Poinsettia Growing Tips - Part II.By Dr. Claudio Pasian More on nutrition. Once plants are rooted, they need an adequate supply of nutrients in order to sustain active growth. If the EC of the growing mix is maintained in the range 1.5 to 2.0 mS / cm for the SME method or 0.6 to 1.0 mS / cm for the 2:1method, active growth can be sustained with no negative effects. Growers who tend to apply high fertilizer concentrations should do it with caution. Although poinsettias fall under the category of "heavy feeders", high EC levels can reduce plant growth. It is very important to monitor pH and EC of your poinsettias on a regular basis. More important is to plot those periodical measurements on charts that allow you to see a trend well before things get out of control. Today, everyone should be able to afford a portable pH and EC meter and monitor these characteristics of the growing medium without any difficulty. If you are not familiar with the use of these instruments, I suggest you take my OFA Short Course workshop. Do you know the alkalinity of your water? The extension community has been preaching the importance of this water characteristic for years. Still, too many growers don't know their irrigation water alkalinity levels. Alkalinity can be measured very easily using inexpensive (fairly accurate), easy to use alkalinity kits. Every year, growers have an opportunity to learn how to use them at Dr. Jim Metzger's Alkalinity workshop during the OFA Short Course. I suggest you take this workshop if you are not familiar with alkalinity. If you are in Ohio and are using well water, chances are the alkalinity is higher than desirable and cause high media pH. More on stem breakage. Do not pinch too high. A soft pinch produces too many branches that are weak. Be sure that you do not space your plants too early. Having the plants next to each other for some time forces the new branches to grow upwards. Upright branches are less prone to breakage than horizontal ones. Keep in mind that crowding crops for too long causes stretch and may mean more growth regulators. High light levels and adequate calcium levels in the medium are also a factor reducing stem breakage. If after taking all these precautions you are experiencing problems with some cultivars, seriously think about replacing the cultivar by one with stronger stems. Marathon®. Over the last two years, some growers have reported white flies despite the use of Marathon. This prompts speculation that we may be facing white fly resistance to this project. Olympic rejects this idea, suggesting the problem results from product misuse. Use some precautions when applying this product. First, remember: Marathon is preventative, not curative. If you have a heavy infestation of whiteflies, this insecticide is not the product to eliminate the pest. Marathon is absorbed by roots and favors new growth as it moves up into the plant. Older leaves draw less insecticide and here whiteflies can hide and survive. Application timing is very important. Do not apply too early. By the same token excessive delay is a problem because you will have more and older leaves in the plant. Read the label before applying! Apply to uniformly moist soil and restrain irrigation for a few days to avoid leaching the product out of the container. |
