Welcome to plant cultivation-houses

In Swedish

TUB FARMING

A crop-growing house is a greenhouse built primarily for growing food year round. It is designed with ease of energy-conservation and irrigation in mind and to support a high yield year round. We consider it bizarre to import lettuce from New Zealand when we can grow our own fresh daily salad all year, should we wish, with relative ease at home or as a neighborhood cooperative.

First a schematic drawing:

vhus

This greenhouse was designed by Abby Rockefeller and Carl Lindström and won a competition for the greenhouse that could produce the most eatable salad greens per sq. meter (1978) in the USA. It was arranged by the National Center for Appropriate Technology -- NCAT
http://www.ncat.org/

This growing house has a heat-storing foundation made of rocks under the floor which tempers the air in the green house. It takes the peak heat off in the day and stores it under the floor to cut the night chill. A fan regulated by a simple differential thermostat blows the hot air through the rocks when the sun is out and the temperature in the green house is higher than the temperature in the rock-storage under the floor. This gives us an active cooling during the days and a passive heating during the colder nights. But during winter it is equally important to take the extreme cold temperatures off during both nights and days. The important thing is to not let the temperature drop too far below freezing since most salad greens can stand a light frost but not a real cold spell. This too is taken care of by the structure of the building.
The subsoil irrigation is arranged through greywater irrigation (see http://www.greywater.com ). After a rough filtration though a "pantyhose" stretch filter the still luke-warm greywater is injected just under the surface of the soil in the one meter deep soilbeds. This way the water gets good purification at the same time as the soil stays moist even when water evaporates and/or is used rather infrequently. The deep soilbeds get their warmth both from the stone magazine and from the greywater. During the coldest and darkest months, it may be necessary to add a little heat (by burning some propane inside the greenhouse and use the higher CO2 concentration in the inside air to compensate for the lower light conditions.

We used a wood burning stove to raise the temperature in the stone magazine during the coldest part of winter but a simple propane-burner works well too.

What we grow.

The trick to having a daily salad year around is to only pick the outer leaves from the head of lettuce or the broccoli plant. You don't remove the plant from the soil bed until it has gone to seed. This way the plant keeps producing leaves until spring when they molt. Choose salad-greens that can tolerate a light frost ( if you live in an area of cold winter weather conditions) and recover from a temporary set back. Broccoli is actually a great leafy salad-green where both the head and the leaves are tasty. Same with cauliflower.

 

veggies

In the picture above you can see the small 2x3 m greenhouse in Cambridge, Mass. during one of the classic snow storms ... this one from 1978. ALL traffic stood still for three days and we were the only people who had fresh greens to share with our neighbors.

1978

Tomatoes are sensitive to frost, cold weather, and attacks from white flies and aphids. We got pretty good protection from lady bug larvea and predatory mites.

The growing-house in New Hampshire

Inspired by the small greenhouse in Cambridge, we wanted to build a larger greenhouse, this time near Concorde New Hampshire which is known to be one of the real cold spots in the US. This second one was also a lean-to a barn and faced south. As the first one, this one also had a heat storing foundation with about 80 tons of rocks under the floor.

The hot air was drawn into the ventilation system at ceiling level and then pulled down a generous shaft to the fan in the stone storage (to reduce t fan noise). We built a plenum from cinderblocks lying on their sides, and passed the air through the rocks and up through the holes in the cinderblock wall. The air is finally exits under the window sill to create a bit of air movement over the soil bed and prevent fungi and mold growth. The soil remains moist since the greywater injection pipes are only a few inches under the surface.

The excess water is drained out of the soil beds down at the bottom and lead out through pipes in the cement floor.

Heating with gas gives you three good things for a greenhouse: heat, water and CO2

2 C4H10 + 13 O2 → 8 CO2 + 10 H2O (Butan)

C3H8 + 5 O2 → 3 CO2 + 4 H2O (Propan)

Pictures from the construction:

These soilbeds are made about a meter high to be at a conveniant height ... kind to our backs

The soil-boxes are constructed with blocks and block-bond on the surface to hold the blocks together. Block-bond is a cement and fiberglass mix that creates a strong surface layer holding the blocks together, instead of the usual masonary method of "glueing" the blocks together with cement.

We put a layer of coarse sand in the bottom to create good drainage.

 

Here the soil-boxes are filled with sand and soil. The opening in the wall holds a glass window to see if there is earthworm activity in the soil.

Here we have laid the irrigation pipes and will add the final soil cover.

In the other end of the greenhouse there was a fish pond, getting its nutrients from what is drained out of the soil beds.

Now the growing-house is finished with glass on the vertical sides and Acrylite resting on ceder-rafters for the roof,

The chimney comes from a wood-stove that can add heat to the stone storage with a good fire...

Here Abby has planted rows of seedlings for the winter -- lettuce, spinach, broccoli, cauliflower, herbs like rosemarine and an orange tree in the corner.

A few weeks later everything was lush and doing really well and we had already gotten our salad bowl filled every day for a week.

It keeps coming all winter long.

This is later in the spring when all the lettuce has gone to seed and the garden is doing well outdoors

This cultivating greenhouse was built into the side of the house and resulted in a very good integration

So why should we do it ? To extend the period we can grow things in a cold region but also because industrial, chemical food can not be trusted ... we have to know what we put into our food !

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Next is a Swedish greenhouse where light and temperature conditions are even more severe than in the US

 

finished construction and waiting for being seeded

 

This is only 8 days after being seeded with lettuce and spinnache

... and this 2 weeks after seeding and it is what we want abundant growth so that we can

start thinning which is how you keep getting your greens all winter long ...

In this greenhouse we got started late in the season so the stone heat storage didn't
get charged during the warm summer days ... the indoor temp is 13°C and the outdoor is 10°C

Later in winter the Outdoor temp is -13.4°C and temp in the greenhouse is +3.9°C

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Below is the differential thermostat that starts the circulation fan whenever the temp.
in the greenhouse is higher than the temp. in the heat storage ... so if we have a wood-
burning stove in the greenhouse, it will put all the excess heat into storage !
No need for a stove that store heat in itself ...

 


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