
But apparently we can grow sweetcorn outside here in Ireland, which was a pleasant surprise for me,
so if polytunnel space is scarce, it makes more sense to grow these tall
self-supporting plants outside. But I think I might try to find some space in one of the
polytunnels for this crop. as I think we're a long way from having too much sweetcorn.
I’m obviously not filming this from my gardens in Ireland, as I'm currently visiting my family
in Canada. But I'll be back in the gardens in a few days, and we'll be busy harvesting crops for
storage, clearing up the gardens and planting in some overwintering crops. There are lots of
videos that I want to make about a wide range of different crops that we grew this past year,
and it will take quite a few months to work through all of this content. If you
like these videos, and appreciate the type of explorations that I do in these gardens,
make sure to subscribe so you don't miss any of these upcoming videos. And if you want to
support this channel even more, and to help with all of the different explorations there
are links to my Patreon and PayPal account in the video description below. The more
support and engagement that I get with this channel, the more I will be able to explore
as part of this RED Gardens project but most importantly thank you for watching.