Perennial Impatiens: Planting and Care

Description and Botany

The Impatiens or Busy Lizzies are herbaceous plants from the balsam family, much like our annual impatiens that adorn our terraces and balconies in planters and pots. The genus includes nearly 1000 botanical species, tender perennials and annuals, along with numerous hybrids. They originate from New Guinea, Sri Lanka, Asia, Africa and certain regions of the Himalayas. Most are tender annuals and therefore generally prefer mild climates, but there are some perennial species with rhizomatous roots that offer good hardiness. Among these rare cultivated curiosities, capable of surviving our moderately harsh winters, we find Impatiens omeiana or Mount Omei balsam, a superb ground cover, and Impatiens tinctoria, a tall species from African tropical forests, hardy down to -12/-15°C with protective mulch.

Impatiens Noli tangere (botanical plate circa 1920)

The habit varies by species. Impatiens omeiana forms a bushy clump 35-45 cm tall, spreading to about 90 cm, while Impatiens tinctoria can reach about 2, even 3 m in height and 60 cm wide. Fast-growing, they form a bush with brittle, more or less branched and fleshy stems. The deciduous, abundant foliage emerges in spring and disappears in winter. It consists of lanceolate leaves, pointed at the tip, with serrated margins. Impatiens omeiana is remarkable for its large, exotic-looking foliage. The lamina has prominent veins and is dark glossy green, sometimes with bluish or silvery-white hues in Impatiens omeiana ‘Ice Storm’.

Abundant flowering occurs from August to November. They typically bloom until the first frost. In their upper part, the flower stems bear clusters of 3 to 9 small orchid-like flowers. Suspended from long, slender peduncles that make them mobile, they are very elongated and tubular. The irregular corolla consists of 3 sepals, the posterior one extending into a spur. They have a very distinctive appearance, quite different from the flat flowers of New Guinea impatiens. They emit a light gardenia fragrance, and are white with a violet throat or yellow depending on the cultivar. Those of Impatiens tinctoria measure up to 7 cm. Once pollinated, the flowers turn into small fruits, dehiscent capsules that burst when touched at maturity, projecting their seeds some distance. These balsam species go dormant in winter and re-emerge in spring.

Impatiens tinctoria is traditionally used for its dye pigments. Impatiens omeiana is an endangered species in its native habitat.

Left, Impatiens tinctoria (©Scott Zona) and right, Impatiens omeiana and Cordyalis (© Peganum)

Main species and varieties

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Planting

Where to Plant?

Hardier than their annual counterparts, perennial impatiens can withstand temperatures as low as -15°C, provided they have a good protective mulch. All impatiens require fresh, even rather moist, rich, humus-bearing soil: these are plants adapted to cool woodland settings. They thrive in shade or partial shade and need soil that remains consistently fresh to moist in spring and summer, but always well-drained, especially during winter. In cooler, wetter regions, they can tolerate gentle morning sun if the soil remains sufficiently moist. In soils that retain too much moisture or are clay-heavy, their rootstocks risk rotting. This perennial spreads via its rhizomatous stump: allow enough space around each plant, as they dislike root competition. They are ideal beneath deciduous trees, in fresh borders or rockeries, and why not near water features. They suit shaded urban gardens where sunlight is scarce. Impatiens can also be grown in outdoor containers or in dimly lit indoor spaces.

Impatiens tinctoria (© S. Rae)

When to Plant?

Plant perennial balsams in autumn from October to November to encourage rooting before winter, or in spring from March to May, avoiding frost and drought periods.

How to Plant?

In the ground:

These perennial plants will flourish best in humus-rich soil. Add a generous spadeful of well-rotted compost or manure at planting time. In heavy soil, incorporate river sand to improve drainage.

• Soak the root ball in a basin of water to rehydrate it
• Dig a hole 3 to 5 times wider than the root ball
• Loosen the soil well and place a layer of coarse sand (1/3) at the bottom for drainage
• Position the plant in the centre of the hole
• Backfill with a mix of potting compost, garden soil and compost
• Firm down gently
• Apply a mulch
• Water thoroughly and maintain regular watering until established

In pots:

The growing medium must be well-drained yet rich and moisture-retentive. Impatiens dislike waterlogging, which can cause their root system to rot.

• In a container with drainage holes, add a 3cm layer of clay pebbles
• Plant in a mix of potting compost, optionally blended with garden soil
• Keep the root ball slightly moist at all times
• Adding mulch helps retain summer moisture

Maintenance, Pruning and Care for Perennial Impatiens

Perennial impatiens cannot tolerate drought, but they appreciate soil that remains cool, so we recommend regular watering in summer, whether they are in the ground or in pots. Reduce watering during dormancy. As they disappear in autumn and only reappear in spring, mark their location. In pots, water very regularly as soon as the soil begins to dry on the surface, but without excess to avoid any risk of rot. Do not leave water in saucers.

A layer of organic mulch (linseed pales, fern fronds, dead leaves, or straw…) around the clump will help keep the soil cool for longer and reduce the frequency of watering and weeding. Mulch the stump in spring to keep the roots cool during summer.

In regions with harsh winters, renew this mulch in autumn to protect the plant from severe frosts. Remove the mulch in late March or early April, just before regrowth begins. If you fear very hard frosts in severe climates, you can dig up the tubercles in autumn and store them in dry sand over winter.

In poor soil, add a good layer of well-rotted compost or crushed horn or dried blood by lightly working it into the base of the plants each year in early spring.

Remove faded flowers regularly to encourage impatiens to rebloom.

The giant Impatiens tinctoria can be pruned once a year in May-June, which will stimulate the growth of new stems and promote abundant late flowering.

Impatiens tinctoria (© Juniperus_scopulorum)

Diseases and potential pests

In case of excessive moisture, botrytis may affect the flower buds. If you notice infestations of red spider mites (common in greenhouse-grown specimens), spray the foliage to eliminate them.

Propagation

Perennial impatiens can be propagated by division in spring or autumn. Choose an established plant that has been in place for several years.

• Using a garden fork, lift part of the rootstock by levering gently
• With a clean, sharp blade, take sections of rootstock, each with a leaf bud
• Replant immediately in the ground or in pots with moist soil
• Water generously

Herbaceous cuttings can also be taken in June:

• Cut stems about 10cm long
• Place them in a glass of water
• Once roots appear, transplant the cuttings into compost
• Plant them in their final position when they are strong enough

Pairing

Perennial Impatiens easily find their place in shade gardens, in borders or woodland settings. They brighten up even the coolest corners at a time when most other woodland flowers have faded. Impatiens omeiana makes an excellent exotic-looking ground cover for woodland areas, under trees. You can pair it with other shade-loving ground cover perennials such as Heuchera, small ferns, and hostas, which thrive in similar growing conditions and create a stunning effect in dappled shade. Japanese anemones will extend its flowering season into late autumn, as will the exotic and refined Tricyrtis ‘Hirta’, also known as Toad Lily.

Impatiens omeiana, Heuchera ‘Mint Marquess’, Hosta plantaginea and Dryopteris Filix Mas fern

With its lush, generous foliage, Impatiens tinctoria has a distinctly exotic look, perfect for creating a tropical-style garden alongside other luxuriant foliage such as gunneras, majestic ferns, Rodgersia, and banana plants (Musa basjoo).

Impatiens tinctoria (© Scott Zona), Musa ‘Basjoo’, Rodgersia pinnata ‘Superba’ and Dryopteris ‘Wallichiana’ fern