March 2010 - The Best Time to Re-Pot

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It may not feel like it yet, but spring is just around the corner and it is time to think about repotting. For many new to the hobby of orchid growing, the thought of repotting can be terrifying. For those of us that have been growing for awhile, it is a lot of work, made much easier if all the supplies needed are ready when the orchids are.

Many new growers are anxious to repot so they can divide their orchids. The real question should be, “Does this plant need to be divided?”. If the medium is degraded the orchid should be divided. Orchids that have 3 or more bulbs out of the pot are likely candidates too. However, if grown in some type of inorganic medium, e.g. Aliflor, one can simply cut the 3 bulbs that are out of the pot off and leave the remainder in the pot.

Determining if the medium is degraded or not can be tricky, even for experts. This was discussed in January’s column. If growing in some type of bark, shove a finger into the medium. If it is easy to push through the medium or if the medium feels mushy, then it is time to repot. If some of the bark feels hard, but there are mushy spots jet some water through the pot or hold the pot upside down and then jet water into the pot. If the orchid falls out it is ready to repot. If not, you can get another year in this pot by adding a handful of new bark as a top dressing.

Paphs and phals usually need to be repotted each year unless grown in large bark or rock. Typically, most phals are purchased in a soilless mixture or sphagnum, both of which seldom last more than a year. Paphs are especially prone to root death unless repotted frequently or top dressed with dolomite lime.

Treat intergeneric oncidiums and dendrobiums as you would cattleyas with respect to both timing and frequency of repotting. Dendrobiums prefer to be in pots into which they just barely fit, making large plants prone to tipping over. Just place the small pot into which your newly repotted dendrobium was just potted, into a larger clay pots to prevent tipping. Never over- pot a dendrobium, no matter how large the plant.
Early spring is usually the best time to divide because most orchids are going into a growth mode and will be able to replace roots damaged during repotting. Most orchid hybrids and species have or are about to initiate new growths, so care needs to be exercised so that these fragile green nubs are not damaged. There are some exceptions to this rule, notably with species. Some bifoliate (two leaves per bulb) cattleyas should only be repotted when getting new roots even with the risk of damaging the new root tips. Repotting before or after this time will severely set the plant back or even result in its death.
Repotting assumes that you have everything you need, which should be done now if you have not already done so. Do not wait until the last minute to purchase what you need since supplies can often be hard to find once all of the growers in the U.S. begin repotting. Always overestimate what you will need. If stored properly, unused supplies will last for years.

Be sure to keep track of each plant’s name. That is critical, not just for exhibiting, but also so that you can check the growing requirements if needed.