Xpath: how to select an option based on its text not value property?

consider both types:

<select name="garden">
    <option>Flowers</option>
    <option selected="selected">Shrubs</option>
    <option>Trees</option>
    <option selected="selected">Bushes</option>
    <option>Grass</option>
    <option>Dirt</option>
</select>

Is @val for actually indicating the value="" attribute ?

Is @value for indicating the innerText value ?

for example what happens if <option> doesn't contain any value="" property. how would you select it then ?

select/option[@value = "Grass"] 

Does Xpath automatically ignore white spaces for the case above? Should it be trimmed?

EDIT:

for selecting multiple options would this suffice ?

select/option[normalize-space(text())="Grass" or normalize-space(text())="Trees"]