answersplease

If any visitor to this web-site has a citrus question that I can't directly answer, I'll also put them here.
For the moment, please E-mail me your answers and new questions. If I get too many, I'll think about some other system or maybe a message forum.

1. Some of my potted Poncirus trifoliata seedlings have leaves which turn bright red from the veins outward, before eventually dropping off. Although other plants are treated identically and are normal, it looks to me like a nutrient deficiency of some kind. Or is it some plants usual Autumn colouring? Any thoughts?

2. A specimen of Fortunella obovata - the Fukushu Kumquat - is growing on a rootstock that has produced flowers and fruit from a single stem that I have allowed to grow. The fruit is virtually spherical, yellow-green when ripe and about 6cms diameter. It is seedless, juicy, and quite acidic.Can anyone identify this rootstock? Some kind of lemon or lemon x lime?? See pictures below.

I have now had two independent suggestions that this is Cirus volkameriana or Volkamer Lemon, which is sometimes used as a rootstock.
I still have some doubts, because the only colour pictures I could find of Volkamer Lemon (from the INRA Corsica web-site and in James Saunt's book) showed much more orange-coloured fruit. Also my fruit are seedless - but that might not mean anything because my Rough Lemon fruit (another rootstock) are also so far without any seeds!
Further update: Eventually the fruits do turn more orange-coloured, so perhaps this confirms Volkamer.
On the other hand, the fruits now look very much like Meyer's Lemons. Has anyone heard of this being used as a root-stock??
A German correspondent remains convinced that this is Citrus volkameriana, but an English expert confirms Meyer's has been used as a rootstock by some Portuguese nurseries.

4. To produce a 'standard' potted citrus (ie. about 5' or 1.8m tall with a single tall stem), is it better to let the rootstock grow tall and then bud/graft high up, or to bud/graft low down and train the scion upwards?
The consensus seems to be that it doesn't make much difference!

5. A QX3 microscope picture. Taken at X10 magnification, this grub is about 8mm long and 4mm across. I found it in the soil of a seedling citrus plant that had died, about 6cms deep.
What is it? Could it be the dreaded Vine Weevil?
Or is it some kind of solitary bee? - I have seen some leaf-cutting bees around. Any experts please let me know what you think!

I've been asked this question several times, and I've always answered that, like many citrus, it usually takes 12 to 15 years. This was the case with my two oldest plants.
But in 1998 I planted some seeds of Poncirus trifoliata 'Flying Dragon' and some of the variety 'Kryder'. I now have about 15 Flying Dragon seedlings and around 25 of Kryder, all in small pots. In Spring 2002 I was amazed to find one of each type had begun flowering.

Phil from Texas e-mailed about this: Out of a few hundred seedlings (potted), I had one that bloomed the first year! I've also had seedling limequat (potted) bear fruit the first year, seedling sunquat (in ground) the 2nd year, and seedling sour orange (in ground) the 3rd year. I have no explanation and the more experienced citrus growers I know say 5 years or so. I live in a marginal citrus area near Houston, TX .

7. Winter Leaf Drop. A grower from the Czech Republic suggests that extra magnesium in Autumn and Winter may help prevent this problem. He writes "I understand plants a bit and I have suggestion. You also say that you give to your citruses a dose of Mg in spring, but it might help them to have it during winter too. It helps them to produce more chlorophyl and they might not have to drop off leaves to save it in their bodies. Because what happens to trees in the fall is that they drain Mg from leaves to store it. Does it make sense?" (Petr - your return e-mail address doesn't work!)
Any comments?