Question: The following stanza is from Robert Frost's *Into My Own*:

> 
> One of my wishes is that those dark trees,  
> 
>  So old and firm they scarcely show the breeze,  
> 
>  Were not, as ’twere, the merest mask of gloom,  
> 
>  But stretched away unto the **edge of doom**.
> 
> 
> 

(Emphasis mine.)

I am guessing that the "edge of doom" is referring to the end of time -- as in, The trees are stretching into the end of time and space. Is this reading correct? Where does the phrase the "edge of doom" come from? At first when I read it, I thought that the "edge of doom" was a dark reference (similar to "mask of gloom"), but it seems to be closer to a wedding vow, such as "Our marriage will last unto the edge of doom".

Answer: 
Your reading of the poem makes sense. It might help to know that the dark trees are symbolizing the future in this poem. The second line tells us that these trees rarely show a breeze. This means that we cannot predict the future. 

In the fourth line, Frost expresses his wish that those dark trees in the first line were stretched away to the edge of doom. This means that he hoped that the future is stretched far away. So, the edge of doom means here far away (in time). This seems consistent with your view, since it is also used in that way in the sentence you quoted, "Our marriage will last unto the edge of doom". 

Based on: [Analysis of "Into My Own"](https://letterpile.com/writing/Robert-Frosts-Into-My-Own-Analysis).
In Sonnet 116 of Shakespeare, we also find the phrase "the edge of doom":

> 
> Love's not Time's fool, though rosy lips and cheeks  
> 
>  Within his bending sickle's compass come;  
> 
>  Love alters not with his brief hours and weeks,  
> 
>  But bears it out even to **the edge of doom**.
> 
> 
> 

Indeed, it suggests "the end of time", since according to the sonnet, love could not be altered by hours or weeks (weight of time), nevertheless Love will remain and bear the time out until the end of time and space.