My temps have been in the 75-45 degree range for a while now. I have stopped adding fertz for two months now, but there is slow release in soil. Is there any point in adding liquid fertz this time of year?

Also, it's gotten down the the mid 30's a few times and I've seen some leaf drop, but so far all trees are seem to be hanging in there.

Hello,
well... if the trees have cold roots, the roots won't have any activity. So the uptake of water and nutrients are strictly limited, und thus fertilizer will not taken up that good by the roots.
So this uptake of water and nutrients will hardly be reduced by root temperatures below 68° F, and is nearly zero at temperatures below 54° F...

So adding fertilizer is possible and recommended, if the roots can take up water and nutrients properly. If it is to cold, the nutrients will deposit in the compost of the pot, and if the roots stay cold, and you still add fertilizer, well, more and more salts from the fertilizer will deposit in the potting mixture, which than can cause root burn by to much salt in the potting mixture....

So, adding fertilizer is depending on the root temperature... but: if there is less light, don't use the full dose... I recommend in winter, because of less light conditions only to use a quarter or half dose, as in respect of the reduced metabolish of photosyntesis...

If the trees are not in a greenhouse or otherwise protected from the cold I would not add any nutrients until just before your average last frost date. Warm spells can promote new growth which will then be damaged or lost when the next freeze comes along.

.....Alan.

Quite a good facts, but because it's the container citrus forum, I surely guessed it would be some trees, which are not anymore outdoors...

He may have them protected but as he mentions them being exposed to temperatures in the thirties that caused leaf drop it leads me to believe they are not.

My container trees are in a greenhouse and I fertilize them all the way through the winter as I like them to go into spring (and the inevitable leaf miners) looking as good as I can make them. If I couldn't provide good winter protection I'd want them to stay as dormant and cold tolerant as I could possibly make them.

.....Alan.

No, they are not indoors or protected, but we are getting some decent day time temps, so I was wondering if I should continue with liquid fertilizer. The new growth was a good point, much of it would probably die on some of these colder nights.

The reason inground trees are not fertilized between Sept and Feb is so that they will not put on new growth that will then be killed by frost--the same applies to container plants that are not protected (in temperate climates where frost is possible).