Rit Búvísindadeildar - 10.07.1996, Blaðsíða 49

• Satisfactory results were not achieved with cabbage lettuce unless the plants
were pre-cultivated in a heated greenhouse. Growing period after planting was
35-45 days. If the seeds were sowed directly in an unheated greenhouse, a
growth period of 60-70 days was required for butterhead lettuce, and 70-80
days for crisphead lettuce, in order to get acceptable yield. The risk of damage
caused by various diseases increases with a longer growth period.
• Damage caused by leaf spot diseases was frequent in the plastic greenhouses at
Hvanneyri, probably because the temperature and humidity was too high
during the day. The light nigts of the Icelandic summer possibly increase the
threat of growíh-diseases.
The following varieties seemed to be well suited to conditions in unheated
plastic greenhouses, and were only slightly affected by leaf spot diseases:
Oresto, Tannex, Nabucco, and Hansen lmproved.
• Through most years of the experiment, growing celery proved successful in
unheated plastic greenhouses. Attempts to grow celeriac failed.
• The variety of leek which gave the best yield in the unheated greenhouse, was
Varna.
• To keep two leek plants together in a 3.5 litre pot gave better results than
keeping individual plants in 2 litre pots.
• It is quite possible to grow onions in unheated greenhouses but they must pe
pre-cultivated in heated greenhouses. Such cultivation is bound to be
uneconomical but can still be justified for kitchen-gardening, as people could
select varieties with a rniid taste to use in salads. An example of such a variety
is Expando.
• Herbs which were cultivated with successful results in an unheated greenhouse
were: Dill, Tarragon, Thyme, Kainilla, Chervil, Mints, and Parsley.
Herbs which gave partly successful results were: Basil, Coriander, Meiran,
Sage, and Fennel.
Herbs which gave unsatisfactory results were: Anise, and Rosemary.
43