USDA Hardiness Zones are intended to help determine the average expected low temperatures for the winter in your zone at a depth of about 8-10 inches below the soil.   The zone chart is also supposed to be a guide in determining which plants are best suited for your area.  Checking what zone you are in is not the only factor we should consider when figuring out if our water plants will survive winter.  Of course, if you live in the southern most regions of Florida, the temperatures won’t be a problem most of the time.  If you live in Alaska, or North Dakota, you would have to be concerned if water plants will survive the winter.  The most important factor in growing water plants is the water temperature.  That is where the plants are growing, so logically this is one very important factor any water gardener should be concerned with.

The reason for this is the water versus the soil.  The water does not retain heat like the soil, and it cools much faster than the soil.  The other side of that is that it heats faster than the soil, so at night, the water temperatures will dip down and then in the daytime, with the heat of the sun, the water will quickly warm up.  This is going to be what is happening in the early  spring where temperatures can really fluctuate, and this can take a toll on the plants that are introduced into your pond for the first time.  Those that are already there and have wintered over, will start to wake up as soon as the temperatures level off and start getting warmer on a steady basis.

  Many times, people tell us they put plants in their pond the same time as last year, and they don’t understand why the plants are not doing the same as the year before.  Here is where checking your water temperatures is so important.  Don’t pay attention to what happened last year because it won’t be the same in most cases as far as the weather goes.  Here in Colorado, during the beginning of spring, and sometimes even in mid to late spring, we can experience 2 or 3 days of beautiful weather only to have freezing rain the same week!!  Many places in the U.S. are the same.

 Keep in mind, that the plants in a man made pond can only go as deep as the container they are planted in, and how deep the pond has been dug.  So they cannot go any deeper to keep from getting their roots frozen if they are not below the freeze level.  So it is important to dig your pond deep enough to place the containers at the level they need to be at in order to keep from getting their roots frozen.  Here is where water gardeners in  places like North Dakota, Minnesota, and Wisconsin,  would definitely need to know if your frost line is going to be 1 foot or 5 feet!!! Keep in mind that not all the plants over wintering in the pond will wake up at a 3 to 5 foot depth.  Some you will need to raise up to the level they need to be at to wake up and get going.  Be aware of the depth the  plants you have in your pond need to be at to survive.

 

Micro environment is another important factor for the success of your water plants.  This factor is determined by where your pond is located, if there are any barriers around the pond or if the pond is out in the open.   Are there trees or bushes around the pond.  Is the pond in full sun or partial shade.  How deep is the pond, and how large or small it is.  Many times there can be two similar ponds next door to one another, but the plants will not always grow the same.  The water won’t be as clear in one pond as the other.  Sometimes even from one end of the pond to the other, plants can perform differently.  Some micro environments may have more moisture than others.  If the pond is very large, there is bound to be more moisture circulating than in a small pond, this is because of the larger water surface.  Waterfalls and rocks surrounding the pond will also factor into your micro-environment.