Polyscias guilfoylei 'Roble'

Origin and identity of Polyscias guilfoylei 'Roble'

'Roble' has been sold for many years as a glossy, lobed Polyscias. The 'Roble' name is also used with Polyscias guilfoylei, while the exact species behind the cultivated plant remains uncertain.

P. guilfoylei grows in wet tropical conditions and has a long cultivation history across New Guinea, New Caledonia, Vanuatu and other parts of the western Pacific.

Care for Polyscias guilfoylei 'Roble'

• Light and form: give Roble bright indirect light to support a full, compact crown. Once settled, it can take some mild morning sun. Keep the light bright but filtered around midday.
• Pruning: growing tips can be cut just above a leaf joint to control height or encourage another branch. When moving a larger plant, support the pot and main stem to protect the side branches.
• Watering: allow the upper layer of potting mix to dry before watering generously. Let the container drain completely and empty any water left beneath it.
• Temperature and humidity: warm, steady indoor conditions around 18–27 °C are suitable. Normal to moderately humid room air is usually enough. Keep the crown away from cold draughts and direct hot airflow.
• Potting and repotting: use a loose houseplant mix with organic material and chunky drainage ingredients such as bark, perlite or pumice. Repot when roots fill most of the container or the mix has become compacted.
• Feeding: feed with a complete houseplant fertiliser as new leaves appear, using the dose recommended on the label. If Roble stops making new leaves, wait until growth resumes before feeding again.

Problems and solutions for Polyscias guilfoylei 'Roble'

• New stems grow long with large gaps between leaves: low light is causing stretched growth. Move the plant gradually closer to a bright window with filtered light.
• A cluster of leaves drops after a move or cold draught: the sudden change can trigger leaf loss. Keep the plant warm in the same bright position with filtered light and check the mix before watering again.
• Lower foliage yellows while the container remains wet: persistent wetness is stressing the roots. Let the upper mix dry further and make sure excess water can drain freely. If root rot is present, cut soft dark roots back to firm healthy tissue using a clean tool, discard all rotten material and repot in fresh mix.
• Sticky residue, white cottony deposits or brown shell-like bumps appear: mealybugs or scale insects are likely. Isolate the plant, remove visible pests and treat with a product labelled for the pest you identify. Repeat the treatment only at the interval given on the label.

Polyscias guilfoylei ‘Roble’ is toxic to cats and dogs

• Keep this plant away from cats and dogs that may chew it.
• It contains saponins that can irritate the mouth and digestive tract.
• Chewing may cause drooling, vomiting, stomach pain, reduced appetite or weakness. Contact a veterinarian if symptoms develop.

Who first published Polyscias guilfoylei, and what does the name mean?

Polyscias combines Greek polys, many, with skia, shade, parasol or canopy. The species epithet guilfoylei honours William Robert Guilfoyle.

Johann Reinhold Forster and Johann Georg Adam Forster established the genus Polyscias in 1776 in Characteres Generum Plantarum, second edition, page 63.

William Bull first described it as Aralia guilfoylei in 1873 in Gardeners’ Chronicle, volume 1873, page 606. Liberty Hyde Bailey later placed it in Polyscias as Polyscias guilfoylei in 1916 in Rhodora, volume 18, page 153.