Wednesday, February 13, 2013

General Fertilizing Techniques
I find Stanhopea to be easy feeders and only require light to moderate amounts of fertilizer.  I use standard granular fertilizer that you can mix in water for feeding orchids during most months of growth.  This fertilizer has a nitrogen-phosphorus-potassium concentration of 15-30-15, and also contains some micronutrients.  For more detaled information on fertilizer components (see Specific Fertilizer Details).  During the fall and winter when growth is slower, I switch to either a kelp-based (0.13-0.0-0.60) or fish-based (5-1-1) fertilizer to provide the plants a different source of food.  I also switch to these more organic forms of fertilizer because they do not leach out of the growing media as quickly as the granular fertilizer during the heavy rains in the winter.  Other growers find the opposite to be the norm for organic fertilizers, but I find that the organic forms require less use.  Be careful using the fish based fertilizers so that you do not damage the plants, because too much nitrogen can cause leaf burn.  If you are going to use the fish-based organic fertilizer, make sure to use the deodorized form.  This fertilizer still has a slight fish scent, but dissipates after a few days.

For all fertilizers I apply at a rate that is half of the recommended concentration on the package.  During the spring and summer I fertilize every time I water, and in late fall and winter I only fertilize the orchids once a week that are still growing.  Several species need a rest period during the winter to induce flowering  and I find these species are not actively growing during the winter (unlike several species such as S.oculata, S. tigrina, and S. wardii that continue to grow until January or February).  The species that require a rest period from fertilizing are the same species that need less water during the winter (e.g., S. hernandezii and S.insignis, S. jenischiana, S. lietzei, S. maculosa, and S. martiana).  I discontinue fertilizing these species completely in the winter and only resume when growth initiates in spring.
My general rule of thumb is to fertilize frequently during the growth and blooming seasons and provide enough food for the plants to produce large growth and thick pseudobulbs to store enough energy for the next blooming season.  I have noticed Stanhopea that have thicker more mature pseudobulbs and growth tend to bloom more consistently, and are more floriferous (see How Do You Know Your Stanhopea Is Happy? and Why Won't My Stanhopea Bloom?).  I have listed the size of the pseudobulbs for reference when I post examples of species on this blog. You should take the sizes I provide for blooming sized growth and pseudobulbs only as a guide because pseudobulb size does vary between species and forms.

Pseudobulbs of
Stanhopea graveolens
Pseudobulb of
Stanhopea tigrina var. nigroviolacea

Fertilizer Amounts
The amount of fertilizer you should use varies according to your water quality.  A component of water quality is provided to you in the amount of dissolved solids, and is available from your local water provider.  In general, the lower the amount of dissolved solids in your water the better it is for your orchids, and the more fertilizer is required. Conversely, the larger the amount of dissolved solids, the orchids have slower growth that is often stunted or disfigured leaves, and require less fertilizer.  For example, my average dissolved solids is 337 parts per million (ppm) which is a high concentration of solids.  This level of dissolved solids requires less fertilizer in my fertilizer regime, therefore I use half the amount of the specified fertilizer in my water mix.  Large amounts of fertilizer mixed with moderate to large amounts of dissolved solids can lead to leaf burn.  This is an accumulation of salts at the leaf tips and provides an unsightly brown leaf appearance.  The best way to deal with poor water quality is to either obtain a reverse osmosis system that will purify the water, or reduce the fertilizer used in your watering regime, but increase the frequency of the fertilizing.  I am currently using the latter option. It is also a good practice in regions that have high dissolved solid concentrations to water your orchids thoroughly and leach the solids from the growing mix once a week.


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