Potatoes are an important crop in many vegetable gardens, especially here in Ireland,
and it is one of the few staple crops that it is relatively easy to become self sufficient in,
to have lots of potatoes to eat all year round, if you have lots of space to grow them in. But
if you don’t have lost of space to grow them in, and a place to store the harvest, I think it makes
more sense to grow a smaller crop of high value early potatoes. It can be worth growing even a
few plants in small gardens to be able to harvest these delicious early potatoes in early summer,
and they can generally be harvested in time to get another crop in for the second part of
the growing season. And that is why I have generally only grown one early variety of
potatoes in 5 of the gardens that make up this RED Gardens Project. And this year the harvest
from these early potatoes has been quite good, with a few issues I'd like to improve on, and it
was interesting to see the differences between the same crop grown in five different gardens.
In three of the gardens we used a more traditional method of planting the seed potatoes at the base
of one long trench, which was gradually filled in as the plants grew in order to earth up or burry
the base of the stems and prevent sunlight reaching any of the developing potatoes. In
the Polyculture Garden they were planted into a small depression in the soil, and only slightly
filled in later in the spring to reduce damage to the roots of the other intercropped plants. This
less invasive method worked quite well, with only a few potatoes in a few plants
developing the poisonous green patches, and I suspect that I may be digging an unnecessarily
deep trench in the other gardens, at least for this variety of potato.
In the No-Dig Garden the seed potatoes were placed in a small hole, with the top of the
potato roughly level with the surface of the compost layer, and then we added more compost
to form a pile at the base of each plant as they grew to provide the needed protection from the
sun. This additional compost was added on three separate occasions as the plants grew,
adding almost half a bucket of compost per plant, which is equivalent to a layer 50mm or 2 inches
if spread out over the full bed, in addition to the 25mm of compost that was added at the
beginning of the year, which is a lot of compost. This method worked for the most part but as the
plants began to die back, the rains began to wash away some of the pile of compost and the local
blackbirds dug away at it some more in search of worms, exposing some of the potatoes to the sun.
I planted the potatoes into the enclosed space of the Polytunnel Garden in the middle of January,
but I waited until the third week of March to plant the seed potatoes into the ground in
the four outside gardens. This is the traditional time for planting early potatoes here in Ireland,
but I find that I usually need to provide protection from frost for these early planting
here in the midlands. I had covered all of the plants outside for most of the spring, until the
risk of frost had past, using multiple layers of horticultural fleece and a more robust crop cover,
a combination that I have found works quite well to keep in the warmth and it stands up
to the strong winds that we can get. In some of the gardens I used hoops of wire or pipe stuck in
the ground to hold the material up off the leaves of the plants. This worked quite well to prevent
frost damage on most of the leaves, but as the plants grew larger in this sheltered microclimate,
the hard frosts that we had in May did cause some damage to the leaves that had pressed up against
this material. But the plants had fully recovered from this damage a few weeks later when the risk
of frost had past and the weather warmed up enough to remove the coverings. I started digging up the
plants to harvest the potatoes from the Polytunnel Garden at the beginning of May, and continued to
harvest from the long row of plants until the end of June, and then started harvesting from the
batches of plants grown outside from the beginning of July. I could have started harvesting from the
outside gardens earlier, though the yield from each plant that I dug up would have been lower,
and I continued to harvest as needed from these four gardens until the first week in August. By
this time the plants had started to die back, and probably would not produce a lot more,
so I dug up all the remaining plants, and stored the potatoes until needed.
The average yield from each potato plant was different across the 5 gardens,
partially because different amounts were harvested at different times earlier in the season
when the tubers were still developing quickly. But if I only looked at the yield per plant of the
final large harvests, and extrapolate to what the full crop would have been at this time, then a
more relevant comparison can be made. The yield from the Intensive garden was lowest with just
over 1kg from each plant, but the harvest from the No-Dig garden was about double that and the
other three gardens in between. But, because there was almost twice as many plants per square meter
in the Intensive Garden, the overall yield from approximately the same area within the two gardens
was actually fairly similar. The difference in spacing or density of plants is the significant
factor here, and there seems to be a direct relationship between the amount of space each
plant has to grow in and the amount of potatoes it can produce, which makes a lot of sense. The
Polytunnel Garden follows this basic pattern, but the plants in the Extensive Garden seemed
to produce less for the amount of space they had available, and I think
this is because I mistakenly didn't add the mix of organic fertiliser that is used in this garden
until the plants had grown for a while, so they may not have had the fertility they needed
earlier on in the season. And the plants in the Polyculture Garden produced more than expected,
but I think this this is largely due to the way that I measured the area for the potato crop
within the section of the garden that was shared with other crops. The
potatoes were planted in two rows down either side of the bed with broad beans, Brussels sprouts and
kale plants growing down a row in the middle, and if I assume the potatoes only had 2/3rds of the
bed then the yield per square meter seems higher than expected. But in reality the early planting
of these strong potato plants definitely occupied more than 2/3rds of the garden bed, but it's
really hard to really put a number on it, and this is one of the key reasons why it is difficult to
compare the yields of individual crops from this Polyculture Garden approach to the other gardens.
In the Polyculture Garden the Brussels sprout and kale plants that were transplanted in between the
established potato plants did struggle at first, lagging behind their counterparts
in the other gardens, but started to catch up as the potato plants reached the end of
their phase of rapid growth. A lot more care was needed in digging out these potatoes,
in order to reduce the damage to the roots of the brassica plants, which would have set them back
even further, and I was pleasantly surprised by the number of large tubers in good condition. In
the Extensive and Intensive Gardens the potatoes were possibly affected by the rapidly growing
courgette and squash plants in the adjacent beds, and there were a surprisingly large number of
roots from these aggressive plants in amongst the potatoes that we dug up. I am not sure how early
this root competition would have started or how much of an impact it would have had on the yield,
but it is likely that it made the fertility issues of the Extensive Garden worse. We
still dug up a reasonable yield of good quality potatoes from this garden, but it definitely
could have been better. The cold frames that were used to shelter the squash and courgette plants
in the Intensive Garden would have caused some overshadowing of the potato plants,
but it also offered some shelter from the winds, though the plants seemed to die back earlier. I
think the plants may have been stressed with deficiencies in soil fertility or possibly not
enough soil moisture at times, caused by so much competition between the closely spaced plants,
and the tubers we dug up were definitely smaller than in the other gardens. The
potato plants in the No-Dig Garden didn't have any significant competition from adjacent crops,
and with the wider spacing and abundance of compost
it's not surprising that there was a bigger yield from this garden. And
the potatoes were easier to harvest as well, as we only needed to scrape back the pile of compost by
hand to unearth the crop, with only a few potatoes partially embedded in the soil below. The plants
in the Polytunnel Garden grew very large in the sheltered conditions, with a reasonable yield from
such an early crop, which I think would have been better if there had been more consistent watering.
I do find it interesting that early potato plants die back so quickly, but this variety at least
seems to have been bred to produce a crop of tubers quickly, but not to be able to grow for
the full season. There did seem to be some potato blight on a few of the leaves, and a few of the
potatoes were rotten in a way that seems to be blight, though I am not so certain about this. One
of the reasons for sticking with growing mainly early crops of potatoes is to get something
to harvest before the risk of blight, which is usually worse later in the season, although the 4
main crop varieties of potatoes that I am growing in the Simple Garden are still growing strong with
no sign of blight damage yet. There was some slug damage to the leaves, especially in the Intensive
Garden, but I am not sure if they were causing the damage, or just cleaning up on the leaves that
were already dying back. Thankfully there was not much slug damage to the buried crop of potatoes,
and part of this due to not leaving them in the ground for longer than is necessary, and it
seems that this variety is more resistant to slug damage than the variety I grew a few years ago.
And we're also getting better at clearing the slug population out of these gardens. There was some
scab on the potatoes, which seems to be common in the alkaline soil that we grow in, and it was
worse in a few gardens compared to the others. I don't know what contributed to this difference,
apart from perhaps not keeping the soil consistently moist during the dry periods we had.
Growing only one variety of new potatoes in all these 5 gardens makes sense in terms of comparing
the different growing methods, and it is easier and cheaper to buy in one 25kg bag of disease free
seed potatoes. Of course it would be even cheaper to set aside enough of this years crop for growing
next year, but that would increase the risk of blight and other diseases being carried over,
removing that consistent baseline start that is useful in this comparison.
But Brexit has become a serious barrier in our ability in Ireland to be able to import
disease free seed potatoes, which are normally produced in Scotland,
and it makes sense for me to hold back some of the potatoes that I harvested this year for growing
next year, just in case my usual supplier can't import enough seed potatoes for sale next year.
I really like the taste of this variety that I've been growing when it is still young and small,
but I am not as fond of the flavour when it has been harvested later for storage.
It would be good to be able to grow a number of different early and mid season potato varieties,
each one maturing slightly later than the others, so that that we have a better chance of harvesting
really good quality potatoes that are at their prime for longer period during
the growing season of the summer and autumn. Harvesting some of the crop later in the year
will reduce the chance of getting another late season crop into the ground after the potatoes,
which is a definite benefit with growing a very early crop. But I would expect the yields to be
better with late maturing varieties, and there would be less of a need for storage,
though I would need to be mindful of the increased risks of blight and slug damage. I
would also like to adjust the planting densities or spacing of the plants, and how they can fit
into the fixed bed widths, and to not plant them so deep to make harvesting easier.
But this season I did appreciate the convenience of buying in and planting a big bag of early
potatoes, and to be able to harvest loads all at once for sharing with our neighbours and to
store enough for ourselves, at least until the large batch of main-crop potatoes is ready to
harvest from the Simple Garden. And hopefully the blight resistance of these main crop potato
varieties will hold out for at least another few weeks, as it looks like it is going to
be a really big yield with more than enough to store. This will keep us well fed with potatoes
right through the winter and into the spring, at least until the first of those delicious
early potatoes is ready to harvest from the polytunnel again in April or May next year.