Growing "Stock Plants"

(Presented by Elmer Ogryzlo)

The “hot water treatment of stools” is the technique most commonly used to prepare stools from which cuttings are normally taken in February and March.  In this technique the root ball is removed from its container, reduced in size to about 5 or 6 inches and the earth is washed off the roots.  These roots are then immersed in water at 46°C for between 1 and 5 minutes.  This hot water treatment removes common problems such as bugs, worms, and other pests, as well as salty deposits, fungi, and viruses.  It is also thought that it enhances the subsequent growth of shoots.

The process is quite labour-intensive.  Consequently, in the commercial production of rooted cuttings it has been replaced by the use of “Stock Plants”.  Not only does it also get rid of pests, but it provides a method of multiplying the number of rooted cuttings that you can get from a limited source of a particular cultivar.

In late November, the stools are cut down to under 9 inches, and are exposed to cooler weather for vernalization (the cold exposure that the plant require so that they enter a vegetative state).  I then grab a 5 inch ball of soil surrounding the roots of the stool by driving my fingers into the soil, pulling the ball out, and depositing it into a shallow box (4-6 inches deep).  Depending on the size of the box I fill it with 6 to 8 stools (preferably of one particular cultivar).  I then place it on a heating cable, and under a fluorescent light.  In a few weeks there should be shoots that are ready for cutting.  These cuttings are dipped in a fungicide and then in #1 rooting compound and planted in a sterile rooting medium that is also bottom heated and illuminated with a fluorescent light.

In about 3 weeks the roots should be well established and ready to be transplanted into fertilized potting soil in 4-inch pots.  The rooted cuttings no longer need to be bottom heated but the temperature should be above 10 degrees during the day.  In a few weeks some sunlight and warmth should produce rapid growth.  When there are at least 8 leaves on each plant, cut the stem leaving four leaves on the cuttings and 4 leaves on the stock plant.  The cutting can now be rooted to produce another plant.  The stock plant is then allowed to grow by sending out laterals from each of the leaf axils.  These are allowed to grow to the point that they each have 4 leaves again.  If we then “stop” the four laterals, the resulting plant can produce an additional 16 laterals that yield 16 cuttings.  Combining these with the one that we obtained earlier, each stock plant can thus produce as many as 17 plants.

In the figures below, the original rooted cutting is on the left showing the point at which the first stem cut is made.  The stock plant is shown on the right at the point where the plant with 4 laterals is stopped by pinching off the tips so that 16 new laterals can grow from the 16 leaf axils…

Elmer Ogryzlo (e-mail)