Poncirus trifoliata question?

[MartinNicklin]

I have just ordered this plant anticipating it to be hardy. However, and this is a big however, I have just been reading about its hardiness and figures range from almost every source stating that it is fully hardy across the whole of the UK and tolerant of cold down to -23 C to the RHS (from where I bought it) stating that it is tender and requiring a temperature of 10 C. I don't think I have ever come across such a massive gulf in opinion for any other plant so does anyone grow it and can vouch for its hardiness?

[Chad]

Trees and Shrubs online says;

It is hardy at Kew, having survived 30° of frost without injury.

It needs a hotter summer than I get in Cornwall to flower or fruit well.

I suspect the RHS have correctly noticed it is now Citrus trifoliata and cut and pasted the cultural information for 'Citrus' without noticing trifoliata's distinctive features.

Chad

ps. The RHS have it as fully hardy here.

[charlie]

There is a big one at Kingston Bagpuize near Oxford where we do one of our plant sales, been there at least 20 years - I would say that makes it bone hardy!

[MartinNicklin]

Thanks for that. I’m sure you are right Chad that the RHS have lumped it under Citrus with the associated Citrus hardiness rating as all other sources confirm its hardiness. Having done a bit more looking on the net, I see that there are some fabulous fruiting trees in the gardens next test Paul’s Cathedral in London, though of course pushing the borders is commonplace in London.

[Chad]

To save people time in hunting for the St Paul's Cathedral ones, click here.

Chad

[ian s]

Definitely very hardy and not touched by heavy frost and snow even when small if mine's anything to go by but it's slow growing and hasn't flowered, maybe because it's too young/small or more likely because in the summer when everything is in leaf it's in too much shade at it's present size. (the top of the picture is facing south-east)

[MartinNicklin]

It does look a bit crowded in Ian!!!

So reading the article on the London plants and not being a botanist Chad, does that mean that the suckers produced on my citrus plants from below the graft are probably Poncirus? I did notice they were particularly thorny.

[Chad]

Nothing is that simple Martin.

trifoliata is a possible rootstock, but commercially it is a bit 'slow' so other rootstocks are usually used.

Most commercial Citrus are grafted on to a rootstock that determines vigour and suits local soil and climate. So your regrowth is likely to be from the rootstock rather than the original fruiting variety, but could be one of many different possible rootstocks.

Chad

[LostInJapan]

I remember seeing this plant in north Florida where it is naturalized. It is an odd thing, with seemingly more massive thorns than leaves, and the twigs almost look like curly cues. One thing, don't fall into it or you are going to come up on the losing end. As for hardiness, it has been reported growing into southern Pennsylvania (again naturalized), so it should be plenty cold hardy. I'd plant it in a place you aren't likely to walk by, or children are going to play.