I have a mature, in ground Eureka lemon. It is in Palo Alto, CA, on the mid San Francisco Peninsula. We are in a 'frost pocket' at 10' above mean sea level and just far enough from the Bay to miss its moderating influence. We are regularly a few degrees below the spot forecast low.

The tree is an espalier on a fence in a 6' wide side yard. One of its main functions is as a visual screen from the power drop to the neighbor's house.

Earlier in the week I went out to drape the tree with old sheets and turn on 125W heat lamps under it to protect it against a predicted low of about 29F. For mild frost warnings I just point the lights up through the branches and hope that the convection triggered by the lamps will provide some air motion that will protect the growing tips of the tree.

In a word, I should have pruned it earlier. It is so tall, over 12 feet, that I cannot cover it effectively. Can I safely prune it back to 8-9 feet now, in early December, or will this trigger an early flush that will just exacerbate frost sensitivity?

My future plans are to follow Joe Real's observations and graft out the uppermost portion of the tree in Satsuma's and kumquats in the hopes of providing a natural, more frost resistant cover.

Thanks for any opinions and/or suggestions.

baumgrenze

I would wait until the spring. You are correct that pruning now will force new shoots in any warm spells.

Laaz, with, or without pruning, the tree can produce new growth with an extended warm spell. The limited light at this time of year will also somewhat limit new growth. - Millet (403-)

Millet you are correct, but pruning usually brings on a major flush. If the tree has not been fertilized recently it should keep the new flushes to a minimum...

Gentlemen,

Thank you both very much for confirming what "I knew" by gardening instinct. I will wait for the spring flush to cut it back. Perhaps frost will start the process for me.

Is it safe to cut back really dead looking frosted branch tips before spring or will that trigger a flush as well? I know that a mature Bearss lime in my yard froze to the ground in the late 80's or early 90's. The stump was several inches across. I selected a sprout and started a new tree. In 2010 we added to the house and the tree had regrown to about the same size again. I have scions from it grafted to the Eureka lemon and a Meyer lemon, but they have not yet matured enough to start bearing again.

Perhaps next spring I will get to the topworking of the Eureka.

Thanks again,

baumgrenze

Pruning dead wood out of the tree, will help the tree no matter what time of year it is done. - Millet (402-)