Jun 152012
 

by Susan Taylor
Originally published in BellaOnline

Foliar fertilizing promotes better growth
During the peak growing months of summer use a very dilute foliar fertilizer (half normal strength) with 1/2 teaspoon per gallon soap as a wetting agent so that the fertilizer will stay on the leaves long enough to allow the plant to absorb the nutrients. Be sure to spray early in the morning before the sun gets to the plants and provide excellent air circulation to allow for rapid evaporation to prevent rots. Be very careful with the crowns of Phals and Paphs.

Increase your watering for outdoor plants
Outdoor or greenhouse plants will need additional water during the warmest months of the year. In most areas this is their peak growing season. In the hottest areas they will almost go into a hibernation period. Watch out for under watering signs such as wrinkled pseudobulbs, especially on Oncidiums and Cattleyas. I put extra sphagnum moss around those plants that appear to have problems with the heat and then spray early in the morning making sure that the moss gets some water. You increase your humidity this way and the plants will pull water out of the moss if they need it.

Phalaenopsis or Moth Orchids
Phals can still be in full bloom by the middle of the summer. If you want them to re-flower next year, cut back the inflorescences around the middle or end of July even if they’re still looking good. This will allow the plants to concentrate on growing and gathering energy to flower next year. If repotting is necessary, go ahead and repot now. If you bought new plants make sure you repot. Many Phals are sold in straight sphagnum moss and this medium is too soggy for most plants for long. Repot in coconut husk or bark mix.

Paphiopedilum and Slipper Orchids
Phragmipediums will need constant moisture during the hot summer months. I grow mine in a saucer of water year round to provide this moisture. Semi-hydroponic culture is even better. They need lots of light in order to produce flowers. Paphiopedilums also like warm temperatures, but require low light so as to keep the leaves from burning. Check the pots often during warm months to make sure that the moisture they need is provided at all times.

Cattleya Alliance Plants
Watch for roots on your fall blooming Catts and when the roots are about 1/2 inch or 2 centimeters long, repot them if necessary in appropriate medium. Watch your plants for over- and under-watering problems and rots during this growth period. A monthly application of fungicide will help reduce the chances of all kinds of rots.

Aug 012010
 

Ideally, most orchids do best in the 70’s and 80’s, going cooler at night. During mid-summer, when they receive week after week of 90 degree temperatures, they need a bit of extra TLC to keep them happy.

Misting your plants will help to cool them off. In very humid climates, one needs to mist very lightly so that the plants don’t stay too wet. In a hot and DRY climate, one can mist more heavily to create a bit of humidity. The water droplets on the leaves help to cool off your orchids’ leaf tissue.

Shade your plants heavily during hot summers. Think of yourself sitting in the hot sand at the beach. If you sit in the shade, you feel much cooler. Taking a dip in the water (or misting yourself) will bring down your body temperature. The same holds true for plants.

Back off a bit on fertilizer when extreme heat hits. When it’s 95 degrees plus in the greenhouse, I very rarely feel hungry during the day. Orchids also seem to slow down their growth in extreme heat. Skip a week or two of food every so often during those high heat weeks to give your plants a break from the high nitrogen rush!

Air movement is also a key. Just as I like to stand in front of a fan during a warm spell, our orchids also will benefit from extra air movement.

The flowers on those few orchids that are brave enough to bloom this time of year don’t last very long. This time of year our Phalaenopsis fold after 4-6 weeks, whereas during the cooler winter/spring season they last 3-4 MONTHS. This is why most orchids bloom between Thanksgiving and Mother’s Day. Summer is more of a “growing” season for plants.

Try not to add undue stress to your plants during extreme heat. Usually it is fine to repot throughout the summer months. However, when extreme heat hits, it is best to wait a week or two until things cool off. We usually try to repot our most tender orchids in Springtime (March through May), leaving some of the sturdier varieties (i.e. Cattleyas and Dendrobiums, etc.) for summer potting.

If growing in a bark mix, watch for moldy bark (snow mold) this time of year. It is very common due to the high humidity levels. It helps to use a fungicide periodically during very humid months. Physan 20, Captan, and Phyton 27 all will help to keep mold and rot at bay. If you do see mold in your mix, it is usually best (and cheapest) to simply repot the plant in fresh mix.

Stay cool,

Liese

May 012009
 

By Andy Easton, V.P. Life Sciences, Kerry Bromeliads,
Homestead, FL

These are a few things, in no particular order, that you might wish to consider that could help your plants through what is often a very difficult growing season in South Florida.

It’s hot and the plants are growing like crazy so we need to fertilize more, right? Wrong! The two periods of most rapid growth in our area are Spring and Fall. When the days and nights get uncomfortably hot for us, they are too hot for many of our orchids too. The respiration rate will exceed the photosynthate storage rate for much of the 24 hour period and consequently, just like when we go on a diet and exercise more to lose weight, our plants will actually struggle to hold their own or may even go backwards. In the months of July, August and September, it is prudent to actually feed at a lower concentration and also to make sure you are feeding a formulation that is at least even concentrations of Nitrogen and Potassium and preferably with a Potassium level around 25% higher than Nitrogen. Don’t skip feeds however as the higher temperatures mean that fertilizer is quickly metabolized by media microflora. Now if you just grow Vandaceous types these comments are less applicable but anything in the Cattleya Alliance will benefit from the above regime.

Be sure too that you water and fertilize in the early or late hours, I personally prefer morning but the orchid leaf stomata are open at either time. It is not necessary to get into a debate about foliar feeding here but I am sure the elevated bacterial leaf presence in warmer months greatly assists in plant nutrition by converting fertilizer into gaseous ammonia which is then readily taken up through the leaf stomata. Research has shown that Phalaenopsis stomata are open at night but be careful watering them in the evening as crown rot will be a problem. People say to me that if Phalaenopsis can survive in their natural environment where it rains every day in Summer and often in the evening, why can’t they behave the same in cultivation? There are two main reasons why we run into problems with cultivated plants. Firstly. The plant orientation is all wrong. Phalaenopsis in nature develop so that the leaves drain water away from the crown. We place them in pots and all the water essentially runs backwards and accumulates in the crown, just where we don’t want it at nighttime. Secondly rainwater is a different “cat” to well or city water with added fertilizer and it is much less likely to support pathogen growth.

Plant disease researchers have found that elevated levels of certain nutritional elements like Magnesium will contribute to a plant’s ability to resist fungal and bacterial infection. Epsom Salts (Magnesium Sulfate) is a cheap and effective source of this critical plant nutritional element. Once a month in Summer, instead of watering and feeding, water and feed Epsom Salts. It doesn’t mix well will fertilizers so should be used on its own and even if you don’t have the capacity to liquid feed it, you can even apply it as a topdressing without any risk of injury to your plants. Feed at the rate of a level teaspoon per gallon or top-dress at the rate of a level teaspoon per six inch pot.

There are oils and oils. Some people have done major damage to their plants by using the wrong oil at the wrong time of day or year! But, the paraffinic oils like Ultra-Fine which can be purchased for around $11.00 a quart at Home Depot are wonderful for home growers. I spray all my plants in the greenhouse at home with Ultra-Fine every month, year round. You have no toxicity issues to worry about so you can spray in your swimsuit if you wish and these paraffinic oils will really keep mites, scale, thrips and mealy bug on the back foot. If your water is high in Calcium, they will also help keep your plant leaves shiny. I tend to spray in the early hours because it is more pleasant for me but even if the sun is higher in the sky, only the thinnest leaves and most sensitive plants would be likely to be affected, if at all. Caution: with any spray it is always better in terms of efficacy and for systemic uptake, to spray when the stomata are open, i.e. in the cooler hours.

Although summer is not the most pleasant time to be in your greenhouse, make some time each week to do a slow walkthrough. For people who hand water this is not a problem but if you have overhead watering capacity, don’t just water and run!

Things can go bad very quickly in the summer months and a small spot of bacterial infection can become a sorry mess in hours rather than days. Spacing plants and a good fan for night air movement is critical to the prevention of most fungal and bacterial problems. Never let your plant roots come within 18 inches of the soil. The ubiquitous Fusarium wilt fungus is just waiting to attack your prize orchid and it is essentially, incurable. Just a splash of water which hits the soil under your bench and then bounces up onto a healthy Vanda root can spell disaster. Whenever I see people placing plants on the ground for easy watering, I just shudder. It is one of the most dangerous and unhygienic practices for your orchid plants.

Good growing! Make it through summer and be ready for the pleasures of the Florida Fall with a group of robust and healthy orchids.