Acacia or Mimosa

Acacia (Acacia) — a large genus of flowering plants of the legume family (Fabaceae). The genus comprises about 750 species of deciduous or evergreen shrubs and trees, distributed in the tropics and subtropics of both hemispheres. The majority are inhabitants of arid regions of Australia; fewer species are found in Africa, and individual species occur in the Americas, Asia and Polynesia, where they often form whole landscapes.

The name of the genus comes from the Greek word akis — a point or thorn, and is related to the fact that in some Acacia species there are two spines at the base of the leaves, which are modified stipules, while in others the leaves themselves end in spiny points.

Leaves are bipinnate, mostly with numerous small leaflets. In many (predominantly Australian) species the leaf blade is completely or partially undeveloped and then the function of photosynthesis is performed by a leaf-like expanded petiole (the so‑called phyllodium). A characteristic feature of other acacias is the presence of stipules modified into spines. In the American species A. sphaerocephala, A. costaricensis, the African A. drepanolobium, and some other species the spines are very large and are inhabited by ants. Acacia usually has small yellow or white flowers, noticeable mainly because of numerous stamens that protrude far beyond the corolla; these flowers are in capitate or spike-like inflorescences, which in turn are gathered into a compound, mostly paniculate inflorescence. The fruit is a two-valved or indehiscent pod. An acacia with an umbrella-shaped crown is a characteristic landscape element of African savannas.

Many species of Acacia have great economic importance. Some are fast-growing timber species, others provide valuable timber, for example the Australian blackwood — A. melanoxylon. From A. senegal the higher grades of gum arabic are obtained. From the wood of A. catechu the tanning agent catechu is extracted. Silver wattle (A. dealbata) is cultivated in the south as an ornamental plant; its cut flowering branches (known as mimosa) are brought to cities of the temperate zone in January – March.

Silver wattle - Acacia dealbata

Known as mimosa, often given as a gift on March 8, it originates from Australia. It is an evergreen, spreading tree reaching about 10 meters (various sources state it can reach 15-25 meters, and in its native habitat up to 30-45 meters). It has smooth bark without spines. Branches are thin and pubescent, covered with a whitish bloom, as are the bipinnate leaves. It received the name "silver" for the ashy tint of its foliage. It grows quickly.

Flowers have a delicate scent – spherical heads 4-8 mm in diameter, gathered in complex paniculate inflorescences located at the ends of last year's shoots. Acacia flowers are small; each flower has many stamens with pale yellow filaments and bright yellow anthers. The abundance of golden stamens makes the inflorescences extremely delicate and fluffy. Flowering occurs in mid-winter to early spring.

Prickly or paradoxical wattle - Acacia armata = Acacia paradoxa

The most common species in indoor cultivation.

This is an abundantly branching compact shrub 1-3 meters tall with thin, ribbed, pubescent branches. Shoots are densely covered with dark green phyllodes (no more than 2.5 cm) that are oblong and slightly curved. At the growing buds there are spines – modified stipules, which is the source of the name "armed" (armata). Leaves are ovate, slightly asymmetrical with a blunt or shortly pointed tip, dark- or silvery-green. Aromatic bright yellow flowers are gathered in solitary capitate inflorescences. Flowering is abundant and occurs in March-April. Acacia armata, thanks to its thin shoots, can be used as an ampelous (hanging) plant.

Temperature: In summer ideally within 20-25°C; the plant can be moved outdoors to a yard or balcony. In winter provide a cool and sunny overwintering with temperatures not above 8-10°C.

Lighting: Acacia is well suited for greening bright and cool rooms, greenhouses or winter gardens. All members of the genus Acacia are sun-loving plants and tolerate some direct sunlight well.

Watering: in summer – abundant; in winter water so that the top layer of the substrate dries out between waterings.

Fertilizer: Acacia should be fed from spring until the end of summer. It is not recommended to fertilize during the dormant period.

Humidity: Tolerates average or even low air humidity well.

Repotting: Repot after flowering; since the plant is vigorous, choose a spacious and deep container. Young plants are repotted every year; mature plants can be repotted every two to three years.

Propagation: By seeds and cuttings.

Possible problems:

Buds dropping: The cause may be drying out of the root ball.

Wilting leaves: The cause may be either drying out or overwatering of the root ball. Adjust watering. Another cause may be a too-heavy substrate. Replace the substrate with a more suitable one.

Leaves losing color, leaves pale: The cause may be insufficient light. Adjust lighting. If the plant has been in shade for a long period, acclimate it to increased light gradually. In winter, supplemental lighting with fluorescent lamps is desirable.

Dry brown leaf tips: The cause may be excessively dry indoor air or insufficient watering. Dark spots appearing on leaves: the cause may be chilling or drafts. Another cause may be disease.

Pests: at low humidity it can be attacked by spider mites.