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Re: Aquatic Plants Digest V3 #929

On Thu, 25 Mar 1999, Alysoun McLaughlin wrote:

> >PS: some of the leaves are turning yellowish (as apposed to the nice deep
> >green of the other leaves)... this looks like a nutrient deficency... which
> >deficency would cause yellowed leaves on swords?
> Are the affected leaves on the outside of the plant?  As long as the new
> growth is a deep green, and it's just the older leaves that are affected
> (which you can just pick off), I don't think you have anything to worry
> about.  I think it's normal for the outer leaves to be shed, especially if
> the plant is moved around or suffers some other kind of minor injury.  If
> it's the new growth, then I'd start to worry about a nutrient deficiency.
> Someone please weigh in, if my speculation is only half-right.

I think Alysoun's idea is 3/4 right.  Yellowing older leaves can indicate
deficiency in "modile" nutrients.  Mobile nutrients - nitrogen, for
instance - are those that plants can rob from older tissues to supply new
growth.  Unless this reaches the point where it's really an aesthetic
problem then you don't need to worry about it.

When I see this happening in my plants I try to leave the older, yellowing
leaves on the plant.  I figure that the leaves are a source of nutrients
and removing them would force the plant farther into its nutrient
shortage.  Once the leaves are really dead they can be removed without
causing problems.  O'course, if you've got too many dying at once then you
you probably shouldn't just leave them there; you actually need to do
something to find and fix the problem.

Roger Miller