I think I need a horticulture lesson here.

I have 2 Myers Lemons, 1 Trovita Orange, and 1 Key (Mexican) Lime so this question is on these particular trees.

According to FourWinds Growers (this is where I got my trees from), the temps for protection are as follows,
Trovita Orange - protect at 28 degrees F.
Key Lime - protect at 32 degrees F.
Myers Lemon - Protect at 32 degrees F.
http://www.fourwindsgrowers.com/solver/varietyinfo.html

Now according to many sources citrus roots cease to function properly at 55 degrees F. Optimum growing temp for roots is around 70-80 degrees F.


If the trees are kept outside with with christmas lights wrapped around the pots and insulated against heat loss will they survive with minimal problems IF ambient air temp is above freezing( probably closer to 40 degrees F)? Only the root zone/pots would be protected while the tree itself would be unprotected. If there was a chance the ambient air temp were to be forcasted to drop below freezing the trees would then be protected in a small but heatable greenhouse.

Its my thinking that the sun would warm the leaves and stems sufficiently to complete photosynthsis. This would also give the trees direct sun from around 7am until 5pm. This would allow for 10 hrs of direct sun vs 4 hrs + grow lights in the house. This would also allow for wind/insect pollination. Its been rather warm here and although our last frost date isn't until March 15th for zone 6b/7a Mother Nature could still suprise me.

I also read somewhere that citrus must recieve X amount of hours below 60 degrees F. to stress the trees into flowering/fruiting.

At what temp do the leaves and stems cease functioning properly to where they no longer process the energy from sunlight.

What are your views and/or concerns on this?

Hopefully I have explained what I am wanting to do so its not too confusing. I need the bedroom these trees are in for a plant nursery and am quickly running out of room.

Andi

Here are some thoughts:
1) keep one tree inside, move the other two outdoors. That way, at least one will survive.
2) figure out a way to bury the pots and let the soil keep the roots warm.
3) put christmas lights in the limbs
4) find a way to shelter the trees from north winds and the open sky.
5) find a way to back the plants up to a brick or stone wall with southern exposure. I've heard that trees in far North East Texas have survived hard freezes by training limbs to a brick wall with southern exposure.
6) damage is related to time subjected to sub-freezing temperatures. Many citrus trees will handle 2 or 3 hours at 28 degrees (a normal winter night in North Texas), but subject them to 28 degrees for 48 hours (a norther blows through) and they die back to the roots.
7) look at this as an opportunity to learn about citrus hardiness. Don't be afraid to lose a tree.

Mark

Mark,

1) keep one tree inside, move the other two outdoors. That way, at least one will survive.

Hopefully all the trees will survive.

2) figure out a way to bury the pots and let the soil keep the roots warm.

The pots will be wrapped with christmas lights that are wrapped with an insulating material.

3) put christmas lights in the limbs

This I can do but why?

4) find a way to shelter the trees from north winds and the open sky.

The trees will be on the SOUTHEAST side of the house in a protected corner

5) find a way to back the plants up to a brick or stone wall with southern exposure

See #4

6) damage is related to time subjected to sub-freezing temperatures

IF there is a threat of freezing temps the trees will be moved into a small but heatable(above freezing) greenhouse

7) look at this as an opportunity to learn about citrus hardiness. Don't be afraid to lose a tree.

Heaven forbid. I love my trees. Loosing them is not an option!

Andi

andi,

>>3) put christmas lights in the limbs

>This I can do but why?

Unlike evergreen trees, citrus will suffer vascular damage when water internal to the leaf or branch freezes and expands. The heat from Christmas lights can delay internal freezing on nights with 2-3 hours of freezing temperatures or frost.

Gardner_Dragon, You ask ...."At what temp do the leaves and stems cease functioning properly to where they no longer process the energy from sunlight?" The answer is 55 degrees F (same as the roots). Also the temperature that citrus must be below for good fruit set is 68F for approximately 850 hours. If the ambient air temperature is 40F I doubt the the sun would heat the leaves enough to cause them to produce photosynthates. Sun light generally raises the surface temperature of citrus leaves 8 - 10 C. However, the low winter sun would not cause the leaf surface temperature to rise that much if the trees were outside in 40F weather. Take care. - Millet
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