To answer both your questions. (Any cheques or monetary donations gladly accepted). If you cut off a stem or stems, you will not notice where they came from within a day or so. You need to trim it anyway because, like many other hygrophilia, it grows like stink.
Information from
liveaquaria.comThe Wisteria, also known as the Water Wisteria, is an undemanding, extremely attractive aquarium plant. The lace-like leaves vary in appearance under different conditions. If the water is colder, they will be small, and lobed in appearance, instead of pinnate. If insufficient light is provided, they will only be slightly pinnate.
The Wisteria is an excellent plant for the new aquarist or for the newly set-up aquarium. It requires a nutrient-rich substrate, with iron-rich fertilizer added regularly. Provide a moderate amount of lighting of at least 2 to 3 watts per gallon of full spectrum (5000-7000K) light. CO2 fertilization is also recommended.
For Wisteria to thrive, the water should be kept between 74°-82°F, with an alkalinity of 3 to 8 dKH and a pH of 6.5-7.5. To propagate, plant cuttings that have been removed from the healthy mature plant. Simply remove any leaves from the bottom 1" to 2" of the stem, and new root growth will form from the last node on the stem.
Please Note: As its scientific name suggests (Hygrophila difformis) the shape and form of Wisteria's leaves differ greatly depending on light and aquarium conditions. When your plant order arrives, it will appear different than its mature form.