Pond Advice Needed

[cecilia]

Our pond is infested with an invasive week (Hydrocleys nymphoides).

At the moment we've managed to dry out the pond (well, the drought has) and I think it's a good opportunity to get the whole base of the pond dug out to get rid of the weed. I tried glysophate on it but with no success.

My question is - with a clay based pond, once the backhoe has done the scraping out, should I pour in something like a truck load of granitic sand to help prevent the water being always muddy?

Any advice would be appreciated.
cecilia
www.duckpond-design.com.au/theduckpond

[Amanda_931]

Well, here's a site that, ahem, thinks you might want it in North Carolina (USDA zone 8 at the moment, and the stuff is supposed to be hardy starting in zone 9), says it likes pretty shallow water and rich topsoil.  And to over-winter it in damp soil.

http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/water-garden/floatingplants/hydrocleys_nymphoides.html

Not much help there.  Expecially as I'm wondering if that's what I see in a couple of very shallow ponds a few miles from here that either survives or self-seeds annually.

This site wants us to join and tell them how dangerous it is, and what happens with seeds.

But apparently you can divide tubers or corms or whatever it has.  One site said it was viviparous--which means, in plants, approximately, that you divide tubers or corms.

http://davesgarden.com/pf/go/1136/

Plowing and laying a foot or so of pond soil out in something that will dry out completely sounds like it would get enough that you'd have a year or so of relative freedom from them.  

I've no idea if sand would help.

Water poppy sounds like an aquatic version of johnson grass--kind of pretty and miserably invasive around here--poisonous to grazing animals under kind of odd circumstances--leave any part of the rhizome and you've still got a growing plant.  But I'd think that aquatic would be a lot more annoying to try to destroy.  Push comes to shove you can use Round-Up on johnson grass.  Wouldn't want to pour gallons and gallons of it in a pond.

Actually the johnson grass story is pretty interesting--here's one site's idea for removing it--quote is from the second link.  If your pond is completely dry, you might try it.  I've also heard people recommend black plastic, especially for weeds that need lots of light.

http://www.seedsource.com/medicine/curse.htm

http://www.seedsource.com/garden/grasstips.htm

Using Solarization to Eliminate Existing Unwanted Vegetation
As an alternative to tilling lawn-sized areas, you can use an approach known as "solarization." This works best during the growing season, either in the late summer months or early spring when you expect a string of sunny days. It involves covering the area to be re-seeded with clear plastic (6mil thickness is best, though 4mil will probably do for smaller areas) and letting the sun and natural processes of nature do the work for you.

Dig a shallow trench around the site perimeter, approximately 4-6 inches deep. Water the site thoroughly and deeply first. Then fit the sheets of clear plastic over the site and tuck the edges of the plastic down into the trench. Refill the trench to make the edges of the plastic secure. On larger areas it may be necessary to use several sheets of plastic and secure the overlaps with rocks or some other weight to hold them in place. You want to make it as "airtight" as possible and secure it firmly enough so that it won't get blown loose by the wind.
You have now created a well-watered greenhouse, so that when the sun penetrates the plastic it will warm the soil and provoke more growth, including increased activity of natural soil molds and bacteria. When the unwanted vegetation is trapped under the plastic in these intense growth conditions and has nowhere to go, it essentially becomes compost. The whole process takes about 3-4 weeks when nature cooperates by providing enough sunny days.

Once the process is complete, you can rake off the debris and compost it further. If there is not too much debris, it can be tilled into the soil as part of your seedbed prep.

[glenn-k]

I once read about a natural swimming pond but their solution was to run gigantic pumps circulating and filtering the water most of the time.

What about a epdm liner ?

How big is the pond, Cecilia?

[cecilia]

Glenn, the pond is about six metres x four metres.

I did think of trying to put down a liner - my sister in law has a huge amount of commercial quality black plastic that was used when their house was moved from near Melbourne to their property in the country. It was put on the house until the roof was fixed back together.

My worry about lining the pond is that it would need to be so well sealed around the edges, or water would seep under it (we get pretty heavy rain, if it ever rains again) and then that water may become stagnant.

The base is just clay, so I don't think any pump would really like the job of continually filtering that water. Also, as we are trying to be as energy efficient as possible, it would have to be solar powered somehow.

Problems, problems.

But I'll get it sorted out in the end I think!

cecilia
www.duckpond-design.com.au/theduckpond

[glenn-k]

With a liner you probably wouldn't have to continually filter it.  Make it oversized and fold the edges back and put them under dirt a ways.  Try to have some depth at the edges to cut down on algae growth.  Planting shade trees and shrubs - trellis over top for vines etc will cut down on algae also.  

Raising the edges a couple feet with wide  burms allows the water to be higher than the surrounding ground so you can use a siphon to clean the pond a bit to change water.  It also prevents rain from washing silt and washing your liner loose etc.  The higher level will keep water outside from pushing the liner up.  

Slight water loss from punctures can be offset by adding a float.  Your clay underneath should keep small hole losses to a minimum.   A pool cleaning hose works well for siphoning. Fill it with water then carefully throw the end out to the lower ground to get the flow started.  Note that not all of the pond has to be above surrounding ground level for this to work.  The bottom can be below grade.  I would suggest the water level be a minimu of 18 inches above the surrounding grade.  Deeper at the edges rather than making much of it shallow is better for fish and algae growth prevention.

If adding a filter put the intake on the opposite side of the pump outlet for cross filtration.  Our pond at the other house stays clear without filtration however gunk does build up on the bottom causing low oxygen levels for fish especially when stirring up while cleaning.  Leave water on flowing in at this time.  We concreted the bottom of that one.  Water is toxic until washed out at first - highly alkaline from the concrete but ok after a washing.

[Amanda_931]

Sounds like a pretty good idea.  One of the things recommended on one of the sites was to wade through and pick the stuff out with your toes, IIRC.  (I could be thinking about some native american foods.)

Or if there's very little water in your duckpond now just black plastic it until you start getting rain again and hope all the ##$%&&+ water poppy has been killed off.

Above ground, that's what's recommended here for an invasive amaranth(?), although part of the reason for the recommendation is that it needs light to grow.