我从1960年就开始进行这个实验了，当时瓶子园艺很火。我想看看植物在独立的环境能否活下来。...这个实验是为了看看植物能活多久，今天有一棵活着。紫露草一直在长，现在它们几乎撑满了整个瓶子。我在1970年初浇了两次水。“
一些人并不知道这个实验的目的是什么，但事实上我没什么太特殊的目的，只是为了看看植物能活多久。
植物为了活下来，必须从日光中吸收太阳能，从它自己产生的水蒸气中获取水分，从落下的腐叶中获取二氧化碳和营养物质。它自身也会产生氧气。

The 80-year-old buried four ­seedlings in a huge jar in 1960 and one is still flourishing – even though it hasn’t been watered in 40 years.

David wanted to test a theory that plants can survive in a self-contained environment.

Three of the four died after he sealed the container, but this beauty – called a ­spiderworts or tradescantia – just kept growing.

Retired electrical engineer David, of Cranleigh, Surrey, said: “I started it at Easter 1960 at a time when bottled gardens were a big craze.

“I had an idea to see if plants could survive in an isolated environment.

"It was an experiment to see how long it would last and it still is.

“The tradescantia just kept growing until it filled the bottle. I have watered it twice, in the early 1970s.

"Some people don’t see what the point is and the truth is that there is no point, it’s just to see how long it lasts.”

To survive, the plant absorbs solar energy from daylight, water from the moisture it creates and carbon dioxide and nutrients from rotting leaves it drops.

It also produces oxygen.

David took a picture of the plant to Radio 4 Gardener’s Question Time.

Host Chris Beardshaw said: “It is a great example of just how pioneering plants can be and how they persist.”