Senecio: Planting and Care

Description and Botany

Evergreen shrub, perennial plants or succulents from the vast Asteraceae family which includes sunflowers, chrysanthemums, and daisies, Senecio or groundsel comes in various appearances.

Senecio saxifragoides

The genus Senecio includes over 1,600 species primarily native to the Southern Hemisphere, the Mediterranean region, and South Africa. They are typically found in rocky areas, sand, and between rocks, near the sea. This is a Mediterranean plant perfectly adapted to drought, sea spray, and long hot summers, making it essential for coastal and Mediterranean gardens. It is valued for its ability to thrive in dry, saline soils. More or less hardy depending on the species, it is an excellent coastal garden plant.

The choice of senecio is more extensive than it seems. The most common is Senecio maritimus (Senecio candicans, Cineraria maritima, or Dusty Miller), an evergreen subshrub grown as an annual, very distinctive with its decorative, finely cut, downy, and silvery foliage. It has given rise to many interesting varieties such as ‘Angel Wings’ and ‘Donkey’s Ears’. Senecio serpens (blue chalksticks), a popular succulent groundcover for Mediterranean rock gardens, Senecio mandraliscae, a shrubby succulent species, and Senecio greyi ‘Sunshine’ or shrubby groundsel are also commonly cultivated. Senecio rowleyanus, also known as “String of Pearls” or “Rosary Vine”, is a botanical curiosity with round leaves resembling small green pearls cascading down.

The genus is highly diverse. Three main categories of Senecio can be distinguished. The habit can be upright, climbing, or trailing. Some species are creeping groundcovers not exceeding 25 cm in height, while others form a highly branched shrub reaching up to 1.50 m in height and over 2 m in width over time. For example, Senecio cineraria forms a small bushy shrub. Growth occurs at a steady, rather rapid pace.

Senecio rowleyanus (© Jukka Heinonen), Senecio vitalis (© Megan Hansen), Senecio mandraliscae and Senecio maritima ‘Silver Dust’.

The foliage, highly decorative, varies from one species to another. Senecio leaves also come in various shapes but are often fleshy and relatively thick. The leaves are felted and deeply lobed, somewhat resembling oak leaves, and silvery in colour, sometimes almost white in Dusty Miller, forming a grey, woolly mane that earned the plant its name, “senex” meaning “old man” in Latin. This is the senecio instantly recognisable, the one used by florists and seen in cemeteries… The fleshy, blue leaves covered with a white bloom and shaped like claws in Senecio mandraliscae evoke bluish fingers, while Senecio serpens displays small, equally succulent leaves resembling rosemary. In these two “succulent” species, the leaves allow them to store water to withstand heat and drought. The powdery bloom is another characteristic of their adaptation to dry conditions.

While the foliage is most often remarkable for its grey-white tones, some senecios exhibit bright green foliage, such as Senecio polyodon, or grey-green in Senecio greyi ‘Sunshine’. The leaves are evergreen or semi-evergreen if winters are mild.

Flowering occurs in summer, from June until frost, depending on the climate. Leafy, branched flower stems rise among the foliage. They bear small, more or less discreet heads 1 to 3 cm across, clustered in corymbs. The flowers are golden yellow to mustard yellow, creamy white, exceptionally magenta pink in Senecio polyodon. This colourful, daisy-like flowering contrasts beautifully with the leaf colour.

These small melliferous and nectariferous heads renew continuously throughout summer, attracting numerous pollinating insects, particularly butterflies.

Once pollinated, the flowers turn into small achenes topped with a pappus of bristles, easily dispersed by the wind.

Senecio maritima, Senecio erucifolius and Senecio serpens (© Jim, the Photographer)

Main species and varieties

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Planting and sowing Senecio

Where to Plant It?

The Senecio is a quintessential plant for maritime climates and dry gardens. Some varieties, like Senecio greyi ‘Sunshine’, are relatively hardy if planted in very well-draining soil that doesn’t retain water in winter and sheltered from cold, dry winds. Others, such as Senecio mandraliscae, are frost-sensitive and can only be grown in the ground in the orange tree zone. Very tender, Dusty Millers are often grown as annuals.

Senecio thrives particularly well in coastal areas and Mediterranean gardens, as most varieties generally cannot withstand temperatures below 5°C. In colder, wetter regions, it’s best grown in pots.

Naturally found on arid slopes, often rooted in sand or between rocks, it loves full sun and adapts easily to any ordinary, very well-drained soil, even stony ground. It tolerates summer drought but fears excess moisture, both in summer and winter: waterlogged soil will prove fatal. If your soil is heavy, add gravel or coarse sand to improve drainage. It fits perfectly in a scree garden or rockery. Heat, dry conditions, and full sun will enhance the colour of its foliage, as is typical for plants with grey, white, or silvery leaves. It can tolerate partial shade in warmer climates.

Versatile in mild climates, Senecio forms attractive, luminous clumps year-round in borders, large rockeries, dry slopes, or as ground cover in the garden’s toughest spots.

It’s also useful for filling gaps in sunny borders. It can be grown in pots on patios or balconies, overwintered indoors in wetter regions.

Silvery-leaved Senecio thrives in dry or rock gardens

When and How to Plant or Sow?

Plant Senecio in spring (March–April) after frosts or in autumn (September–October) in warm climates. Sow seeds in trays from February to March.

How to Plant?

In the Ground

In heavy soil, incorporate drainage materials like gravel and compost at the base of the planting hole to protect the stump from moisture and improve drainage. If your soil is too wet, plant on a slope or raised rockery.

• Dig a hole 2–3 times wider than the root ball
• Loosen the extracted soil and lighten it with coarse sand or grit
• Add a layer of pumice or clay pebbles at the base
• Plant potted Senecio in the centre, without burying the collar
• Backfill and firm gently
• Water thoroughly
• We recommend topping with a mineral mulch to retain warmth

In Pots

Senecio adapts well to containers if given a very free-draining mix to prevent waterlogging and root rot.

• Add 5–10 cm of drainage (grit, pumice, or clay pebbles)
• Use a mix of 2/3 Mediterranean plant compost and 1/3 sand
• Water after planting

How to Sow Senecio?

• Fill a tray with seed compost
• Sow Senecio seeds thinly on the surface
• Cover lightly with compost
• Firm gently and water with a fine spray
• Place in bright, indirect light at 18–24°C
• Keep moist (not soggy) until germination (10–21 days)
• Prick out seedlings into 8 cm buckets once they have 2–3 leaves
• Transplant outdoors after frosts, usually late May/early June

How to care for a Senecio?

The Senecio can remain in the ground all year round in Mediterranean regions and only during the warmer season elsewhere. It’s an undemanding plant that is truly low-maintenance as long as the soil remains well-drained. Once established, it is rarely affected by diseases, as it only fears excess moisture. Water once a week during the first summer after planting: a few thorough but spaced-out waterings in summer, in dry and hot climates, will stimulate its growth. Once well-rooted, it can easily withstand several weeks without watering. Always allow the soil to dry out between waterings.

In pots, water once a week in summer. Never leave a saucer under the pots, especially in winter.

When winter arrives, protect the stump with straw or dead leaves.

In regions north of the Loire, bring your pots indoors before the first frosts to a sheltered cold greenhouse or frost-free conservatory. Keep the substrate almost dry during winter by watering only once a month.

How to prune a senecio?

Regular pruning in March-April or after flowering will prevent it from forming old wood and becoming bare at the base. Remove faded flower heads by cutting them at their base with pruning shears. Prune annually by lightly cutting back the clumps to 20 cm from the ground to keep them longer, maintain a dense and bushy habit, and ensure beautiful foliage.

Propagation

The Dusty Miller propagates easily from seed. Propagation by cuttings in summer is another easy method to multiply all senecio species. Moreover, some species naturally tend to develop roots as soon as a stem touches the soil. Propagation can be done by leaf or stem cuttings.

Leaf Cutting

• Take a few leaves
• Simply place them on a mix of compost and sand without burying them
• Transplant into pots or directly into the ground once sufficiently rooted

Stem Cutting

• In summer, take 8-10 cm long stems, making a clean cut just below a node
• Remove the leaves at the base
• Let them dry for a day or two
• Insert the cuttings into a tray or buckets filled with a well-draining mix of river sand and compost
• Gently firm the soil around the stems
• Keep the substrate moist until rooting occurs
• Place these young cuttings outdoors in partial shade
• Then, in October, protect your young plants from frost under a cold frame
• Plant out the following spring

Pair

The Senecio can easily be incorporated into a dry garden, a scree garden or rockery alongside other drought-resistant perennials and Mediterranean perennials that share the same requirements: dry, well-drained soil and a sunny position. If you live by the sea, it’s the ideal plant for borders or beds with sandy soil. With their beautiful silvery foliage, Dusty Millers soften compositions in beds or create striking contrasts with complementary colours like the yellow of Coreopsis, for example. To create a symphony of grey foliage, pair them with Artemisia or Helichrysum italicum. In pots and planters, they’ll contrast beautifully with the colourful foliage of Coleus and miniature purple Dahlias or a Salvia greggii ‘Mirage Burgundy’.

Helichrysum italicum, Senecio candicans, Coreopsis verticillata ‘Moonbeam’ and C. auriculata in a harmonious blend of yellow and grey

On arid slopes or in large dry rockeries, plant Senecio mandraliscae with Delosperma and other undemanding ground-cover perennials like Sedums, Mouse Ears and Dianthus.

Senecio mandraliscae, Delosperma, Stachys byzantina, Dianthus and Sedum rubrotinctum

In a dry, predominantly mineral Mediterranean garden, plant Senecio, for example, at the front of a bed composed of dwarf palms (Chamaerops humilis), American agaves, Opuntia, cacti and other succulents, or with garrigue plants like rosemary or rockroses.

At the edge of a mineral bed, it will add a touch of greyish or bluish colour, nestled among ornamental grasses like Stipa pennata, Stipa tenuifolia and Carex.

In naturalistic sunny gardens, it pairs easily with lavender, some Achillea and Perovskia.