Error when relating tables in laravel 5.5

Veran I want to do with laravel 3 tables: Plants, User and Comments. The story is that a user can write comments about the plants to ask or answer questions about the plant.

Migration of the Plants table:

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreatePlantasTable extends Migration{
    public function up(){
        Schema::create('plantas', function (Blueprint $table) {
            $table->increments('id');
            $table->string('nombre'); // Nombre de la planta.
            $table->string('tamaño'); // Clasifica segun si es arbol, arbusto o hierba. 
            $table->string('flor'); // Si tiene o no flor.
            $table->string('hoja'); // Si es de hoja caduca o perenne.
            $table->text('descripcion'); // Caracteristicas del vegetal.
        });
    }

    public function down(){
        Schema::dropIfExists('plantas');
    }
}

Migration of the user table:

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateUsersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('users', function (Blueprint $table) {
            $table->increments('id');
            $table->string('name');
            $table->string('email')->unique();
            $table->string('password');
            $table->rememberToken();
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('users');
    }
}

And the migration of the comment table:

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateComentariosTable extends Migration{
    public function up(){
        Schema::create('comentarios', function (Blueprint $table){
            $table->increments('id');
            $table->unsignedInteger('usuario'); // Primero creas la variable. Luego creas la relación foranea.
            $table->foreign('usuario')->references('id')->on('users');
            $table->unsignedInteger('planta'); // Primero creas la variable. Luego creas la relación foranea.
            $table->foreign('planta')->references('id')->on('plantas');
            $table->text('comentario');
        });
    }

    public function down(){
        Schema::dropIfExists('comentarios');
    }
}

The index.blade.php code:

@extends('layouts.app')
@section('content')
<div class="row">
    <div class="col-md-8 col-md-offset-2">
    <h1 class="text-center text-mute"> {{ __("Plantas") }} </h1>
        @forelse($planta as $plantas)
        <div class="panel panel-default">
            <div class="panel-heading">
                <h3><a href="plantas/{{ $plantas->id }}">{{ $plantas->nombre }}</a></h3>
                <span class="pull-right"> {{ __("Comentarios") }}: {{ $plantas->comentarios->count() }} </span>
            </div>
            <div style="background-color:#00AA00; color:#000000;" class="panel-body">
                <h4>{{ $plantas->descripcion }}</h4>
            </div>
            <div class="panel-body">
                <b>Tamaño:</b> {{ $plantas->tamaño }}<br>
                <b>Flor:</b> {{ $plantas->flor }}<br>
                <b>Hoja:</b> {{ $plantas->hoja }}
            </div>
        </div>
    @empty
        <div class="alert alert-danger">
            {{ __("No hay ninguna planta en este momento") }}
        </div>
    @endforelse
    @if($planta->count())
    {{$planta->links()}}
    @endif
    </div>
</div>
@endsection

Now I'll show the relationships between the tables.

Plants:

class plantas extends Model{
    protected $table = 'plantas';

    protected $fillable = [
        'nombre', 'descripcion',
    ];

    public function comentarios(){
        return $this->hasMany(Comentario::class);
    }

User:

class User extends Authenticatable{
    use Notifiable;

    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'name', 'email', 'password',
    ];

    /**
     * The attributes that should be hidden for arrays.
     *
     * @var array
     */
    protected $hidden = [
        'password', 'remember_token',
    ];

    public function comentarios(){
        return $this->hasMany(Comentario::class);
    }
}

Comment:

class Comentario extends Model{
    protected $table = 'comentarios';

    protected $fillable = [
        'planta', 'usuario', 'comentario',
    ];

    public function vegetal(){
        return $this->belongsTo(plantas::class, 'planta');
    }

    public function usuario(){
        return $this->belongsTo(User::class, 'usuario');
    }
}

But here's the result:

Edit: Here I include the content of web.php:

<?php

Route::get('/', function (){
    $crawler = Goutte::request('GET', 'https://duckduckgo.com/html/?q=Laravel');
    $crawler->filter('.result__title .result__a')->each(function ($node) { dump($node->text()); });

    return view('Welcome');
});
Auth::routes();

Route::get('/home', 'HomeController@index')->name('home');

Route::get('/', 'PlantasController@index');

Route::get('/plantas/{planta}', 'PlantasController@show');

Also, here I bring the Plant controller:

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\plantas;

class PlantasController extends Controller
{
    public function index() {
        $planta = Plantas::paginate(5);
        return view('vegetal.index', compact('planta'));
    }

    public function show(Plantas $planta){
    $comentario = $planta->comentarios()->with(['usuario'])->paginate(2);
    return view('plantas.detail', compact('plantas','comentarios'));
    }
}