In the ideal world, when a plant name is changed, you’d prefer for the new moniker to be simpler than the old one. But life isn’t always fair, and there’s no better example than that of the plant commonly called Blackberry Jam Fruit. Long known as Randia formosa, the species is now named, alas, Rosenbergiodendron formosum.
Fortunately, the species is as desirable as ever! A native of Central and South America, the Blackberry Jam Fruit is a small evergreen shrub – trainable as a small tree – that matures to 4-5 ft. tall. As a member of the family Rubiaceae, it is a gardenia relative, and its 1½-2 in. white, tubular, star-shaped flowers produce a nice fragrance.
And that’s not the end of the show. After pollination, olive-shaped yellow fruits develop. Inside each mature fruit are two cells containing a seed wrapped in soft, black pulp. Eaten out of hand, the pulp is sweet, a virtual match to blackberry jam.
R. formosum has other attributes, too. It begins blooming at a fairly early age, 12-18 months, and flowers and fruits in the fall/winter season, when other fruit trees are barren. New blossoms appear as the earliest fruits are maturing. Even a small specimen can yield a couple of dozen fruits. The species can flower and fruit in filtered light in addition to full sun. As a slow grower, it is quite amenable to container culture. It is also fairly hardy – down to 28-29º.
R. formosum is not difficult to grow, but it’s important to keep a couple of cultural requirements in mind: (1) Provide ample moisture and good drainage, but reduce watering during the coldest times of the winter. (2) Apply acidic fertilizers for optimum appearance and growth.
Richard Lyons’ Nursery keeps a good supply of the Blackberry Jam Fruit on hand. Come take a look.