The compound leaves are held on petioles up to 15 cm (6 in) long, with 3–7 leaflets arranged around a common attachment point (i.e. they are palmate).

[4][5][6] The inflorescence is terminal and takes the form of an umbel of umbels - that is, a number of stalks of equal length emanate from a single point on the plant, and these in turn branch into a number of flower stalks (pedicels), again of common length and attachment point, and each carrying a single flower.

[5][6] This species was first described as Panax macrosciadeus in 1860 by the Victorian colonial botanist Ferdinand von Mueller, and published in his multi-volume book Fragmenta phytographiæ Australiæ.

The description was based on material collected by the Irish botanist and collector Eugene Fitzalan from the Cumberland Islands.

[7] Four years later, in 1864, Mueller revised his description and transferred the species to its current genus Mackinlaya.