Tall perennials: indispensable giants for the garden

Classic" giant perennials

Let’s start with those we all know, which are no less interesting in the garden. These blooms borne on sturdy stems provide welcome verticality to create rhythm and lift the eye upward :

Foxgloves

Often treated as partial‑shade perennials, foxgloves are in fact biennial, flowering in the second year after planting (they form a rosette in the first year). With heights of 1.50 m for Digitalis purpurea at full bloom, they enliven many garden styles (cottage, shady, country). Beware, however, of their toxicity!

Delphiniums

Striking at full bloom between May and July, and reflowering in late summer when the faded spike is cut back, delphiniums belong to that group of timelessly charming plants. Blooms on the erect spike range from white to pink or deep blue depending on the variety. Among the largest delphiniums are the ‘Pacific’ series and the species Delphinium elatum, nearing 1.80 m at full bloom! Hardy, they can be planted almost anywhere, but they need sun to flower well.

Hollyhocks

Alcea rosea, known as Jacob’s staff and more commonly as hollyhocks, are also among those large, beautiful countryside plants that can grow to over 2 metres. Don’t hesitate to place them at the foot of stone walls or to frame an entrance, door or gate. They come in many colours, from yellow to almost black purple, single or double. They self‑seed freely where happy (a poor or stony soil suits them). Plant or sow in sun or light partial shade.

Some salvias

Salvia guaranitica particularly lights up the garden with its intense blue, much sought after by lovers of true blue. It has another asset: very generous dimensions, carrying its flowers up to 1.75 m tall, with a spread of at least 1 m.

Verbena bonariensis

The Buenos Aires verbena has become almost commonplace in our gardens in recent years, thanks to its drought resistance and ethereal habit. It reaches up to 2 metres and self‑seeds when planted in dry, free‑draining soil. Attracting butterflies like a magnet, Buenos Aires verbena delights for months with its tiny flowers in panicles of vivid purple or mauve. It is a champion of stony, poor soils and a plant of the future, adapting to successive heat spells in summer.

Verbena bonariensis

Solidago and Silphium

Two impressive perennials for lovers of yellow blooms: Solidago altissima lives up to its name, rising to 2 metres in height. Silphiums from the great American prairies are true giants of the garden, growing between 2 m and 3 m tall! Silphium laciniatum, the best known, and its cousin Silphium terebinthinaceum, produce flowers in the characteristic heads of the Asteraceae, as does goldenrod (Solidago).

Solidago

Giant asters

Among the wide range of asters — indispensable perennials of the late season — there are around fifty giant varieties. These giant asters are useful in naturalistic gardens, mingling with tall grasses, a pairing that is perfect in late summer and autumn. Examples include some Aster novae-angliae such as ‘Violetta’ with intensely violet flowers and an orange‑yellow centre, or Aster laevis forming a blue cloud. Aster carolinianus, sometimes called climbing aster though not truly so, is often classed among the asters and can reach up to 4 m in height.
These giant asters should be planted at the back of a border and in areas sheltered from strong winds in the garden.

Aster novae-angliae ‘Violetta’

Original giant perennials

These blooms are also spectacular, climbing as they grow to reach 1.50 to 2 metres in flower.

Thalictrum ‘Elin’ and ‘Anne’

Beloved by British gardeners, meadow-rues (Thalictrum) have now found their way into our borders. Species delavayi includes some lovely specimens, such as ‘Spendide‘. Also look to giant meadow-rues ‘Elin‘ and ‘Anne’, both equally beautiful with their delicate, airy presence.

Thalictrum delavayi ‘Splendide’

Cephalaria gigantea

Another graceful beauty despite its height, Cephalaria gigantea, a kind of giant scabious perched on a slender stem, lends itself to many combinations with its very soft yellow flowers. Completely hardy, it has a place in all gardens and in naturalistic or wild plantings.

Selinum wallichianum

Behind this tricky-to-remember name hides a garden gem, a sort of angelica with white flowers. Selinum wallichianum has, like angelica, channelled stems here flushed purple, a long flowering period in domed cymes typical of umbellifers, and very attractive, finely cut foliage. It grows to about 1.20 m and suits fresh, well-drained soils, in sun or partial shade.

Veronicastrum

These handsome perennial plants excel at lifting their fine, elegant spikes above other plants in a border. Virginia speedwell occurs in several cultivars, all equally attractive, bearing white, iridescent, pink or violet flowers. Foliage is always inserted in a whorl around the stem.
While smaller forms reach 1.20 m in height, taller ones such as ‘Lavendelturm‘ or ‘Adoration‘ peak at 1.80 m. Another bonus: they are nectariferous!

Veronicastrum virginicum ‘Erica’

Inula helenium

Inula helenium, the elecampane, like the more common Solidago or the Silphiums mentioned above, is another large perennial with yellow flowers, both tall and of generous spread for country gardens or yellow-themed gardens.

Allium ‘Red Mohican’

Allium amethystinum ‘Red Mohican’ certainly catches the eye in the garden with its stature and unusual graphic form. It grows oddly, producing tall stems with the head curved… which gradually straightens to finally open into a small elongated garnet ball, slightly bicoloured. Like all alliums, it needs sun to thrive and very well-drained soil. It suits naturalistic gardens and meadow areas, but given its character it can also feature in contemporary gardens.

N.B.: In my garden it displayed up to 1.85 metres, a real phenomenon!

Eremurus

Also called foxtail lilies, these bulbous plants are garden eccentrics, visible from afar with their immense spikes, like tapers, bearing spectacular racemes in colours ranging by species from yellow to salmon-orange or white. These bulbs (a kind of earth-star) are somewhat costly to buy and take time to establish, but after a few years they enhance dry gardens, contemporary gardens and naturalistic or country-style gardens in spring with their extravagance and elegance: between 1.50 and 2 m for most species, Eremurus robustus being the champion, reaching up to 3 m! Eremurus himalaicus is another giant. Eremurus have the advantage of being drought-resistant.

Eremurus himalaicus

Helianthus salicifolius

As attractive in leaf as in flower, Helianthus salicifolius is ornamental for many months. First with its soft green, very fine foliage that droops like dozens of small umbrellas along the stems, giving it much originality. In late summer it still dazzles in the garden, bearing its golden sunflower heads on stems around 1.80 m. Completely hardy, this perennial sunflower is wonderful in large gardens, at the back of borders, in areas sheltered from wind.

Foliage and flowering of Helianthus salicifolius

Also worth mentioning: Macleaya cordata reaching nearly 2.50 m and the angelicas, likewise indispensable for the back of borders.

Grasses

When they flower, some grasses become real highlights in the garden. Les Calamagrostis et les Panicum sont certainement les two most interesting grasses for adding verticality, thanks to their particularly erect habit. We love to use them in the style of Piet Oudolf in naturalistic gardens.

Panicum ‘Cloud Nine’ is a giant, able in good growing conditions to reach 2.20 m. ‘North Wind’ readily reaches 1.50 m. Among Calamagrostis, we particularly appreciate the imposing presence of the species C. x acutiflora, reaching 1.80 m by late summer, which, like other Calamagrostis, remains ornamental and very attractive in winter.

Stipa gigantea also grows very tall, up to 2.25 m, but its airier habit is less imposing.

Finally, some Miscanthus are also impressive in flower, such as Miscanthus ‘Zwergelefant’ or ‘Kaskade‘ which raise their inflorescences to over 2 metres.

Calamagrostis acutiflora