MARCH CLIMATE DATA

Average high: 80.7
Average low: 64
Average mean: 72.4
Average rainfall: 2.56"

Whilst March never comes in like a lion in South Florida, occasionally it slinks in like a bob cat. Frost is not unheard of in the first few days of the month. The more cold sensitive genera, hard cane dendrobiums, phalaenopsis and vandas may well need some protection even into the middle of the month. Overall, however, March brings us some of the most ideal orchid growing conditions of the entire year. Dry air, low humidity and wide swings of day to night temperatures optimize both blooming and rooting of most orchids. In March, Nature gives orchidists growing outside a free sample of what life would be like with a covered green house. With little or no additional water falling from the sky and drying breezes acting like fans, we are in total control of our plants’ water needs. Now, we can water properly: very heavily, and allow the plants to dry thoroughly in the near desert air before the next heavy application of water.

The ideal growing conditions of March present a great opportunity to get our plants off to a superlative start on the new growing season. The virtuous among us, who have already re-potted their cattleyas and other sympodials as they have finished blooming across the winter, can smile serenely, assured of their place in orchid heaven. For us few reprobate it is still not too late to catch up with virtue. In addition to flowered-out plants, now is also the time to replant those genera which are breaking or ready to break their dormancy; i.e. catasetums, mormodes, calanthes and those Himalayan species that have finished flowering. Now is also an excellent time to re-pot those hard cane dendrobiums that need it, with the reminder that they really don’t like to be disturbed and relish their roots being crowded in the pot. For those commercially mass produced plants grown in peat based mixtures, repotting is necessary in any case as the peat mix will not last out the summer and will likely rot all the roots. Hopefully these will have rooted so thoroughly that the roots have formed a solid mass that can be shifted undisturbed to a new only slightly larger pot. Otherwise the roots will need to be washed clean and lightly trimmed. Rock, tree fern, coconut husk, charcoal/wood chip mixes are best replacement media for the long haul. All of these materials have a life expectancy of several years before they break down in South Florida wet humid summers.

Attention to fertilizer in March will pay high dividends later on. As many sympodial orchids are commencing their growth cycle, now is a good time to apply slow release fertilizer to last the season. The 13-13-13, 180 day formula marketed at Home Depot as ‘Dynamite’ (Nutri-cote in commercial sizes) is the best available. Its plastic coating is superior to others and relatively unaffected by heat, an especially important consideration in S. Florida. Applied now it will be exhausted by September when we want to slow our plants down in anticipation of bloom and dormancy. The wide temperature swings of March also maximize the effectiveness of high phosphorous ‘Bloom Booster’ fertilizer. The extra phosphorous in these formulas probably does not really stimulate flowers ( most likely the opposite) but does help rooting. Two applications a week apart will speed the rooting process. Return to regular 15-5-15 fertilizer weekly thereafter as the excess phosphorus in the “Bloom Booster” interferes with minor element absorption to an inordinate degree in our highly alkaline South Florida water.

Vandaceous orchids should be breaking vigorous new roots in March. This is the moment to top them if they have grown too tall and if they have three good roots on the top cutting. Conserving one or more leaves on the old plant’s stump will insure a bountiful production of offshoots. Sliding the knife or shears down the stem before making the horizontal cut usually preserves an extra set of leaves. Now is also the ideal time to remove and reset offshoots of vandas and ascocendas. Again take care each has three or more roots and be sure you tie them firmly in their new container until they have rooted solidly.

March is also the month for acclimatizing sun-loving plants to full sun. Vandas, dendrobiums and reed-stemmed epidendrums that have not been blooming as they should because they are in too deep shade can be gradually moved to more light. This is best done in two or three stages, moving the plants a short distance every few days and always keeping them with the same side orientated towards the sun. Without this gradual acclimatization, The bright clear sunlight of March can scorch even the most sun-loving of orchids.

The chief blot on the otherwise nearly ideal growing scenario of March is thrips. March is the month when we are asked most frequently “Why do my vanda flower spikes grow ½ inch and then die?” The answer, like the answer to so many problems with orchids in South Florida, is thrips. The hot dry weather of March favors thrips which are ubiquitous in our landscapes. The drought of March drives them from their homes in our lawns and shrubberies to seek the cool lush oasis of our orchid collections. Most orchidists recognize the symptoms of thrips on their flowers, :the silvered, sand blasted appearance and the withering of the flower parts. Many do not recognize the earlier symptoms which show up on the root tips of vandas and ascocendas as a pitted ring at the point where the green growing root tip is maturing into white. Left unchecked, this damage will cause the root tip to wither. When it re-starts growth, a brown ring remains. Orthene (acephate)is the chemical of choice for thrips because of its low toxicity and residual action. Knoxout and Malathion are recommended also by the Florida Department of Agriculture. A non-chemical solution is liquid dish soap applied at the rate of 2oz (6tbs) per gallon of water. Be sure to water the plants the day before applying soap and take care to drench the plants thoroughly, covering not only all the surfaces but penetrating into leaf axils and other nooks and crannies where the reclusive thrips loves to loiter. Root the thrips out of your collection and you will get the growing season off to a good start.