Othonna ARBUSCULA

Othonna ARBUSCULA - Tree-like othonna, Bushy othonna, Othonna arbuscula.

Can be grown in bonsai style!

Othonna is a genus in the aster family (Asteraceae), comprising about 85 recognized species distributed predominantly in southern Africa, from Angola and Namibia to the Cape Provinces, Lesotho, Eswatini, KwaZulu-Natal, Free State, Northern Provinces, and Zimbabwe. Representatives of the genus are found in dry shrub communities, on sandy and rocky slopes, in rock crevices, on plains, and in seasonally arid subtropical habitats.

The genus is characterized by tuberous or thickened underground organs, sometimes a pronounced caudex, as well as succulent or semi-succulent shoots. Growth forms vary from small tuberous herbs to subshrubs and dwarf shrubs. The leaves in different species are entire, lobed, or dissected, sessile or petiolate, often fleshy, adapted to seasonal moisture deficit.

Inflorescences in othonnas are flower heads (capitula), most often yellow, solitary or gathered in small clusters. The fruits are represented by single-seeded achenes, usually very light, equipped with a pappus of bristles, thanks to which they are dispersed by wind. Many species exhibit seasonal growth, in which leaves develop during the cooler and wetter period of the year.

Tree-like othonna is a rare caudiciform plant.

Seeds are small, enclosed in light single-seeded fruits equipped with a white pappus of bristles. Before sowing, the achenes are cleaned of inflorescence residues. Scarification and stratification are usually not required. To prevent fungal infections, brief soaking can be conducted, first in warm water at 50-60 °C (122-140 °F) for a few minutes, then in a 1% potassium permanganate solution for 1-2 hours. Additionally, the use of stimulants such as SUPERthrive, HB-101, Aminozol, Epin, or Zircon is permissible.

Sowing is preferably conducted in autumn, which corresponds to the natural cycle of the species, although under controlled conditions it is also possible at other times of the year. An air- and water-permeable substrate based on coarse sand, fine perlite, and a small amount of organic material is used. Seeds are laid out on the surface or lightly covered with a very thin layer of sifted sand. Moistening is done from a spray bottle. The container is kept in a greenhouse or under film at a temperature of about 15-22 °C (59-72 °F), in bright diffused light, with daily ventilation. Overwatering and complete drying out of sowings are impermissible.

The first sprouts usually appear in about 10-14 days. The most typical germination period is 2-3 weeks. The maximum germination period can reach 4-6 weeks. After sprouts appear, the covering is removed gradually, lighting is increased, and watering is transitioned to a very careful regime. Pricking out is performed after the formation of several true leaves, when seedlings are strong enough to endure transplantation without damaging the young tuberous base.

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For most cultivated Othonna species, the brightest possible lighting is used. The best placement is south-, southeast-, or southwest-facing windows, where several hours of direct sun are provided. With a lack of light, shoots stretch out, internodes lengthen, and flowering weakens. Supplemental lighting may be used in overcast seasons.

During the active growth period, which in tuberous South African species usually falls in autumn, winter, and spring, a cool-temperate regime of about 12-22 °C (54-72 °F) is maintained. Summer dormancy is best conducted at 20-28 °C (68-82 °F) in dry and well-ventilated conditions. A short-term drop in temperature is possible only when kept almost dry, while sustained hypothermia below 5 °C (41 °F) is undesirable, especially in wet substrate.

Watering is carried out moderately during the period of active growth, after the top layer of soil has dried out. Soft or settled water is used, without waterlogging the root zone. Excess water from the drip tray must be drained. In summer, when the plant enters semi-dormancy, watering is sharply curtailed and an almost dry regime is maintained. Overwatering quickly leads to rotting of the tuber and base of shoots, while prolonged complete desiccation during the active season retards growth and bud initiation. Spraying is usually not required, but dust is gently wiped from the leaves.

A very loose mineral-organic substrate with a high content of perlite, coarse sand, and fine drainage is used for planting. Shallow pots with mandatory drainage holes are suitable. Repotting is carried out as the volume is filled, usually once every 2-3 years, before active growth begins. The plant is fertilized rarely, once every 3-4 weeks during the growing season, with a weak solution of fertilizer for succulents. Heavy pruning is usually not required; only dry or weakened shoots are removed.

Cuttings are not always possible for the genus and are used in a limited way for tuberous forms, so seed sowing most often remains the main method of renewing a collection. In species with elongated shoots, rooting is possible only in very light mineral soil and under strict moisture control.