page updated 22nd October 2005
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a new Citrus glauca hybrid!
The Australian Desert Lime, formerly Eremocitrus glauca but now re-classified as Citrus glauca, is known to hybridize readily with other citrus species.
The  classic 1946 reference book "The Citrus Industry, vol.1" names three such hybrids - Eremolemon, Eremorange and Emoradia (x C. aurantium) but, after much discussion, cannot assign any actual plant to these hybrids. W.T. Swingle, author of the first edition, believed the Coachella Eremolemon was a hybrid with Meyer's Lemon (itself probably Lemon x Orange), but later editors throw some doubt on this.
In 1996, I was sent seeds from the University of California, Riverside, said to be Eremocitrus glauca. But it was immediately obvious that the one viable seedling produced was not 'true to type' but a hybrid. The leaves were noticeably wider, and with distinct upper and lower surfaces. The plant grew rapidly, whereas my true Australian Eremocitrus seedlings gradually died off.
This year, 2005, the first flowers appeared and five fruit reached maturity.
Citrus glauca hybrid - fruiting twigs
Citrus glauca hybrid - fruit detail
citrus glauca hybrid - immature fruit
The tiny fruits were initially  tinged red, but finally matured into a pale translucent lemon yellow - paler on the underside and with just a hint of green on the upper.
The mature fruits are only 12mm to 18mm in diameter (about half an inch) and slightly pear shaped. They taste horrible - just extremely sour which masks any other distinctive flavour.
What are they?
I have no idea what the pollen parent was. The Eremocitrus glauca I saw growing at Riverside was surrounded by all species and varieties of citrus.
The fruits are certainly different from those of my Eremolemon - but if that itself is a Meyer's Lemon hybrid, then it has  some orange in its ancestry.
Perhaps my hybrid is another Eremolemon, but this time a true lemon hybrid. That's my best guess from the shape and colour of the fruit!
Eremolemon & new Citrus glauca hybrid
Cut fruit. Eremolemon & new Eremocitrus hybrid
These are scans of Coachella Eremolemon (20mmx18mm) with 5 segments, and my 'Eremowhat' hybrid fruit (15mmx20mm) with four segments on the right of each picture.
The Coachella Eremolemon arose from a seedling of a fruitful Australian desert lime at the US Date & Citrus Station, Indio, in the Coachella Valley of California. The research centre closed in 1979.
The variety 'Razzlequat', originally distributed by the US nursery Oregon Exotics, is almost certainly Coachella Eremolemon. The nursery's catalogue classifies it as "Eremocitrus x C. Limona Meyer". It has no kumquat in its ancestry at all!
Swingle, in The Citrus Industry, briefly describes trigeneric hybrids of Eremocitrus x Citrange. Named Citrangeremos, I have never yet seen any of these varieties, although AgrumiVoss nursery does list them.