81/80-year-old parents who live in Orewa HBC have a small lemon
shrub (maybe a meyer approx 3 years old and which in the past has
had a few lemons) which has mysteriously developed a complete crop
of extremely sharp thorns approximately 3 cm each in length.
The affected wood is all new/green growth whilst the only remaining
conventional-looking branch appears to be dying. The entire bush
is a maze of very sharp thorns.
thorny growth that has appeared is from the rootstock onto which
the meyer lemon is grafted. This growth is shooting up from below
the graft and needs to be removed. The rootstock has a more vigorous
growth habit than the meyer lemon and does not bear productive fruit.
As you have described, it also reduces the vigour of the lemon.
Remove the thorny growth.
Now is a good time to feed citrus with a specially blended citrus