Lines 11-19 Summary

Get out the microscope, because we’re going through this poem line-by-line.

Masses of flowers
load the cherry branches

Now she describes the cherry tree, which is also in bloom.
There's that word "masses" again, and the repetition is important to note. The beauty of the flowers is being compared to a burden, and the sense of it weighing her down is made even more powerful with the word "load."
Who knew flowers could be so heavy?
Of course, we have to ask, is it really the flowers that are heavy? Or do they just seem heavy because something else, like, say, her grief, is heavy, too?
Whatever the case, there is clearly a connection between the way this widow sees the natural world around her (mainly in her yard), and the way she feels emotionally about the death of her husband.
Which makes sense, if you think about it. When we experience loss, it tends to change the way we see the world around us, right? Just as when we experience joy, everything around us seems just a little bit shinier.

and color some bushes
yellow and some red

Flowers, flowers everywhere! There are blooms on the bushes in the yard as well, some yellow and some red. Gosh, these colors are even more vibrant than the bright white of the plum blossoms.
She seems to be making note of the power that flowers have to color or transform things – in this case the bushes in her yard.
It's spring, the time of transformation. What can this tell us about her inner state? We'll just have to keep reading to find out.

but the grief in my heart
is stronger than they

After such beautiful flower imagery, these lines give us the Big But. As it turns out, the force of the grief she feels is greater than the brightness and renewal of the flowers.
You see, she notices the transformational nature of the flowers, but it doesn't quite work on her anymore. Her inner grief is just too powerful.
Now that her husband is dead, she both mourns his loss and the loss of spring, which no longer seems quite as beautiful as it once did.

for though they were my joy

These flowers used to be her joy, and why shouldn't they have been? They sound downright gorgeous. This metaphor, which is given to us in the past tense, shows us just how much has changed.
Flowers, and by extension all the color and renewal of nature during spring, used to give her great pleasure. Maybe she was a gardener. Maybe she and her husband used to enjoy gazing at the flowers out their window.
In any case, none of this is true anymore. All the joy she used to find in those flowers is gone, which makes her current state all the sadder.
The flowers are still there – they haven't changed – but the widow can't find pleasure in them, and the loss of that pleasure parallels the loss of her husband. It seems her grief is all consuming.

formerly, today I notice them
and turn away forgetting.

Now she's not moved by the flowers; she turns away from them and forgets them.
She really seems to be emphasizing how things have changed. Her experience was one way before, and now it's very different.
"Forgetting" is an interesting word choice, don't you think? We assume it means that the flowers are now so unimportant to her that she forgets them right away.
Or maybe she's referring to the fact that she has forgotten what they used to mean to her.
At any rate, it also reminds us of all the things she cannot forget: the memories of her husband; his absence; all the thoughts that weigh on her now, and that have spoiled her relationship with the natural world.