The definition of an ‘invasive’ plant is rather fluid. Some plants, like certain bamboos, can spread incredibly quickly and destroy an area by killing off all the other species and creating, in some cases, a vast monoculture unless rigorously controlled. In small gardens species that grow strongly can be perceived as invasive; if you’re growing a lot of small, gently spreading plants and then plant a big plant that squashes everything else then you’re likely to regard this plant as ‘invasive’, while the same plant in a bigger space and surrounded by other plants of a similar growth rate.
We sometimes unfairly pick on certain genera as being invasive based on the activities of a few species. There are rampant species in Rudbeckia but it would be unfair to tar R. fulgida var. deamii with the same brush, and while some of the bigger (and rarely seen) Persicarias can be terrifying in their rate of spread it would be unfair to call the widely creeping but tiny P. vaccinifolia anything but charming. That said, put the P. vaccinifolia in a trough with tiny mound forming Saxifragas or Androsace and you’ll regret it very quickly…!
Knowing your plants, and taking the time to learn about them, is the foundation of plantsmanship, but also of great gardening. If you have the right conditions for a plant then it will thrive, but you must also have the right partners in the border or you might regret your choice of plant.
Geranium procurrens is tantalisingly close to being truly ‘invasive’. This sweet little species lures you in with the promise of its charming flowers over a long season, but is able to cover substantial areas of ground in a single season. Part of its success is the habit of rooting at the nodes, which means that every few centimetres/inches or so the plant is creating a new plantlet, consolidating the species’ dominance. It’s hard to believe that this species was introduced from the Himalayas in the 1840s but was actually lost to cultivation until a Dr. G. A. C. Herkelots reintroduced it in 1967. Since its reintroduction the species has certainly established itself in cultivation.
Despite its strongly spreading habit, and despite difficulty in eradicating it, this species is not without its uses. As a low spreading plant under mature shrubs it is superb, especially if it’s hemmed in by lawn and therefore mown or strimmed to stop it escaping. This is certainly a species best grown either on its own or with strong species that can hold their own against it.
It is a marvel how Geraniums with G. procurrens in their parentage are so well behaved! If you like the flowers of G. procurrens but would prefer to grow a ‘safe’ version then look not further than G. ‘Salome’; this hybrid between G. procurrens and G. lambertii is superficially very similar to G. procurrens in growth habit (minus rampant rooting!), but with slightly larger flowers with improved veining. G. ‘Salome’ makes a fine groundcover under shrubs, and while the bulk of the flowering is usually in late spring or early summer it will provide flowers all through summer and autumn.
The best known of G. procurrens hybrids is G. ‘Ann Folkard’, a cross between G. procurrens and G. psilostemon made by the Revered Oliver Folkard in 1973. As with G. ‘Salome’, this is a plant with a rather ranging habit, but is often seen at its full potential sprawling over low walls or climbing into the branches of shrubs or more tolerant perennials. Its fierce pink flowers, each with a black ‘eye’, contrast magnificently with its pale foliage early in the year.
Very similar to G. ‘Ann Folkard’ is G. ‘Anne Thomson’, a hybrid raised by Alan Bremner (who also raised G. ‘Chantilly’ and G. ‘Patricia’, amongst others). G. ‘Anne Thomson’ is from the same species as G. ‘Ann Folkard’ and has the same fierce pink flowers, but differs in lacking the pale foliage of G. ‘Ann Folkard’ and having a more compact habit, particularly noticeable towards the end of the season when G. ‘Ann Folkard’ can seem almost straggly.
It’s beyond doubt that G. procurrens has given its genes to some excellent Geraniums, but is it gardenworthy as a species? I would argue yes, but with some fairly important conditions. It won’t be enough to allow this species a space in a border; it will rapidly outgrow any allocated space and become a nuisance elsewhere. Grow this species under shrubs, where there are no other desirable plants that it can interfere with, and where its spread can easily be controlled or doesn’t matter. This species is tough and charming, but just be 100% sure you can cope with it before you grow it, and if you’re in any doubt choose G. ‘Salome’ as an alternative.