This haiku has me both excited and confused but...it is most definitely a haiku or....is it? Suffice to say, I do love it anyway so...here are my thoughts...

Pan chased springtime dreams

This is where my excitement/confusion comes from because...Pan is a person from mythology...(I think?) so...he is not someone you would have observed/experienced in your daily life...I mean..there's no way you would have come across him so..does that break the rules in haiku...yes it does but...I did like the notion here...
as whimsical Lilacs cried;
^^^^
This is a nice follow up line and quite in fitting with a haiku.

a purple story.

^^^

I was slightly disappointed with the last line to be honest...if Pan is, in fact, who I think he is he should have more impact....

a purple legend

a purple epic.....something like that...he needs some oomph haha!!!

I agree with Hellon that story should be changed to legend. It would fit perfectly in the syllable count and make the ending much stronger.

Dashiel- This poem has such a beautiful flow and tone to it. I believe the way you write about flowers is the best I have ever seen. Okay. First of all spring time is great to use here. And that's when all the flowers seemto sstart to come to life. I like the use of dreams as well. I think what you are saying is that with a new birth becomes new dreams.

Lilacs are very beautiful and I believe underrated as a flower. The imagery is impactful in so many ways here. I like the use if the word cry here. And the word whimsical is outstanding as well. It seems to me you are saying that there is some kind of magical beauty inside the purple of the lilac and when you look at it's beauty you feel heart warming and happy. There is nothing much more I can say here. This poem is gorgeous.