Unknown kumquat ID

[JSea]

Wondering if anyone can help ID this kumquat. I actually suspect it's not a known variety and is a seedling, but I thought I'd better get some second opinions as I'm not a kumquat expert and have never seen e.g. Marumi or Changshou.

The fruit are oblate shaped, and with slight ribbing. The peel is sweet without bitterness, and the inside of the fruit is mostly sweet with some acid. At least the fruit I ate was seedless.
The leaves are very large for a kumquat, larger than any other variety I grow such as Nagami, Meiwa, "Nippon", Indio, Eustis, Calamondin (maybe my "Nippon" is an off-type, it doesn't match online photos).
The crushed leaves have a very volatile scent, sort of like paint thinners.
This variety was incompatible with calamondin seedling rootstock (a Meiwa trait), but seems fine on trifoliata.







Compared to a Meiwa (on the left), the leaves are visibly a lot larger, and also have unique venation:



Largest leaves can become very large:

[Radoslav]

Definitely not a Kumquat.

[JSea]

I think it's probably a mandarinquat or similar to be clear. I can't think of anything else that is not related to a kumquat that is similar to this fruit.

[70Malibu]

It looks similar to my Fukushu, but your fruits are much smaller than Fukushu. The leaves are broad shaped like yours.
You can tell if it is the same fruit, just look at the end of the fruit, the Fukushu will have a slight dimple.

https://citrusvariety.ucr.edu/crc3475

[JSea]

From memory it didn't really have much of a dimple, and the size of the leaves I think would rule it out as being Fukushu itself, but it could be a seedling. I strongly suspect (but cannot yet prove) this tree is a seedling and not a grafted variety.
Unfortunately I don't have easy access to the original tree so I can't get more photos of the fruit easily, and my plant is very small so will be a while before I get any fruit.

[brian]

Does not like any of the orange kumquats available in US.  Different shape than fukushu, meiwa, marumi, indio, nippon.

How does it taste compared to meiwa/marumi/fukushu? 

[JSea]

We don't have Marumi / Fukushu, so can't compare to those

I think I've only ever tasted 1x Meiwa fruit (they are reluctant to fruit for me), and so it's hard to compare. From memory Meiwa I would describe as sub-acid, but this unknown kumquat as sweet (but not high acidity).

[brian]

Fukushu and Marumi are both sweet & sour.  Sounds like yours is similar.  It sounds really good, you should try to get some fruits from the other types to compare, and if yours is better start propagating it

[70Malibu]

I zoomed up on your 3rd photo of the fruits hanging on the tree, it has no dimple, not a Fukushu. May be a seedling from a Kumquat.

[JSea]

The original tree of this 'kumquat' was found with some other rare Citrus that I think were also seedlings. I didn't notice any trifoliata rootstock on those for example (but the old owner of the garden was definitely using trifoliata for other Citrus and even had a trifoliata rootstock bed), and the trees were very small for their age (1.5m tall for the kumquat, 3m for the other Citrus that were presumably seedlings, after 20-30 years).

Will try and get it to fruit and will keep it propagated anyway