First the basic Botany: Lesser Celandine (Ranunculus ficaria) is part of the Buttercup family, and is not related to Greater Celandine (Chelidonium majus) which is part of the Poppy family. This is why you have to learn the "proper" names of plants and wildflowers; common names are often seriously misleading!
If you are lucky enough not to know about this little beastie, this is what it looks like:
The leaves are glossy, sometimes heart-shaped, sometimes kidney-shaped, but always indented where the stalk joins the leaf - "cordate" is the technical term.
They flower now, April, then the whole thing dies back and disappears for another year, so they can only be dealt with while they are visible.
They spread quickly, forming a dense mat of foliage which tends to smother all other plants, choking out all the dainty spring wildflowers - it is often described as an "aggressive and unwanted garden invader" but in a woodland setting, it can create a carpet of shiny yellow.
It spreads in no less than four ways - each individual rosette grows in size and spreads by rooting, creeping stems: by seed, by small white bulbils in the leaf axils above ground and (worst of all) by tubercles, which are tiny tubers, each of which can grow into a new plant. These form at the base of the plant, so when you try to dig it up, they easily get dislodged and fall, unseen, back into the soil.
Here is a photo of the base of a plant, showing the collection of tubercles or tubers.
So, how do we get rid of this little blighter?
As usual, catching it before it gets too bad is the real answer, but - as usual - that is easier said than done, and if you move into a garden with a heavy infestation, then hard work will be required.
The bad news is that smothering them - with black plastic, or with deep mulch - does not work, so digging them out is the only answer.
If you have a "spotty" coverage of them, then take a trowel and chop vertically downwards around the plant just inside the range of the leaves.
Hang on, a picture is worth a thousand words: *quick search of google images and application of Paint*
There: to remove a single clump, lift up the leaves and cut vertically downwards with a trowel, roughly where the circle lies. Go down about 3-4", then lever out a plug of soil with the roots in it.
This is specifically to avoid the risk of dislodging any of those pesky tubers.
Place each plug carefully in the bucket or wheelbarrow, then put the whole lot into your "green waste" bin to be disposed of by the council, whose heat treatment plants should kill it all. When you have done them all, either fill the plug holes with home-made compost, or fluff up the soil around the hole with a small fork, so that it fills in the gap.
Whatever you do, don't even think about dumping this garden waste over the back fence, or on a road verge somewhere, as that will just spread the infestation.
If you don't have a green waste bin, then put the material into bags and take it to your local dump: again, the waste there will be heat treated.
If you have large areas to deal with, there are three ways to approach it.
1) Get on your hands and knees and dig out plugs day and night for the next month. This is quite hard work, boring, and will leave you with lots of little pits. But it will get rid of them.
2) Dig up the top 3" of the entire area. This will be very hard work, may even require a small digger, and what do you do with the spoil? You will probably have to pay for a skip and proper disposal, otherwise wherever you tip it out, a colony of Celandine will appear.
3) Weedkiller.... yes, I know, howls of protest from Christine the glyphosate-hater, and everyone else who abhors the use of chemicals, but there are times and situations where it is the only sensible option. Bearing in mind how invasive this plant it, and the risk that anyone you pay to cart away a couple of tons of soil/tubers may well just illegally dump it in the nearest layby, well, it might actually be more responsible of you to use a weedkiller. If you do, read the instructions carefully, apply it exactly as per instructions regarding dilution, time of application, etc, use the minimum, don't do it on a windy day, and take photos before and after, so that you know which areas have been sprayed.
4) Unsubstantiated internet research: "a dressing of coal or wood ash is said to reduce an infestation of Lesser Celandine" according to this website but I have not tried this for myself, so I can't comment on its effectiveness.
With regard to timing, it would be better to dig the plants up in very early spring, as soon as you see the first leaves, and before the bulbils have formed, thus reducing the risk of spreading viable material around. Likewise for the use of glyphosate, better to catch them in early spring when the leaves are fresh and before they flower, thus hopefully killing them before they set seed.
And a final word, be careful to clean all soil off your tools (and boots) before using them elsewhere, to avoid spreading the plant around.
Like all these garden invaders, it can be dealt with, but it takes hard work, and patience: but the more of them you can get up this year, the fewer there will be for next year.
UPDATE: After receiving a question, I have written another article dealing with the topic of how to remove this pesky weed when it has infested a lawn.
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