As the major blooming season for most of our orchids is approaching the finale, it is now time to focus on repotting and possibly dividing. Orchids such as Cattleya, Oncidium, Dendrobium and Cymbidium are sympodial, meaning they grow from a rhizome and are great candidates for propagation by dividing. Do not attempt to divide your plant unless it has at least six to eight pseudobulbs, with two growths that have flowered this past season.
Dividing orchids can sometimes be a quite a task. If done incorrectly, your plants could be put in jeopardy. However, if done correctly you can multiply your collection, which is exactly what we at Orchids Garden Centre/Oakhill Gardens are doing now. Hence, the new bare root specials we are offering this month!
When dividing there are some important rules that one needs to implement for success. First, always sterilize any cutting tools that come in contact with the juices of your plant. A small flame is the most widely recommended method for sterilizing your tools. This is the best preventative for the spread of the fateful viruses that plague the orchid family. Keep in mind that your hands and the surface that you are working on, can also become contaminated so good hygiene should be practiced there as well. We use multiple sheets of newspaper on our cutting surface and each new plant gets a fresh sheet to work upon. Wear some disposable latex gloves and change them between each plant for best results, or wash your hands thoroughly with warm water and soap between each plant. More information on sterilization to prevent virus spread can be found in our April 2013 newsletter.
One of the most misunderstood rules of dividing orchids is where to cut the rhizome. Of course, there are many schools of thought in this department, however, we follow the 3-4 pseudobulb rule. Simply put, start with the most recently flowered growth and count backwards along the rhizome and make your cut behind the third or fourth pseudobulb. With this technique you should have a nice clump consisting of the intact 3-4 pseudobulb group that will make for a great division. Leave some of the original potting medium around the roots of your new division if the media is not terribly rotted or molded. This will aid the new division in getting off to a good start.
Next you will want to prepare your potting medium itself. If you are using a fir bark based mix, it is recommended to moisten the mix slightly before potting. We like to use Physan 20 mixed at 2 teaspoons per gallon as a moistening agent to help quell any pathogens or fungus molds that may be harboring in the fir bark. Slightly moistening the fir bark and stirring it up allows the components to bond, because in most cases there is some separation during storage or transit of the mix. If you are using the Orchiata bark, it is not recommended to moisten this product before using. Just pour it into your potting box and go to town potting your orchids! (We really love the Orchiata bark. For more information on Orchiata bark, check out our previous newsletter from January 2013.)
Then, select a clean, new pot that is appropriately sized for your division. Try not to give your newly divided plant too much space as they like to be potted on the crowded side for best revitalization. Place the cut side of the division against the inside perimeter of the pot and fill the pot with your potting mix. Try to keep the rhizome about 1/2" below the potting mix and pack the mix in firmly with a blunt tool to ensure the plant is secure in the pot. If you are potting with a moistened fir bark based mix, wait about one week before watering thoroughly. If you are potting with Orchiata bark, water your repotted plants upon completion. We avoid fertilizing for about 3 weeks to allow new roots to start growing.
More information on how we repot our orchids can be found on the culture sheets posted on our web site: www.oakhillgardens.com
Happy growing!
Chuck
