Perennial Impatiens: Planting and Care

Description and Botany

Les Impatiens ou Impatiences ou encore Balsamines vivaces sont des plantes herbacées de la famille des balsaminacées, tout comme nos impatiens annuels qui fleurissent nos terrasses et balcons, en jardinière ou en potées. Le genre réunit près de 1000 espèces botaniques, vivaces peu rustiques et annuelles et de nombreux hybrides. Elles sont originaires de la Nouvelle-Guinée, du Sri Lanka, d’Asie, d’Afrique ou encore de certaines régions de l’Himalaya. La plupart sont des plantes annuelles gélives et préfèrent donc en général les climats cléments, mais il existe certaines espèces vivaces à souche rhizomateuse qui offrent une bonne rusticité. Parmi ces curiosités rares en culture, capables de survivre à nos hivers moyennement rigoureux, on trouve l’Impatiens omeiana ou impatiens du mont Omei, un superbe couvre-sol et l’Impatiens tinctoria, une espèce haute issue des forêts tropicales africaines, rustiques jusqu’à -12/-15°C sous un paillis protecteur.

Impatiens Noli tangere (botanical plate circa 1920)

Le port varie selon l’espèce. L’Impatiens omeiana forme une touffe buissonnante de 35-45 cm de hauteur, pour environ 90 cm d’envergure, quand l’Impatiens tinctoria atteindra environ 2, voire 3 m de hauteur pour 60 cm de large. De croissance rapide, ils forment un buisson aux tiges cassantes, plus ou moins ramifiées et charnues. Le feuillage caduc et foisonnant émerge du sol au printemps, et disparaît en hiver. Il se déploie en feuilles lancéolées, pointues à leur extrémité, aux marges dentelées. L’Impatiens omeiana est remarquable par son feuillage ample d’allure exotique. Le limbe présente des nervures saillantes et est de couleur vert foncé brillant avec parfois des reflets bleutés ou blanc-argenté chez l’Impatiens omeiana ‘Ice Storm’.

La floraison abondante a lieu d’août à novembre. Ils fleurissent généralement jusqu’au premier gel. Dans leur partie supérieure, les hampes florales portent des bouquets de 3 à 9 petites fleurs aux allures d’orchidées. Suspendues à un long pédoncule fin qui les rend mobiles, elles sont très allongées, tubulaires. La corolle irrégulière est formée de 3 sépales, le postérieur est prolongé en éperon. Elles présentent une physionomie très particulière, bien différente des fleurs plates des impatiens de Nouvelle-Guinée. Elles diffusent un léger parfum de gardénia, sont blanches à gorge violette ou jaunes selon les cultivars. Celles de l’Impatiens tinctoria mesurent jusqu’à 7 cm. Une fois pollinisées, les fleurs se transforment en petits fruits, des capsules déhiscentes qui explosent à maturité lorsqu’on les touche, projetant alors leurs graines à distance. Ces espèces de balsamines entrent en dormance en hiver pour ressurgir au printemps.

L’Impatiens tinctoria est traditionnellement utilisé pour ses pigments colorants. L’Impatiens omeiana est une espèce en voie d’extinction dans son habitat d’origine.

On the left, Impatiens tinctoria (©Scott Zona) and on the right, Impatiens omeiana and Cordyalis (© Peganum)

Main species and varieties

Impatiens omeiana Ice Storm

This cultivar stands out with its finely silver-powdered foliage, as if frosted. Highly ornamental in cool and shaded areas.

• Période de floraison October, November
• Hauteur à maturité 45 cm

See the product sheet

Impatiens tinctoria

A giant for autumn! It produces large, beautiful, and stylised flowers in late summer and autumn.

• Période de floraison October to December
• Hauteur à maturité 2 m

See the product sheet

Planting

Where to Plant?

Hardier than their annual counterparts, perennial impatiens can withstand temperatures as low as -15°C, provided they are well mulched. All impatiens require a cool, even moist, rich, and humus-rich soil: they are plants suited to cool woodland settings. They thrive in shade or partial shade and need soil that remains consistently moist to wet in spring and summer but always well-drained, especially during winter. In cooler, rainier 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 rhizomes may rot. This perennial spreads via its rhizomatous root system: ensure enough space around the plant, as they dislike root competition. They are ideal under deciduous trees, in cool flower beds, rockeries, borders, or near water features. They are perfect for 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?

Perennial balsams are best planted in autumn, from October to November, to encourage root establishment before winter, or in spring, from March to May, avoiding frost and drought periods.

How to Plant?

In the ground:

These perennials will thrive in humus-rich soil. Add a generous shovel of well-rotted compost or manure at planting time. In heavy soil, incorporate river sand to improve drainage.

• Soak the root ball in a bucket of water to rehydrate it
• Dig a hole 3 to 5 times wider than the root ball
• Loosen the soil and add a third of coarse sand to the bottom of the hole for drainage
• Place the plant in the centre of the hole
• Fill with a mix of potting soil, garden soil, and compost
• Firm the soil
• Apply a layer of organic mulch
• Water thoroughly and regularly until established

In pots:

The substrate must be well-drained yet rich and moisture-retentive. Impatiens are sensitive to excess moisture, which can cause root rot.

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

Care, Pruning and Maintenance of Perennial Impatiens Perennial impatiens, also known as busy lizzies, are popular garden plants prized for their vibrant blooms and lush foliage. To keep your impatiens thriving and looking their best, follow these essential care tips: **Watering:** Impatiens prefer consistently moist soil. Water regularly, especially during dry spells, but avoid waterlogging. Mulching around the base helps retain moisture. **Fertilising:** Feed every 2-3 weeks during the growing season with a balanced liquid fertiliser to encourage continuous flowering. **Pruning:** - Deadhead spent flowers regularly to promote new blooms. - Trim back leggy stems to maintain a bushy shape. - In late autumn, cut back plants to about 15cm above ground level. **Winter Care:** - In colder regions, lift and pot plants before the first frost. - Overwinter in a cool, bright location (10-15°C). - Reduce watering during dormancy. **Pests and Diseases:** Watch for aphids, spider mites and downy mildew. Treat promptly with appropriate organic or chemical controls. **Propagation:** Take stem cuttings in late summer for new plants. Root in water or moist compost. By following these simple care guidelines, your perennial impatiens will reward you with a spectacular display of colour throughout the growing season.

Perennial impatiens cannot tolerate drought but appreciate soil that remains moist, so we recommend regular watering in summer, whether they are planted in the ground or in pots. Reduce watering during their dormant period. Since 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 avoid overwatering to prevent any risk of rot. Do not leave water in the saucers.

A layer of organic mulch (linseed flakes, fern fronds, dead leaves, or straw…) around the clump will help keep the soil moist for longer and reduce the frequency of watering and weeding. Mulch the base 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 the growing season resumes. If you are concerned about very severe frosts in colder regions, you can dig up the tubers in autumn and store them in dry sand over winter.

In poor soil, add a good layer of well-decomposed compost or crushed horn or dried blood by lightly working it into the soil around 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 humidity, botrytis can affect flower buds. If you notice infestations of red spider mites (common in greenhouse-grown plants), spray the foliage to eliminate them.

Propagation

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

• Using a garden fork, lift a portion of the clump by levering it gently
• With a clean, sharp blade, cut sections of rhizome, each with a leaf bud
• Replant immediately in the ground or in a pot with moist soil
• Water generously

Propagation by softwood cuttings in June is also possible:

• Cut stems about 10 centimetres long
• Place them in a glass of water
• Once roots appear, transplant the cuttings into potting compost
• Move them to their final location when they are strong enough

Pairing

Perennial Impatiens easily find their place in shade gardens, in borders or wooded areas. They brighten up even the coolest corners at a time when most other woodland flowers have faded. The Impatiens omeiana makes an excellent exotic-looking ground cover in woodland settings, 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 complement its flowering until the onset of winter, as will the Tricyrtis ‘Hirta’, also known as the Toad Lily, with its exotic and refined appearance.

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

With its lush and generous foliage, Impatiens tinctoria has a distinctly exotic look that allows you to create a tropical-style garden, paired with other luxuriant foliage such as gunneras, majestic ferns, Rodgersia, and banana trees (Musa basjoo).

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