Hot and Steamy: What You Need to Know about the Ups and Downs of Orchid Temperature

Photo Courtesy of Allen Black's Photo Site

Temperature can be one of the trickier points of keeping orchids. Usually it is better to choose plants that conform closely to the temperature conditions you already have. If you choose plants for looks, or interest and ignore temperature, you will most likely end up with orchids whose temperature needs directly conflict.

Most orchids require intermediate temperatures. This means daytime high temperatures in the low seventies to eighties and nighttime low temperatures between sixty and sixty-five degrees. Luckily, this is also the temperature range that most closely resembles household temperatures. Cattleyas, most Oncidiums, Ascocendas, most Paphiopedilums, Brassias, Miniature Cymbidiums and most Encyclias fall within the intermediate range, along with a number of other specific species and hybrids. The most commonly grown orchids in the cool range are large Cymbidiums, Odontoglossums and Zygopetlums (which can also be grown in cooler intermediate ranges). Cool growing orchids grow well with a nighttime low temperature of approximately fifty-five degrees and a daytime high of about sixty-five to seventy degrees. Warm growing orchids include Phalaenopsis and Vanda orchids. They like daytime temperatures of close to seventy-five to eighty degrees and nighttime low temperatures between sixty-five and seventy degrees.

Seedlings like to be kept warmer than full grown plants and should not be allowed to get as cold at night.

General Orchid Temperature Guidelines:

Cool Growing Orchids: High 65-70F Low 55-60F Zygopetalum, Cymbidium, Zygoneria, Ondontoglossum

Intermediate Growing Orchids: High 70-80F Low 60-65F Cattleya, Oncidium, Brassia, Encylcia, Cymbidium (miniature)

Warm Growing Orchids: High 75-85F Low 65-70F Phalaenopsis, Vanda, Cochleanthes Amazonica

For more information about temperature requirements for getting different types of orchids to flower, check out my post Getting the Right Temperature Change for Orchids to Bloom.

What Everybody Ought to Know about Buying Orchids

Don’t purchase orchids from big box stores, such as Target and The Home Depot (this is also true for the giant Albertsons, or Rainbow down the street). Okay, maybe one, but generally try to avoid it. I know it’s hard, but these orchids are mass produced and often in poor conditions. I have had one or two good experiences buying an orchid from a big box chain. However, most of the orchids I bought were either infested with insects, or their roots were rotten. If the roots are rotten you often won’t even get to enjoy the full length of the flowers' blooming time, because the plant will begin to die and drop its flowers before it’s even finished blooming.

Top 5 Reasons Not to Buy Orchids from Big Box Retailers this Christmas

1. The orchids often lack specific tags, which might not matter to you now, but will in a few years if you become really interested in orchids. A plant without a specific tag will often just be labeled by its species, which is not always accurate either (see below). If you don’t know the parentage of the plant (this is its cross) you won’t be able to enter it in shows, sell it, or trade it to other growers.
2. Nine times out of ten these orchids are rotting at the roots. You will need to go to some extraordinary lengths to save a plant that has rotten roots. Usually the Nursery repots their orchids in really soggy moss before shipping them. Then the store workers keep the plants completely soggy for days or even weeks on end. Orchid roots are designed to remain dry. They are covered with a substance called velam, which quickly soaks up water, however, orchid roots are designed to dry out between waterings. This comes from the fact that in nature these orchids are epiphytes, meaning that they grow suspended on tree branches and catch rain when it falls (which is often in the jungle). However, if the roots are soggy all the time, they will rot and die. The picture to the right is used courtesy of Allen Black's Orchid Photo Site. A great site for pictures of orchids growing in the wild in Belize and Honduras.
   
3. More often than not the flowers will fall off soon after you get the orchid home. Phalaenopsis are the most commonly available orchids at Big Box Stores and also one of the most finicky in terms of holding onto their flowers. These orchids should be in bloom for 2-3 months at a time, but if their roots are rotten, or they undergo too much shock, they will almost certainly shed their flowers.
4. Watch out for diseases and insects. Big box stores are notorious for sending their plants home with all sorts of organisms, so be careful. I have learned the hard way that an orchid that looks fine on the shelf at Home Depot may in fact be harboring not one, but two types of destructive insects. These can then easily spread to your other plants and can spread diseases, which are the other common problem with these orchids. Viruses are less common than insects, but poorly grown plants are more susceptible to them.
5. The orchid will most likely not come with any specific information on how to grow that genus of orchid. It may not even tell you what sort of orchid it is so that you can look the information up yourself.

Check out my previous post on What to Look for if You Must have that Big Box Store Orchid.

Check back soon for recommendations on finding reputable orchid retailers.

10 Things You Can do Right Now to avoid Bud Blast

Yesterday I explained that humidity levels are extremely important for growing and blooming successful orchids.

Here are 10 practical tips on how to raise the level of humidity for your orchids:

1. Invest in a room humidifier, these can be inexpensive and add humidity to a whole room. I recommend evaporative pad humidifiers instead of cool-mist humidifiers.
2. Group orchid plants together, as they release humidity into the air and add in other houseplants and companion plants that can be kept moist all the time. These will help to increase humidity over a confined area.
3. Use humidity trays. These can help to raise the humidity immediately getting to the plants by five or 10 percent. There are two ways to make these, you can use a plastic tray filled with small gravel (I use a plastic drip tray for pots), and fill the base with water, keeping the orchid pots on the gravel, just above the water line. Alternatively, you can buy pre-made plastic grates that you fill with water and place the orchids on the grate, above the waterline. These are usually available from mail-order orchid retailers, such as Oak Hill Gardens, or Orchids Limited.
4. I have recently acquired a “Mist Maker” that uses ultrasonic waves to create mist. These can be really effective, but they are a bit tricky to use and really raise the humidity, so be careful.
5. Place the orchids in a location that is already humid. Don’t put them in a bathroom, because orchids hate for the humidity to fluctuate drastically. However, basements are often a viable option.
6. Summer the orchids outside. In colder climates it still may be possible to keep the orchids outside three or four months a year. Avoid this option if you live in a desert region with low humidity and high temperatures.
7. Buy orchids that will withstand lower humidity. Some orchids are from the cloud forest and hat low humidity, an example would be Masdevallias. Other orchids, such as Cattleyas Phalaenopsis and Encyclias can adapt to lower humidity levels, closer to 50%.
8. Designate a room for growing. This will make humidity, as well as other conditions more manageable.
9. Try to keep the humidity at 50% or greater, this is a general rule of thumb.
10. Buy a digital clock that measures humidity. They sell these at target, as well as specialty nurseries.

Some of the information for this post and the previous one was taken from Charlie Baker, “Orchid Culture” cmbaker@orchidculture.com and from Orchids For Dummies by Steven A. Frowine.

The Secret to Growing Gorgeous Orchids

Humidity, Humidity, Humidity.

This can be a very tricky one, but you need to raise the humidity. Humidity in a normal household is far too low for orchids to thrive. It is important to bring it up to at least 40 or 50 percent. In cold climates during the winter relative household humidity often averages close to 20 percent (Frowine). Household humidity can be even lower in desert areas. At humidity that low orchid leaves will begin to shrivel and flowers will brown and drop off. Something called Bud Blast will often occur in low humidity situations (especially on Phalaenopsis orchids). This is where the developing flower buds drop off before they have a chance to open.

Some orchids can adapt to lower humidity than others, so it is important to know how adaptable your orchids are. However, in general, no orchid is going to thrive at humidity below 35%-40%. Last winter my humidifier broke and the humidity around my plants was hovering near 35%. Most of my orchids survived this period, but they didn’t love it. I was also misting them several times a day. Misting is generally not recommended, because it only brings up the humidity temporarily and can cause orchid plants to rot.

Check back tomorrow for 10 Tips on How to Raise the Humidity in your Orchid Room

The Top Myth Every Successful Orchid Grower Needs to Avoid

A little light never hurt an orchid, only a lot of light can.

Lack of light is one of the main reasons orchids won’t flower in the home. Don’t believe what they tell you about light in the basic guidelines for growing orchids. Many orchids benefit from filtered, or even direct morning and evening sun. Different types of orchids require different light levels. Vandopsis orchids can sometimes be grown in nearly full sun, as can some kinds of Cattleya. However, most orchids, even most Cattleya’s will burn from too much, or mid-day sun.

This is not caused by the light as you might think, but by the building up of heat within the leaf. Just like freezing, too much heat can actually break apart the cells, causing damage to the leaf and in extreme cases the entire plant.

Here is a list of suggested footcandle ranges for different orchids (see below for a definition of footcandles):

• Cattleya: 2,000-5,000 Footcandles
• Phalaenopsis: 1,000-2,000 Footcandles
• Oncidium: 1,000-3,000 Footcandles
• Dendrobium Phalaenopsis: High Light Levels
• Miltonias: 1,500-2,500 Footcandles
• Vandas: 4,000-5,000 Footcandles
• Paphiopedilums: 1,000-2,000 Footcandles

Several of these numbers were borrowed from the Orchids Limited website.

Generally, if the weather is not too hot then morning sun, or light during part of the day through an east, south, or west facing window can be very beneficial to orchids.

Light is necessary for orchids to flower. In fact, light is one of the main reasons orchids won’t flower in the home. They may be growing just fine, but that doesn’t mean they’re getting enough light to flower. Flowering takes a lot of energy and orchids get their energy from light and water. That orchid may look great in the middle of the room, but it will most likely never flower. This is true of most orchids, but not always true of Phalaenopsis and Paphiopedilums, as well as amazonica species and hybrids which can do well in normal household conditions in close proximity to a window. These orchids thrive in a range of light close to 1,000 lumens, which is what they’ll get next to an east or north facing window, or in a very bright room. However, they are especially low light orchids and cannot withstand direct sun on their leaves, with the exception of winter sunlight for a brief period in the far northern and southern latitudes.

Definition of Terms: Lumens, Footcandles

Light is generally measured in Lumens, or Footcandles. A footcandle is the amount of light produced in comparison to candles at one foot away. Therefore, two candles from one foot distance will emit two footcandles of light, a normal fluorescent light bulb will produce a couple thousand. One lumen is the amount of footcandles distributed over a one square foot area. In general an object will receive about 10,000 footcandles in full sun, on a bright sunny day in the middle of summer.

On the other hand, the middle of a room on a dull grey day, with only one incandescent light fixture will probably receive only a couple hundred lumens. Far too little for almost any orchid to grow and flower. Generally 1,000 footcandles can be achieved in a bright north or west facing window. As well as in the middle of a brightly lit room, on a bright day. For higher levels of light, an east or south facing window, or artificial light will be necessary. Be careful to guard orchids from hot midday or early afternoon sun, by using a sheer curtain (one that still lets light through). Lumens and Footcandles are best measured with a light meter (often used by photographers).

I will cover artificial lighting in a later posting. There are many options available to the light gardener, from High Pressure Sodium light fixtures to good old standard fluorescent lights.