There has been a rise in interest in pretty woodland plants including Heuchera, × Heucherella and Tiarella. This is partly because of several excellent breeding programmes, particularly in North America. These include the formidable Terra Nova Nurseries in Oregon, run by the effervescent Dan Heims, that produced favourites Tiarella ‘Spring Symphony’ (PBR), T. ‘Pink Skyrocket’ (PBR) and T. ‘Sugar and Spice’ (PBR).
I had the pleasure of attending a presentation by Heims several years ago and I have to say he is one of the most enthusiastic people I have ever met in horticulture — and so passionate about his product.
It is not hard to see why. The three genera are highly ornamental and Tiarella is perhaps the most delicate of the trio. Many varieties are now available, with deeply lobed leaves decorated with fantastic contrasting markings, that really add impact to flower borders and even containers.
T. ‘Mystic Mist’ - image: Floramedia
Another feature is their pretty flowers. Tiarella is known as the "foam flower" because of its frothy spikes of star-shaped flowers in shades of white and pink. The name literally means "little tiara", referring to the fruit that resembles a diadem or turban. Part of the Saxifragacaeae family, they come from Asia and North America. They are hardy, classified as herbaceous perennials, but many keep a clump of leaves over winter that makes them useful in borders and in containers for winter display.
One of the best known species is T. cordifolia Award of Garden Merit (AGM), the heart-shaped foam flower, which is a vigorously spreading woodlander. Using stolons to spread, it is successful enough to be seen by some as invasive, but it can be very useful ground cover. Its leaves are said to be rabbit- and deer-resistant, which is a huge benefit when planted in an unprotected woodland setting.
Another species from which many good varieties have been bred is T. wherryi AGM. It is a smaller plant overall and has more slender racemes of flowers than T. cordifolia and does not spread via stolons.
The ideal conditions for Tiarella are moisture-retentive soil in shade or partial shade. They need more moisture than Heuchera but will not do well in waterlogged conditions. However, using them in a dry, shady spot — such as under deciduous trees — can work, but you may have to do some careful, even watering in the hotter months. If you remove faded blooms it will encourage more, prolonging the flowering period. Too much fertiliser can kill them so take care with mulch. Applying a dry mulch around the crown before winter can prevent frost damage. In spring, tidy the clump of leaves ready for the season ahead.
What the specialists say
Kevin Scott, managing director, Amati Plants, Dorset
"Tiarella is a fantastic genus, just getting more and more popular all the time. Interest really started in the 1980s when good foliage forms started coming out of breeding programmes in North America. Now the flower spikes are being looked at, with pyramidal forms versus frothier types.
"A new feature, being championed by Janet Eggers at Terra Nova, is the trailing form. These suit hanging baskets and are just a new way to use Tiarella. Look out for ‘Appalachian Trail’ and other ‘trailers’.
"They are not fussy, perhaps preferring more moisture in the soil than they are sometimes given. They are, after all, woodland or montane plants, used to moisture-retentive soil but one that is not too rich."
T. ‘Sugar and Spice’ - image: Floramedia
Maryanne Deakin, owner, The Tiny Garden Centre, Kent
"When in full bloom Tiarella fly off the shelf quicker sometimes than we can put them out. They are that attractive to customers.
"The pinky white flowers of ‘Pink Skyrocket’ or the slightly subtler ‘Spring Symphony’ are clear bestsellers, but the strongly marked or deeply divided foliage types like ‘Jeepers Creepers’ are also much asked for.
"They are marketed alongside other ground-cover foliage plants, including close relatives Heuchera and their hybrid × Heucherella. While Tiarella can’t match the colour range of Heuchera when in flower they are often selected over them as more dainty and with prettier flowers."
T. wherryi AGM- image: Floramedia
Species and varieties
T. ‘Angel Wings’ is a small, neat variety that has very dissected, lobed and sometimes tiered mid-green leaves with deep-crimson central markings. The flower buds are a deep pink, open a pale pink and become frothy white wands over a long period from spring to summer. Height: 20cm. Spread: 30cm.
T. ‘Appalachian Trail’ is a trailing variety that can be planted in a hanging basket but is also great ground cover for shade. It has well-marked leaves with a prominent, dark, central splatter pattern and short white flowers. Vigorous without getting out of hand. Height: 10cm. Spread: 60-90cm.
T. cordifolia AGM (H5) is a stoloniferous, herbaceous perennial that spreads easily, with lobed green leaves that become bronze-tinged in autumn. Produces erect stems bearing small, creamy white flowers in the summer. Height: 30cm.
T. ‘Iron Butterfly’ (PBR) has well-cut green-bronzed foliage with black fingers down the centre of each lobe and large fragrant flowers. Height: 30cm. Spread: 45cm.
T. ‘Jeepers Creepers’ (PBR) is a neat plant with a trailing, creeping habit and white foamy flowers on long spikes in spring and summer. Deeply cut maroon foliage turns to red with pink tones in autumn. Useful runner for shady areas. Height: 25cm.
T. ‘Mint Chocolate’ produces mint-green leaves with large chocolate markings and masses of creamy-pink flowers. Height: 30cm. Spread: 40cm.
T. ‘Mystic Mist’ (PBR) has beautiful bright-green leaves with white speckled variegation featuring prominent red veins all year. In autumn the foliage develops pink tones. It has pretty white flowers. Needs shade from direct sunlight. Height: 20cm. Spread: 30cm.
T. ‘Pink Skyrocket’ (PBR) is considered Terra Nova Nurseries’ best flowering Tiarella. Pyramidal spires of shrimp-pink buds open to dainty white flowers. Deeply cut foliage turns bronze in autumn in a sunny position. Height: 15cm. Spread: 30cm.
T. ‘Spring Symphony’ (PBR) is a clump-forming variety with deeply lobed green leaves that are dark purple along the midribs. Produces upright spires of small, starry, creamy-white flowers opening from pale-pink buds in late spring and early summer. Height: 30cm.
T. ‘Sugar and Spice’ (PBR) is a compact variety with dissected mid-green leaves that have striking dark-brown central markings. It produces frothy spikes of small pale-pink flowers from spring to early summer. Height: 35cm.
T. wherryi AGM (H5) is a compact species that has deeply three-lobed green but purple-tinted leaves and short flower spikes bearing pale-pink buds that open as white starry flowers from late spring. Height: 25cm.
T. wherryi ‘Green Velvet’ has leaves like green velvet and delicate spires of starry white flowers in midsummer. Height: 25 cm.
Thank you to Floramedia, which supplied the images for this article from its photo library www.floramedia-picture-library.com