As soon as you start to get into gardening, you discover that not everything green is welcome. Hay vegetable covers and seemingly harmless plants that can become a real headacheThey take over the soil, invade your neighbor's property, damage other plants, or even the structure of your house. And, to top it all off, some are toxic to people and animals.
Furthermore, if you have a farm or woody crops (olive groves, vineyards, almond trees, citrus trees, etc.), the issue of plant cover is not just an aesthetic matter: The new CAP 2023-2027 rewards the use of certain live and inert cover crops with financial aid.provided that very specific rules are followed. Therefore, it's important to be very clear about which species to avoid, which are regulated by law, and which alternatives are truly worthwhile.
Plants and vegetation cover that are legally prohibited or highly controlled
Before discussing classic garden invasive plants, it's worth reviewing the species and the control measures which in some European countries, such as France, They are already directly prohibited by regulations due to their environmental and health impact. Although the law varies from region to region, they serve as a warning of what should not be encouraged in any garden.
Pampas grass (Cortaderia selloana) This is the clearest example. Those giant, highly decorative plumes produce millions of seeds capable of traveling great distances on the wind. The result is a massive colonization of ditches, embankments, and natural areas, displacing native vegetation. In France, this is already happening. it is forced to be eliminatedIn Spain, several communities consider it an invasive species and it is not at all advisable to use it as decorative ground cover or in hedges.
Something similar happens with the tree of heaven or ailanthus (Ailanthus altissima), example of an exotic plant It grows quickly and has showy flowers. Its roots are very aggressive, lifting pavements, damaging infrastructure, and its seeds colonize any crevice they find. Furthermore, it is toxic. Planting it near vegetable gardens or flower gardens is inviting it to smother your other crops.
Ragweed (Ambrosia artemisiifolia), which looks like a simple weed, is another serious case: it produces pollen extremely allergenicIt can trigger respiratory problems in sensitive residents. In some areas, it must be removed if it appears in the garden. As a "spontaneous" ground cover, it's a terrible idea, both for health and because it competes with other crops.
Lastly, David's buddleia (Buddleja davidii)The butterfly tree, also known as the butterfly tree, is a beautiful but very problematic plant in its fertile botanical formIt self-seeds and invades slopes, vacant lots, and roadside verges. In certain regions, its planting has been restricted or prohibited. If you like it, it only makes sense to choose sterile cultivars and always keep them under control; never use it as an unkempt hedge or as free-ranging ground cover.
Six invasive ground cover plants you shouldn't plant
Beyond the species already banned in certain countries, in Spanish gardens and patios there is a group of plants that are readily sold in garden centers but which, when used as ground cover or covering plants, They end up invading the entire space and driving the gardener crazy.Let's look at six of the most typical and dangerous ones for your peace of mind.
1. Mint (Mentha spp.)
Mint is fantastic in the kitchen, in infusions and cocktails, but in the garden soil it's another story. It forms a network of creeping rhizomes that advance tens of centimeters each seasonsprouting where you least expect it: in the rose garden, in the vegetable patch, between the joints of the pavement.
It doesn't matter how much you dig or uproot: Any bit of root that remains underground will sprout again.In a short time, it goes from a charming plant to an invasive carpet. Therefore, it should never be used as direct ground cover, especially near other, more delicate plants.
The only sensible way to enjoy it is grow it in pots or planters isolated from the groundEven better if the pot isn't in direct contact with the soil (because it can "jump" through the drainage holes). As an alternative aromatic ground cover in the garden, it's preferable to use thyme, oregano or chamomilewhich are much better controlled.
2. Creeping bamboo (Phyllostachys spp. and similar species)
Bamboo has an exotic feel and is very useful for creating privacy, but invasive rhizome varieties are a real danger. Its underground roots extend several meters in all directionsemerging in the lawn, under the neighbor's fence, or even lifting floors and slabs.
The same story is repeated in many gardening forums: a small plant is planted to cover a corner and, in a few years, the entire plot is full of reedsEradicating it requires deep trenches, well-installed anti-rhizome barriers, and a lot of patience.
If you're drawn to bamboo, it only makes sense to use "non-creeping" species and always with quality physical barriers that completely surround the plantationTo fulfill the function of a screen or high cover, the following may be preferable: viburnum hedges, laurels or even controlled ornamental cane, which are much less aggressive.
3. Comfrey, periwinkle and St. John's wort as groundcovers
Three other common species used as shade covers or slopes are the comfrey (Symphytum officinale), the periwinkle or vinca (Vinca minor and Vinca major) and the St. John's wort (Hypericum spp.)They all have in common that, once installed, They spread rapidly through stolons or rhizomes and take over the space of neighboring plants..
Comfrey spreads vigorously and is very difficult to eradicate completely. Periwinkle forms a dense carpet that blocks the light and prevents other herbaceous plants from growing. St. John's wort, for its part, It regrows vigorously after cutting or pruning., colonizing areas that you wanted to reserve for other flowers.
Solution? If you like them, confine them to well-defined flowerbeds or large plantersavoiding their use as general ground cover under trees or on open slopes. In shaded areas, one can opt for ferns, hostas or mixtures of ornamental grasses and low-aggressiveness flowers.
4. Bellflowers and bindweed
Garden bellflowers may look lovely, but some species and varieties They self-seed at high speed and appear in any cornerTo that we must add the dreaded bindweed, a spontaneous vine that resembles a small bellflower, with white or pale pink flowers, and which is considered a first-rate weed.
Bindweed twines around shrubs, saplings, and herbaceous plants, suffocating them by blocking their light and competing for waterAs a "romantic" covering, it's a trap: it ends up invading walls, fences, hedges, and everything nearby.
Before introducing bell-shaped structures as wall or slope coverings, it is better to consider less uncontrolled alternatives, such as controlled clematismodern climbing roses or native vines that better respect the balance of the garden.
5. English ivy, black acacia and Bermuda grass
In some gardens, the real invasive queens are the English ivy (Hedera helix), Black locust (Robinia pseudoacacia var. invasive) and the Bermuda grass (Cynodon dactylon)Each one acts differently, but they all share one problem: They displace the surrounding vegetation..
Ivy climbs walls and tree trunks and, as ground cover, forms an impenetrable blanket. Its adventitious roots grip tightly, and removing an old planting can be a real feat of engineering. Black acacia, on the other hand, It sends out abundant shoots from the roots.Colonizing ditches and verges. Bermuda grass, highly resistant to trampling and drought, creeps in where it shouldn't: vegetable gardens, flowerbeds, decorative gravel areas.
If you're looking for dense eyeshadow coverage, it's best to apply blends of adapted shrubs and less aggressive ground coverFor lawns, it is advisable to opt for mixtures adapted to the local climate that will not become invasive outside their area.
6. Wisteria and bignonia (unstoppable vines)
La wisteria (Wisteria spp.) and the bignonia or trumpet vine These two climbing plants are highly prized for their spectacular flowers. But without control, they become veritable devourers of structures. Its shoots can appear meters beyond the planting point., even creeping into neighboring plots.
Many gardeners report how the bignonia has invaded pergolas, facades, and roofs, sending shoots several meters in all directions. Wisteria, with its woody trunks, It is capable of strangling railings, bursting gutters, and damaging lightweight structures. if it is not strictly pruned every year.
These climbing plants should not be used as a "quick cover" to conceal an old fence or wall without first properly assessing their aggressiveness. Instead, less invasive climbing plants can be used. such as trachelospermum (star jasmine), modern honeysuckle, or well-tamed liana roses.
Invasive plants versus recommended alternatives
In many cases, gardeners choose invasive plants because they are marketed as easy solutions: "they grow fast," "they cover everything," or "they can withstand anything." The problem is that, precisely for that reason, they become a nightmare in the medium termIt's best to start with a simple idea: if a plant promises to cover a lot of ground in a very short time and with almost no care, it should be viewed with suspicion.
For example, instead of using the winged euonymus (burning bush) Because of their autumnal red color, many experts recommend them as an alternative. They provide flowers, fruit for wildlife, and autumnal color without behaving as a problematic species.
Instead of the Rose of Sharon (Hibiscus syriacus)For those who plant their gardens using seedlings grown from dried seed pods, it's more sensible to choose less aggressive flowering shrubs Or, if you love their flowers, look for sterile cultivars or those with very low self-seeding capacity.
To cover slopes where someone might be tempted by the orange daylily or ditch lilyIt is more logical to resort to mixtures of ornamental grasses and controllable perennialsAnd in pergolas where one would think of bignonias or wisteria, mixed hedges or less fiercely vigorous climbers offer a much better balance.
Something similar happens with the Norway maple, including the famous Crimson King cultivarIts leaves (samaras) spread throughout the neighborhood, giving rise to seedlings everywhere. A maple of this type provides shade and color, yes, but at the cost of creating a problem with tree weeds. It's preferable to opt for native or less invasive species.
Toxic plants to avoid in gardens with children and pets
Another large group of problematic plants are those that, while not necessarily invasive, They are very toxic to people and domestic animals.If you live with dogs, cats, or curious young children, there are some species that are best left unconsidered.
The classic list of extremely poisonous plants includes Hemlock (Conium maculatum), belladonna (Atropa belladonna), foxglove or foxglove (Digitalis purpurea), castor bean (Ricinus communis) y Datura (Datura stramonium, D. innoxia, etc.)In all these cases, the ingestion of leaves, seeds or fruits can be deadlyThat's why almost no one voluntarily introduces them into a family garden.
More delicate is the case of highly ornamental but dangerous plants such as oleander (Nerium oleander) or lily of the valley or lily of the valley (Convallaria majalis)Toxic principles are present in leaves, flowers, fruits, and roots. Ingesting even a small amount can cause vomiting, headaches, serious heart problems, and even death.In pets, even the water from a vase that has contained these flowers can be lethal.
It is also advisable to take special care with other species that, while not as deadly, They cause digestive problems, irritations, or cardiac and respiratory disturbances.This group includes the autumnal colchicum (Colchicum autumnale), the yew (Taxus baccata) and the aconite (Aconitum napellus)all of them highly toxic.
On a slightly lower level, but equally important to watch out for, we find lantana, hydrangeas (Hydrangea macrophylla), arum (Arum maculatum), clematis (Clematis spp.) y mistletoe (Viscum album)They can cause anything from vomiting and diarrhea to mucous membrane irritation and, in serious cases, respiratory or cardiac problems. If you suspect a child or animal has nibbled on any part of these plants, it's wise to consult a doctor or veterinarian.
Today, to clear up any doubts before buying a plant you don't know, you can turn to Plant identification apps that warn about toxicityIt's an extra step that's well worth it if your garden is a space shared with "furballs" or little explorers.
Ginkgo biloba: ancient, resilient… and quite problematic
El Ginkgo biloba It is one of the oldest trees on the planet, famous for its elegant bearing and the spectacular golden hue its leaves acquire in autumn. On paper, it has everything, but as a street tree or in a private garden... It has several significant drawbacks. that many overlook.
The first problem arises with the female plants. After flowering, they produce fleshy, yellowish fruits, similar to small plums. When these fall to the ground and are crushed, They release an extremely intense and very unpleasant odor.It smells like rancid butter or vomit. It's the butyric acid present in the pulp that causes this odor.
Many people think the solution is to plant only male Ginkgos, but it's not that simple. This tree develops deep and powerful roots that can extend over great distancesOver time, its root system can damage foundations, walls, buried pipes, and even nearby sidewalks, which is highly undesirable in confined spaces.
In small gardens or those attached to houses, it is best to avoid it or, at least, Plant it a good distance away from buildings, pipes, and pavements.There are many less problematic shade species for urban and residential environments.
Compost and soil life: the other side of plant cover
You can't talk about green roofs without mentioning the role of Compost and organic matter in soil improvementMany home gardeners and farmers manage their own compost bins, mixing fruit scraps, vegetables, dry leaves, small chopped branches, eggshells, white napkins, and uninked cardboard.
These homemade systems allow you to transform kitchen and garden waste into a dark, loose, nutrient-rich material, which It is incorporated into the soil to gradually improve its structure and fertility.In patios with very poor soils, this task becomes almost mandatory to achieve healthy plants in the medium term.
During the composting process, it is normal for the following to appear: fruit flies, ants, earthworms, and even small, harmless reptiles, such as blind snakes, which benefit from the humid, life-rich microclimate. Their presence, far from being a problem, indicates intense biological activity in the pile.
Some common practices for managing a compost bin properly include Lightly cover the container to protect it from the rainAllow lateral airflow, balance wet and dry materials (adding some soil or cardboard when there is too much moisture) and do not overuse animal remains, which can generate odors and attract unwanted fauna.
In many cases, those who compost at home end up using several containers, filling them successively and allowing each one to mature its contents. Although it may sometimes seem "unnoticeable" in very poor soil, Over the years the improvement is evident, and combined with suitable vegetation covers contributes to a much more sustainable and resilient system.
Understanding which plants and ground cover are invasive or toxic, taking advantage of CAP incentives without falling into problematic species, and supporting all of this with good compost and biodiversity management, It allows you to enjoy a healthier garden and properties that are easier to maintain and more environmentally friendly..
