Nairobi, Sept. 14 -- Would you spend Sh144,000 on three trees? Last Friday, someone did at Planty Kenya, a small shop in Lavington, Nairobi. Three European olive trees, each at ShSh48,000, left the shelves in a single morning.

"These plants don't stay in the shop for long. By the end of the week, not a single one will be left. Most of them are pre-ordered, and the rest are for walk-in customers," said Lucy Kioi, who runs the shop.

While most plant shops in Nairobi sell seedlings and common shrubs, Lucy sells plants that take years, sometimes decades, to grow into what they are: mature olive trees, bonsai shaped over a lifetime of pruning, hybrid roses grafted onto thick trunks, and magnolias already old enough to flower.

She imports mo...