A monthly growers advice column by Courtney Hackney. Hackneau@comcast.net
Got Milk? – For many years there has been a rumor that milk was an effective agent for killing viruses on tools used to repot orchids. It turns out that firms in Europe have been using this method exclusively in their everyday work with plants. Now, a 2004 scientific paper published in the journal Plant Disease confirms that a 20% (wt/vol) solution of non-fat dry milk, killed 100% of the viruses on contaminated cutting instruments if soaked for 1 minute. This is great for both metal tools and tools, such as potting sticks, which do not respond well to flaming. Milk was superior to heating with a propane torch and worked as well as a concentrated solution of Tri Sodium Phosphate (cleaning agent) or a 10% Clorox solution. Mom was right! Milk is good stuff. It does not, however, kill bacteria.
Spring Checklist
Spring is the busiest time of the year for Orchid growers. Given the recent weather in the Carolinas it may be difficult for us to tell that spring has indeed arrived, but your orchids know. Cattleyas have begun to put out new growths and roots in response to increasing day length. Vandas too are starting to grow because high daytime temperatures convince them that they are at home in the tropics. What you do in the next month will have a lot to do with your success as Orchid growers for the next year. Much of this is just common sense, but that is usually what we usually forget.
1. Clean Growing Area - Greenhouses have been cramped, as have windowsills and space under lights. Remove Orchids from your growing area and remove all dead material as well as algae. Some hobbyists spray growing space with a 5% Clorox solution to kill bacteria, fungi, and just about everything else. Physan or RD-20 will work as well. Repair benches or replace surface if it is needed while you have the area clean and open.
2. Organize - Straighten growing space by moving some plants outside or by eliminating non-performing plants. Remove weeds and ferns from pots.
3. Plant Inspection – If your collection is small, future problems can be avoided by carefully examining each plant. Use 10x-reading glasses even if you do not need them for reading. Look for scale, mites, or any signs of damage to leaves or roots. If you find damage on an Orchid look for the culprit that caused it. Tiny nicks on roots or under Phal leaves suggests snails while large chunks and slime trails indicate slugs. These pests have been relatively dormant during winter, but will now feast in summer’s warmth. Repotting will eliminate snails and help you find slugs. If you find only minor damage try stale beer for slugs and snail bait for bush snails.
4. Clean Plants - Remove dead tissues around Cattleya bulbs and/or dead leaves. Check the base of dead tissues for sign of scale, especially if leaves died but did not fall from the plant. If scale is found use a soft tissue to wipe them off and then spray with insecticidal soap or light oil. If a major infestation is found the plant should be repotted. When the plant is out of the pot use a sterile toothbrush to gently scrub the underside of rhizomes in Cattleyas and around the base of Phals. If you find heavy infestations on many plants, you may have to resort to harsher pesticides.
5. Straighten Plants – Orchids tend to lean towards the light in winter. Some growers prefer to tie plants up with either wire rings or bamboo stakes if they have fallen over because erect plants are easier to spray and water, and take up less room. In addition new growths and leaves will grow better.
6. Repot – Repot all plants whose media has decomposed and those that have reached too far from the pot. Rapid summer growth will quickly replace lost and damaged roots. Newly damaged roots are also less likely to be infected by fungi and bacteria in your now clean growing area in the less humid air of spring. Fungi and bacteria will become a problem in mid-summer. Newly repotted Orchids need a convalescence period while they recover. Accomplish this simply by giving them a little extra shade and humidity.
7. Water More– Orchids will use more water in the next month than they will in the heat of summer because of the lower humidity. Water thoroughly when you do water and review the moisture requirements of the different groups of Orchids you grow. In general, Cattleyas and Dendrobiums need to dry thoroughly before being watered while Phals and Paphs like to dry some but need constant moisture. Phrags and Bulbophyllums crave moisture while most of the Vanda group wants high light, abundant water, and lots of air movement. Air movement is just as important for Orchids in summer as during the winter, but for different reasons. Now it is important to keep leaves from overheating while in winter it was to keep bacteria and fungal infections at bay.