Hothouse Practices

Having almost finished building my own hothouse, I thought it would be great to learn from other Food Garden Group members with experience in this area.  I asked them what they grow in their hothouses, what their successes have been and what did not work so well.  Here is what I found out.

Max K at Lindisfarne has had this hothouse for around 15 years

Every year Max K sows tomato seeds early July in an electrically heated propagation tray and then puts them in his hothouse in mid August.

In mid August - early September he then sows cucumbers and capsicums in the same tray and transplants them to the hothouse when the seedlings are big enough.

He usually continues to pick tomatoes in his hothouse until the end of June.

Max opens the door of his hothouse every morning and then gives his flowering plants a bit of a tap to encourage pollination if he thinks of it.  Years ago he used to use a hormone tomato setting spray and that did help to set the early flowers. In past years Max often had bumblebees in his hothouse to help pollination, but he found that there were fewer around this season.

He currently has a whitefly infestation in the hothouse that does not harm the plants or fruit, but that he can't get rid off.  Yellow sticky strips he installed are covered with them, but the plague is not gone.

This season the weather was cold for a long time with a few hot days in between.  After those hot days Max found that flowers on some of the plants in his hothouse had shrivelled up, resulting in less fruit.

At the end of July Max sowed Chantenay carrots (a short variety) in a deep polystyrene box in his hothouse.  They grew much faster than they would have done outside and Max had great-tasting carrots in September.

After using soil in his hothouse for a number of years Max switched over to a hydroponics some years ago because he and his wife like to travel in their camper van.  Max uses two hydroponic systems, one called 'Fill and Drain' and one called 'Smart Valve'.
With the Smart Valve system water and nutrients are fed to pots from a 50 litre rubbish bin filled with water + nutrients (see photo below).  A cropping tomato plant will use around 1.5 litres of fluid per day, so a system like this can be left unattended for a week without any plant dying.  The medium he uses is 4:1 perlite and cocoa-peat (ground up coconut fibre).
For those of us who like to grow crops organically, no, this is not an organic system. Max K is not sure a completely organic hydroponic system exits.

Max had a polytunnel once that was a lot longer than his current hothouse.  Ventilation in the polytunnel was a lot easier and it was easier to keep down temperatures.  Humidity in a hothouse that is too hot can cause leaf mould and other disorders.  Once a year Max lime-coats the glass panels of his hothouse and this helps dot diffuse the light and reduces temperature.  However, very high temperatures at times this year caused problems.

Like Russell, Max K feels that it is great to have a hothouse, but he advises people to get a sturdy one.  Max showed me a few hothouses that were wrecked by strong winds.  The bent metal supports, warped and broken 'corflute' panels showed me what can happen if you put up a hothouse kit in a spot that is too windy and you don't look after it.

Russell at Acton has had a hothouse for around 4 years

Every August Russell buys tomato seedlings as soon as a nursery has any and gets them going in his hothouse. He then has his first ripe tomatoes in November.  In mid January - early February, while these bushes are producing, he plants additional tomato seedlings in his hothouse and these bushes will produce tomatoes right through winter until the end of October.
In other words, Russell has his own tomatoes all year round.
He sometimes shakes his tomatoes or uses a brush to pollinate if they do not set fruit by themselves. His favourite hothouse tomato variety is Moneymaker.

In his hothouse Russell now also grows Basil and that too produces fresh leaves all year round.

This year Russell tried Cucumber in his hothouse, but it had plenty of flowers, but no fruit.

He has also grown Capsicums in the hothouse successfully.

In December he sows Brussels Sprouts in his hothouse and then plants the seedlings outside in January.  He also uses the hot house to sow other vegetables and flowers if he is having trouble getting them to grow from seed in the open garden.

The soil Russell uses in his pots is K and D premium potting mix.  This year he has added 20% loam with chicken manure as an experiment.  Keeping the soil just moist enough but not too wet is a constant challenge.  Russell now uses a moisture meter. When you poke it into a pot with soil it gives an instant reading which Russell uses to tell him whether he needs to water the pot or not.

Russell does not use shade cloth on his hothouse.  In colder months he just opens the door during the day.  In summer he opens the door, window and a hatch in the roof (see photo).

The benefits of the hothouse for Russell and his family are that growing your own produce year round is very satisfying and it is tastier than anything you buy and chemical-free.

Russell's advice for those contemplating buying a hothouse is that you need to secure it properly because it can be blown to bits easily and you should not use the soil that is already there, but use pots with fresh potting mix and soil.  If you don't want to use pots soil in your hothouse, you need to refresh the soil every year.

If you go away your garden may survive, but plants in your hothouse won't, so you need an automatic watering system or someone who is prepared to water your hothouse for you in your absence.

Ilse at Snug has had a hothouse for around 1 year
Ilse has two hothouses.  The first one has been in use for around a year.  The second one has just been erected.  Both have windows with heat sensors, so windows automatically open and close as needed.  They have an automatic watering system, but this is only switched on when they go away.

Ilse rarely buys seedlings.  She likes to start from seed because she finds it satisfying to start with a little seed and harvest vegetables a bit later.  She buys her seeds from Southern Harvest and sows most things in her hothouse.

Sofar she has had in the hothouse cucumbers, melons, chillies, lemon grass and tomatoes.  Tomatoes were deliberately mentioned last because her main crop was outside this summer and last summer. She feels it might be a bit too hot in her hothouse at times.

Ilse sowed her tomatoes in August.  Cucumbers, Melons and Chillies were sown in September.

She hand-pollinated very occasionally, but found that, because the windows of her hothouse open automatically, the are some insects in the hothouse most of the time.

One of her tomato plants in the hothouse (a Tommy Toe) was held over from last year and is now producing tomatoes for a second season, which raises the question 'how long can a tomato plant be productive if it is never exposed to cold conditions'.

Ilse's Chillies were kept in the hothouse over winter and started producing chillies again in spring.

All the plants in her hothouses are in pots filled with standard garden mix soil from a nursery, with complete organic fertiliser, worm juice and fish emulsion added.

Melon variety Mountain Sweet has been one of Ilse's successes.  She sowed the seed in early September in warm conditions in her home and then moved the seedlings to the hothouse later on.  The melons have been tasty, but a bit small.  This could be because the soil is missing some nutrients.

Because of the automatic opening and closing of windows, temperature is not a big issue in her hothouses, except on really hot days.  A shade cloth over part of her second hot house is also helping to overcome this problem.

Ilse realises that a hothouse is not cheap and takes up space.  She enjoys growing plants in her hothouse, but says not to worry if you are not able to install one, it is not something that is absolutely necessary.

My own hothouse at Lindisfarne

Built from recycled materials (some donated and some bought), except for the transparent roof and framing timber which are new, this hothouse cost me around $800 all up.  I live in a very windy spot and now have a hothouse that will withstand any wind, no problem.

My first experiment is going to be to grow and hopefully harvest Celery over winter.  I will also follow Ilse's example and try to get a second season out of my Galapagos tomato (the tomato plant in the photo).

The soil I am using in pots in the hothouse is a mix of potting soil, sand, peat moss and sheep poo.

Max, Russell and Ilse all commented that the purchase price of a hothouse can really not be justified by what produce you get from it. However, they all love their hothouse because:

1. You are less dependant on the unpredictable Tasmanian weather
2. You can experiment with things that normally don't grow in Tasmania
3. You can grow fresh organic fruits and vegetables out of season
4. (if you don't leave the door and windows open overnight) a hothouse is completely safe from wildlife

Thank you Max K, Russell and Ilse for your contributions to this blog post!