This is some notes from an interactive gardening session at All About Gardening, a programme of the Canterbury Horticultural Society
Talk to CHS All about Gardening February 2016
Alan Jolliffe, with help from Michael Coulter and the audience.
Glasshouse, Greenhouse or Hothouse
All these terms are variously used to describe what we will call a Glasshouse. That is a structure that has a foundation, frame and clear glass or polycarbonate panels to let light into the structure.
Why a Glasshouse
Purchasing or thinking of purchasing a glasshouse for your garden?
Answers vary from person to person with the most popular being
- To extend the growing season
- To grow tomatoes
- To grow other fruit and vegetables
- To grow seedlings, cuttings etc for the garden
- Have we got the time to devote to the glasshouse?
- What other add-ons do we need?
- What size?
- What costs are involved?
What sort of Glasshouse
There are different types of glasshouses on offer.
There are several designs one could choose, depending upon budget and what you are trying to achieve. Rather than describe these in detail use the internet to look at different types.
- Aluminium frames with glass panes are the most expensive and probably the longest lasting. A good long term choice. Usually small flat pack type aluminium glasshouse constructed on a concrete or timber “foundation”. The glass covers the roof and all the vertical sides.
- Powder coated steel. These are offered in increasing numbers and varieties from difference suppliers. Long lasting provided there is no damage to the coating allowing moisture and rust to attach the steel.
- These can come with glass or clear corflute type polycarbonate material. This material is quite good as it acts as a form of double glazing. It may become more opaque over time.
- New or second hand. If buying second hand my choice would be an aluminium frame.
- Wooden glasshouse. These are probably rather older types today and maybe purchased second hand and will likely need considerable restoration.
- New wooden glasshouses are more likely to be of a conservatory style today due to the higher cost of being handmade. They may also be added onto a house to provide another room and add to the capital value of the house.
- Stove houses were a design of a glasshouse with uses forced preheated warm air around the glasshouse. Heat was from very early well designed slow burners.
- Lean to glasshouses were used extensively in the UK where maximum heat was gained from facing the main glass house roof directly into the sun.
- High sided glasshouses. These have low brick, concrete block or concrete walls to about 1.2 metres with the glasshouse frame on top. This allows the walls to trap heat during the day and release it at night and also reduce the cost of the glass and framing.
What does a glasshouse do for you?
Climate control is probably the best way to describe the benefits of a glasshouse. By this we mean it provides protection from the extremes of the weather to give plants a more even growing climate.
- Protects the plants from cool or cold winds which can slow down growth of the plants.
- Provides protection from
- Protects the plants from low temperatures at night time by trapping heat in the soil or structure and releasing it slowly over night.
- Warms up soil to speed up early season’s growth.
- Controls the atmosphere but keeping it warm and raising humidity depending upon the growing conditions you want
Glasshouse are best located where they get maximum sunlight from all angles.
Additionally it should be constructed so that the central ridge line runs north to south. This will enable maximum sunlight to all plants growing in the glasshouse.
Lean to glasshouses are usually an exception but the main glassed in section should face north.
A poll of the audience showed that people grew plants either directly into the soil or into larger containers in the glasshouse.
- Those growing directly into the soils did so to reduce constant watering and to make use of a wide variety of nutrients available from compost rich soil.
- Those growing in containers did so to reduce the effort of replacing the soil annually by not having to dig out the soil and remove it from the glasshouse.
- Hydroponics was mentioned but did not seem popular.
As Prof Walker used to say soil is like a new born baby “you must keep its face clean, bottom dry and tummy well fed”.
Like all buildings a glasshouse needs to be kept clean and tidy. In particular each spring make sure that it receives a good clean and use a disinfectant to wash into all the nooks and crannies to kill bugs, eggs and spores.
During the growing season also keep it clean and tidy by removing dead and dying plant material.
By far the most common crop everyone wanted to grow was tomatoes. This was followed by
- Peppers or capsicum
- Indoor plants
Great growing conditions include warm, but not hot, growing conditions, regular watering (but not too heavy) good ventilation or air movement though the glasshouse and potentially some shade in mid-summer. (If you need lots of shade then you probably need more ventilation). Regular top up of fertiliser (a little and often) and maybe one additional top up of compost is recommended.
Pest and Diseases
Pests are insect which may include sucking insects on the underside of the leaves, whitefly and caterpillars. Check out which intervention you need to apply by looking at a good garden guide.
Diseases include viruses (which can be brought in by infected plants) and fungi such as black spot. Again check out which intervention you need to apply by looking at a good garden guide.
Although not popular people are experimenting with growing the following in the winter
- Silver beet
This guide is simply that a guide. Please use it but follow up any ideas you find in here with your own research and knowledge. All we can do is provide you with the basics.
Yates - http://www.yates.co.nz/