Plant Doctor Archive

Buttercups and Agapanthus

HOW can I get rid of buttercup, which is invading my garden? I tried Roundup, but it has killed off other plants. And what's the best way to get rid of agapanthus. Roundup made them go all gooey and smelly.

THERE are several different types of buttercups, most of which you can effectively control with glyphosatebased weedkillers such as Roundup. But, of course, glyphosate will damage almost any plant whose leaves it comes in contact with, so you need to be very careful when applying it to only get it on the target weeds.

To get rid of buttercups in lawns you can use selective weedkillers, like Turfix and Woody Weedkiller, which kill broadleaf weeds but don't affect grasses. Elsewhere in the garden careful spot applications of Escort or one of the many glyphosate brands, such as Roundup, Zero, Glypho 360 and Weedmaster Blue, should do the trick.

With agapanthus, you can do what I've been doing in my garden - simply digging them out. Fortunately for me, though, the clumps I'm attacking are growing in dry, semishade, so they're relatively weak-rooted and easy to dig up. Agapanthus in full sun can become an impenetrable clump, resistant to the assault of almost anything less than a small bulldozer. In this case you have to resort to an effective weedkiller and, as you have found, glyphosate on its own has little effect on agapanthus.

Quite a lot of research has gone into finding an efficient way of dealing to agapanthus and one of the latest articles I read recommends a spray consisting of 4g Escort plus 200ml glyphosate and 10ml penetrant (such as Pulse or Sprayfix) in 10 litres of water. They also suggest bruising the leaves before spraying to encourage more active uptake. Alternatively, you can cut the leaves off close to the ground and treat the fresh stumps with a mix of 1g Escort plus 50ml glyphosate and 2ml penetrant in one litre of water, or apply Vigilant gel. You'll probably need to apply three to four follow-up treatments completely get rid of the agapanthus problem.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.