Garlic is a strange crop, as it is one of the few vegetables that are primarily grown
each year by planting part of last year’s crop rather than growing from true seeds,
like with most of the rest of the plants that I grown in my vegetable gardens.
Potato plants are also grown by replanting one of the potatoes harvested from the previous season,
but I usually buy in fresh seed potatoes each year for a few reasons. So it is only with garlic that
I use a process of vegetative propagation to grow the crop each year, simply by separating
out the individual cloves from the bulbs of garlic that I harvested from the previous year.
And I have been repeating this process of continuing to replant the same lineage of garlic
for almost 10 years on this site, always saving the best bulbs for planting next year’s crop.
And in the process the bulbs of garlic that I harvest have gradually gotten bigger,
which is often seen as the garlic adapting to the local climate. But an experiment that I did
this year indicates that something else might be going on, or at least it opens up to the
possibility of a more nuanced understanding of how garlic crops might change from year to year.
The bulbs of garlic that I have grown in the past few years are definitely bigger than
the bulbs I originally purchased all those years ago. But this is especially the case
with the garlic I have continued grow in one of my polytunnels. It is unusual to grow garlic in this
valuable microclimate which is usually reserved for the heat loving crops,
as garlic can be so successful in the outside gardens in this climate. But
I have found that It is definitely worth it as I have been able to grow huge garlic bulbs that
weigh an average of 135g each once dried, and are up to 9cm or three and a half inches across.
This is significantly larger than the bulbs that I originally started growing in this polytunnel
and a lot larger that anything I'm able to grow outside, but I'm interested in why this gradual
increase has happened. No doubt part of it is the better growing conditions within this protected
microclimate, with more warmth and less hassle from the wind. And part of it is because I select
the biggest cloves from the biggest bulbs each year for planting the next crop, which gives the
young plants a strong start, helping to produce bigger plants by the summer, resulting in bigger
bulbs being harvested with even bigger cloves for planting the following year.
But I also suspect that there are other factors involved such as improving soil conditions
and soil fertility, and hopefully because I'm becoming a better grower with more experience.
I have also seen this gradual increase in bulb size in the plants grown in the outside gardens,
though the difference is not as pronounced, and I’ve always thought that it was because
it is not as warm or there aren't as ideal growing conditions outside.
There is also this idea that garlic plants gradually adapt to local growing conditions
after years of replanting. I've always thought that this was a part of process, though I never
really understood the mechanism involved as the plant one year is essential just the continuation
of the plant from the previous year. And with this vegetative propagation, no matter how
many times it is replanted it is still the same plant, and is essentially a clone. This is very
different from the process of cross pollination of flowers, where the natural variability that
exists within the genetics of the selected plants produces variations within the next
generations of seed that are produced, where each seed can be subtly different from the next. This
can be the mechanism through which you can end up with significantly different strain or variety of
vegetables than you had started with, or how new varieties of vegetables can actually be developed.
But this natural variability that's inherent within seed propagation, is apparently not
there with vegetative propagation, where there is supposed to be an identical genetic match
between one season and the next. And this is why some people claim that garlic doesn’t adapt to
local conditions, and instead any changes are due to the increasing size of cloves
that are actually planted, or the improving skills of the grower, or some other factor. I
am not sure about all of this, but an exploration that I did with the different batches of garlic
that I grew this year has led me to think that something interesting is going on.
I have been been replanting the same lineage of garlic in the polytunnel for 8
seasons. Although they are variations in the weather from year to year, it is essentially the
same microclimate for the garlic plants to adapt to, if that is what actually happens. But for the
outside gardens I usually have planted the larger cloves that were grown inside the polytunnel,
because I wanted to start the plants off with the bigger cloves, and it saved the effort of saving
separate batches of bulbs for regrowing. I knew that this was distorting things and preventing me
from seeing what would happen if the garlic adapted to the weather outside, or if there
would be any divergence from the original strain that was continuing to grow in the polytunnel.
For this reason a few years ago I started to save bulbs from the four gardens outside,
in addition to the original lineage from the polytunnel, and started the process of planting
each garden with cloves grown in that garden. It has only been a couple of cycles of replanting
and probably not enough for much adaptation to actually occur, but this year I decided to plant
half of the garlic patch grown in each of the four outside gardens with the best bulbs from
that garden last year, and half from larger bulbs grown in the polytunnel. I mainly wanted to see
if there would be a difference in the plants based on the clove size, so I weighed the cloves that I
selected for planting in each batch, and there was significant difference in the average weight. I
selected the largest cloves for replanting in the polytunnel, and the ones selected from the same
batch for planting outside were slightly smaller at an average of 8 grams each. The average weight
of the cloves planted from each of the outside gardens ranged from 5.2 grams to 6.8 grams.
And all of these cloves were planted into the ground at about the same time, and with the same
basic care, but with different planting densities and soil conditions in the different gardens. But
within each garden the two sets of plants from different cloves were treated the same.
I wasn’t sure what to expect but I was hoping that the larger cloves would in fact produce
significantly larger plants and bulbs. And the initial growth in the spring did show slightly
stronger growth and larger plants at the start, which is to be expected as there would be more
energy and nutrients available in the larger cloves to give the young plants a head start.
But it was later in the season when the plants were bigger that I noticed significant difference
between the pairs of batches, in all four of the outside gardens. The plants growing
from cloves produced in the polytunnel were consistently larger than the plants grown from
cloves originating in the outside gardens. Some of this could definitely be explained by the
larger average clove size, but the difference seemed to be disproportionate. For example the
cloves from the polytunnel were only 17% bigger than the cloves from the Polyculture garden,
but the plants seemed to be much more than 17% bigger. And while the 17% difference was with the
average clove size, there were some cloves grown outside that were bigger than the cloves grown
in the polytunnel, but this overlap didn’t seem to be reflected in the plants in the garden. I
felt that something else was going on here, in additions to the larger clove size at the start,
and the plants grown from the polytunnel cloves seemed stronger and healthier as
the season progressed into the summer when the plants started to mature.
There was also something strange with the timing of the secondary growth that I typically find with
this garlic variety. I don’t have a any experience with our varieties of garlic,
but the variety that I’ve been growing for years seems to produce double or triple clothes,
with new leaves growing up through the stem of the plant. I don’t know if it is very common or
something that has just developed with the particular strain that I've been growing,
or a result of plants being able to grow much bigger than usual. It does seem to help to make
the bulbs grow a lot bigger, Increasing the yield, so I’ve never really worried about it. The plants
grown in the polytunnel developed this secondary growth first, and then a few weeks later the
secondary growth started with outside plants that were grown from the outside cloves. But
at first these additional leaves did not appear on the adjacent plants grown from the cloves produced
in the polytunnel. It took another few weeks before the secondary growth started to form on
these plants, and this delay in developments was the same across all 4 outside gardens.
I harvested most of the garlic in the polytunnel first, as usual, though a bit earlier this year
than in previous years to catch the bulbs before they grew too big and split their skins. A
few weeks later I began digging up the plants in the outside gardens,
and I was quite surprised at the difference in the development between the
pairs. The plants grown from outside cloves seemed a bit over developed, as if they had
been in the ground for too long, and the skins on some of them were already starting to split. But
the plants that were grown from the polytunnel cloves were quite large,
but definitely seemed immature, and would have benefited from growing for another few weeks.
These bulb did not yet have the characteristic bulging of the cloves,
and the bulbs were smaller in proportion to the size of the neck or stem and the leaves,
at least compared to what I expect from this variety when it is mature. It
was as if they were from a different variety of garlic that matured later,
or that they had been planted later, but they had all been planted at the same time. And
the difference was the same across all the pairs of garlic batches in the 4 outside gardens.
So the garlic plants grown in the polytunnel developed the secondary growth and matured first,
and the batches of garlic grown in the outside gardens from cloves produced in those gardens were
a few weeks later. But the plants grown outside from cloves produced in the polytunnel last year,
took an additional two weeks to reach the same stages of development,
and it seems that they needed a couple more weeks for the bulbs to properly mature. I think this
delay allowed the tops of the plants to grow larger before the plants started to put all of
the energy into developing the bulb underground which would have been significantly larger if
I hadn’t harvested them to early. But the only difference, beyond a moderately larger average
clove size at planting, was that the lineage of the cloves were separated a few years ago.
And I expect that a couple of years is not have been enough time for this kind of adaptation to
take place in the genetics or characteristics of the different strains of garlic. And if garlic
does adapt to the local climate I would have thought that the plants grown from cloves that
were grown in the same climate would do better, but the opposite seem to have been the case.
The only thing that makes sense to me is somehow the clove that was planted outside remembered the
warmer conditions that it was grown in within the polytunnel. And the plants delayed the date
that they stopping growth of the leaves and started focusing energy on developing the
bulb under the soil, as if it was expecting more cumulative growth before it reached that point.
I have no idea how this would happen or if there is something else going on that I am not aware of.
In the past it made a certain amount of sense to use the bigger cloves from the
polytunnel for planting all of the garlic in all of the gardens, and
after this year’s exploration, I was much happier with the results from these polytunnel cloves,
even if the crop matured a few weeks later. Perhaps it's unfair to compare the two,
as the garlic that was grown outside had not had many years to adapt to this outside climate,
so I am not comparing like with like. But on the basis of this one limited trial,
I seem to get better garlic outside from cloves grown in the protected climate of the polytunnel.
And perhaps I don’t need to know why or how this is the case, just that it works for me,
at least with the variety or strain that I'm currently growing. But id does seems to go
against the general idea that plants that are adapted to the local conditions will do better.
Whatever the reasons I decided to leave about one third of the polytunnel garlic crop in the ground
for a few extra weeks before harvesting, so that the cloves could grow even bigger
for planting all of the gardens next year. But perhaps I should also save the best bulbs from
each of the other gardens, and to replant them again next year in the same side by side trial,
to see if the observations that I made this year are repeated.