Yuzu has plenty of seeds, and it is cold hardier than kumquats, so why not use them as rootstocks over here in the colder north California. Well, based on multi-year studies, trifoliate orange would be a lot better, and cleopatra is slightly better, performance, sugar to acid ratio, etc., than Yuzu when grafting the Ponkan types scion cultivars. Overall, it would still be okay to use, but not preferrable. Perhaps for multiple rootstocks...

Joe

Below is a translated abstract from Japanese Journal that I ran across:



Effects of rootstocks and scion cultivars on fruit quality of ponkan mandarin (Citrus reticulata Blanco)
Accession number;04A0467888
Title;Effects of rootstocks and scion cultivars on fruit quality of ponkan mandarin (Citrus reticulata Blanco)
Author;TOMINAGA SHIGETO(Kagoshima Univ., Fac. Agriculture, JPN) KAWAGUCHI SHOJI(Kagoshima Univ., Experimental Farm, JPN) TANIMURA OTOKI(Kagoshima Univ., Experimental Farm, JPN) YAMAMOTO MASASHI(Kagoshima Univ., Fac. Agriculture, JPN) SATO MUNEHARU(Kagoshima Univ., Fac. Agriculture, JPN)
Journal Title;Bulletin of the Experimental Farm, Faculty of Agriculture, Kagoshima University
Journal Code:Y0635A
ISSN:0386-0132
VOL.;NO.27;PAGE.1-17(2004)
Figure&Table&Reference;FIG.10, TBL.1, REF.9
Pub. Country;Japan
Language;Japanese
Abstract;The effects of rootstocks and scion cultivars on yields and fruit quality of ponkan were examined. A series of experiments was conducted for 13 years from 1989 to 2001. The ages of trees varies from 4 to 16 years. Three rootstocks used are trifoliate orange, yuzu, and Cleopatra mandarin. And three scion cultivars were used, namely, Ohta-ponkan, Yoshida-ponkan, and Kitazono-ponkan. The results were as followed. Analyses of variances by year showed significant independent differences between rootstocks and scion cultivars on yield per tree and fruit qualities of ponkan respectively. However, interactions between rootstocks and scion cultivars were not observed. On yield per tree trifoliate orange rootstock was the highest, and much difference was not observed between Cleopatra and yuzu rootstocks. Fruit weight, peel color, fruit shape index, titratable acidity and values of color difference meter did not differ among three rootstocks. Flesh percent of fruit on yuzu rootstock was significantly lower than that on other two rootstocks because of its thick peel. Granulation occurrence of flesh on yuzu rootstock was significantly higher than that on other two rootstocks. Granulation occurrence of flesh on Cleopatra and trifoliate orange rootstocks were very low. Brix was highest in fruits on trifoliate orange, followed by Cleopatra and yuzu rootstocks of 9 years or older. Brix-acid ratio tended to high in fruits on trifoliate orange. Yield per tree and fruit weight were higher in 'Yoshida ponkan' and 'Kitazono ponkan' than 'Ohta ponkan' if they are 9 years or older. Peel color was better in 'Ohta ponkan' fruit until 10 years old; thereafter the difference among three cultivars became negligible. Fruit shape index was lower in fruit of 'Yoshida ponkan' than those of 'Ohta ponkan' and 'Kitazono ponkan'. Flesh percent was higher in fruit of 'Ohta ponkan' than those of other two cultivars....

The Yuzu used on which Citrus as some Citrus, even clonal varieties of Oranges can differ when standardized rootstocks are used on them. What I am getting at is that Parent Washington Navel may do well on Yuzu rootstock but a Newhall Navel may not do so well in certain areas. When we use one rootstock across the board for varietal Grapefruit, Lemons, Oranges, Limes and Mandarins, as examples, we may feel compelled to know if the Kara Mandarin will be as good a tree for us as it would be had the Kara been budded onto a different rootstock, let's say just for fun, budded onto Cleopatra. The issue is that the Kara may yield acceptable fruit being budded onto a Yuzu but may yield better quality fruit when budded onto Cleopatra. Then we have to recognize that not all Mandarins may do as well as the Kara budded onto Cleopatra does but Yuzu may be acceptable for them.

Years ago for Oranges certain rootstocks were felt to be almost specific for that Orange in that one rootstock may be good for the Parent Navel but may not be so hot for the Newhall or the Frost Navel. It took time to determine which rootstocks could be used as a viable understock for certain Oranges until one or a select few could work well for the homeowners but not so well for the production growers. This dilemma is what separates the commercial growing nurseries, intent on amassing trees for the production end, from the nurseries that are growing much of their Citrus for the collectors and the homeowners. We do not see too many dwarf growers selling trees to go into the ground for production purposes but for homeowners these standardized dwarfing rootstocks have panned out well. Bear in mind there is always one Lime or one Lemon that may not yield extensive root systems for some time as opposed to other Limes and Lemons from the same grower. This is the bugaboo situation using a single rootstock right across the board but that does not mean that the one Lime that has sparse root development for three years grown in containers or in ground will remain that way, as in time with some babying to the tree, the root system may develop for that variety but it may take a while longer than the other similar varieties do.

We forget that even today much of our dwarf form Fruit trees do not compare well to the standard trees. This is not the case for Citrus in that Mr. Don Dillon did something years ago that was far ahead of its time in being able to produce dwarf form Orange trees much closer to the commercial Orange in fruit quality than we have with the Fruit trees still today, aside from some Apples.

There seems to be no control plant to compare the propagated Citrus to in the study. Why is that? A control plant being one that has been perpetually propagated on its own roots to compare the quality of the put together plants and fruit to. Acceptable is fine for most people but may not be altogether great or compelling to the long term or potential commercial grower.

Do some experimenting, Joe, on your own with Yuzu as a rootstock. You may find it better for certain Citrus than Trifoliate is on certain varieties. I would be curious to see how well Yuzu does on the old standard, commercialized Orange varieties in cooler areas, or for this state in areas where Citrus used to be commercially grown years ago, back in the teens such as in Shasta county.

Jim

Thanks for pointing those out Jim! Will try some out of curiosity. I may not need to purchase a land after all. A friend of mine is willing to let me use up to 20 acres of his property in Tulare, California. It is so far away, but let me see what I can do.