Why do the flowers fall off my Eggplants?

I had a call from Alister because the flowers on his Eggplants kept dropping off without developing fruit. Does he need another plant nearby to ensure pollination? I have to be honest although I thought I knew the answer, I had to re-check.  The answer is definitely no, Eggplant like their relatives Tomato, Capsicum and Potato (the Solanaceae family) are self pollinating.  The flowers have both male and female sexual parts so pollen doesn't even have to travel from one flower to another (not to say that it can't, that's just provides an opportunity for plant variation and development).  It is the self pollinating nature of these flowers that ensures plants grown from your own seed collection will grow true to form season after season.

So what is happening to Adrian's Eggplants?  Blossom Drop.  Blossom Drop is usually associated with stress.  Too Hot, Too Cold, Too dry, Too wet, Too humid, Too hungry, any of the above alone or in combination. The response of some plants like Coriander and Bok Choi is to bolt to seed when stressed and flounce off to produce the next generation. The Solanaceous plants appear to be made of sterner stuff, when the going gets tough they knuckle down and concentrate on surviving, there'll be time enough for reproduction when conditions improve.

The solutions?  The usual response... do whatever is necessary to remove the stress, it's fair to assume at this time of year that water, or lack of is the most likely issue.  If the plant is growing in a pot is the big enough to hold enough water for the plant to grow, even on hot days? Could pots be moved to a position to avoid the most intense heat of the day? Would mulching help retain water for plants in garden beds? Is the plant hungry? Now that the frame of the plant has developed does it need some extra tucker for flower & fruit development? One point to note here, too much Nitrogen in the plants diet can encourage lots of foliage and plant growth at the expense of setting flowers and fruit. Organic fertilizers (manure) generally give a better balanced diet. Fertilizers using terms like Super Green, Turf and Citrus are generally plant junk food.

The mechanical solution is to tap the flowers.  Tapping the flowers releases any pollen available. Because the flowers are self pollinating there is no need to spread the pollen from one flower to another, the pollen just has to let go and reach the Stigma in the flower.  A brush to transfer pollen from one flower to another is not essential but will certainly help physically move pollen from one place to where it is needed.