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Glasshouses / Greenhouses · Hydroponics Daily

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Hi, welcome back to Hydroponics Daily. I'm Dr. Russell Sharp and today we're
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talking about glass houses or greenhouses.
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I prefer the term glass houses because they always have glass in them.
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It sounds strange but if you go to Spain they refer to their greenhouses that
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are made of plastic film as being greenhouses but they're not really greenhouses,
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they're more polytunnels.
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So today we're just focusing on those ones that are made out of glass.
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The glass is important because it re-radiates the
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infrared heat a lot better and so it's a
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superior form of growing compared to polytunnels and
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also it excludes ultraviolet light whether
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that's a benefit or a negative it depends on the
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crop and the and the grower and a
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greenhouse is also a lot more a lot
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more easy to control the environment than
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a polytunnel because you can have self-opening vents
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and you can put lighting in there and things
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like this whereas polytunnels you don't send out lighting in or certainly not
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automated vents very often so a
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glass house is probably the most controllable growing
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environment outdoors using sunlight obviously if
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you can grow indoors with it in a grow room you can exclude
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pests and disease which you can't really do with a greenhouse and
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you can put you can put you know a mesh on vents
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but pestanities can get in so greenhouses
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are very important and you can grow hydroponically in
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greenhouses and i've got a greenhouse that's
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about how old is it it's about 30
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years old it's a red rest western red.
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Cedar greenhouse and it's a bit like if you're in the uk if
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i said triggers broom you'd know what exactly what i meant if
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you're outside of the uk you won't know what that means basically means
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that every part's probably been replaced at least once
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or twice in its entire lifespan in that 30-35 years but wooden greenhouses on
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the face of it are not the best greenhouses to have because you get less light
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penetration in there and so the plants won't grow as well as say you had an
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aluminium or even a carbon fiber greenhouse or something like that.
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They just wouldn't greenhouses just look cool if
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you go to cambridge university you'll see
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they've got a greenhouse there that's made out of teak and it
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looks amazing and also if you went to
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kew gardens you'd see the palm houses made out of steel
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and they look amazing but they
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wouldn't necessarily be as good at growing
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plants in as aluminium or a
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modern what we call venlo greenhouses in
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europe which are these really tall glass houses
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that commercial tomatoes are grown in in northern europe
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they're called venlo because they're named after
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the town of venlo in the netherlands and that's
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where either they were invented they were commercialized or
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they were popularized but they're known as venlo so that's
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a venlo greenhouse we're in the spring now and
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greenhouses are really starting to come into their own because you
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can start crops off in a greenhouse you can transplant
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them outside you can you can grow
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all year much longer growing period than
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outdoors so i've been growing sunflowers and
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tomatoes chilies spring onions in our grow room utreema and then i've started
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to transfer them out into a heated greenhouse you couldn't do this outdoors
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you couldn't do this in an unheated polytunnel but with a heated greenhouse
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at night, you can prevent them from being frost-free.
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So in the UK and the northern parts of North America, they are an extremely
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valuable tool at this time of year.
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Just like a grow room, you can add CO2 to a greenhouse.
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And commercially, this is done with burners and you triple the amount of CO2
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going into the environment.
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In a domestic situation, you can still use burners.
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Burners like small small scale ones based on
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gas or i think it's kerosene the oil
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that's used in those however you will you do have
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to balance that co2 addition with especially as
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the as you get into summer with the increase in temperature as well
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and obviously environmental concerns and costs of adding co2 when it comes to
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heating a greenhouse at this time of year you can use oil-based heaters you
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can use electric heaters although they are a more expensive option they are
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more adaptable to sudden changes in temperature.
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You can insulate certain parts of the greenhouse with bubble wrap.
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This can help with maintaining a temperature.
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So many of the same sort of heating options that you have for grow rooms you can use in a greenhouse.
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So yeah, an electrical heater will have a thermostat on it so you can precisely control it.
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And then if you're germinating cuttings, then you can use heated propagators,
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which are a very efficient way of heating in very small space and
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with precision very precise thermostat attached
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to the to the heater i'm not i don't
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know anyone who's got a geothermal heat pump or a ground source
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heat pump in their greenhouse but that would be ideal really
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because you you could you could store a
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lot of heat down in the summer and bring
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it out in the winter that would be a really good one what i
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do in my greenhouse is I have loads of bottles from like soft drinks and from
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the factory where we've been making fertiliser and we've had you know polycans
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left over and I fill them with water and then I put them under the benches so
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my greenhouse is just full.
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Of plastic bottles and what that does is that water is
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extremely good absorbing heat energy so during
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the day this time of year it's absorbing the heat
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and then in the winter in the winter at night it's
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releasing that heat over at least a few
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hours so whether that does any effect or not i'm not
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sure but i have got hundreds and hundreds of water
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filled water bottles in my greenhouse you could
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even extend the central heating system of your house if it's
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a domestic greenhouse over to the greenhouse that's
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not that's a potential option commercially there's
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a number of other options people have looked at for heating recently i
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listened to a podcast about linking up greenhouses with
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brewers and using the waste heat
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and waste co2 more importantly in the
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in the greenhouse you can link greenhouses to
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factories and commercials and power stations and
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use the excess heat from them so i
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think british sugar have got a big tomato greenhouse that was
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then converted into the crop that cannot be named cultivation
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and they've got greenhouse and i guess they produce a
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lot of waste heat and co2 in sugar extraction and then in places like iceland
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they they have lots of commercial greenhouses and their geothermal obviously
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heat's there and even like in Finland there's a lot of greenhouses there and
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I'm not sure how they're heated though.
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At this time of year it's also important to note that you obviously want to
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keep your greenhouse frost free as a minimum but many plants will still suffer
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extreme if not permanent you know fatal damage if even if the temperature goes
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to temperature that's not below zero degrees Celsius.
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So pelargoniums, fuchsias, and then cucumbers, tomatoes, peppers,
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tomatoes, tobacco, they will all suffer if the temperature goes below seven degrees Celsius.
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And your tomatoes classically will go purple. That's a sign that they've got,
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not frost damage, but cold damage. And then other crops like lettuce,
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lettuce will survive in cold temperatures, but it won't grow if the temperature's
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below 7 degrees Celsius.
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And just like in a grow room, you have to balance the desire to maintain a nice
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temperature with the requirement for ventilation, to get humid air away,
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CO2 into the greenhouse, and that's a
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big issue because obviously you don't want to encourage
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fungal diseases that will thrive in high humidity but
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but you do want to maintain a temperature
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so it's the ever existing playoff
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between ventilation and temperature so domestic
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situation the issues are normally that you
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your issues are the temperature's not high enough and then in commercial greenhouses
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the big problem is getting the humidity down because because they're so big
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the greenhouses and they've got this long roof that getting the air flow through
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them is actually the most difficult part of that.
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Commercial greenhouses obviously will have computerized ventilation that's linked
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to a thermostat whereas a domestic greenhouse will have what's called an auto
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vent where you have the vent automatically due to chemical and physical.
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Properties of the vent will open or close. So they have different compounds
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in them, specialized liquids and metals that expand differently and open the
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vents depending on the temperature.
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So the coefficient of thermal expansion is important there.
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But the disadvantage of these is that they're harder to control at precise temperatures.
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And obviously if you have a large greenhouse, an automatic system is obviously the best option.
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So rather than just manually opening
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them and closing them so if you've got space for a greenhouse they're
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obviously great places to hang out especially when it's raining one
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of my favorite places to be is a greenhouse when it's raining with the
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radio on they're certainly nicer place to
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hang out than a grow room with artificial led lights and
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higher temperature normally they are
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less conducive to controlling the environment
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so you you know spores and insects will
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come into a greenhouse no matter what your ventilation system's like you
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can even get mice and rodents things like this so you have to be careful of
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but they are a big big barrier
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you know big big step up to outdoor growing so things
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like tomatoes i would never ever contemplate growing
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tomatoes outdoors because the not
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only is it you'll get blight because of the rain you'll you
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just you'll get really tough horrible tomatoes i find growing
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outdoors but the greenhouse you'll get you'll get amazing tomatoes especially
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if you can have an automated irrigation system the biggest problem with tomatoes
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is you just get absolutely sick of watering them all the time if you're watering
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them by hand whereas in the greenhouse that's great and then obviously things
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coming out of your greenhouse have fumes and plant odors you can't control them
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so you don't tend to have inlet and outlet of.
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Pumped, pumps? Fans, that's what I mean. Fans going, you don't have ducting
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and things like this in a greenhouse.
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If you do need to control the air coming in and the air going out,
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then obviously a grow room is the best option.
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I don't know of anyone who's selling a system for controlling the airflow in
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and out of a greenhouse in an outdoor situation. They're normally only for indoor growers.
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When it comes to hydroponics and greenhouses, pretty
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much any form of hydroponics can be used apart
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from vertical farming that they tend
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that wouldn't work in a greenhouse because you need the there's
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maybe pointless because you just every stack needs light
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from artificial lighting as opposed to
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sunlight so commercially greenhouses will
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use nft is by far
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the most common in europe northern europe for growing
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tomatoes cucumbers like things like that for strawberries it will be a gully
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system with cocoa and it's still nft but it's it's it's cocoa rather than rockwool
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a lot of growers are moving to cocoa now in tomatoes because of the issues about getting.
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Dealing with the waste after they've had a
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crop in it so if you hit just cocoa you can
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donate it to a local allotment or farm and they can
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put that on whereas rockwool that is a that's a serious waste
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issue in america deep water culture is
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very popular not popular in europe that i'm
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aware of i don't know many i don't know of any commercial dwc growers here in
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the uk i've seen grow towers they've seen them in eve shim growing lettuce they're
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easier for people to harvest from what other methods have we seen not many many
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pot-based cocoa growers maybe raspberries.
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Methods. Aeroponics. Aeroponics is becoming more popular. There's a company called Let Us Grow.
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They're trying to commercialise aeroponics throughout Europe with various degrees of success.
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What are the forms? Aquaponics. Aquaponics, more of North America and developing world.
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Europe, not so much, not many major aquaponic growers, but there are people
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trying to commercialise it and grow it.
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A lot of people trying to bootstrap that rather than investment.
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What are the forms of growing? Soil-based growing is not as popular as it was
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in greenhouses just because of the build-up of pests and diseases.
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So companies that were just soil-based growers, a lot of them have gone out of business.
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I know a major chrysanthemum grower that went out of business because the pest
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and disease just built up too much in the soil year after year.
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If you are going to grow in soil, you might want to change your...
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You'd certainly need to rotate your crops just as you would in a soil-based system in a farm.
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In japan they tend to grow more in
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the soil in their greenhouses which is unusual because
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it's normally high-tech so they might have high-tech growing but
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it's actually soil-based probably ebb
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and flood is the least used but is grown is used
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every now and again certainly with ornamental growers but yeah i don't know
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of anyone using really ebb and flood i like ebb and flood it's got its uses
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but it's not really commercialized much as the other things like nft it certainly
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is So that's been Hydroponics Daily for today, greenhouses or glasshouses.