from: http://www.citrusvariety.ucr.edu/citrus/ethrog.html


History: Ethrog or Etrog citron is a variety of citron commonly used in the Jewish

Feast of Tabernacles. The citron is believed to be one of the original kinds of citrus.

Characteristics: Etrog trees are small and shrubby with an open growth habit. The new growth and flowers are flushed with purple and the trees are sensitive to frost. The leaves are oblong but slightly pointed and somewhat rumpled with serrate margins. The aromatic fruit is shaped somewhat like an oblong lemon but is considerably larger than a lemon. The yellow rind is glossy, thick and bumpy.

The flesh is pale yellow and acidic, but not very juicy. Citron rind is traditionally candied for

use in holiday fruitcake. The fruits hold well on the tree.

from: http://www.citrusvariety.ucr.edu/citrus/bouquet.html

Characteristics: Bouquet de Fleurs is a sour orange variety planted primarily as an ornamental. The tree has a low spreading umbrella shape. The mature foliage is dense and bright green, and the new growth is lighter green giving the tree an attractive appearance. Because of its low growth habit, it is sometimes used as a hedge. The fruit is small to medium in size, somewhat oblate in shape, and has a rough orange rind. The low-seeded fruits mature in winter and hold very well on the tree. Bouquet de Fleurs fruits are bitter and acidic and typically are not consumed.

http://www.citrusvariety.ucr.edu/citrus/hongkong.html

Characteristics: Hongkong kumquat, Fortunella hindsii, is the smallest-fruited of the

kumquats with round fruits that rarely exceed one-half inch in diameter. The tree is very small and very spiny and the leaves are small and narrow. The fruits are red-orange at maturity and hold on the tree well. The rind is thin, and there are several large seeds in each fruit; thus, the fruit is virtually inedible. Hongkong kumquat is grown primarily as a novelty. The common (wild) form of the species is naturally tetraploid. A cultivated diploid form, usually designated Golden Bean kumquat, has slightly larger fruits, larger, more slender leaves, and shorter spines.

http://www.citrusvariety.ucr.edu/citrus/millsweet.html

History: Millsweet lemon is a limetta of very low acidity. Although strongly resembling the lemons, the limettas have distinctive characteristics that set them apart from the true lemons.

Characteristics: The tree itself grows as vigorously as the common lemon, with a similar form, but the leaves are more oval, round-pointed, and cupped than the typical lemon leaf. The new growth leaves and blossoms are faintly purple. The fruit is medium-sized, round with a distinctively flattened blossom end. The nipple is prominent and surrounded by a deep areolar furrow. The rind is slightly bumpy, pitted with sunken oil glands, and is yellowish-orange at maturity. The flesh is pale yellow, low-seeded, and low in acidity, giving the juice a sweet taste. Millsweet flowers and sets fruit throughout the year, but the main flowering season is in the spring. The fruits hold on the tree well. Other limettas are Limonette de Marrakech, which is highly acidic, and Mediterranean Sweet Limetta, which is an acidless form. Externally, the fruits are indistinguishable, and the trees are also similar, except that the new growth and flowers of Mediterranean Sweet Limetta are not tinged with purple.

Just as I have suspected, Sanguinelli seems to be my longest holding blood orange on the tree:

http://www.citrusvariety.ucr.edu/citrus/sanguinelli.html

History: Sanguinelli is a late midseason blood orange variety from Spain. The variety originated as a limbsport of Doblefina which came to light about 1950.

Characteristics: The tree is small to medium in size, spineless, and very productive.

Description from The Citrus Industry, Volume 1: Fruit said to be similar to Doblefina, but larger, seedier, and often asymmetrical; persistent style; blood coloration of both rind and flesh much more intense and constant. External red pigmentation rarely equalled by other blood oranges and excelled by none, making the fruit most attractive. Reported to hold on tree longer than Doblefina and to store and ship fully as well or better. Late midseason in maturity. Intensity of external pigmentation and purplish-red color of the chalazal spot (Chapot, 1963e) place this variety in the deep blood group.
Tree small to medium, spineless; foliage light green; productive.
Spanish Sanguinelli is the preferred name to distinguish this new variety from the Italian light blood group (singular sanguinella, plural sanguinelli).
The variety originated as a limb sport of Doblefina which came to light about 1950. Its market reception has been excellent and it seems destined to replace the parent variety and most other Spanish blood oranges.

http://www.citrusvariety.ucr.edu/citrus/buddha.html

History: Buddha's Hand/Fingered Buddha’s Hand or Fingered citron is a unique citrus grown mainly as a curiosity.

Characteristics: The tree is small and shrubby with an open habit. It is very frost-sensitive. Citron leaves are distinctive in form, being oblong and somewhat rumpled, with serrate margins. The flowers and new growth leaves are heavily tinged with purple. The very small immature fruits may also be flushed with purple. The six to twelve inch fruits are apically split into a varying number of segments that are reminiscent of a human hand. The rind is yellow and highly fragrant at maturity. The interior of the fruit is solid rind with no flesh or seeds. Fingered citron fruits usually mature in late fall to early winter and hold moderately well on the tree, but not as well as other citron varieties.