I would suggest they use a variety that has no scent. Supermarket freesias, and roses, etc have no scent. Shame.
All the things you mention are in the soil for a long time. If I were you I would take Dove's advice and grow things which are quick to give results.
Don't bother with Glyphosate - they are very easy to pull up.
Received wisdom is that one third of the branches - the oldest - should be removed every year.
Before you do anything establish what they are!
Frankly they are better gone. They were out of scale and just wrong. Rest easy, you have done the right thing.
Never pick beyond the longest day. I don't know if this applies to young asparagus plants like yours, but it does to older ones.
You don't bear them any ill will - so you killed them!!
Make sure to spread lots of seeds where you do want them later in the year.