Why do I kill houseplants?

I am the kiss of death to houseplants.

I try incredibly hard to keep them looking beautiful and green, but somehow or other I always seem to get it wrong. i have no idea whether I overwater them, underwater them, place them in a draught, deprive them of light, give them too much sun or whatever, somehow or other they all seem to die, usually slowly and, from the look of them, fairly painfully.

I am writing this looking at a lovely lily plant I was given for Mother's Day. When it arrived in the house, it was a luscious dark green with glossy leaves and tight buds full of promise to be pure white flowers filled with fragrance. Now, after almost three weeks of my tender care, the leaves are going yellow and falling off from the bottom of the stem and the flowers, whilst they have come out and smell nice, are curling and looking brown at the edges. I have done my best with it,  keeping it moist but not sitting in water, in good light but not brilliant sunlight and out of a draught. But still it is dying.

It's all the more surprising that I can't do this because I was brought up in a family that had a massive garden and practised horticulture with a considerable degree of success. My Dad was a groundsman for a big school whose gardens he kept looking immaculate, and he also gardened and grew vegetables as a hobby, winning prize after prize at the local horticulture society's annual show. My Mum could garden too, and after my Dad's death kept on his allotment from which she shared vast quantities of fresh veg each summer along with some beautiful flowers.

Although I can do OK in the garden and the greenhouse (although last year my tomatoes were a dismal failure and something ate all my potatoes while they were still in the ground), I simply cannot keep plants in the house, so clearly my parents' talents have not rubbed off on me. On my dining room table at the moment I am nurturing a variety of baby plants for the summer; some fushias and geraniums for pots on the patio and several chilli plants. They are all doing OK with the aid of Miracle Gro, but the begonias I bought at the same time look decidedly sick. They are flopping over, one or two have rotted at the base and they aren't growing. What do I do wrong?

I never buy myself plants any more, because I know it is a waste of money. I prefer fresh flowers anyway, and those I never seem to have trouble with. I have some chrysanthemums in a vase in the lounge which have also been here two weeks and with just a little fresh water and a new sachet of flower food they still look lovely.

I will continue caring for my remaining healthy baby plants in my little table top nursery, because flowers and home grown food both look and taste much nicer than shop bought. They aren't cheaper, don't make the mistake of thinking that, but there is a certain satisfaction from saying "I grew that!". I hope I get to say it this year - fingers crossed!