Plants:
Plants are a welcome addition to any tank. Plants provide hiding spaces for shy or harrassed fish, resting spots (bettas love to relax on broad plant leaves), help oxygenate the water, help remove dangerous toxins, and give the tank a more natural look. There are numerous plants which are easy to maintain and easy to find at your local pet store. All of the following plants require minimal lighting (25-50 watts pet 25 gallons) and are useful in both community tanks and spawning tanks.
Apogneton ulvaceus This is the most common type of apognetons I have been able to find. Apognetons are one of my favorite plants - they are easy to grow, very hardy, and grow quite large. I've been able to find packages of bulbs at Wal-Mart to start my plants from, and they have grown to be over 18 inches tall. The bettas love these. Apognetons have large, broad dark green leaves, and multiple stems from each bulb. These are perfect for 10 gallons and up. Apognetons don't need to be rooted, which also makes them perfect for the bare bottomed spawning tank. Several of these floating in a 10 gallon provides shade, protection from other fish, and a great relaxing spot.
Pygmaea Helvola or Dwarf Water Lillies: These are much like the apognetons, and have the same care and benefits of the apognetons. Dwarf lillies do not grow as tall as apognetons.
Echinodorus, also known as Amazon swords and raddican swords: These broad leafed, rosette plants are very sturdy and can grow quite large. These do best when rooted, althogh they can be successful as free-floating plants. Swords are most often found as already sprouted plants. They can grow up to 1.5-2 feet, and their broad leaves are another favorite sleeping spot of bettas.
Ceratopterus thalictroides, also known as water sprite or water fern. A very pretty feathered, bright green plants with a dense rosette growth from the roots. This grows up to 20 inches, and is very prolific. Great for babies and harrassed adults to hide in.
Lemnaceae family, also known as duckweed. There are several different types of duckweed, each of which are different sizes. Duckweed is a floating plant that produces readily by budding. Duckweed is great to provide a shade for the bettas, and males love to incorporate duckweed into their bubble nests.
Vesicularia dubyana, also known as java moss. This is a favorite among fish breeders,. Java moss is a leaf moss with thin stems and teeny leaves. It forms a fairly dense clump that baby fish love to hide in. Bettas also like to go and bury themselves face first into it, as its easy to move through. It grows very well and can form mats across the tank. Java moss doesn't need to be rooted, and is often left to just float free in the tank.
source: http://www.deepbluebettas.com/BettaCare.shtml