I am looking for the potted plant that has the highest survival rate when planted outside on a balcony, in a small trough pot in direct sunlight, supplied only with rainwater, without any regular human care.
Ideally it should also have
- any color different from dried-up brown for a significant part of the spring/summer season and
- either survive snow and temperatures slightly below zero during winter or automatically reseed itself in the spring.
- be strong enough to not be pushed aside or supplanted by other weeds
In other words, what I am looking for is an organic plant that closely resembles astroturf or a plastic flower.
Which plant would work the best in this setting?
The climate would be European continental with temperatures between about -3°c and 23°c. The pots/troughs would be long but narrow: 15cm * 15cm * 1m or 6in * 6in * 40in (they are permanently mounted to the outer wall of the balcony)
My current survival-of-the-fittest experiment show clover to be a strong contender. However I do not know what sort of clover it is, just that it comes back each year and stays green for quite a long time.
Are there any other contenders? Is there a particular sort of clover that is specifically suited for this? Perhaps some form of cactus that can survive a few snow days? Some sort of sunlight-resistant moss? A nice-looking lichen?