Some of my citrus trees are about to start flowering soon. I've kept the air temperature around 50F (+/- 5F) for months - but I'm not sure whether it would be a good idea to continue so. What do you think? The soil temperature has been 48...50F as well.
Look at the pictures:





Harri.

Temperatures between 75 to 86 tend to produce fruit having a good soluble solids (sugars) and acid ratio. These temperatures make for a good eating orange. High temperatures, such as in the tropics produce a fruit with higher sugar content, but less acid, which would be good for the processing industry (juice manufactures), but not a good orange for the fresh fruit market. - Millet (1,068-)

Thank you, Millet!
But more I kept in my mind the possibility that such a low temperature may occur too low for forming fruitlets after blooming. Is such a danger real? Normally, temperatures +75F and higher in my greenhouse occur only in the middle of March or so... If necessary, I could rise the temperature also already now - but I wouldn't do this if not definitely necessary.

Higher temperatures are not absolutely necessary. Lower temperatures will just make the growth to be slower. As the days are getting longer, your greenhouse temperatures will increase to a more ideal range. The best to you and your tree. - Millet (1,068-)

All of my trees are starting major growth flushes and small blooms. Our temps are averaging 72-45 degrees I would say. I will probably start fertilizing them again soon. The problem is with these temps, it takes a little longer for the soil to dry out enough for another watering. I'm surprised at the new growth with these still fairly low temps.

OK, thanks - this was exactly I wanted to hear... So, I'll just act as usual and let the greenhouse warm up in it's natural way. Days are still too short and dark for an intense growth, I think.

Be careful of spring in a greenhouse for the sudden hot greenhouse day with a lot of direct sunshine on the tree's foliage, while the root system is still cold. These conditions are ideal for WLD. - Millet (1,066-)