Umbilicus RUPESTRIS

Umbilicus RUPESTRIS - Navelwort, Pennywort, Rock navelwort, Umbilicus rupestris.

A rare and very unusual plant.

Umbilicus is a genus in the family Crassulaceae, comprising about two dozen species. They grow from Western Europe to Southwestern Asia, on rocks, stone walls, and in rocky crevices.

Plants are perennial, succulent, herbaceous, 10-40 cm (4-16 in) high, with a tuberous rhizome. The stem is solitary, erect, dense, fleshy, and glabrous.

Leaves are alternate, few in number, concentrated mainly at the base of the stem, 1.5-7 cm (0.6-2.8 in) across, rounded-peltate, fleshy, flat, glabrous, and crenate along the margin. A petiole 10-15 cm (4-6 in) long attaches not to the edge, but to the center of the leaf blade, forming a deep depression at the point of attachment. The flowers are numerous, nodding, greenish-white, gathered in a dense erect raceme.

Navelwort is a species from the Atlantic coast of Europe and the Mediterranean, growing on shaded damp walls and rocks. Unlike most crassulacean plants, it prefers partial shade and cool conditions rather than scorching sun.

Its annual cycle is winter-growing: the rosette grows back in autumn, the plant overwinters green, blooms in May and June, and enters dormancy for dry summers, shedding foliage and retaining the tuber.

Umbilicus seeds are very small and light-sensitive. Soaking such tiny seeds is impractical, so the substrate itself is sanitized: prior to sowing, it is drenched with a weak solution of potassium permanganate and dried slightly. Scarification and stratification are not required.

Sowing is performed in autumn, on the surface without covering: the seeds need light. A sterile loose substrate with a top layer of washed sand is used. The sown seeds are moistened from a spray bottle with a solution of growth stimulants: SUPERthrive, HB-101, Aminozol, Epin, or Zircon, covered with a transparent cover or placed in a mini-greenhouse, and germinated in diffused light at a temperature of 15-20 °C (59-68 °F).

Seedlings emerge in 2-4 weeks, unevenly. Crops are ventilated daily, and condensation is removed. Seedlings develop slowly and build up mainly a tuber in the first season; pricking out is performed only after noticeable strengthening of the plants.

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Partial shade or diffused light suits the plant. Direct midday sun scorches the fleshy leaves, especially in the heat.

Active growth occurs during the cool part of the year, from autumn to spring. In winter, the plant is kept at 5-12 °C (41-54 °F); mature specimens tolerate brief light frosts. In summer, Umbilicus enters dormancy.

Watering is moderate and regular during the growth period, after the top layer of substrate dries out. During summer dormancy, watering is almost ceased, keeping the substrate barely moist.

The substrate should be loose, permeable, with the addition of sand and fine stone chips. Drainage is required at the bottom of the pot; a shallow container is selected.

Fertilizer is applied rarely, only during the period of active growth, with a weak solution of complex plant food.

Repotting is performed in autumn, at the start of the growth season. The plant looks great in a wide shallow pan and in crevices of a rockery where root coolness is maintained.