Tip of the Week: Repotting Orchids—Transferring to a New Pot

Posted in Exhibitions, Gardening Tips, The Orchid Show on March 22 2010, by Sonia Uyterhoeven

Sonia Uyterhoeven is Gardener for Public Education. For hands-on demonstrations and orchid tips, join her in the Conservatory’s GreenSchool every Saturday and Sunday at 2 p.m. throughout The Orchid Show.

Part 3 in a 3-part series

Read Part 1 and Part 2

In the past two weeks I’ve blogged about making a potting mix for orchids, removing the orchids from their pots, and cleaning up the roots. Now let’s actually repot some Cattleyas.

You might have thought you were in charge of the process, but in reality, the plant ultimately dictates how it is repotted. For example, as Fintan O’Sullivan and I were tackling our orchids to repot, we saw that the foliage on one of the plants was badly puckered, a sign of either overwatering or underwatering. When we removed it from its pot, we discovered that most of its roots had rotted (overwatering).

The plant was left with a negligible root system. It was, however, pushing new growth, and we were optimistic that it would shortly produce some new roots. So, rather than putting it into the free-draining, coarse fir bark mix, we, instead, placed it in a small, shallow pot stuffed with moist sphagnum moss. The full but loose fit offered the orchid moisture without suffocation. So that the moss would have good contact with the orchid, Fintan held the orchid in one hand and clustered the moss around its base with the other and then inserted it into the pot.

The other orchids we repotted needed a more straightforward approach. Once we cleaned out the dead roots (which you’ll most always have) and groomed it (see last week’s post) we assessed how much of the old orchid we wanted to keep.

The general rule is that when you divide or repot an orchid you should keep a minimum of 3-5 healthy pseudobulbs (the swollen modified stem that stores water and nutrients). In some cases we removed some of the older pseudobulbs.

Orchids should be placed in pots that allow for 1–2 years of growth. Remember that they need a free-draining environment. If you place an orchid from the Cattleya alliance in too large a pot, the mix will retain too much moisture, potentially causing a hazardous environment for sensitive new roots. Error on the small side, since these orchids are fine being pot bound.

Place the orchid with the older pseudobulbs against the edge of the pot and the new growth facing the center. If the rhizome of the orchid has branched and you have new growth coming from several directions (this is common), place the orchid in the center of the pot.

The orchid’s rhizome should be just slightly lower that the edge of the pot—once planted it will essentially run over the surface. Older pseudobulbs and pieces of the rhizome can be planted deeper if that helps to secure the orchid in its pot.

Fintan holds the orchid in one hand and empties handfuls of bark mix into the pot with his other hand, pushing the mix firmly down with his fingers. He works his way around the pot in an even fashion, slowly filling in and firming the bark mix as he goes. By the time he is finished, the orchid is so firmly secure in the pot that he can lift the orchid by its foliage and the pot will rise with it. The rhizome will be just barely on the surface, and the new growth will be abutting the upper layer of fir bark mix.

Some of the orchids we were working with were large yet had small root systems. We often cut these orchids into two pieces so that they could be placed in a smaller pot. Remember, most orchids don’t mind being crowded together—we lined up the pieces and planted them as one.

Orchids are tougher than you think, yet in order for them to thrive and flower (always the goal with these plants), observe these important lessons:

• Don’t plant in too big a pot.
• Cut off deteriorating and damaged growth.
• Take a moment to inspect for pests.
• Find a potting medium that is appropriate for the orchid type and considers the condition of the orchid (particularly the root system).
• Work in a clean, sterilized environment.
• Label your orchids and include the repotting date—I promise you that after a few months you will have forgotten what you have done. Good recordkeeping is important.