Could be this a new trend on green cars?  

Ha Ha !  How old is your car ?
There are drain holes in the bottom of the door, to let rain water out.  How soil -- call it "growing medium" -- got in there -- and the seed(s) -- is beyond me.  But I'd take the interior door panels out and clean up.  Or, you could wait until rust does the job for you -- everything will fall out, sooner or later. But by then you might be driving around in a Jungle Car !

I´d love to say that the car is 10 months old, with 10 months of ¨growing medium¨on it, OR that is 44 years old  (and I wash it daily since the first day). But I´m not as cooler as any of the options. It is 2 1'2 years old.
Indeed, to clean it, is easier, it is not in the panel, is in the rubber, and could clean it easy.... But I can't kill that nature, perhaps put it in a pot. 
But, but, but....driving In a ¨Jungle car¨, That,s It, a car full of plants.

Yeah -- cool idea, no ?  As you say, "Green" to the max !  You might start a revolution.

Ha Ha...Sure!
I don't know if a revolution, but your Jungle Car sound so great, that's hard to resist.
Something like this....

Why the hell don't cars come with big solar panels on their tops?

That's great, Gustavo -- why not !  Buildings now have vertical gardens growing on their sides . . .
Yes, why not, objectworship . . . ?

If the purpose of the solar panel would be to charge an electric vehicle's battery, I don't think the numbers work out well.
Let's assume there's room on the car's roof for a 1-square-meter solar panel.  In the USA, a panel that size will typically generate 0.75 kilowatt-hours per day if it's outdoors and unshaded all day.  Average electricity cost across the USA is 13 cents per kilowatt-hour.
0.75 kWh/day times $0.13/kWh = $0.10/day saved by the solar panel if you let your car bake out in the sun all day, every day.
It's left as an exercise for the reader to determine the break-even point by dividing the installed retail cost of the solar panel by $365/decade.
 

Well that answers that.  Gardens are prettier anyway.

Right -- sadly.  But the solar panel(s) might be able to run the radio . . . ?
The only cars able to propel themselves by solar power are ultralight single-seaters shaped roughly like a sheet of paper on wheels, where every square inch of opaque bodywork on the upper side of the car is covered with photovoltaic cells.  These cars win college-level tech competitions, by travelling some hundreds of miles -- as I recall it.

Update
 
Hi Object! Yes! why not?
When you said, roof car, the only other use came to mind was….ads…, will be possible to combo both?  (from heaven to hell.. non stop…..)
 
Hi Fastfwd!
Nice to meet you!, I always read your comments, your rationality, and the hard numbers here are very helpful, to me at least.
And the comments and always very interesting: sometimes very interesting because I agree, and other times much more interesting, cause I think the opposite 🙂  
The main reason I think,  I guess you work in the "industry"; and me... in another….:
In this case, for instance,
You work in the hard industry of making things, and here I'm working on the industry of manifestos and experimentation…
That,s why I think:
what are $ 365.00…  to start a revolution !!!
 
Helllooo SDR! Yes, you said it, the green walls in buildings!, that’s is the image I had mind indeed!

Is it parsley?  (in the very first photo  #1 post)
I think it is…:
Double green then…, your farm in your car
“Your mobile farm jungle” ...
 
Perhaps the plant grows because an unconscious envy on me, when I saw this last February, summer here, the van that's in the next photos, in Villa Crespo-Palermo, 5 blocks from the trendiest district….
 
What an envy….Those are pumpkins flowers, with (real) pumpkins!
 
I was following how the pumpkins were growing, when passing…(with the car, by the way) every week, but in less than a month,, the van was removed !!!!. I don,t know if it were the people, provably the goverment because the people asked…such a cruel world!
 
Or perhaps the plant grow because of  my car, that felt how happy I was, and felt jealous…., and said, I can do it too…I will grow you parsley, you´ll see.
I don,t know, I don,t know.

Not exactly a new concept, apparently.
Sorry to interject, but this was too good to not post:
 
http://www.youtube.com/watch?v=NET86rSnMI8
 
 

Thanks Tktoo, Not interjecting at all! 
It´s great.

The project goes better now...
 
As I imagined , the use for these ideas, if dosen’t work as a revolution, at least end as a commercial use / advertising campaign. ( At least didn't end in a drawer, and people will see that we are that not that crazy….    🙂
 
😉
After large negotiations, the brand accepted the idea, and the first prototype was made.  
And yes, the logo will be made with solar panels.  
😉