Dividing Orchids

Dividing orchids is an effective way to propagate them. As with keikis, it produces plants that are genetically identical to the parent. It's mostly a technique for sympodial orchids, though monopodial orchids can be divided too. The best time to divide a plant is when it's ready for repotting, and the process is similar, but with an added step. One advantage of dividing orchids is that you can keep plants from growing so large that their large pots retain too much moisture in the potting mix, and so they don't dry quickly enough. (Selling divisions can also help finance your orchid addiction hobby.)

Dividing Sympodial Orchids

Sympodial orchids are those that have a horizontal rhizome, with a series of new growths emerging from it as it grows along; each growth expands, blooms, and then may linger for a number of years before dying. To divide these orchids, first unpot the plant and remove the potting mix from around its roots, as when repotting orchids. Then, cut the rhizome between growths, leaving at least three or four growths per piece. (For orchids which die back after flowering, such as Disas, new growths are often not connected to each other and so each plant may be potted individually.)

Carefully tease apart the root systems of each division. Cut off any old, dead roots and any old pseudobulbs that have turned brown and/or mushy. (Use sterile cutting tools. You can soak them in bleach in between plants, or use razor blades that are thrown away after use. The idea is to avoid spreading viruses and other diseases among your plants.) Then you can put each division into its own pot or basket, or onto its own slab, as appropriate to the species. Pack a potting mix around its roots, water the plant, and you're done! (You'll also want to copy the plant's label.)

Dividing Monopodial Orchids

Orchidists sometimes want to divide monopodial orchids, such as Vanda and Vanilla. Monopodial orchids have a single stem that grows upward, producing a series of leaves. Cutting the stem to divide the plant can be scary, as the upper part doesn't have an established root system and the lower part lacks a growing tip. It's easy to kill one half or the other, so this should only be undertaken by people who are experts in orchid care.

To divide a monopodial orchid, the stem has to be cut somewhere that has leaves on both sides. The lower half can be left in its current pot, or repotted, and should be cared for carefully until it starts to grow again. The upper half has to be put in a pot, but since it may have few if any roots, do whatever is necessary to keep it stable, such as tying it to a stake in the pot. To help a root system develop, provide plenty of humidity and mist frequently, but water less often than normal for a few weeks as this may help coax the plant into developing new roots.

If a monopodial orchid's stem has branched, so that it has two leads producing new growth, you can cut off just one branch and pot it as described above. The other half of the plant still has a growth tip, so it is much more likely to survive than if you had cut off its only lead.

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