Tuesday, January 29, 2019

My Year of Orchids: How do orchids respond to fertilizer?

I’m curious how orchids respond to fertilizer because of their particular growth style. Most orchids are epiphytes, plants that grow on top of other plants. They have root systems but unlike other terrestrial species the roots of most orchids are not anchored in the ground. So the orchid sits harmlessly on top of its host. It is thoroughly dependent on its environment and thoroughly capable of utilizing the nutrients in its surroundings. It transforms these resources into the orchid body. But does it do so quickly? Slowly? Somewhere in between?

It seems to me that the orchid must be able to withstand periods of drought and low nutrient availability. How else could it survive in the changeable conditions that surround it? By extension I would assume that under certain conditions it can use water and nutrients slowly, going into a kind of dormancy when supplies are short. Does it follow that nutrients might be taken up and used very gradually or is there a kind of one way valve, metabolically speaking, that allows the orchid to absorb and utilize nutrients quickly but lose them slowly?

From what I’ve seen in my orchid garden it appears some species respond to resources quickly, others less so. Hybrids seem primed for quick action, species less so. Rest season means less response and growing season more? Maybe. Yet there’s more to it I think.

Most people I read say steady low level fertilizer over the long haul is best. This would suggest that orchids in nature are used to a steady low-level nutrient diet based on whatever the environment delivers. This makes sense. If you have evolved in a cloud forest your almost day-long misting keeps you bathed in a low level of constant nutrients. We might assume from this that there are few spikes in nutrition and perhaps relatively few low points. The key is constancy.

So if there’s constancy maybe there is no genetically coded instruction for an exceptionally quick response to increased nutrients. Or maybe there’s an inherited response for nutrient flushes so that the orchid can take advantage of them. But conversely the outflow of nutrients in times of stress is slower. Lots of room for conjecture. As well, many orchids evolved in less constant conditions, such as forests with distinct dry seasons. There are even orchids from the arctic, where conditions are very changeable. 

Little “fact” here in my first few months of orchid growing. Lots of conjecture and lots of observation still necessary. And most of the recommendations I see are from people who grow their orchids in pots.

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