Are you growing one of these 10 banned plants without realising?

RHS Chief Horticulturist, Guy Barter, explains that “knowing which plants are on Schedule 9 helps gardeners avoid inadvertently contributing to the problem of unwanted plants outside gardens and also of course breaking the law.” But he also notes that “if gardeners keep all garden plants within their gardens preventing their spread to other areas and do not dispose of surplus plants outside their plots, they are unlikely to contribute to the invasive plant problem.”

EU Regulation on Invasive Alien Species

The EU Regulation on Invasive Alien Species is a list of invasive non-native plants that are considered to pose a risk due to their ability to spread. It's illegal to import, keep, propagate, transport, sell, grow or cultivate these species, or permit them to reproduce. Aquatic plants can also be problematic as they're easily transferred from pond to pond, or into local water courses, and can become extremely invasive in the wild. For this reason, some aquatic plant species are banned from sale in the UK.

10 banned or restricted plant species

We’ve put together a list of 10 banned or restricted plant species, to help you avoid some of the most problematic plants in your garden.

1. Cotoneaster horizontalis

The most popular cotoneaster on Schedule 9 is the evergreen wall shrub, Cotoneaster horizontalis. There are also several other less popular cotoneaster species on the Schedule 9 list, so it's best to check before you buy, to ensure the species you've chosen isn't considered invasive.

Commonly used to cover walls, Cotoneaster horizontalis has ornamental red berries in the autumn. These are often eaten by birds, which then spread the seeds into the wild. Once in the wild, cotoneaster can spread over the ground, particularly in limestone and heathland habitats, outcompeting native plants.

What to grow instead: Alternative wall cover plants include wild honeysuckle (Lonicera periclymenum) and Japanese quince (Chaenomeles japonica). For wildlife-friendly berry-bearing shrubs, consider native species such as hawthorn, guelder rose and holly.

Although Schedule 9 plants can still be bought and grown in gardens, you should stop them spreading outside your garden and we’d advise not purchasing or accepting gifts of these species. Guy Barter recommends that “all Schedule 9 plants should be avoided, but there are also a number of thuggish plants best not planted, particularly in moist fertile gardens.” Two other plants he advises avoiding (because they can spread even in dry sandy infertile soils) are “horseradish (Armoracia rusticana), which is remarkably tenacious unless confined to a bucket and gardener's garters (Phalaris arundinacea var. picta), which is a forceful plant that people often regret introducing into their gardens.”

2. Chilean rhubarb (Gunnera tinctoria)

Gunnera tinctoria and Gunnera manicata (actually likely to be Gunnera x cryptica) are perennials with huge, rhubarb-like leaves. They’re considered invasive plants in the UK and banned from sale under the EU regulations. They're established in the wild in areas of the UK such as Cornwall and the West of Ireland. Gunneras can reproduce by seed (250,000 per plant) and small pieces of rhizome. They spread in wetland areas causing issues with erosion and flooding.

Gardeners already growing either gunnera must ensure they don't let it spread beyond their gardens. To remove a gunnera from your garden, cut it back completely and then dig it out. Or to stop it spreading, cut off the flowerheads in summer before they set seed and burn them on site or take them to an authorised landfill site or other suitable disposal site.

What to grow instead: Although Gunnera tinctoria is no longer available, small gunneras such as Gunnera magellanica and Gunnera perpensa are still legal to buy and grow in gardens. Other plants that create a similar effect to large gunneras include Rheum palmatum and Crambe cordifolia.

3. Virginia creeper (Parthenocissus quinquefolia)

This vigorous climber has foliage with spectacular autumn colour. It grows quickly to cover walls and fences, and can spread for 15m or more. It’s listed on Schedule 9 due to its vigour and its ability to damage trees, shrubs and buildings. If you are growing Virginia creeper, make sure it’s kept well pruned so that it doesn’t escape your boundaries.

What to grow instead: As an alternative, try planting Chinese Virginia creeper (Parthenocissus henryana). It’s a more compact species, making it less likely to escape into the wild and more suitable for growing in smaller spaces.

4. Japanese rose (Rosa rugosa)

Rosa rugosa is a vigorous shrub often planted as a hedge. It has white, pink or red flowers in summer and large red hips in autumn. It’s listed on Schedule 9 because of its tendency to smother wild plants on dune systems, destroying complex ecosystems and colonising bare patches of sand where species like sand lizards bask and breed. It spreads by seed and by suckers, and can create dense thickets, especially on sand dunes, shingle beaches and other coastal habitats, where it suppresses native plants and damages ecosystems.

What to grow instead: Rather than growing Japanese rose, choose other roses that are less likely to be invasive.

5. Yellow azalea (Rhododendron luteum)

Rhododoendron luteum is also on the Schedule 9 list. It has yellow flowers in late spring and early summer. It spreads via seed and branch growth, and can create thickets that dominate native flora. Rhododendron ponticum and Rhododendron ponticum × Rhododendron maximum are also listed on Schedule 9, and should be avoided in gardens.

What to grow instead: All three of these rhododendrons can be replaced with less invasive species of azalea and rhododendron.

6. Variegated yellow archangel (Lamiastrum galeobdolon subsp. argentatum)

Lamiastrum galeobdolon subsp. argentatum is an ornamental dead nettle with green foliage with silver variegation, and yellow flowers in late spring and early summer. Variegated yellow archangel is on the Schedule 9 list because it spreads via overground runners and can outcompete native woodland flora in the wild.

What to grow instead: Groundcover alternatives for dappled shade include primrose, wood sorrel, ground ivy and forget-me-not.

7. Montbretia (Crocosmia x crocosmiiflora)

Montbretia originates from South Africa and has been a garden favourite in the UK for over a century. By 1911 it had escaped from gardens into the wild, where it spreads via rhizomes and can dominate the native flora.

What to grow instead: Cultivated varieties of Crocosmia are less likely to become invasive, so these are your best option in place of Crocosmia x crocosmiiflora. Or you could opt for other late perennials with hot colours, such as dahlias, heleniums and rudbeckias.

8. Water lettuce (Pistia stratiotes)

Water lettuce is an evergreen floating perennial. It’s listed on Schedule 9, but isn’t one of the aquatic plants banned from sale in the UK, except in Northern Ireland. Water lettuce spreads quickly via runners and create large floating mats on the water. These can block waterways, creating issues with navigation, flood control and water flow. Large mats of water lettuce can also reduce the oxygen concentration of the water, lower water temperature and prevent aquatic wildlife from getting to the surface.

What to grow instead: Alternative floating plants to water lettuce include the native plants frogbit and common water crowfoot. As aquatic plants have such a tendency to spread into waterways via seed or on birds or other animals, it is advisable to choose native pond plants so you can eliminate the risks associated with non-native invasive species.

9. Japanese honeysuckle (Lonicera japonica)

This evergreen or semi-evergreen climber with scented yellow and white flowers is on the Schedule 9 list in Northern Ireland. Japanese honeysuckle spreads via seeds and by suckers that root as they travel across the ground.

What to grow instead: Lonicera periclymenum is an ideal replacement for Japanese honeysuckle as it supports a wealth of wildlife and, as a native species, will not have a negative effect on ecosystems if it grows in the wild.

10. Spanish bluebells

Spanish bluebells are not dissimilar to wild bluebells (Hyacinthoides non-scripta), though the flowers aren’t scented and they are larger, growing on all sides of the upright stem, rather than just one side of a drooping stem. The two species hybridise readily and the hybrids are fertile. Spanish bluebells are on Schedule 9 for Ireland and Northern Ireland because of their tendency to hybridise and spread vigorously in woodland.

What to grow instead: Although they’re not Schedule 9 plants in England, The Wildlife Trusts recommend choosing Hyacinthoides non-scripta or other woodland plants to grow rather than planting Spanish bluebells.