Mangroves like to live in a tight group so propagules can support each other
Mangrove seedlings will grow under almost any condition as long as their environmental temperature does not drop below 40 degrees, their roots are wet, and they receive a bit of fertilizer once in a while. We recommend 1/2 tsp of MiracleGro and 1/2 tsp of epsom salts mixed into a gallon of tap water.
Living indoors, the seedlings require a certain amount of light. If you can see a shadow by passing your hand a few inches over any surface, you have enough light for a mangrove. You can add a plant light (not over 40 watts) kept at least 12 inches away. If the light is too close, the leaves will burn and turn brown. Mangroves will grow faster with more light, requiring more water.
Mangroves need humidity. If you live in a dry climate and keep them outdoors, or if they reside indoors with heat and/or air-conditioning, mist them at least once a week so the leaves fully develop.
For outdoor plants, mangroves don't tolerate full sun very well. They prefer filtered light or shade. How much sun they receive and the size of the pot will determine how often you'll have to water.
Prop roots become silt roots when they take on the function of flying buttresses. When the tree is older, the bottom of the trunk becomes an upside-down cone shape and may even loose contact with the ground. Prop roots and drop roots improve the stability of the tree by providing a broader base and support in soft mud. Ultrafilters in prop roots exclude salt while extracting water. Above-ground drop roots transport oxygen from the atmosphere to the root system.
When they arrive, they will have be wrapped in damp paper towels, sealed in plastic bags and bubble wrapped. Remove the plants from the shipping material and gently rinse them in room temperature fresh or tank water (if you are placing them in an aquarium). This will allow the seedlings to "breathe" and adapt to their surroundings, before placing them into their new home.
You'll need ... any container that will hold water and ... pea gravel (enough to nearly fill pot)
Measure your total seed length. The height of the container should be 1/3 to 2/3 seed length plus 1". Example: Seed length of 9" needs a pot from 4" to 7" deep.
Pour 1" of pea gravel into the bottom of your pot. Hold the seeds in the pot with their roots resting on the gravel. Pour remaining around the outside of the seeds to hold them upright. Push rocks down in between the seeds to space them out.
How you want the pot to look will depend on how many mangroves you add and how far you space them apart. If you want a more horizontal look, space the plants further apart in your pot and trim the sprouts after they've grown a bit, leaving at least 2 leaves at all times. This will force the plant to branch. For a more vertical look, don't leave as much space between the seeds and let them grow straight up. They will eventually branch themselves, but can be trimmed back at any time. Should you trim your plant, be patient for it to start growing again.
Pour water into your container to the top. How often you water your mangrove will depend on the amount of light, humidity and pot size. As long as the roots are wet and the leaves receive enough light, your plant will thrive. Check water levels in small pots often by picking them up and shaking them. Listen for water sloshing. If in doubt, fill 'er up.
Mangroves grow best in a humid environment, so if you keep your plants indoors, shower them with a kitchen sink sprayer to remove any dust or place them outdoors to enjoy an occasional rain storm.