Instead of scales, skin, feathers, goo, light, or anything like that it has something else. Instead of bones and muscle, bladders, exoskeletons or anything like that it has something else.

It communicates with odors.

Stanislaw Lem's sentient ocean in the book Solaris which has been made into two movies. He was critical of popular science fiction depicting aliens as either humanoid or something that comes from our nightmares. In either case, meeting aliens is about us. In the most recent adaptation of Solaris to film, a recording of a scientist studying Solaris claims that our enthusiasm for space exploration is a sham. We're looking for mirrors, not the truly other (aliens).

The book and movie Contact get around this problem by having the aliens take the shape of a human known by the characters (Jodi Foster's in the movie). This is to make communication more comfortable (and possible for us).

Which is interesting, because in Solaris, a deceased loved one appears to the main character, possibly as an attempt at communication, but unlike with Contact, it's painful and incomprehensible.

Side Note:

The Solaris alien is compared to an infantile God at some point in the book. I think it would have served as a decent explanation for the Cyreneacs of our experiences.

It communicates with odors. — Wosret

You're describing a plant.

Damn you noticed, lol.

You're describing a plant. — Benkei

Do you think that plants from another planet could not be intelligent?

It is difficult to imagine all of the possibilities for intelligent life, because almost anything could be possible. What would be less difficult to describe would be the kind of alien that might come to visit and that would be humanoid. Simple reason is that they have to have some way to interact and manipulate their environment to be able to construct machines.
It is really not easy to imagine a blob or slug like being being able to do such things. The same applies to ethereal or liquid beings and any other without some sort of appendages for interaction with the tools and machines necessary to reach us.

Plants already communicate, reacting to their environment. That is a certain level of intelligence already.

It is really not easy to imagine a blob or slug like being being able to do such things. The same applies to ethereal or liquid beings and any other without some sort of appendages for interaction with the tools and machines necessary to reach us. — Sir2u

Maybe they can reach us without using appendages to design machines. Perhaps their equivalent of skin is hard enough for them not to explode in a vacuum (perhaps they have an evolutionary process similar to ours and their ancestors lived in something similar to an asteroid belt). Perhaps they can consciously design the genes of their offspring and their equivalent of sex is like a human brainstorming session.

Maybe they can reach us without using appendages to design machines. Perhaps their equivalent of skin is hard enough for them not to explode in a vacuum (perhaps they have an evolutionary process similar to ours and their ancestors lived in something similar to an asteroid belt). — Ovaloid

And perhaps they fart instead of using propulsion motors. It would have to be an extremely weird being to be able to attain speed enough to launch it self from where ever it is and then be able to steer itself in the emptiness of space.

Perhaps they can consciously design the genes of their offspring and their equivalent of sex is like a human brainstorming session. — Ovaloid

How would that help them to get around? By giving their kids the ability to fart at near light speeds.

But the thing is, how would they even know we are here to come visiting? I suppose it would be possible for them to be able to detect radio signals as some animals can detect types of radiation energy that we cannot. But don't you think that if they had that ability they might also be able to breed in the ability to communicate with us by using it instead of coming here directly?

Plants already communicate, reacting to their environment. That is a certain level of intelligence already. — Benkei

Yes they are intelligent to a certain level, but they would have to purposefully interact with their environment which ours don't. I think it is more that possible that in some other place they have developed this ability.

Yes they are intelligent to a certain level, but they would have to purposefully interact with their environment which ours don't. — Sir2u

Why must they?

How would that help them to get around? By giving their kids the ability to fart at near light speeds. — Sir2u

Maybe that would be their substitute for human technological advancement.
Maybe they didn't have that ability at first but they gave it to their offspring.

Why must they? — Benkei

Would it be possible for our plants to get into space?
No way unless they develop the ability to manipulate the environment to their benefit instead of just being affected by it. That doesn't mean that they don't affect their environment just that they don't do it deliberately.

Would it be possible for our plants to get into space?
No way unless they develop the ability to manipulate the environment to their benefit instead of just being affected by it. That doesn't mean that they don't affect their environment just that they don't do it deliberately. — Sir2u

Sure, I'm just not clear why they must be able to do this? Are we just trying to fit the bill for them being aliens that can visit earth from outer space? Where's the requirement coming from?

Sure, I'm just not clear why they must be able to do this? Are we just trying to fit the bill for them being aliens that can visit earth from outer space? Where's the requirement coming from? — Benkei

Ok, do you think that earth plants could reach another planet? It is obvious that in their present state, even taking into account the fact that they can communicate, they would not be able to reach the other side of the road by themselves.

But if, if the distant future, they developed the ability to create things from the environment in which they live they might develop the ability to travel in space. I don't find it hard to imagine that plants could develop appendages and thinking/reasoning capacities enough to be able to construct things, at least not as hard as a blob.