Overseas gardeners find our attitude to agapanthus perplexing. These plants are much more prized elsewhere, whereas we largely consign them to roadsides. It is much rarer to see them used as garden plants in New Zealand, even though there are some very good named cultivars which are sterile, so don’t set seed. Their future is sometimes under threat as they are seen by some to be noxious weeds. And they are very difficult to get rid of if you no longer want them.
But I think our summer roadsides would be dull without them. While they set prodigious amounts of seed, these do not appear to spread far and certainly the birds are not expanding the range. But such is the concern, that we try and get round to removing the spent flower heads and we feel obliged to stop them from encroaching on the neighbours’ boundaries.
This leaves the problem of what do with the seed heads. While we make a hot compost mix, it is not always hot enough to destroy viable seed. In the past, I have been guilty of putting seed and noxious weeds out for rubbish collection but we now think that sending even very limited amounts of green waste to landfill is not justifiable.
This year Mark has set up large barrels into which unwanted seeds and bulbs are put to soak in water until they rot down. It would give a valuable liquid fertiliser but liquid feed has not been part of our routine so it is more likely to all end up in the compost heap eventually. Allow at least a month for the rotting process to take place.
If you want to get rid of clumps of agapanthus, most people will have to get digging. The most common weedkiller, glyphosate (Round Up) is largely ineffective. To spray, you have to resort to heavier duty, controlled brush killers like Grazon and few people have access to these. It may be the difficulty of eradicating existing plants that puts most people off the plant, more than their seeding ways.