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Opinions and advice sought on a second growing season plan


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  • Opinions and advice sought on a second growing season plan

    Hello all
    Have just found this community and realise that there are many here who have a lot more experience than I have of growing food undercover and in particular out of the usual season. I would love to hear anyone's thoughts on what I would love to do.

    Before I outline my plan, just a bit of background about my garden. We have a small vegetable plot (8 deep beds 4' x 12') which we have used for many years to grow spuds, brassicas & beans etc between Mar-Oct. We also have a traditionally built lean to greenhouse (6' x 10') for summer tomatoes. Surrounding vegetation and trees have now matured to such an extent that it gets less sun during the winter than it did and this coupled with my wife developing a strong interest in the husbandry of begonias and geraniums mean that in the winter we keep it frost free and fill it with her collections to overwinter.

    This year, because of C-19 we have really appreciated what we have and although our garden is not huge it has become an even more important part of our life and I count our blessings on a daily basis for having it. Each of us has health reasons to really not want to catch the dreaded lurgi and for 6 months we have hardly gone out into the outside world - I am retired, my wife has an amazing computer link up with her employers and all our food and shopping has been delivered.

    The fresh crops from the garden have been wonderful and now I don't want them to stop coming !

    It occurred to me a few weeks ago that there may well be a way to have another growing season. At the start of lock down we had bought a 6'x 6' greenhouse with a polythene cover. We put all our food deliveries in this and blasted them with ozone to destroy any possible virus but now find an old cold frame is big enough to do the job so the little greenhouse was carried onto a bit of the veg gerden where my wife immediately filled it with micro salads and various other things she has grown from seeds taken from stuff we've bought to eat such as chillies etc. This greenhouse was so amazingly cheap for its size (50ish) that I have been thinking of getting more.

    Obviously, veg plants are not stupid enough to grow during the winter even if I was to provide toasty little greenhouses for them. The position of our veg plot in relation to our house means that the sun in winter only gets high enough in the sky to provide just a few hours of sunshine. But of course it is not just that, it is the fact that as I write this post on the autumn equinox we now start to have more hours of darkness than light.

    Fortunately, there seems to be strong desires by many of today's young people to smoke mind altering herbs that can be grown to be so powerful they would make the version available when I was their age feel like the most remotest of distant cousins. There appears to be so many consumers and such large amounts of money that it has stimulated a fast moving and vibrant market producing the equipment needed to grow the stuff and in particular artificial sunshine. I remember toying with the idea of getting a grow light just a few years back and it was quite an esoteric object then. When I started looking at them a few weeks ago I was amazed just what a huge choice there is now and not only that, how cheap are entry level products. It turns out that in my hometown there is a specialist supplier of this equipment and this is no small scale operation - they sell several lighting technologies, each with many models and some of the more advanced ones are extraordinary with price tags of many thousands and wouldn't look out of place on a space station on Mars. Equally impressive was discovering that everything on their website is available from stock. I could understand this if we were in Canada or one of the states in the US where cultivation of their target crop is legal but here it isn't. I couldn't even stop myself from making clear that my enquiry was to do with growing tomatoes and peppers under cover - I even considered dialling 1470 before dialling goddammit

    So finally to my question which is about the design on the structure where my man made suns are going to do their work. For various reasons I have settled on a size around 10' x 15' which I hope will be big enough to be self sufficient in tomatoes, salad leaves, green beans of a couple of varieties and some kind of mangetout type pea. My wife is also making the whole project conditional on a weekly crop of spray carnations and a couple of other flowers so she can continue producing the three flower arrangements she makes each week. I reckon half the area will need some kind of hydroponic system where I can make use of vertical space.

    I suppose my first question should be - am I being wildly unrealistic thinking that 10 feet by 15 feet can produce enough of the above crops for 2 people (assuming I can provide optimum heat and light).

    The route to the design I am considering moved on from cheap polythene covered Amazon jobs to cheap polycarbonate aluminium framed jobs and then to slightly better (thicker) twin walled polycarbonate aluminium ones and then stopped. Not because half of these types that are built seem to disintegrate when the first gale arrives but because costs started to get out of control. I was getting into that horrible territory where the sensible thing would be to pay twice as much (at least) and get something fit for purpose. I might be able to brace a cheapish model to stand up to the conditions in our sheltered walled garden but I can't do anything about poor quality metal etc. I was (and am) attracted to twin wall polycarbonate because of heat. Even on a cold winters day it would heat up rapidly as soon as the sun gets on it and I read of a system of blowing this hot air into a couple of sunken plastic barrels and then on into a matrix of porous pipes buried in the soil. The reality is though as I said earlier, the amount of hours of sun per week would be very low from now, end Sept through to March.

    So it's back to a plastic covered structure probably based on a polytunnel hoop shape. Unlike the relatively new, highly competitive Aluminium polycarbonate products coming out of China the polytunnel market seems much more mature and many do seem fit for purpose. There are still the amazingly cheap imported ones but a quick Google reveals several UK manufacturers who all reckon they have super strong models. Does anyone have any strong preferences to any particular supplier? Also, am I wise in spending at least double the cost and getting a UK made one or are the really cheap imported (I assume Chinese) good enough ?

    I now plan to get the most robust frame I can afford with a reasonable cover and then lay pool cover over it (which sounds like large bubble wrap). On top of this will be a layer of marine grade shrink wrap which is used by boat yards to protect boats that are being dried out or painted etc.. These two layers will reduce any sunlight significantly but that is not an issue as I plan to use LED grow light panels which will either be on for lengthy periods or what I really fancy will mimic natural day lengths - my target is that March 1st starts for the second time in about three weeks time. I can then program my Raspberry pi to provide the sunrise and sunset each day and longer & longer days. This may be a sentimental approach and better crops may be produced by just blasting everything with artificial sun for artificially long periods - need to get further up the learning curve on this one.

    As for heating. I am hoping the pond cover will work well but maybe two layers may be better. Also, maybe conventional bubble wrap is better or even another material I haven't considered. The function of the shrink wrap is to keep the insulation in place and improve overall rigidity. Whatever I use under it I need to keep daytime heat losses to a minimum. I am going to use electric undersoil heating (not sure how yet) but this will hopefully only need to be on between 1 and 5 in the morning as the electricity tariff we are just about to move to has prices that are often less than 20% of what we pay per unit now during those hours. On several occasions each year when there are strong winds the grid needs to dump electricity and we will be paid to use it ! I suspect this will be mainly in the warmer months though. We were planning to do this because of the electric car we have just got (it is quite common to charge these at night when electricity is not so much in demand). This availability of cheap power together with a whole new generation of low consumption LED grow lights seem to me to combine and make two season veg growing a much more realistic proposition than it would have been just a couple of years ago.

    Sorry for such a lengthy first post but I would love to hear all thoughts, both positive and critical. This is such a new thing for me I may well have ended up with something that could easily be bettered.

  • #2
    Hi and welcome, big project you have in mind there, most equipment for sale for the home use seem to be just for that, on a windowsill in the home. Now I know there are folk in the Shetlands growing in polytunnels under lights to extend the season, but I think the crops grown are limited. LED's seem to be the way to go, good light colour and consume a lot less energy. There will no doubt be commercial systems used by professionals, but I'm unsure where you would get those, here's a list to start you off and good luck .
    Keep us posted on how you get on.
    If I'm not on here, I'm probably fishing.


    • #3
      I use a grow light in our house to start some tomatoes,peppers & flower seeds off a bit earlier in December/January,then they go outside & fruit a bit earlier,then you don’t need a heater as it’s inside,a pool cover sounds expensive & difficult to get to the plants? Have you got any broccoli,brussels sprouts,carrots,parsnips outside growing now,that will be ready to harvest in the winter,we can use the growing seasons we have by planning what crops to grow to cover the winter season. What exactly do you want to achieve so that we can help because say you wanted to harvest tomatoes in January,the plants would need starting earlier,they take a long season to grow but things like radish & spring onions would be quicker. I make tomato sauces & freeze them for winter use,could you freeze some fruit?


      • #4
        Hi guys - thanks for the replies.
        I appreciate your warm welcome burnie and I will certainly update this topic with my progress. I have more or less settled on the hardware I will need and cash flow dictates I will be buying it bit by bit. The biggest expense is 4 x LED light panels which are around 450 each but I will not need them for a while yet These should provide full sun for c.100sq' of the 150sq' space I'll have available. I am going to be slowed down because of having to wait until my seeds germinate - I should have started this project a couple of months ago ideally.

        So this evening I took the first step and have ordered the seeds I need. Tomorrow I have to decide which make of Polytunnel and order that and I'll have time to build that while I wait for stuff to germinate. Luckily I will have a good few weeks to decide on insulation and design a heating system that can be switched on during the night.

        I take on board the points you make Jungle Jane and my lack of foresight in the spring means that I am going to have some space unused during the winter so have just ordered some green manure to protect the soil.

        Exciting times ahead but I'm dreading having to choose the Polytunnel supplier tomorrow as there are 3 or 4 who each have compelling products. I wish I had the time to get some opinions but I just have to get on with it and hope I make a good choice.


        • #5
          It might be prudent to do this in phases, once you have your tunnel maybe create a small part of this and insulate/heat/light that and begin your growing and then expand as funds/time allow. I did something similar in a part of a greenhouse when I lived in Leicestershire, heating with a paraffin heater and used a mercury vapour lamp. Biggest problem I had was damp, which created mould.
          If I'm not on here, I'm probably fishing.


          • #6
            There's a really long lead time at the moment for all things greenhouse related; I'm not sure if this is the same for polytunnels now, but it might be worth ringing any suppliers to confirm whether they really do have things in stock. A neighbour of ours has finally just received their greenhouse after ordering it in June (and were told it was in stock). It's not suppliers being difficult, but that the supply chain is not great at the moment.

            It's an interesting concept blowing air into the ground; have you considered burying a layer of expanded polystyrene under the soil of the greenhouse? An awful lot of heat is lost that way as well as sideways and upwards.

            I've been looking at a small grow light system but an indoors one. A lot of commercial LED light panels are available at more competitive prices than dedicated horticultural systems; for my indoor version I was looking at a 600mm x 600mm LED panel with a CRI > 80 and this is 25 inc. VAT, so competitively priced. It's also a standard power rating for mains AC with no need for transformers.

            It's certainly an interesting project.


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