Lesser celandine

(Ranunculus ficaria) Lesser celandine looks attractive when in flower in spring. But it can quickly colonise large areas of the garden, thanks to the numerous small tubers it produces.

Some celandines are very attractive wildflowers, and there are even cultivated varieties that are grown for their ornamental and attractive flowers and leaves. Lesser celandine, on the other hand, is a pernicious perennial weed, which can quickly colonise and take over large areas of the garden if not controlled early.

Although new plants are sometimes produced from seed, it persists and spreads through its numerous small tubers and mainly by the many bulbils (tubercles) that form in the leaf axils.

The carpets of foliage can smother and kill smaller plants. The tubers and bulbils grow up through cultivated plants, making them awkward to remove and control. It has a short growing season, making it difficult for employing successful control methods.

Lesser celandine is usually worse in moist and heavy clay soils and in shady positions.

• Beds
• Borders
• Lawns
• Gravel paths
• Waste or uncultivated ground

Lesser celandine looks very similar to other Ranunculus plants and is often confused with creeping buttercup (Ranunculus repens). It produces bright yellow, glossy flowers from March to April/May. The leaves are glossy, fleshy, dark green and heart-shaped. It is low growing, rarely reaching more than 5cm (2in) high.

New growth usually starts to appear above ground in February, and then usually dies back down again in late April/early May.

As with most perennial weeds, never allow lesser celandine to become established. This will make it more difficult to fully control. Early identification and eradication is very important.

You could start by digging out the plants as soon as they appear above ground level. However, this can spreads it further if not done carefully, as it helps to spread the bulbils/tubercles.

Regularly hoeing the new leaves as soon as you see them will weaken the plant over time, but this will probably take a few years to completely kill plants – and needs lots of dedication to not allow them to grow.

Covering the soil with weed-control membrane (landscape fabric) or even thick black polythene will exclude light and may starve the plants, so they die. This can take several years until the plants are completely exhausted and eradicated.

Mulching the soil with organic matter, such as a bark mulch, will help reduce or eliminate growth. For this to work properly, the mulch needs to be a minimum of 7.5cm (3in) thick, but 10cm (4in) deep works better.

If lesser celandine is growing among established plants, you may have to lift these when dormant, from autumn to the end of winter, and clear the soil of celandine. Replant them in clean soil or pot them up for planting out later.

In lawns, regular mowing throughout the year and the use of lawn weedkillers may weaken it and eventually kill it. Although the mower blade is likely to miss the low-lying plants and, thanks to its glossy leaves, it can be resistant to lawn weedkillers.

You may unknowingly introduce lesser celandine into your garden when buying topsoil or manure. So be vigilant when buying these.

There are a number of weed control options available to treat lesser celandine. In addition to traditional weedkillers there are now also a range of more natural alternatives.

Contact weedkillers will burn and kill the foliage, but will have no effect on the roots and tubers, which will continue to grow, producing new plants and helping it to spread further.

For best results, spray with a systemic weedkiller. A systemic weedkiller, which is absorbed by the leaves, then moves down to the tubers and roots to kill them.

To ensure the weedkiller works effectively:

• Spray the leaves when the lesser celandine is growing actively; because it has such a short growing season, this gives a very small window when you can spray it.
• The larger the leaf area present, the greater the amount of weedkiller that can be absorbed and move down to the roots. So don’t bother spraying until the leaves have enlarged.
• Use a fine spray to thoroughly coat the leaves in small droplets.
• One application of weedkiller is unlikely to kill all the lesser celandines. You may have to repeat spray over several years to completely kill it, depending on how extensive it is.

A residual weedkiller, such as Bayer Garden Ground Clear, can be applied once a year to uncultivated ground and around and under established trees and shrubs. This kills existing plant growth and prevents or reduces developing plant growth.

Most contact weedkillers are total weedkillers – that is they will damage or kill any plants whose leaves they are sprayed on. Make sure you keep the spray off wanted plants – including lawns – and, if necessary protect plants by covering with polythene or similar when spraying.

Gel products, which are smeared onto, and sticks to, the weed leaves, may be a better option when trying to treat lesser celandine growing through or close to wanted plants.

Use weedkillers safely. Always read the label and product information before use.

As lesser celandine prefers heavy soil that remains damp or moist, it may pay to thoroughly cultivate the soil, digging in lots of bulky organic matter (such as well-rotted manure, compost, leafmould) and even sharp sand or grit to improve the drainage.

• Spade
• Fork
• Hand fork
• Hand trowel
• Hoe
• Weed-control membrane
• Weed killers