Know that if you grow citrus trees inside a warm house or greenhouse during the winter months you will need to be SURE to start following citrus flower bud induction conditions around November 1st for the coming year's bloom. Citrus grown in warm home or greenhouses needa to receive approximately 850 hours of temperatures below 68F(between November 1st and Christmas) to set a good crop of flower buds. If the trees are continually grown at higher temperatures the buds will NOT develop as flower buds but rather as leaf producing buds. It is the 850 hours below 68F that differentiates the buds from foliar (leaf) buds to flower buds. After the 850 hours of below 68F temperatures, which is sufficient for flower bud induction to occur, then give the trees 7-12 days of temperatures greater than 75 to 80 degrees F. which will trigger flower bud growth and bud swelling. This will give you a good crop. Conversely, if you do not want flowers thus no fruit but would rather produce a lot of stem and leaf growth (to enlarge the tree) then keep the temperature above 68F. - Millet

For those of you who are using bottom heat on your trees to promote growth, duing the fall and winter, on your container trees, but are also interested in cool temperatures (<68F) to promote good blooming thus higher fruiting next spring, this might be of interest to you. I read today on page 72 in the book "The Biology of Citrus" the following." Longer exposure to chilling temperatures, two to eight weeeks, (336-1,344 hours) increased the total number of (floral) shoots as well as the INTENSITY of flowering. While most studies indicate that the chilling treatment is perceived by the AERIAL part of the plant (leaves, twigs, buds), some reports suggest a role for the roots as well. I take this to mean you can have your cake and eat it to. Maintain tree growth, and at the same time chill the foliage to induce flower bud differentiation. Vince is currently experimenting on a copper coil system for bottom heat, in a outside planter in the Los Angles area. Thus his trees foliage is subjected to the outside winter air, while the trees rootzone is maintained at a temperature conducive for root growth. Perhaps Dr. Manners has some thoughs on this? - Millet[/b]

Millet I REALLY enjoyed reading your above postings, We now have about 18" of snow an all my tree's are still in the greenhouse, no WLD yet

I do plan on bringing them indoors, Our front porch is facing South/West
with very good winter sun. I had planned on keeping the air temp. lower and using x-mas lights for bottom heat.

At this time I have no bottom heat an the air temp. within the greenhouse is 64 degree's. I plan on taken it down a few degree's. Maybe this coming week I'll be able to make the move Dale

Hello, and again, great forum.

Getting the chilling requirement for citrus won't be a problem for me. I have questions about the 7-10 days of 75-80*F that follow.

It seems to me that the only way to get this is to turn up the thermostat in the greenhouse. This would be done precisely when it is coldest outside.

I'm wondering whether is is OK to skip this step or at least delay it a few weeks if only to save some money on propane.

TIA,
Robert

Robert, nice to have you as a member of this forum. Your most welcome here. To answer your question, yes you can delay the heating stage in two ways. One, by continuing the "cold" treatment longer than the 850 hours, or by starting starting the "cold" treatment at a later date. The important thing is to be sure to give the tree the required amount of cold stress required to get a good bloom. A longer cold treatment would possibly produce more leafy inflorescences rather than leafless inflorenscences. Leafy floral inflorenscences have a much better chance of setting and remaining on the tree , because the extra leaves provide more photosynthates (food) for the fruitlet. - Millet

I would like to bump this thread for clarification of a point and a question.

I have obtained Litchi chinensis, Punica granatum 'Nana', and Ficus carica, and in researching their culture, I learned that each has a chilling requirement...not much, just 100-300 hours, but at a temp of 32-45*F.

In researching the chilling requirements, I found that citrus is usually listed as having NO chill requirement. This is not consistent with Millet's comments above.

The key point, I guess, is that the temperature for "chilling" varies depending on the species. Millet's "chill" is <68*F whereas the requirement commonly used on the web for other plants is the lower temp of 32-45*F. Citrus does have a chilling requirement, but the required temps just aren't as low as with other species. Correct?

Now, for my questions... for figs and lychees, I'm apparently going to have to drop my greenhouse minimum winter temp for a few days each winter. Any advice on the best way to do this so that the citrus do not suffer? Would the citrus suffer without bottom heat during this brief period? Thanks for any input. Robert

Well, I never knew this, makes complete sense, but it's too late now. I'll even have a hard time with that next winter. Our appartment is at 21°C minimum all winter. Where I have no problems with the consecutive days of warmth afterwards, I will never manage 850 hours in 2 months at that temp!

My meyer is showing one puny little blossom. I think it may be my only only this year after reading this.