[gertrude]

Our  agapanthus have been very poor this year, only one plant has flowered,  any help would be greatly appreciated. 
One of the plants (white) has never flowered since being planted out in the garden two years ago.  We garden on solid clay.

[JTh]

Maybe solid clay is not ideal for the agapanthuses, since they like free-draining soil. I saw this in an article from The Telegraph:
¨...Most critically, make sure they have good drainage. In pots he uses two parts of compost to one part of coarse sand or gravel. Where they grow naturally in South Africa, on cliff tops, crevices and ledges, there is precious little soil.
Restricting them makes the plants flower sooner, but when they mature over several years in the open ground, they get to their full size.
In containers, even when they are fully mature they will not get to their ultimate size because of the bonsai effect, unless it’s a very large container or a dwarf agapanthus. This is why plants directly planted in the border can take years to flower reliably, but when they do their flowers are more spectacular.
Thirdly, feeding is key. High potash feeds, such as the one Hoyland sells for agapanthus (which is 30 per cent potash and trace elements), applied every three or four weeks in the growing season, with a general feed twice or so in the summer, will keep the flowers coming.¨

[Caroline]

Down here in the southern oceans the idea of having difficulty with agapanthus makes me smile.   They are regarded as a weed, and in the greater Auckland area we are asked to plant only varieties which do not set seed.  They come up unasked in the vineyard and we have to dig them out as they are resistant to Round-up.  Clay - and ours is sticky and yellow - doesn't seem to deter them!

But on a more helpful note, two years and no flowers doesn't seem that long to me unless the plant in question was a monster to start off with.