Temperature and Fertilizing -- Welcome to Orchids, etc.

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Date Posted: 17:54:57 10/26/00 Thu
Author: Anonymous
Subject: Temperature and Fertilizing
In reply to: Anonymous 's message, "Water and Light............." on 17:52:56 10/26/00 Thu

TEMPERATURE

Like most plants, orchids have their limit as to how hot or
how cold they want to be. Each genera and each species have
their own unique preferred temperature range. You need to
learn what the proper temperature range is to successfully
grow your orchids. Orchids grow best when there is a
difference of the temperature between day and night. In
addition, many orchids will not flower unless they receive a "
cool down period." The very best tool for checking your
temperature is to use a maximum-minimum recording type
thermometer. Mount the thermometer as close to your plants
as you can. Keep the thermometer out of the direct sunlight
for the best readings.

- - LOW TEMPERATURE - -

Orchids exposed to freezing temperatures and below will
cause ice crystals to form in the plant tissue killing the
effected area. Depending on the extent of the damage, the
entire plant may be killed. Temperatures above freezing and
below optimum temperatures, may cause less damage, but
damage will still occur. Here is an example of cold damage.

How do I know if the temperature is too low?

1.If your orchid has been subjected to freezing
temperatures, the plant, especially the leaves, will turn
dark and mushy. An orchid placed near a window exposed
to freezing temperatures may receive damage to only
the leaves that may have been touching the window.

2.Orchids grown in too low of temperature, but not
freezing, will become very weak over time leaving the
plant incapable of defending itself against attacks by
fungi and bacteria.

What can I do?

1.If you are growing your orchid outdoors, watch the
night-time temperature. If the temperature is going to
be below 50 degrees for more than two hours bring your
plants indoors or protect them by covering them with
newspaper, burlap, a light blanket, plastic bags, bubble
wrap, etc.
Even the cool growing orchids do not like temperatures
much below 50 degrees. Simply covering them will NOT
protect them if the temperature drops below 40
degrees. Keep in mind some orchids, like the
Cymbidiums, if accustomed to living outdoors, can stand
colder temperatures. I have left my Cymbidiums outside
until it was just above freezing (It has even snowed on
them). As long as the pseudobulbs don't freeze, the
plant will be just fine. I also grow Bletilla striata here
in Utah outdoors and it comes up every year. On the
other hand, a night of temperatures below 55 degrees
can kill a Phalaenopsis.

2.If you are growing indoors, be sure your plants leaves
are not touching the window glass (see above). You can
also add sheets of bubble wrap to the windows to help
insulate them. Turn up the temperature if you are
growing them in a green house or in a room that has it's
own heat source.

- - HIGH TEMPERATURE - -

Temperatures that are higher than your orchid's preferred
range can also do as much damage as too low of temperature.
High temperature, in combination with intense light, is
extremely dangerous. Here is an example of heat damage.

How do I know if the temperature is to high?

1.If you notice yellowing or blackening of the leaves, they
could be burning.

2.The leaf tips are brown and dieing back.

3.Leaves are dropping off, and the plant produces
malformed growths and leaves.

4.Some orchids like Masdevallias will just fall apart.

5.Orchids that are kept too warm at night become
weakened, resulting in weak and leggy growth.

What should I do to lower my temperature?

As you may have expected, reducing temperature is much
harder than raising temperature.

1.If you are growing indoors and do not have air
conditioning, move your plants outdoors under a
covered/shaded patio. The night temperature will be
much cooler outdoors than indoors.

2.Increasing air movement with fans will help the plant
increase evaporation from the leaves, which is how the
plan cools it self.

3.Reducing light will also help. Sunlight is a great source
of heat (infrared radiation) on your plants leaves. Lower
the amount of time your plants receive full sun. Add
shading where necessary.

4.Try and grow orchids that will be happy in your
conditions. If you live where it is always warm don't try
and grow the cool growers.

IDEAL TEMPERATURES FOR ORCHIDS
COOL
Max Day 80F (27C)
Min Night 50F
(10C)
INTERMEDIATE
Max Day 85F (30C)
Min Night 55F
(13C)
WARM
Max Day 90F
(32C)
Min Night 60F
(15C)
Cymbidium
Masdevallia
Miltonia
Odontoglossum
Oncidium
Paphiopedilum
Brassavola
Cattleya
Dendrobium
Epidendrum
Laelia
Paphiopedilum
(molted leaves)
Phalaenopsis
Vanda
NOTE: These ranges are based on the genus as a whole, many
species have different tolerances. Hybrids produced by
crossing cool-growing genera with intermediate growing genera
may grow well in either temperature range.
FERTILIZING

When you are fertilizing orchids, you need to remember that
most orchids grow above the ground (usually attached to
trees) and that they are fed and watered by rain runoff
containing very diluted nutrients. Because of their natural
habitat, most orchids are not heavy feeders. The old saying,
"weakly, weekly" is a good rule of thumb (fertilize using a
weak solution one day per week) when fertilizing orchids.

What kind of fertilizer should I use?

The correct type of fertilizer to use on your orchids is very
important! Avoid using general purpose fertilizers designed
for lawns and gardens.
All fertilizers consist if three main ingredients:

nitrogen--(N)--which promotes general plant growth
phosphorus--(P)--which promotes flowering
potassium--(K)--which promotes strong roots.

The ingredients are mixed in various combinations because
plants have different needs. The combinations are indicated
by a three number code:

The first number is the percent of nitrogen (N)
The second number is the percent of phosphorus (P)
The third number is the percent of potassium (K)

A good balanced fertilizer like 7-9-5 (N-P-K) is good for all
mediums you might be using to grow your orchids in. For
years, it was thought that bark robbed nitrogen from the
orchids and that a high nitrogen fertilizer such as 30-10-10
was needed. However, recent research in this area has
proved this to be untrue.
To help promote flowering, you can use a special type of
fertilizer called "blossom boosters." This is used just prior to
bud formation and is a 3-12-6 formula.
Do not use fertilizer containing urea on any orchid. Urea
requires breakdown by soil microbes. A toxic salt build up can
occur that can burn tender roots.
You may notice that when the three numbers are added up,
they don't total 100%. The missing percent is composed of
inert ingredients.

Fertilizers are distributed in many forms, granules, liquid,
spikes, etc. I recommend you use a water soluble (granules
that are dissolved in water or liquids that are diluted with
water prior to use) type orchid fertilizer which should be
available in most garden centers.

How much fertilizer should I use?

The recommended dosage varies according to the
manufacturer but is usually only 1/4 or 1/2 teaspoon per
gallon of water. Follow the manufacturer's directions and
remember, "weakly" is better! Less is better than more!

How often do I fertilize?

Some orchidists recommend fertilizing every week and others
recommend every other week. I personally water every week
and add fertilizer to my water every other week.

How do I know if I am not fertilizing enough?

Smaller than normal growth or yellowish leaves is an indication
of possible insufficient fertilizer. Most of the media used to
pot orchids offer no nutrition to the plant. Organic media
(bark and moss) will release small amounts of nutrients as
they decompose.

How can I tell if I am over fertilizing?

A salt buildup (which looks like white crusts on the media and
around the pot) is a sign of over feeding. The roots of your
orchid will turn black if they come into contact with this salt
buildup and if the buildup continues, the plant could die. When
the tips of the leaves die, it could also be an indication of
too much fertilizer.
To prevent this condition, you should practice a alternating
watering and fertilizing routine. Give fertilizer to your orchid
at every other watering. This will allow the fresh water to
flush your orchid of any leftover fertilizer, salts, and
minerals that may have built up in the pot.

What should I do if I have been over fertilizing?

The best thing to do is to re-pot your orchid in a new
(sterilized) pot with new media. Before placing your orchid
into its new pot, flush the salt from the roots and around
the growths with running water. Reduce the amount of
fertilizer to the recommenced amounts.

- - Orchid Fertilizing Tips - -

Water your orchid with fresh luke warm water (NEVER
cold water) weekly. Add fertilizer to the water every
other week.

If the tips of your plants become dry and start to turn
black, it could be a sign of over fertilizing. Be sure you
are flushing the excess fertilizer out of your media
between feedings.

Don't fertilize a sick plant.

Don't add extra fertilizer to your plants to help them
grow. This will not help.

Make sure your water is luke warm, don't use cold
water.

Pour the fertilizer thru the pot or over the media just
like you were watering. DO NOT "catch" the fertilizer
runoff and then use it on another plant. This practice
WILL spread diseases.

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Replies:

Humidity and Air Movement..... -- Anonymous, 17:56:26 10/26/00 Thu
- Wow! Thank you! I am printing all of this out -- Anonymous, 22:22:48 10/26/00 Thu