I planted some Nerine bowdeni around my young Judas Tree about 8 years ago, about a foot from the trunk. I got the occasional flower in the first couple of years, but for about 5 years none. The bulbs have multiplied, so there are some clumps of them, probably about 20 individual bulbs now. There were plenty of leaves in the spring and early summer, till they died back in late summer, which I think is normal. I watered them during the dry periods. I scattered some fertiliser about. Other bulbs in the same bed - tulips, alliums - flower. Primulas flower and wild strawberries fruit there. The Judas tree, after sulking for a few years, has got its feet down and is now growing vigorously. But not a flower off the Nerine. What am I doing wrong?