When choosing a location for your pond or water garden, trees in your landscape can be a big problem or their presence can make your pond a shade masterpiece. Shade from trees can be beneficial to your pond especially if you want to keep fish or other wildlife. Shade helps keep algae growth in check. A pond needs to have at least half the top of the water shaded with floating plants. If you have a tree, you can dispense with the floating plants and be able to see your fish better. You will be able to grow plants a sun gardener cannot. Anacharis will grow better for you because it likes to be in the shade.
You can grow ferns in the shade. Ferns, like wood ferns, Japanese Painted Ferns, autumn ferns love the shade.
You can grow broadleaf plants like gingers, birds of paradise, and taro that burn in the sun, but will love being planted around the shade pond making your pond look as if it is in a woodland setting.
You can use callas and taro in the water or out. Callas grow in the water and best in the shade, so you can have the flowers deemed by Katherine Hepburn as 'The perfect flower for any occasion.' Callas bloom early and long, so they will brighten up your early spring. They hate the sun, so make sure it does not hit them. They will shrivel up and die.
Your fish will be cooler in the summer when that hot summer sun beats down on us. They will come to the top to say hi more often because they are in the shade, rather than lying at the bottom trying to stay cool.
While trees can provide welcoming shade and so many other benefits, they can cause numerous problems when they drop their leaves and flowers in your pond.
If you put your pond under a tree, you are adding about ten minutes of maintenance weekly to your gardening chores because the leaves must be removed. I use a net and just dip them out. Some people use special pond vacuum cleaners, either the water powered ones or electrical powered ones. I find a net works just fine. The biggest part of the netting process is removing the anacharis that you dipped out along with the leaves. You can avoid this if you pot up the anacharis in the bottom of the pond. You can do this easily in soil or not. Anacharis does not need soil to grow. An easier way is to put the anacharis in a pot and put some stones on it to keep it in place. It will be happy that way and even flower for you. When it flowers, the tiny white flowers look as if someone threw popcorn on the water surface.
If you do not remove the leaves or other rotting plant material regularly, you take a chance of fouling your water with the ammonia that builds up from the decomposing material, so take that extra ten minutes weekly and remove it. If you do choose a shaded site, make sure you are not under a maple tree or a pecan tree. The maple tree drops those winged things in the spring and there they go into the pond. In the fall, they drop their leaves over a period of time, so you are always having to get them out of your pond.
I built my first pond under a pecan tree. I had to fish out not only winged things in the spring but also leaves in the fall, and then pecans when they dropped later in the fall. I learned that lesson soon and never did it again.
I have seen ponds under trees, but the pond keepers being as lazy as I am, built a canopy for the pond, so leaves fell on the canopy and then onto the ground missing the pond. I have also seen people cover their pond with a net, so that would catch the leaves. I think the net is so ugly that I would rather remove the leaves, seeds or pecans than have to look at that net all the time. Now the net does deter egrets and other fish eating birds, but again, I would take my chances on the birds.
Be aware ahead of time that you cannot have water lilies because they require at least 5 hours of sunshine daily, but your plant palette is expanded rather than compromised if your pond is in the shade.
I rather prefer a shade pond. Algae are not nearly the problem in the shade as in the sun, maintenance is minimal. Leaves do not fall every day or even every week. You have a small amount of time each year when your maintenance time in increased. The rest of the time you can relax in the shade of your tree and watch your fish play.
Be aware of all the good and bad parts of putting your pond under a tree. It can be worth it.