Flowers on a Plant of Blue Potato Bush (Solanum rantonnetii)
Flowers on a Plant of Blue Potato Bush (Solanum rantonnetii)

Blue Potato Bush (Lycianthes rantonnetii) - Description, Care & Uses

With the article Blue Potato Bush (Lycianthes rantonnetii) – Description, Care & Uses we approach a very interesting ornamental plant, which is probably less widespread.

Nevertheless, it is an extremely notable shrub, whose dominant decorative element is its relatively unusual shade and slightly fragrant blue-violet flowers, which appear during the remarkably long flowering period of the plant.

Originating in a fairly small area of the subtropical and, marginally, tropical climate zone of South America, it is a sufficiently adaptable and easy-to-grow shrub that requires minimal care.

However, a little more care needs to be taken by all those who knew it in 1859 as Solanum rantonnetii in order to consolidate the genus change that took place in 1919 by the important botanist Bitter, so that they can now call it by its new name Lycianthes rantonnetii.

However, it is fortunate that it remains in the same family, that of the Solanaceae (Nightshades), making the French author Hector-Henri Malot, the well-known creator of the botanical novel En Famille, rather proud.

The Blue Potato Bush can be pruned to form a small tree or even a climbing plant.

Small Tree Tree Form of Paraguay Nightshade Plant
Small Tree Tree Form of Paraguay Nightshade Plant
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Blue Potato Bush Origin

Lycianthes rantonnetii - syn. Solanum rantonnetii (Blue Potato Bush) - Map of Origin
Lycianthes rantonnetii (Blue Potato Bush) - Map of Origin

Blue Potato Bush (Lycianthes rantonnetii)

Blue Potato Bush (Lycianthes rantonnetii) - Brief Description

Family: Solanaceae

Genus: Lycianthes

Scientific Name: Lycianthes rantonnetii (Carrière) Bitter – syn. Solanum rantonnetii Carrière

Common Name: Blue Potato Bush, Paraguay Nightshade

General Characteristics

Leaf Persistence

Evergreen

Form

Shrub

Texture

Medium

Growth Rate

Fast

Flowering Period

May – September (Northern Hemisphere)

Fruiting Period

September – October

Height

1.5-2.5 to 4.5 m (5-8 to 15 ft)

Diameter

1.8-2.5 m (6-8 ft)

Shapes and Colours

Leaves Shape

Elliptic – Ovoid

Foliage Colour

Green

Autumn Foliage Colour

Green

Flowers Shape

Funnel-Shaped

Flowers Colour

Violet

Fruit

Orange-Yellow Berry

Plantation

Soil Type: Well-drained, sandy, loamy

Exposure: Sun

Soil pH: 6-7.8

Watering: Moderate

Hardiness: -4 °C (25 °F – USDA Hardiness Zone 9b)

Uses

Specimen, in groups, gardens, parks, squares, pots and containers

Blue Potato Bush (Lycianthes rantonnetii)

Blue Potato Bush (Lycianthes rantonnetii) - Etymology

Etymology of the Genus Name

The name of the genus Lycianthes is a compound Neo-Latin word consisting of the Ancient Greek words λύκιον (lykion) and ἄνθος (anthos). The first of these probably comes from the toponym Lycia, a region of Southern Anatolia (Asia Minor), which is of unknown etymology; with the name Lykion, the Pedanius Dioscorides (10 – 90 CE, Greek Physician, author among others of the famous work "Περὶ ὕλης ἰατρικῆς" – De materia medica, On Medical Material) and Roman Pliny the Elder (23 – 79 CE, author of the most important work "Natural History" –  Naturalis Historia) most likely called the plant Rhamnus saxatilis, which grows naturally in that area. The second word ἄνθος, comes from the Proto-Hellenic *αntʰos, and this in turn from the Proto-Indo-European *h₂ιndʰos, which means that even today in Modern Greek, ie flower, blossom and bloom.

Etymology of the Species Name

The name of the species rantonnetii is the Neo-Latin version of the word Rantonnet, which is nothing more than the surname of the extraordinary gentlemen Barthélémy Victor of French origin. Barthélémy Victor Rantonnet (1797 – 1871 CE) was a horticulturist, gardener, and nurseryman, and still a pioneer in the introduction and adaptation-acclimatization of exotic plants. He worked in the garden created by Jean-Baptiste Fihle de Sainte-Anne in the commune of Hyères in the south-east of France – a garden that Rantonnet turned into a commercial nursery under the name "Jardin Filhe", in honor of its creator and former owner. Among the species he cultivated were the Solanum rantonnetii Carrière or Lycianthes rantonnetii (Carrière) Bitter, with seeds he imported from Argentina derived from native plants of the Rνo de la Plata estuary area.

From the resulting plants received the necessary material to study the prominent French botanist Ιlie-Abel Carrière (1818 – 1896 CE, authority of his time in conifers), describing the species and baptizing it rantonnetii.

Blue Potato Bush (Lycianthes rantonnetii)

Blue Potato Bush (Lycianthes rantonnetii) - Origin & Life Span

Origin

The native cradle of Lycianthes rantonnetii is found in South America, specifically in parts of Paraguay and Argentina – and possibly, according to some literature sources, in some parts of Southern and Southeastern Brazil.

The natural populations of the species are mostly found on forest edges and in calcareous soils or wetlands.

Life Span

For Lycianthes rantonnetii, the reports about its longevity are minimal and minimally reliable. However, contributing and the "Kalliergeia" in the dissemination of unreliable reports, and in the base of empirical data, it decides that the life span of the species reaches up to 20 years.

Blue Potato Bush (Lycianthes rantonnetii)

Blue Potato Bush (Lycianthes rantonnetii) - Landscape Attributes

The Blue Potato Bush is a perennial evergreen or semi-evergreen medium-sized shrub, with a height usually ranging between 1.5 and 2.5 m (but under favorable conditions it can reach 4.5 m) and a diameter of 1.5-2.5 m.

It has a fast growth rate, its shape is arched or upright, and the main ornamental element of the plant is its blue-violet color and slightly fragrant flowers.

Flowering is long and abundant, as it begins in late spring and can last until September to October.

It has a moderately dense canopy, symmetrical, with regular outline, which can be characterized as medium texture.

Suitable for any type of pruning formed into a supporting climber or even a small tree.

Blue Potato Bush (Lycianthes rantonnetii)

The Flower of the Solanum rantonnetii
The Flower of the Solanum rantonnetii

Blue Potato Bush (Lycianthes rantonnetii) - Botanical Description

Branches, Shoots & Twigs

The branches and shoots are usually straight or convex, slender, terete and glabrescent. The glands are covered by trichome, while the twigs are puberulent, but as they progress to maturity become glabrous. Branches and shoots are almost angular, extending from the nodes and scantily are striate.

Leaves

The leaves are simple, chartaceous, have green color and an elliptical-oval shape. The size of their lamina in terms of length varies between 3 to 10 cm, and their width between 1.3 and 5 cm.

They end in an acute or acuminate apex, are adaxially sparsely covered by trichome with relatively long soft hairs, lack glands, while abaxially are covered by trichome with relatively long soft hairs, which are compact on the veins.

The margins of the leaves are entire to slightly sinuate, their base is cuneate and oblique or acute, they are carried on a petiole 0.5 to 3 cm long that connects them to the shoots, where they are arranged alternately on them.

Flowers

The flowers are hermaphrodite, monoecious, and actinomorphic. They are carried on an axillary inflorescence 1-2 to 5, and have a slender, terete, pubescent pedicel about 1.5 cm long.

The rotate funnel-shaped corolla consists of 5 fused petals with lanceolate lobes, is blue-violet in color and 2 to 2.5 cm in diameter.

The calyx has a campanulate shape, consists of 10 sepals, is puberulent, and its length varies between 3 and 4 cm.

The flower has 5 stamens which inserted on the tube of corolla, the filaments are unequal in length, that is range between 1.5 and 3 mm, and the anthers are orange-yellow, elongated, erect, about 3 mm long.

The syncarpous gynoecium consists of a superior, glabrous, oval-shaped ovary, with a length ranging between 1.8 and 2 mm, a glabrous, terete style 1.4 to 1.6 mm long, and a slightly bilobed capitate stigma, which forms a dense complex, and has a length of 0.45 up to 0.5 mm.

Pollination

Pollination of Blue Potato Bush is carried out by insects (entomophilous plant).

Fruit & Seeds

The fruit of the plant is smooth, fleshy berry, globose-subglobose to ellipsoid in shape, with a cordate base, in which the calyx is persistent.

It has a yellowish-orange color, length 1 to 3 cm, it is carried on a pedicel 1.5 to 2.5 cm long, it matures in winter, it is poisonous and produces numerous seeds.

The seeds have a lenticular shape, dark brown color, while their length is about 2.5 mm and their width is about 1.5 mm. Their dispersal takes place with birds (ornithochorous species).

Blue Potato Bush (Lycianthes rantonnetii)

Blue Potato Bush (Lycianthes rantonnetii) - Climate and Soil

Temperature

At the low temperature limits of Lycianthes rantonnetii, the lack of scientific research around the plant is highlighted to some extent.

And while it is generally recommended to plant it in areas with mild winters and without strong frost, in which the minimum temperatures range between -1 and -4 °C (25-30 °F), however, the literature mentions as lower tolerance limits of the plant temperatures ranging between −12.2 and −17.8 °C (0-10 °F).

On a practical level, it is almost certain that fully established plants can withstand relatively harsh winters where temperatures of several degrees below zero are recorded, with the loss of only their overground part. The underground part survives, and next spring it resprouts.

In terms of high temperatures, the tolerance of the Blue Potato Bush is high as it withstands values > 40 °C (104 °F) without significant damage.

Soil and pH

The Lycianthes rantonnetii can be planted in a variety of soil types, except the heavy ones (clayey), as long as they show very good drainage properties. However, its growth is favored in light soils, which are deep, calcareous, and rich in organic matter.

In relation to the soil reaction, the soil pH, this can be slightly acidic to alkaline, taking values between 6 and 7.8. But even here, the plant benefits especially if it is planted in neutral to slightly alkaline reaction soils, whose pH ranges between 7 and 7.8.

Exposure

The Blue Potato Bush requires sunny places to be able to give a continuous and rich flowering. On the other hand, in areas where winter temperatures are close to the plant’s lower temperature limits of tolerance or northerly winds prevail, it is not an innovative idea to plant it in sheltered places, such as in front of a wall and in southern exposure.

Blue Potato Bush (Lycianthes rantonnetii) – Description, Care & Uses

Blue Potato Bush in Blooming
Blue Potato Bush in Blooming

Blue Potato Bush (Lycianthes rantonnetii) - Care

Fertilization

Compound and slow-release fertilizers or complete conventional or organic granular are used to fertilize the plant.

In the first case, the application is done once, in the beginning of spring, with a type of fertilizer 10-10-10, and in an amount that depends, among other things, on the condition and age of the Blue Potato Bush.

In the second case, the same type of fertilizer is used, with a rate of once every 15 or 20 days, and in a dose that depends – and here – among other things on its condition and age.

In winter, it is recommended to add a Phosphorus-Potassium fertilizer, while during the period of intense flowering, it can be done every 15 to 20 days by foliar spraying a fertilizer with a high content of Phosphorus.

If the plant is planted in sandy soil, it may be necessary to add lime fertilizer.

Also, as with all fertilizers, the instructions on the product label are followed first and foremost.

Watering

Although the growth of Lycianthes rantonnetii is favored by the presence of moisture in the soil, nevertheless, fully established plants react with satisfactory tolerance in drought conditions.

However, when water supply is not a problem, it is recommended to water the plant normally. And it normally means that throughout the growing season irrigation takes place when the soil at a depth of 3 to 5 cm is almost dry.

However, the attention of the friends of Blue Potato Bush is drawn to the excessive watering: such a treatment of the plant is undesirable, because it leads to the reduced production of flowers.

During the winter months, irrigation is drastically reduced.

Pruning

Pruning the plant is not absolutely necessary, especially if its free growth is desirable. In such a case, pruning is limited to removing any diseased or dead shoots in mid to late spring.

On the contrary, if the controlled growth of the bush is intended, then it is pruned from the end of Autumn until the end of Winter, with the removal by 1/3 of the length of all its shoots.

However, when it is desirable to keep the plant size relatively stable, then the bush is pruned drastically, removing 2/3 of the length of the shoots.

If the plant is utilized in formal hedges or an attempt is made to form it into a tree, then the respective techniques of obtaining or maintaining shape through pruning are followed.

Overwintering

In shrubs planted in the ground, the addition of soil cover material (bark, dried leaves, compost, etc.) around their collars is beneficial, providing adequate protection to the roots from low temperatures.

However, for the complete protection of this category of shrubs from the harsh winters, the diligent reader of "Kalliergeia" is referred to the article on the plants frost protection.

Of course, things are simpler when the plants of Lycianthes rantonnetii are planted in pots: the plant lovers only have to move the plants indoors or in well-protected areas.

Blue Potato Bush (Lycianthes rantonnetii) - Pests & Diseases

Lycianthes rantonnetii will not bother his friends much in terms of protection from pests and diseases – with the possible exception of aphids. But because it is finally fashionable to terrorize various living beings – mainly bipeds – for health and other related and non-related reasons, we also indicate immediately below a list of numerous parasites, aiming to terrorize both the unfortunate growers of the species and gardeners.

Pests

… where the most important pests of the Blue Potato Bush are recorded.

Various Insects
  • Bactrocera latifrons (Solanum Fruit Fly)
  • Bemisia tabaci (Cotton Whitefly)
  • Epilachna vigintioctomaculata (Large Potato Lady Beetle)
  • Helicoverpa zea (American Cotton Bollworm)
  • Leptinotarsa decemlineata (Colorado Potato Beetle)
  • Liriomyza sativae (Vegetable Leaf Miner)
  • Phthorimaea operculella (Potato Tuber Moth)
Aphids
  • Myzus persicae (Green Peach Aphid)
  • Macrosiphum euphorbiae (Potato Aphid)
  • Aphis nasturtii (Buckthorn Potato Aphid)
  • Aphis frangulae
Acari
  • Aculops lycopersici (Tomato Russet Mite)
Nematodes
  • Heterodera glycines (Soybean Cyst Nematode)

By the use of appropriate insecticides and acaricides, the treatment of these pests is from satisfactory to difficult, while the treatment of nematodes is more than difficult.

Diseases

After the pests, the recording of the diseases follows.

Fungi
  • Stagonosporopsis andigena (Black Blight of Potato)
  • Botrytis cinerea (Grey Mould)
Viruses
  • APLV (Andean Potato Latent Virus)
  • APM (Andean Potato Mottle Virus)
  • AVBO (Arracacha Virus B Oca Strain)
  • PRMV (Peach Rosette Mosaic Virus)
  • PBRSV (Potato Black Ringspot Virus)
  • PVT (Potato Virus T)
  • PYDV (Potato Yellow Dwarf Nucleorhabdovirus)
  • TSVP (Tobacco Streak Ilarvirus Potato Strain)
  • TSWV (Tomato Spotted Wilt Virus)
Viroids
  • CEVd (Citrus Exocortis Viroid)
  • PCFVd (Pepper Chat Fruit Viroid)
  • PSTVd (Potato Spindle Tuber Viroid)
  • TASVd (Tomato Apical Stunt Viroid)

By the use of appropriate fungicides the treatment of these parasites is from satisfactory to relatively difficult, while for viruses and viroids there is no therapy.

Blue Potato Bush (Lycianthes rantonnetii) – Description, Care & Uses

Blue Potato Bush (Lycianthes rantonnetii) - Toxicity & Allergenicity

Toxicity

The classification of Blue Potato Bush in the family Solanaceae (Nightshades) indicates the presence of alkaloids in it. Alkaloids are toxic and are distributed throughout the all plant parts, making it particularly dangerous if swallowed by both humans and animals. Symptoms of poisoning, which are very similar to those of swallowing parts of any Solanaceae species (such as tomato or potato – excluding edible parts), include:

  • Weakness
  • Behavior changes
  • Gastrointestinal disorders
  • Depression of the central nervous system
  • Slow heart rate (bradycardia)

For these reasons, and in addition to preventing ingestion, the use of skin and eye protection is recommended during work with the plant (planting, pruning, etc.).

Allergenicity

As an entomophilous plant, it does not cause allergic reactions by its pollen.

Blue Potato Bush (Lycianthes rantonnetii) – Description, Care & Uses

Blue Potato Bush (Lycianthes rantonnetii) - Varieties & Cultivars

Although it does not belong to the most popular plants, however even for this shrub some extremely interesting ornamental cultivars and varieties have been created. On the other hand, the Lycianthes rantonnetii itself has been awarded by the British Royal Horticultural Society with the famous Garden Merit Award in 2012.

Ornamental Varieties

Lycianthes rantonnetii ‘Alba’

It has exactly the same characteristics as the typical species, except the color of its flowers, which is white. Nevertheless, sometimes the blue-violet flowers of the typical species appear. If this "spontaneous" offering of plant colors is not desirable, the annoying flowers are removed by pruning shears.

Lycianthes rantonnetii 'Alba' Variety
Lycianthes rantonnetii 'Alba' Variety

Lycianthes rantonnetii ‘Lynn’s Variegated’

This variety differs in its characteristics from the typical species, in the color of the leaves and in its slightly greater tolerance to low temperatures. Its leaves are centrally green, which is bordered by cream spots, which sometimes tend to dominate the largest percentage of the lamina surface. For its tolerance in low temperatures they range between -4 and -6.7 °C (25-20 °F).

Lycianthes rantonnetii 'Lynn's Variegated' Variety
Lycianthes rantonnetii 'Lynn's Variegated' Variety

Lycianthes rantonnetii ‘Royal Robe’

Shrub similar to that of the typical species, except for the color of its flowers, which is more intense violet, and its slightly higher tolerance to low temperatures, which ranges between -4 and -6.7 °C (25-20 °F ).

Lycianthes rantonnetii 'Royal Robe' Variety
Lycianthes rantonnetii 'Royal Robe' Variety

Blue Potato Bush (Lycianthes rantonnetii) – Description, Care & Uses

Flowering Paraguay Nightshade Plant in a Plant Bed
Flowering Paraguay Nightshade Plant in a Plant Bed

Blue Potato Bush (Lycianthes rantonnetii) - Use

The possibilities of utilizing the Blue Potato Bush concern both the horticultural forms of the plant, as well as the plant itself, in private or public green spaces.

In particular Lycianthes rantonnetii can be used:

  • As a potted plant, in gardens, courtyards and balconies
  • In seaside gardens – due to its high resistance to salt sprays, but in places sheltered from strong winds
  • Individually, as a plant of special beauty
  • In groups or in mass plantings in gardens, parks, squares
  • To create hedges
  • Formed on a climbing or small tree
  • Combined with other ornamental plants such as Blue Rock Bindweed(Convolvulus sabatius/syn. Convolvulus mauritanicus), Weeping Lantana (Lantana montevidensis), Totem Cypress (Cupressus sempervirens ‘Totem’) and Creeping Juniper (Juniperus horizontalis)

References

The References of the article with the unprecedented title Blue Potato Bush (Lycianthes rantonnetii) – Description, Care & Uses are presented by the Paraguayan group Peruvian Harp & Flute Ensemble, with the compose Titicaca.

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