Answer: The texture and drainage of the soil can be improved by breaking up the clay and adding lots of organic matter (compost, aged manure, rotted leaves and grass clippings), as well as soil conditioners like fish emulsion/seaweed solution. You may also be able to improve the clay soil by adding nutrients like gypsum, but you'll have to have the soil tested to find out which amendment is appropriate.
This goes for both lawn bed preparation and planter beds. In the planter beds, you can further improve the soil by spreading an organic mulch over the top of the bed after planting your tropical plants. Organic mulch will help suppress weeds and will help prevent water evaporation. At the end of the growing season you can dig this organic matter into the bed, thereby improving the soil even more. If you practice this routine year after year you'll eventually have garden loam instead of clay soil.
Best wishes with your landscape!
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