What potted outdoor plant most resembles astroturf in terms of required care

Question

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?

Answer 1

Highly restricted range, I'm afraid - even air plants need misting regularly when they are not in humid environments, plus they won't survive low temperatures. Some cacti varieties might work, but will need watering occasionally and need to be under cover in winter; if your balcony has a roof, that might suffice, see here

http://www.organicauthority.com/cactus-varieties-for-cold-weather-climates/

There are drawbacks with most cacti though, which are that many varieties have sharp spines, and that's not ideal in a small area.

Sempervivum varieties,commonly known as houseleeks, might survive quite well, but will need watering until they've grown on a bit, after that, they may be fine being completely ignored, but do better in trough like (shallow but wider) containers than individual pots over time, see here

http://www.gardenersworld.com/plants/plant-inspiration/growing-sempervivums/

In a small pot, relying on rain to keep the plant watered, no matter how regular that rain is, won't work well because unless its a large pot and a small plant, rain will not enter the pot. Any small amount which might won't be sufficient for most plants either.

If you don't like the idea of cacti or sempervivum, I'm afraid you'd be better off choosing a very good fake plant, which needs absolutely no care at all other than occasional dusting/cleaning - but in sunlight, it'll fade.