The Tropical Fruit Forum

Normally, by genetic selection of fastigiate cultivars. In gen Citrus, by pruning and tying the branches to the trunk to force them grow in a narrow angle. Citrus is not a fastigiate growing kind of tree. They always develop a broad canopy with time. Stems in a very acute angle will catch rotten fruits, fallen leaves and diseases

Using several narrow trees, instead a single wider tree, mean less fruits and more trunks/wood in the same space. Multigrafting a tree looks like a better solution

Photos?

Ziziphus is adapted to dry areas

They could have more than one problem. See Thrip damage and Citrus rust damage also to compare your symptoms

The Guinnes book of records is more a marketing tool than a scientific source. People pays money for proposing something, one or a few judges from the organisation travel to your place for one or two days and if nobody says otherwise, put you in the book. The amount of scientific work and effort done by them to refute this proposal is close to zero.

C4 Photosynthesis evolved from C3 several times. Is typical of Poaceae, (grasses, cereal, bamboo), and also appear in a few plants of other families adapted to dry and desertic areas. There is a recent review of C4 plants (Sage 2016, Journal of Experimental Botany 68) that list each known genus with this kind of photosynthesis. In 2016 the huge genus Euphorbia was the only known genus with a few trees using C4 photosynthesis. Bamboo are not trees but its ecological role is similar in any case

Paulownia does not appear in this list. In fact there is not any plant in the list from the order Lamiales

I didn't find a recent scientific source claiming that is a true C4 plant. Maybe C4 is facultative/not the common way of photosynthesis for this tree, a mix between C3 and C4? Maybe has been modified genetically

Or perhaps this is just a myth.

If is not a true C4 plant, could run in standard mode C3 when provided with water and manure, and will move to the economic mode C4 in dry areas, thus the increase of oxigen produced is debatable.

Crassulacean Acid Metabolism (CAM) on the other hand is present in a few Lamiales but not in Paulowniaceae. Is typical of succulents in family Crassulaceae.

Meliponiculture is (most probably) forbiden in Europe. Would be only possible in Mediterranean countries or in a greenhouse, but by law you can't neither import nor release non-native species that could interfere with our native bees in EU.

Melipona bees can't sting, but take in mind that they can (and will) bite instead if necessary. Some species in the same family can secrete formic acid also in their bite, like ants.

They really can't compete with Apis in production (and Melipona honey extraction is more messy than in Apis).

Yup, typical insect damage. Bats are probably cleaning the tree from tree crickets. Microbats can't chew. They don't have molars.  Maybe could scratch, or tear off leaves but can't make chew marks. The other option apart of crickets would be snails or slugs or caterpillars. Two marks of birds can be seen in the photo also. You should encourage bats to keep doing it instead to try to deter them.

The only reason for not wanting benefical microbats in your tree could be a high risk of rabies in your area, I suppose.

What is the minimum temperature that this trees can stand without dying or losing the fruit?

Take in mind that the fastest a tree grows the worst quality of the wood (more perishable, less durable, lighter)

B) temptatively.with this white flowers and fruits looks like a Lauraceae

> I need more info about this obscure and elusive black colour

This is not the same case and looks a real fruit, but it's worth noting that many photos of so called black fruits shown in internet are strongly photoshoped. Its trivial to modify the saturation and tone of a fruit in a photo. Some of them have even a skin smoothing filter applied.

Is the same scam as the seeds of blue japanese maple. If you see a fruit of a stricking and uncommon colour in digital photo most of the times is a fake or the colors are artifitially saturated. Cheap cameras in phones do it all the time to hide its bad quality.

In my opinion is just a fairy tale. Anything that hurts the tree significantly will trigger flower production instead growing wood, but there is a price also. The price is measured in years of life and health of the tree.

Cons: Damaged bark, open wounds welcoming entry of fungus, and nails that can hurt you. There is a risk to catch a brush cutter or scratch your feeth in a nail.

Benefits: My father did the same a lot of years ago in an lazy seedling orange tree. Nothing changed. He has to wait still the same 10 years for their first orange than with a standard tree. Eventually the tree started to produce and currently it gives fairly big harvests each year. Sometimes after a big season is chlorotic and need chelates like any orange tree... And shows two ugly useless nails at the basis. Another orange tree without nails that I planted close behaves exactly the same.

In my experience the benefits are unclear and probably zero and the risks are clear. You can achieve the same with pruning

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Second question. You must assure that everybody working in your place has been vaccinated against tetanus. Be careful also with your dog, pets love to dig and vet bills can be expensive.

I thing that there is a better way. Steel balls would be much better than nails for your experiment IMHO, You can find plenty of it in any garage near to you or in a car scrapping. They are totally safe for paws and hands and (after cleaned of its oil) will rust and blend with the soil like a pebble, so are much more pleasant to see also. Let the nails for furniture only

> Mainly via photosynthesis. ;-)

What? mine are sucking my money for vegetable pizzas all the time. *&*%$ green liars...

Microcitrus flowers had been lazy this year and Asimina weren't in the mood. I will enjoy a Plumavalanche this year and an Oranggedon is coming in 2020 , that's for sure.