Feeding Bulbs. Was Re: [pbs] Slow release fertilizers

Kenneth Hixson khixson@nu-world.com
Thu, 19 Feb 2004 12:18:04 PST
>Those findings dealt mainly with 
>Narcissus, Tulip, and a few other varieties of bulbs that are produced 
>commercially in huge quantities.  We have to extrapolate from those to 
>other bulbs.
>Essentially, all bulbs need to be fed only once or twice a year:  when the 
>roots are active and when the tops are actively growing.  

	Respectfully disagree with how Jim states this.  There are other bulbs
on which a very great deal is known.  For instance, try a websearch  on
"Easter Lilies + fertilizing" or go to Walter Britton's Website
and follow some of the links.  There are numerous studies of lilies showing
when roots grow, nitrogen is translocated, etc, etc.  They aren't necessarily
all in one place or published on the internet.

	Different bulbs have different growth cycles.  Your goal as a grower
of any bulb is to have the fertilizer available to the roots as or just before
the roots are ready to take up nutrients.  You also have to factor in the
fact that nutrients move through the soil/potting mix at different rates,
and are absorbed differently at different pHs.  Nitrogen for instance is
moved as much as 18" into the soil by ONE inch of rain or irrigation.
A pot or container is usually highly leached, at least for nitrogen, but
other, less mobile fertilizers can build up to toxic levels.  Note the
white deposits of salts on the insides of even plastic pots.
	The top growth of the bulb is already contained within the bulb,
and fertilizing by the appearance of the top growth is useless.  (The
top growth does need water, and nitrogen may be taken up by the roots
and translocated, but the topgrowth can be completed even if you grow
the bulb in marbles, without any nutrient but moisture.)  The exception is 
when a particular plant is unable to absorb nutrients from the soil, due to 
poor roots or whatever, and foliar feeding can provide some improvement, 
particularly in appearance.
	Fortunately, most potting mixes contain organic matter, which 
can absorb the nitrogen and later release it as the organic matter decays.
Peat moss has an extremely high capacity to do this (CEC or cation exchange
	Osmocote, Nutricote and similiar fertilizers have a coating which
slows the absorbtion of water and thus the release of fertilizer.  This
works well for plants which need an even supply of nutrients, or a
related supply, such as, say, petunias.  It may not be a good choice for the 
specialized growth cycle of flowering bulbs.  It may work well for seedling 
(juvenile) bulbs however.
	In the end, you have to take the best advice you can get, and adapt
it to your own conditions, bulbs you grow, rainfall and temperture patterns,

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