here's an approx 2 year old mandarin - very slow or no growth.

a 3 year old mandarin - it has fruit, but growth is minimal.

Forgot to mention something about what I feed them and about watering.

In spring I added a few shovels of sheep manure around the tree. Afterwards, molasses foliar ,some worm compost (1 shovel) and aerated worm tea (couple of times), + zeolite foliar. The molasses foliar was an experiment, since I read it kills some "bad" insects and is food for bacteria.

I water them 1/week and now more frequently - I remove the mulch to slow down decomposition/ reduce chance of disease and water away from the trunk.

Everything you have looks dry. You need to water a lot more in that kind of heat if you expect growth. Once a week is probably good depending on your soil. But it sounds like you are dribbling on a little worrying about disease or your mulch. Get it really wet(at least 2ft deep) once a week, fertilize some, and you'll get more growth. Probably not right away but in a couple months or next spring when you really want growth.

On mature trees I'm OK with one good flush in spring and a little later depending on how much I water and fertilize.

OK, thanks - looks like I need to "drown" them - will do so.
I guess you mean to "drown" them once a week (the small trees) ?
Can you be a bit more specific about type/amount/frequency of fertilizer ? Regarding the mature trees - looks like you "drown" them only twice per year, but you still water them - how much/how often - still weekly ?

One other thing - how important is it to avoid overwatering near the "trunk" - should this "drowning" be done only a little
away from the trunk to avoid root rot ?

I agree with fruitnut that your citrus is too dry.You must get the soil wet and keep it somewhat moist in the hot summer months. Getting the soil wet will take a drip or soak system, or you can run the hose at a trickle for an hour or two.

The water source is best at least 1 foot away from the trunk for the size plants i see in the pictures, but don't worry about root rot in hot weather to the point that you dry out the roots. Excessively dry roots die.

I have just gone through a 2 year long experiment with irrigation, type, schedule, & amount of water. Although i have had citrus in the ground for over 24 years, i never paid much attention to them until the last 6. I have citrus in multiple locations and soil types; and with different irrigation systems. Bottom line, they like steady and even moisture. They do like to dry out a bit, but not totally!

Here in dry northern CA, once the temps get into the 90's and hit 100 now and then, i find that i need to water every 2-3 days at minimum and on top of that add a good long soak if needed. The citrus on the "quickie" installed soaker hose set up is far more vigorous and productive than the standard spray / bubbler set up.

good luck and please post some update pics when you can!

Your trees look too dry, meaning you can see the leaves curling inward...that's a sign.

I would like to thank you all for getting me on track with
regards watering. Gardening is an important hobby and success means a lot to me - I know I'm still firefighting with getting basics like watering and feeding under control and have little or no ideas on preventive actions against disease etc. , but hopefully I'll have a green garden one day ;)
I've been working on drip irrigation and the citrus and other plants are showing progress now - will post photos after the drip system is in action for a while. I see new branches coming on the small mandarins. One small orange which I had received from a neighbor had some disease/leaves fell off and nothing grew - but I persisted with vermicompost and vermicompost aerated tea and now with the watering, it has started growing - thanks again until the photos.

Where are you?

I updated my zone info to show I'm in Croatia - a few hours
(by fast plane ;) ) from you ;)

Better late than never - here are some update photos.
OK, it is cooler now, but I saw progress even during summer but I just didn't have time to take some photos then.
Most of the citrus trees have grown new leaves during the summer (a couple are still not showing much growth, but at least they are looking more healthy - just need to feed/water them better I guess.

On the photos you will see the new growth. There is some leaf curl and we had some large grasshoppers eating leaves, otherwise, everything is going well (a few leaves are a bit yellow -I did add some iron, hopefully it helps).

One thing I'm not sure about - when there is a lot of growth and the branches being green/young are bent, are you supposed to do anything about that ? On the small mandarins, I try forming the these weak brances as I have
supports which allow this, but what do you do for trees like
the orange tree where you can see a lot of growth with all branches bent down as they are soft/young.

the kiwis certainly changed form once I watered them well - I was watering them every 3 days during the hot spells

new top leaves - I guess they've been eaten by grasshoppers

loss of color on some leaves of the mandarin - and you can see the strawberries in the background have lost some green as well - I suspected iron deficiency, so I added a light dose of iron solution

this mandarin is some 3-4 years old and has been lagging a bit in growth - now you can see new growth (it started during the summer as soon as I watered the mandarins well a few times (lucky I finished the drip irrigation system with a few circles of drip pipe with emitters around all fruit trees - this made watering much easier)

the growth on the next few mandarins was amazing after good watering

mandarin

mandarin

Isn't that the way it goes! You work hard to create nice healthy leaves and now the grasshoppers want to eat them.

navel orange - this is my favorite fruit tree in my whole garden (for now ;) ), with the tastiest navel oranges you've ever tasted - sweet/sour/juicy (sorry, got carried away ;) ) - is there anything one needs to do regarding forming the new branches ? The fast growth has all new/soft branches bent down

look at this little one go - it's great to see a healthy fruit tree growing