Lisa- Willows are messy plants that will drop a lot of small branches, leaves, and catkins to clog your pool filter. So never a good choice near a pool. And I doubt that they would survive the first winter in a container in zone 5a. (See below) I don’t know of any bamboo that will survive in a container in zone 5a. There are a few types of bamboo that will survive in the ground, but not many. A container is exposed to air temperatures on all but the bottom, rather than being surrounded by a huge mass of soil from the ground around it like with in-ground plants. Because of this, the container soil will freeze solid in cold weather and will have many cycles of freeze-thaw over the course of the winter. Based on my experience as well as what I read, few plants can survive this. The ground, because only the top surface is exposed to air temperatures, may freeze a few inches down, but doesn’t freeze below that unless it is in an area that is without plants, mulch, or snowcover, and even then there won’t be the kind of temperature extremes and swings that happen in even the largest containers because it takes a long time for in-gound soil temperatures to change due to the enormous mass. Year-round container growing works for warmer areas, but not zone 5. I have found one plant only of many tried that will grow and survive in a container, ribbon grass, something that is too much of a thug to let loose in a garden. However, it isn’t tall enough to votive you much privacy, perhaps 2’ tall. So plant large, quick-growing annual vines on trellises in your pots, something like some of the larger cultivars of mandevilla vine or Black-eyed Susan vine (Thunbergia) or scarlet runner beans. Add some groundcover or draping plants like wave petunias or golden creeping Jenny and you will have a colorful set of pots for your pool that will offer privacy. Be sure to read up on container soils and have some type of irrigation system to keep them looking good. Or consider freestanding screens that can be moved into place to provide privacy.

Yeah leyland cypress don't like wet feet one bit. You could plant hybrid willow which..... eeh not such a remarkable plant or possibly someone will have some other more unique and desirable planting ideas for you. And yes you can root them with cuttings from a branch, reportedly you need only stick them in the ground. I haven't tried it myself.

Eastern Red Cedar should grow well there. If you pay attention to watering, they can grow as fast as 28"/yr in good soil but 18" is more normal. Waco has several nice examples of large older Eastern Red Cedar. These trees are drought resistant but can handle wetter years. Arizona Cypress is another conifer that should grow well if you have good drainage. They look similar to ERC but have thicker foliage and are gray-greenish in color. Both Killeen and Waco have several large specimens of these trees. Mine have only grown 12-16"/yr. but reports indicate they can grow faster. These trees are drought resistant. Loblolly pine only does well in a few selected spots where the soil is locally neutral to acidic. If you have a spot like that they will thrive, if not, they will turn yellow and die. Afghan Pine will grow here, but they often die after about 10 yrs or so as the climate here is too wet for them. They do much better planted in west Tx. There are no examples of large Afghan Pines that I know of here.

I love my hybrid willows as farm trees. Pennsylvania deer are not interested in them, and as advertised, they grow three to six feet per year! I am so happy we planted them, as they are in their third year and the most vigorous are already about ten feet tall. I planted them along my pasture fence line, in an area that is always "squishy" and wet. Their aggressive roots have soaked up a lot of that water, making the area more stable, and my horses don't bother them. The branches are dense enough to provide a minor windbreak even in the winter, and in the summer they provide a lot of privacy from the road. Behind them, I planted some firs that will take 10-20 years to grow big enough to provide privacy. I've heard that the hybrid willows can only be expected to live about 20 years, which is fine, because by then my firs will have grown tall enough to replace them. I would echo what others have said about not planting hybrid willows in a small yard, or anywhere near a septic -- 100' away at least. The roots will bust through anything they contact.