Storage unit

A question that comes up regularly from beginners and people buying Cymbidiums at our show is around dividing plants. One chap who was buying a plant looked doubtful when I advised dividing the plant into two when the time came. ‘Oh no,’ he said, ‘there are plenty of plants in there.’ Hopefully, the information on why he shouldn’t divide a plant into individual pseudobulbs proves useful.

The pseudobulbs (so-called because they look like bulbs) of Cymbidiums – and Cattleya, Miltassia, Lycaste, Bifrenaria, Maxillaria, Coelogyne, etc – that sit above the potting medium are storage units for the plant, holding nutrients, energy and water. Even when they’ve lost their leaves and become ‘back bulbs’ they are still working for the orchid and should not be removed while firm and green. It’s only when you finger-test them and discover they’ve gone soft or become a husk, is it time to take them off the plant.

Leafless pseudobulbs can be seen in this illustration of Cymbidium hookerianum by Harriet Stewart Miner, published in Orchids: The Royal Family of Plants (1885).

When you divide a Cymbidium – which should be done only when there is no growing room left in the pot – be sure to have at least one leafless but firm back bulb with every growing pseudobulb, and please don’t divide a plant into single pseudobulbs. Try to keep two or three growing bulbs together, along with a few back bulbs. Why? It’s all about helping the plant remain strong and healthy, recover from the shock of division and getting it back into flower faster.

Another good reason to keep back bulbs is that they have dormant buds on the sides of their base that can activate into new shoots, which will eventually each form their own pseudobulb.

What happens if you divide a Cymbidium into a single pseudobulb and don’t keep a back bulb? It likely won’t kill the plant, but it will drastically slow its re-flowering as there are no reserves of energy for it. The other complication occurs during dry periods as, again, the plant has no reservoir available.

Dendrobium kingianum by Alphonse Goossens, published in 1896 in a ‘dictionary’ of Dendrobium orchids (text in French).

Effectively, what we call canes on some orchids – such as Dendrobiums – are also pseudobulbs and should only be removed from a plant when they become yellow and shrivelled.