I have two daturas, one grown from the seeds of the other, in separate pots. Both have bloomed, but I have yet to see one flower completely opened. They habitually open about halfway, then either totally detach from the stem or just drop the petals and leave the end which then develops a filled pod. What causes this and what can I do to make sure the flowers fully develop before dropping?
I cant tell without seeing your plant but flower drop can be caused by several things, such as Not enough water at flowering time, lack of feed too as these plants like a good drink but also because the flowers are large, they use up a lot of energy to make flowers and follow on to produce seeds, that is the sole purpose for plants, germinate, grow, flower, set seeds and die as the plant without our help is built to go through a cycle, we as gardeners change this cycle by feeding (making more flowers and greenery) dead heading to trick the plant into thinking it still has seed heads to make therefore as we remove the flowers the plant has to make more so it can spread it's seeds to keep the species going.
Is the plant in a large enough pot, or in the soil in the garden is there enough sun light getting to the plant, also after the flower has dropped off immaturely, take a sharp knife and slice the flower / seed-head down the center and check to see IF theres any little bugs lurking inside eating away the buds.
Also can you tell us if the plant is the Annual type or the shrub type that most people call Angles Trumpets, that info will give better ideas as to what is happening. either type are normally as tough as old boots given the right conditions.
I only grow the larger shrub type (angels trumpets) but constant problems with Red spider Mite AND most years have to grow in greenhouse. the annual type Get eaten by earwigs here and that's the reason I wonder IF this could be a culprit for your dropping flowers.
Hope this helps get you on the right cause as either way they are lovely plants if grown well.
Good luck Weenel.