The PLANTS project: top 5 perennial plants

As we approach early spring, gardeners start to plan which plants they would like to grow in the year ahead. Our PLANTS project inventory teams have been auditing gardens across the Trust’s estate since the summer of 2022 and have updated 49,311 living accessions to our IrisBG catalogue, 31,726 of which have been added during the project. Our gardens are home to a diverse and versatile group of plants, from trees like Sorbus intermedia ‘Brouwers’ (Swedish whitebeam) to shrubs like Syringa × josiflexa ‘Bellicent’ (lilac) and perennials like Stachys ‘Pinkie’ (lamb’s ears).

One of the things I love about gardening is the herbaceous border. Over the project I’ve been entranced by voluminous layers of perennials in our gardens – from the beds in the walled garden of Crathes Castle crammed with a complex tapestry of perennial interest, to the mixed planting schemes of Greenbank Garden and the prairie-planting style (grasses and flowering perennials planted in drifts) at Threave Garden.

Perennials are the stalwarts of the garden border. They provide colourful flowers and structure upon which you can depend, year after year, ‘perennially’. But what actually is a perennial? Strictly speaking, they can be subdivided into two main groups:

• deciduous – those plants that die back to the ground in autumn and regrow the following spring
• evergreen – those plants that keep their leaves throughout the year.

To complicate things, there are another two subdivisions:

• Some herbaceous perennials have a flexible green stem throughout their life-cycle.
• Other shrubs develop a rigid, brown and woody main stem.

If you’re a garden novice, the choice of perennials and their associated terminology might seem overwhelming. As a starting point, this blog will introduce 5 herbaceous perennials that have emerged as particularly popular in Trust gardens, whether because they are readily available, reliable, hardworking or good value. These stalwarts are relied upon for good reason; they do the work for you and never let you down. I’ve also included some more unusual cultivars from each species that might tempt you as you plan for the gardening year ahead.

1. Geranium × johnsonii ‘Johnson’s Blue’ (cranesbill)

‘When in doubt, plant a geranium,’ advised influential plantswoman and garden writer Margery Fish. Hardy perennial geraniums, which die back in winter and reappear in spring, are also known as cranesbills. Two Geranium cultivars – ‘Johnson’s Blue’ and ‘Rozanne’ – were most popular within our Trust gardens. There are about 110 species and 600 cultivars of hardy Geranium in British gardens. ‘Johnson’s Blue’ is an admirable cultivar that’s tough and adaptable ... and will add something really special to your garden.

An unusual cultivar that I came across during the Greenbank Garden audit is Geranium × monacense var. monacense ‘Muldoon’. It was named after Spotty Muldoon, a British radio show character played by Peter Cook. Just like any good performer, ‘Muldoon’ really grabs your attention. Its leaves have a pronounced mahogany colour that echo the reflexed maroon flowers, whose petals fade to violet at the base. In the autumn, as the leaves turn yellow, the dark spots become bolder and the plant turns truly spotty!

Geranium × oxonianum ‘Katherine Adele’ was found at Broughton House; it has similarly interesting foliage and is an uncommon cultivar. It was first discovered in Heronswood Garden, Washington, USA, as a seedling, and has rusty-brown-centred leaves. Another new geranium for me was Geranium aristatum. Out of the Trust gardens audited so far, it has only been found at Crathes. This geranium has soft hairy foliage, large flowers with reflexed petals and bright pink venation. In the wild it can be found growing on stony slopes in open woodland, alongside hellebores and cyclamen. If you can grow those well, you should find Geranium aristatum grows well too.

2. Crocosmia ‘Lucifer’ (montbretia)

Perhaps unsurprisingly again, another popular herbaceous plant was Crocosmia ‘Lucifer’, which we regularly came across in Trust gardens (Crathes, Culzean, Drum, Greenbank and Threave). While not many of us will ever be able to collect the 400+ different cultivars listed in the book Crocosmia and Chasmanthe by Peter Goldblatt, most gardens have space for at least 2 or 3.

The PLANTS project has audited 34 different cultivars of Crocosmia so far (also known as montbretia), with many wonderful names. I was drawn in by the rich yellow flowers of Crocosmia masoniorum ‘Rowallane Yellow’, held horizontally along single-sided stems, tapering down in a showy arc. It’s a favourite at Crathes, alongside its sister plant ‘Rowallane Orange’. Each individual floret looks like a lily with stamens and stigmas flung out in invocation. Buds tier beneath, patiently awaiting their turn in the spotlight. As the name suggests, this large, flowered variety is an Irish selection from the National Trust’s Rowallane Garden in County Down.

I couldn’t talk about Crocosmia without mentioning the Trust’s homegrown cultivars: Crocosmia ‘Culzean Pink’ (also known as ‘Culzean Peach’). These robust hardy varieties were bred at Culzean Castle and are forms of Crocosmia pottsii with tall stems, each bearing masses of small tubular blooms, opening peachy-orange and turning peachy-pink. No Crocosmia is truly pink but ‘Culzean Pink’ has definite pinkish tones as the flowers age on the stem. It copes with most conditions but grows even better in soil that doesn’t fully dry out.

3. Ophiopogon planiscapus ‘Kokuryū’ (black lilyturf)

A plant whose popularity surprised me was black lilyturf or mondo grass – Ophiopogon planiscapus ‘Kokuryū’. Its common name comes from its grass-like appearance, but it is not a true grass, nor is it closely related to true grasses (Poaceae). The name of the genus is derived from the Greek ophis (snake) and pogon (beard), most probably in reference to its leaves and tufted growth. A member of the asparagus family (Asparagaceae), it is native to Japan, Korea and China.

‘Kokuryū’ is an Award of Garden Merit winner and is prized for its short, evergreen, near-black grassy foliage. We encountered this excellent plant as ground cover; its foliage creates a lovely foil for winter-flowering plants such as snowdrops or cyclamen.

There are some 50 species of Ophiopogon, and so far we have audited 3. At Greenbank Garden we came across the only known recording of the dark-green-leaved Ophiopogon japonicus within the Trust. Similarly, at Branklyn we found the larger species Ophiopogon jaburan, with strap-shaped leathery leaves. And at Inverewe we found the little known Ophiopogon bodinieri, which originates from Tibet at 10,000ft elevation.

4. Ligularia ‘Britt Marie Crawford’ (leopard plant)