Growing tropical plants from seed is a rewarding way of increasing a garden collection. Commercial nurseries are often limited in the plant varieties available, and growing a much desired specimen from seed is often the only option. Although some tropical plants do have specific seed germination requirements, they can be easily grown by the average gardener.
Growing bananas from seed can sometimes be difficult, depending on the variety. Banana seeds are notorious for having an extremely hard outer seed coat, which can inhibit germination. A combination of techniques will bring the best results. Scarifying, which means removing part of the outer seed coat through mechanical means, is one way of preparing seeds. Scarification can be done with a file, a knife or sandpaper. Only a small area of the seed coat needs to be removed. This allows moisture to reach the embryo and begin the germination process. Soaking the seeds for at least 24 hours is helpful also. After planting in a seed flat, alternating warmth and coolness will often encourage even the most stubborn seeds to germinate. An easy way to accomplish this is to place the seed flat on a heat mat for the daytime hours, then remove it to a cool, but not freezing, area at night. Two or three weeks of this treatment is usually needed before any sprouting activity is noted. Bananas grow quickly after the long initial germination wait and should be potted up when they have two sets of leaves.
Brugmansia seeds have a corky outer covering that can greatly slow germination time. Removing at least part of this outer coat with sandpaper or a knife will allow seeds to sprout before they succumb to rot. Plant in a seed flat filled with an equal measure of sand and peat moss, well mixed. Germination takes two to four weeks. A heat mat will speed up the process and provide the warmth needed for fast growth. Seedlings can be potted up into larger containers after they have two sets of leaves.
Palm seeds will often contain no viable embryo despite a healthy appearance. Placing the seeds in a container filled with water will allow immediate identification of non-viable seed, which will float. Discard the floating seeds. Soak the remaining seeds in water for at least 24 hours. Palm seeds can be germinated in either a seed flat or a plastic bag filled with damp peat moss. The plastic bag method is good for large quantities of seeds with unknown germination requirements. Simply dampen the peat moss, sow the seed, mix well and place on a heat mat. The bag allows easy visibility to check for root formation. As soon as the roots begin to emerge, the seeds should be removed and planted in a flat. Most palm seedlings are very slow growing, and it may be a month or more before they are ready for a larger pot.
Yucca seeds have extremely unpredictable germination rates. Removing part of the seed coat and soaking for at least 24 hours will help, but some seeds can take as long as a year to sprout. Keeping the seed flat on a heat mat, or outside in a very warm and sunny area will encourage germination. Once germination has occurred, yuccas should be transplanted very gently into deep pots. Most yucca species have long taproots that require plenty of room.