It seems that the cold weather we had been experiencing this spring has finally come
to an end, as warmer weather is settling in, even though it's still quite windy.
Ever since I started growing vegetables here in the midlands of Ireland,
I've noticed that we almost always get warm and dry periods every spring,
as well as quite cold, wet and windy periods.
The trouble is that we just don’t know when in March, April or May we are going to get
these longer periods of unseasonable warm or cold weather and this unpredictability
can be difficult to plan around. This year we had a warm period in February and March,
but then a fair amount of April and most of May was unseasonably cold. This has delayed the
growth of a lot of plants in the garden, with a risk of frost damage on quite a few nights.
And this year seemed to be colder than most years I've experienced,
though I have also become more successful at dealing with this by using several different
methods to establishing temporary microclimates for the plants. And I was pleasantly surprised
at the good growth that did occur in some of the vegetable crops during this cold spring.
The summers here in Ireland are always quite cool, or at least compared to the
shorter and hotter growing season that I was use to in continental climate of Canada. And
because so many crops grow slower with the cool days and nights of this maritime climate,
there is a desire to get some crops in the ground as early as possible in the year,
to try to get a long enough growing season, in order to get good yields.
This can be an ok strategy if the weather is warm in May, but this year it wasn’t,
and I had a few frost tender crops that were either already actively growing in the gardens,
or needing to be transplanted in. I’ve used various methods to cover these plants in the past,
and have been continually refining and trying to do new thing as I learn from
trial and error about what works and what doesn’t work so well. But there is still
the risk of significant damage to plants especially when we have much harder frosts
where the temperature drops below freezing for quite a few hours overnight. These conditions
are less common but are much harder to deal with then the lighter grass frost that we also get,
as there is enough time for the freezing temperatures to cause damage to the tender
leaves underneath the covers, and even cold enough to cause damage inside the polytunnels. This
year we had two nights in a row of quite hard frosts on the 6th and 7th of May, which were
thankfully the last frosts of the spring. We’ve had hard frost like that before,
with killing frost on the 12th and 14th of May last year, and the year before we had cold
enough temperatures on the 5th of May to cause damage to a lot of the tomato plants in one of
my polytunnels. So this is becoming something that I expect each season, and generally I’ve
been reasonably successful with balancing the desire to get crops into the ground early
and to prevent frost damage, but it takes a fair amount of work and a lot of cover material.
In the outside gardens, one of the main crops that I worry about are the early potatoes. These
are generally planted in March, and in this area they could grow to become quite substantial plants
before the risk of frost has passed. I always make sure to cover all of the potato plants, and
this year I used a layer of horticultural fleece which provides good thermal insulation, but is not
very strong, combined with another type of woven crop cover that is much more durable against the
strong winds. I find this double layer to be quite effective especially on this windy site, because
I can stretch it over wire hoops to keep it off of the leaves of the young plant as much as possible,
and the combination keeps in a lot of warmth and can handle windy conditions and won’t tear
so easily. And I generally leave this cover on the potatoes from the time they are planted
until after the risk of frost has passed, as this saves me the effort of having to cover the plants
whenever frost is forecast, and it also shelters the plants from any cooler spring weather we
get. The potato plants grow quite quickly in the warmer and more sheltered microclimate created by
the double cover, which is great for being able to get an earlier crop of potatoes, but it does pose
a bit of a problem. The faster these plants grow the bigger they get and the leaves end up pushing
up against the fabric. And when the temperature dropped well below freezing for a few nights,
these leaves ended up becoming quite damaged, but the other parts of the plants underneath were
fine. Several weeks later it was hard to notice that there had been any damage at all,
and it looks like I’m going to be getting an extra early crop of potatoes the season.
The other main crops that I need to provide
protection for are the squash plants and the courgette or zucchini plants.
These large leafed plants are very susceptible to frost damage, and can be really hassled by the
winds, but I want to get them into the ground in May so that I can get early courgettes,
and for the squash have enough chance of ripening in our cool climate.
This season the last frost ended up being before the plants needed to be transplanted into the
ground, but the continuing cold weather and high wins would definitely have been a problem. In
three of the gardens I use the same double layer combination of fleece and crop cover,
stretched over arches made from water pipes stuck in the ground. This gives the plants a lot more
space to grow into, as they could be under cover for quite a while, depending on the weather. It
also gives me space to put in some containers of water to act as a thermal mass,
to store the heat that builds up during the day and release it slowly overnight.
A few weeks later when the weather warmed up I removed the fleece layer, but have kept the woven
crop cover in place as partial protection against the wind. As these plants are just beginning to
flower I need to start removing the cover during the day to allow the bees in to pollinate,
or to do some hand pollination myself, and to help the plants harden off, to adapt to the elements,
but then I still cover them back up at night or when it is reasonably windy.
This year I also build a series of plastic covered wooden panels that I could assemble
into a cold frame or mini greenhouse with a hinged lid. I decided to try to grow the squash
and courgettes in one of my gardens in these more rigid protected growing spaces.
They were a lot of work to build but once they were finished it was quite easy to put them into
place and protect the tender transplants. I do open them up in the morning to prevent
the space from getting too hot during the day, but also to let in the insects for pollination,
and then close them up again in the evening, just like I do with the polytunnels. I
plan to remove the lid entirely once the weather warms up enough, but to keep the side walls in
place, and it will be interesting to see if this will provide enough of a microclimate to
significantly increase the yields and enable the squash to mature more effectively. And
when the weather turns cold again in the autumn I can put the lid back
on to protect from early frosts and to further extend the growing season.
Protecting the squash and courgette transplants is a bit more difficult in the Polyculture Garden,
as they are planted in amongst a diversity of other crops. I decided to try to build
little cloches or mini greenhouses, made out of wood screwed together with the sides covered
with scrap pieces of polytunnel plastic stapled to the frame. And I fixed a double layer of the woven
crop cover to the top, which I figured would let in the rain and hopefully prevent the small space
from overheating. Like the larger cold frames, they took a little while to build, but they should
last quite a few seasons, and will hopefully be useful for other crops throughout the year. But
unlike the other options, I’m going to have to remove them fairly soon as the plants are becoming
too cramped in that small space, and I've started the process of propping them up on stones to give
a bit more space and enable a more gradual transition from the protected microclimate.
So they were really only useful for a couple of weeks for the squash plants,
but if I find that there are useful for other crops at other times of the year,
I’ll probably end up building a lot more of them. In the polytunnels the wind and cool weather are
not normally an issue, and the light frosts don’t have an impact, but the hard frost can
definitely be a problem. This year I had a long bed of one of my polytunnels planted
with an early crop of potatoes which were really big plants at the beginning of May. When really
cold nights were forecast, I spent the time to cover these large plants with a layer of fleece,
which was a more difficult task with the plants being up against the side of the polytunnel
plastic. This second layer of protection was effective for the most part, with only a few
leaves that were touching the polytunnel plastic being damaged by the freezing temperatures.
In my larger polytunnel I had twine already in place to support the numerous tomato plants,
and I repeated a method I used last season of clipping a layer of fleece to either side of the
twine to make a long tent over all of the plants and the soil of the bed. This was quite effective
at keeping in the warmth, and thankfully there was no damage to any of the plants.
In my other polytunnel I had covered the full bed with a double layer of fleece over hoops made out
of water pipes, with a fair number of containers full of water for thermal mass tucked underneath.
I had this in place since the plants were transplanted into the bed,
and these plants grow quite quickly in this very sheltered and warm space,
and were perfectly fine even on the coldest nights in May.
The extra warmth provided by this double layer of fleece inside the polytunnel meant
the tomato plants grew a lot faster, and there definitely seems to be a benefit to keeping
them covered even if there wasn’t a risk of frost. And this seems to have been the same
with the potato plants outside, with faster growth, despite the cool spring, leading to
potentially earlier and larger harvests. And plants that can handle the frosts,
and can grow reasonably well in cool conditions seem to have done much better as well under cover.
I used the same double layer of fleece and crop cover over a few beds in the outside gardens,
including two beds in the Polyculture Garden covering a wide range of more hardy spring
crops. I was pleasantly surprised at how well these plants grew in the cool conditions,
and how much earlier I was able to harvest them with this covering,
and it was nice to be able to harvest leaves of the plants that were not damaged by the wind,
So, I started using covers like this to only protect the crops from frost, but now I have
found that the growth of many plants is better if they are covered for a most of the spring.
Of course I don’t want to cover everything in the gardens with multiple layers,
and with some crops it's just better to plant them later in the season.
But there is a definite benefit to being able to harvest crops earlier in the year,
and to be able to get better yields from the longer season crops. And a double layer
of fleece and crop cover seems to work well in the context outside, the cold frames and
smaller cloches seem to work well, though I want to do more experimentation with them,
and the combination of fleece inside the polytunnel is definitely beneficial.
And I plan to push things even more next year, to plant even earlier in the spring,
and to try out different methods of establishing that more beneficial microclimate,
to be able to consistently harvest really good quality vegetables, even
earlier in the season when they can be very useful.