Citrus > Cold Hardy Citrus

US-1284, SCS rootstocks

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I just received two trees that I ordered in the winter for spring shipping from a nursey in Florida 

Has anyone heard of these rootstocks?

Some searching online I found that
The Meiwa is grafted on SCS = Sun Chu Sha mandarin
Are kumquats commonly grafted to mandarins or is the acronym for something else?
It isn't a hybrid with poncirus so I'm not really interested in propagating it. 

The Xie Shan is grafted to US-1284= Citrus reticulata Ninkat x P. trifoliata "Gotha Road" a vigorous poncirus type.

I am going to let a bud of the US-1284 grow out and either root it or graft it to my outdoors poncirus (or both!). It seems hardy to 5f /-15c from what I've been reading. 

US-1284: Fruit length is 4.3 cm, diameter is 5.3 cm. This selection was developed by Kim Bowman as part of a large effort to develop Citrus rootstocks with less vulnerability to HLB.

US-1279, US-1281, and US-1282 developed during the same time period are 100% zygotic in seed production.

List of leaf images including US-1284:

List of seed production characteristics:

More info:

Sun Chu Sha (SCS) is a mandarin type that has been considered promising as a rootstock in Florida, but testing in California gave disappointing results.  Yields have been lower than trees on Carrizo, but produces a tree about as large as Carrizo.  SCS is susceptible to Phytophthora and citrus nematodes,  but tolerant to CTV.  Its main strength is that it is tolerant to calcareous soils. There is probably little reason to use this rootstock except on calcareous soils.  Info. taken from the Citrus Production Manual.

As you are in zone 7A I presume these will be kept as potted plants.
There is very little relevance in the published information which applies to potted plants.
All the research is directed to commercial growers of in-ground trees.
Tree size will depend to a great extent on pot size.
Cold-hardiness of rootstock doesn't matter if in winter-heated conditions.
HLB and some other insect-borne diseases won't occur.
Soil pH is controlled by whatever planting medium used.
The one thing I find important - unless you are really careful with watering and drainage - is rootstock susceptibility to phytophthora root rot.

Thanks all for the info/resources. Seems like a strange choice for the rootstock on the kumquat even for Florida considering the rain and humidity adds potential for rotting, phytophthora looks serious. Perhaps they were out of everything else and that is what they grafted the meiwa to. I will definitely be grafting that over eventually to a pot friendly rootstock. The US-1284 supposedly increases fruit yield up to 2.4x over other rootstocks per one of the published articles I read, but as mentioned the results of the studies don't directly translate to potted citrus   


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