The mixed house is only successful on a domestic or commercial scale when growing house plants. For single crop plants such as tomatoes, carnations and cucumbers it is very bad practice and should never be considered as the growing conditions are so specialised and are totally different for each crop.
Whatever crop is being grown, the glasshouse should ideally be completely emptied once a year and thoroughly cleaned. Unless this is done there will be a build up of pests and diseases which will be very difficult to eliminate.
Many topics have been superficially covered and further reading will be necessary should the student wish to go into greater depth on any particular related subject.depending upon the species can be very rewarding but you do need to have a deep pocket or good friends to start with.
House plants of the conservatory types may be fine. Cut flower crops from carnations,, , , gladioli, roses could answer all one’s needs.
African Violets will work well in triple glazed houses at 18 – 20°C.
Other problems with white fly, red spider and green fly may occur reducing growth rates by damaging the foliage. Pesticides may help enough. White fly can be particularly troublesome. There are those who grow Tagetes as a companion plant and this keeps the white fly at bay; apparently for some it is very successful. White oil emulsion seems to be one way out and is much less hazardous to the environment than the chlorinated hydrocarbons.
Underground there are pests also – like theknot and potato cyst eelworms, symphilids and even major pests like slugs.
Soil sterilization has been referred to several times. Steam sterilization is costly but effective. Methyl bromide gas is excellent. (This is not available for amateurs and has to be applied by authorised contractors only for commercial growers.) The products available to amateurs include Dazomet which helps against root rots and vascular wilts. It is no help with soil-borne pests.
It is possible to reduce soil problems by grafting thetomatoes on to resistant ( ) rootstocks – one such is K.N.V.F. It is effective but the system needs attention to detail to make it work well for the grower.