Silverbush Plant (Convolvulus cneorum) – Description, Care & Uses

Leaf Persistence
Evergreen
Form
Spreading Undershrub
Texture
Fine
Growth Rate
Moderate

Flowering Period (Northern Hemisphere)
April – September
Fruiting Period
Summer – Autumn
Height
0.6-0.7 m (2-2.3 ft)
Diameter
1-1.2 m (3.2-4 ft)

Leaves Shape
Lanceolate
Foliage Colour
Silver Green
Autumn Foliage Colour
Silver Green

Flowers Shape
Funnel-Shaped
Flowers Colour
White
Fruit
Brown Capsule

Soil Type: Well-drained, sand, sandy loams, neutral to slightly alkaline
Exposure: Sun
Soil pH: 7-8
Watering: Low
Hardiness: −9 °C (15 °F – USDA Hardiness Zone 8b)

Specimen, mass planting, in gardens, parks, squares, rooftop gardens, pots and containers

The name of the genus Convolvulus is a Latin word and means, without complications, ‘bindweed’ and / or ‘caterpillar’. It also comes from the Latin convolvo, which is interpreted as rolling together or twining.

The word convolvo is of course complex, since it consists of the equally Latin con and volvō, which mean the first with, together, and the second roll. The distant origin of both is located respectively in the Proto-Indo-European roots *ḱóm (with, together) and *welH- (to turn, round, but also wind).

The botanical name of the genus as Convolvulus is particularly apt, as it attributes a feature of most of the approximately 200 species included in it.

The name of the species cneorum has a slightly more complex origin. It comes from the Ancient Greek word ‘κνέωρον’, which is of unknown etymology, a word with which the Ancient Greeks called – in all likelihood – the plant ‘κνῆστρον’.

But which is – in all likelihood – this plant? It is the evergreen medium-sized shrub Daphne gnidium, whose leaves are very similar to the leaves of the olive.

And because the similarity between Silverbush plant and Daphne gnidium is only in the silvery foliage and not in the fact that the latter species has poisonous fruits (to be precise, all parts of the Daphne gnidium plant are extremely toxic), the combinational thinking of botanists led them, in the poisonous poetic baptism of Silverbush plant as a cneorum. 

And with this name, the species now goes forward botanically and necessarily.

The Silverbush plant originates from the Mediterranean and specifically from the seaside areas of the Croatian islands, Albania and Italy.

In Italy, populations are located on the island of Capri, the neighboring islands of Capri Li Galli and western Sicily.

In mainland Italy are located in the coastal areas of Tuscany – whose capital Florence remains the place of birth not of Silverbush plant but of the Italian Renaissance.

Silverbush plant, if allow it to carry out its work in peace, spends its life merry and lives for more than 15 to 20 years.

Silverbush Plant is a medium to fast growth evergreen compact subshurb with spreading shoots. Its final dimensions, which it reaches between 5 and 10 years of age, depending on conditions, are approximately 70 cm in height and 120 cm in width.

It has a round or flattened hemispherical shape and a canopy that is fine in texture, dense and symmetrical with a rather irregular outline. The silvery foliage creates pleasant contrasts when combined with plants wich have red leaves.

However, the most ornamental feature of the plant is its rich and prolonged flowering, which often lasts more than 120 days. At that point, the entire plant is literally lost beneath the multitude of flowers.

The nice arch shoots of the Silverbush plant almost all come from the base of the plant and are slightly branched.

The flowers are bisexual (hermaphrodite) and have a funnel-like shape (actinomorphic). Their color is white – sometimes pink – with a yellow center, while they are carried in dense terminal cymose clusters, one to two in in the axils of bracts.

The bracts resemble the leaves but are smaller, while the bracteoles are 9–14 × 1 mm, linear, acuminate and apiculate.

The peduncle of the flowers is 1 to 2 to 4 cm long and the sepals, which are hirsutes and oblong to oblanceolate in shape, measure 7–9 × 2–3 mm.

The corolla is unlobed, densely pilose, and ranges in length from 2 to 7 cm (0.8 to 2.7 in) and in width from 2 to 2.5 cm (0.8 to 1 in). A characteristic feature of the Silverbush plant’s flowers is that they open with sunlight and the evening are closed.

Pollination occurs mainly with the insects among which – weirdly – include bees and butterflies.

The fruit is dry and smooth, a 2-locular, loculicidal capsule, covered at least at the apex with silky fine hairs. It is brown in color and ovate to globose in shape, with a length ranging between 5 and 6 mm. The calyx at the base is covered with hirsute, and the sepals are smaller than the capsule. Each capsule contains 1 to 2 seeds, and more rarely 4 seeds.

The seeds are dark brown and triangular in shape. They are densely pubescent over their entire surface. They measure up to 4 mm in length and 2–3 mm in width.

Silverbush plant is generally a plant highly adaptive since cultivated within the natural temperature range of the species. The minimum temperatures, which are also the lowest tolerance limit, range between -6 and -9 °C (20-15 °F).

However, it is a particularly sensitive plant in the heavily frozen northern winds as and the frosts and it must be avoided to planted in areas where the prevailing wind is north or the regions are frosty.

With high temperatures the plant’s behavior is excellent. The AHS (American Horticultural Society) classifies the plant in zones 8-11 and indeed, temperatures that often exceed 40 °C have no negative effect on the plant.

In relation to the soil, Silverbush plant prefers light to moderately textured soils, which have excellent drainage. In its natural habitat, it grows in calcareous, gravelly soils, even in rocky places in coastal areas.

In terms of pH it is recommended to plant in neutral to slightly alkaline soil reaction with values ranging from 7 to 8.

Silverbush plant fertilization takes place from the end of the winter to the end of the summer. It can be used a complete fertilizer containing the main elements N-P-K at a ratio of 1: 1: 1 (20-20-20).

Administration is done either once, provided it is controlled release, or in doses at a frequency of 1 every 20 to 30 days. The amount of administration for the established plants is 10 to 15 g. Additionally, a trace minerals foliar application in early spring is beneficial to the plant. No other fertilization is made after the end of the summer.

Silverbush plant, as a xerophyte, has minimal water requirements and if established, it can cope with long drought periods. However, where it is possible to irrigate, it is recommended to watery when the soil at a depth of 3 to 5 cm has dried.

In practice, it does not face problems from pests and diseases. However, sometimes, from the insects, the scales can attack the plant, while rusts and root rots are reported from fungi. Root rots are largely due to insufficient drainage.

• Saisetia oleae (Black Scale)

• Coccus hesperidum (Brown Soft Scale)

• Puccinia spp. (Chrysanthemum Rusts)

• Athelia rolfsii (Sclerotium Rot)

There are no reports indicating that Convolvulus cneorum is toxic to humans or pets.

The plant is entomophilous and does not cause allergic reactions in the respiratory system.

Although it is a widespread species, especially for plantings in Mediterranean or xeriscape gardens and landscapes, few varieties of Silverbush plant have been created.

Of these, the most important are:

• Convolvulus cneorum ‘Silvery Moon’
• Convolvulus cneorum ‘Snow Angel’

Silverbush plant is used as an ornamental, thanks to its glowing silver-colored foliage, in its highly interesting form and of course thanks to its rich and continuous flowering, which under ideal conditions lasts from 150 to 180 days.

By specifying it, it could be said that Silverbush plant can be used:

• As a groundcover plant
• In plantings on slopes – in rocky fissures
• In the planting of rock gardens
• In the rooftop gardens
• As a plant for xeriscape gardens and semi-arid areas
• For planting in coastal areas
• In combination with other shrubs and hedges, such as Autumn Sage (Salvia greggii), Pink Rock-rose (Cistus creticus), Common Hibiscus (Hibiscus syriacus ‘White Chiffon’) and Buchanan’s Sedge (Carex buchananii)

A silver artist for a silver plant: the outstanding jazz composer and pianist Horace Silver, with his classical composition ‘Senor Blues’, presents the References of the Senor Convolvulus Cneorum of Κνῆστρον.