[PCA] follow-up questions, native plants for cities, stormwater management

[Louisa Rogoff Thompson]

Thank you, to the many people who have responded to my question about 
native plants for stormwater management.  At the request of several of 
you, I will eventually send the listserve a summary of the replies.  The 
main findings seem to be that (1) soil, much more than plants, takes up 
heavy metals, (2) most salt-tolerant plants do not require salt, and (3) 
because road salt tends to be washed out of soil by spring rains, its 
most damaging effects are on early-germinating seed.

Meanwhile, I have some follow-up questions.  I think there's an 
implication that salt-tolerance goes together with tolerance of heavy 
metals, but I don't know chemistry at all.  Is this correct?

The design I've been asked to submit takes rain from the street and 
pipes it onto the rain garden.  (Please note, we are not dealing with 
sewage or fertilizer runoff.) 

Most bioretention facilities or rain gardens have two planted sections, 
a forebay with tougher plants and a larger bioretention area with more 
varied plants.  It's the plants for the forebay that concern me most, 
because the pipe from the street will empty onto it, and there isn't 
much room to slow down the water.  From the forebay, it goes through an 
underground pipe into the root zone of the main section.

A number of people have suggested using narrow-leaved cattails, which 
are salt-tolerant, flood-tolerant, and have been used for various kinds 
of phytoremediation, and seem to be spreading along the ditches beside 
highways. 

* What I'd like to know about cattails is whether they can survive a 
summer drought without watering.   

How deep is their root system?  They grow in sandy soil, but would it 
help to add organic matter?

Secondly, the water from the street is going to be that filthy dark gray 
color that you see on snow on city streets, and apparently there is 
quite a lot of grit and finer sediment that has to be cleaned out, 
perhaps several times a year.  So,

* Can you cut back cattails several times a year, in order to get in and 
shovel off the sediment?  How do they look after being cut back?

*Switch grass (Panicum virgatum) seems to tolerate salt and heavy 
metals, as well as brief periods of flooding.  Do you see it growing 
together with cattails?  I'd like to create some semblance of a natural 
community, and I need a plant to bridge the transition to the drier soil 
on the berm around the forebay. 

Thanks again.
Louisa

>-----Original Message-----
>From: native-plants-bounces at lists.plantconservation.org
>[mailto:native-plants-bounces at lists.plantconservation.org] On Behalf Of
>Louisa Rogoff Thompson
>Sent: Tuesday, December 07, 2004 9:54 AM
>To: NativePlantseast; WorthleyBotany
>Subject: [PCA] native plants for cities, stormwater management
>
>I'm looking for information about native plants adapted to various kinds of
>stressful environments, particularly salt and heavy metals.  It's my firm
>belief that plants can take care of soil and water better than facilities
>made of concrete and other man-made materials.  And I prefer to use native
>plants, because they are unlikely to turn out to be invasive, and because
>they are more likely than exotics to form collaborative relationships with
>soil organisms and above-ground wildlife.
>
>I'm currently working on a grad school project to design a landscape for a
>vacant lot which will divert stormwater from the street into the lot 
>to be filtered and slowed down.   Most vacant lots previously had 
>buildings on them, which means they now have fill dirt, and infiltration
>facilities are not permitted on fill.  So the water has to be returned to
>the storm drain system, but some will evaporate and the rest will be
>returned slowly, reducing the volume of fast-flowing water during the storm.
>
>The man at Baltimore's Dept. of Public Works who issues permits for this
>kind of thing says a solution would be very valuable, and could be used on
>many vacant lots throughout the city.  If I can get this to work, it could
>have a very significant impact.  Did you know that much of Baltimore's
>stormwater is piped directly into the Inner Harbor?  And it carries cadmium,
>copper, chromium, lead, and other heavy metals, mostly from tires, some from
>diesel exhaust, and some from old lead paint.  And road salt, in winter.
>
>If you have seen plants either survive or be harmed by road salt, air
>pollution (e.g. from bus exhaust at a bus stop), or heavy metals (e.g., lead
>paint chips in the soil), I'd like to know about it.
>
>Also, if you know of published information please tell me.  I have Dirr's
>Manual of Woody Landscape Plants, which has this kind of information for
>many trees and shrubs.  Is there something comparable for herbaceous plants?
>I also have Md. Dept. of Environment's Stormwater Design Manual, which has a
>long list of plants, indicating tolerance to salt and pollution.  The only
>plant listed as tolerant to both is Eastern white pine.  Most likely this is
>a list of known tolerance, i.e., no check mark means no knowledge, not no
>tolerance.
>
>Your help will be much appreciated.
>
>Louisa Thompson
>Institute of Architecture and Planning
>Morgan State University
>Baltimore, MD
>
>
>
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