What is this tall perennial with fragrant white flowers?

Question

My grandmother brought me a bunch of shade-loving plants from her garden to help me fill in a few gaps in my own. She had most of them identified but this one had her stumped. Here's what I know from her:

This is a perennial that thrives in shady conditions. It grows about 5 foot tall and produces small, but very fragrant, white blossoms in July or August. It spreads easily without human intervention. It was found in New York and may be a native species, but that is not guaranteed.

This is a picture of the plant a few weeks after it emerges in Spring:

Early Summer Update: Flower buds have formed.

Answer 1

I am confident that this is Valeriana officinalis.

"Valerian is a perennial flowering plant, with heads of sweetly scented pink or white flowers that bloom in the summer. Valerian flower extracts were used as a perfume in the 16th century." ~ Wikipedia

Description: https://davisla.wordpress.com/2013/07/19/plant-of-the-week-valeriana-officinalis/

How to grow: http://theherbgardener.blogspot.ca/2013/04/how-to-grow-valerian.html

Identification images: http://wildflowerfinder.org.uk/Flowers/V/Valerian(Common)/Valerian(Common).htm

Descriptive identification key (Expand "Show All Characteristics"): https://gobotany.newenglandwild.org/species/valeriana/officinalis/

Answer 2

If the flowers on this plant are long, cone shaped, yet still small, it's Cimicifuga racemosa, also known as Actaea racemosa, common name Black Cohosh or Bugbane. Perennial, flowers around July, does well in shade, highly fragrant white flowers, height up to 6 feet, usually between 4 and 6 feet, including the flowers - the first link shows the leaves, flowers and seeds, the second is general information. Depends on whether you can remember what the flowers are like as to ID of Valeriana or Actaea!

http://swamptromp.tumblr.com/post/105698124917/plant-2-black-cohosh

http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=j790

Answer 3

Missing a picture of the blossoms, I can only go by your description and the leaves.

Going by the leaves, the love of shade and the scent, I would identify this is an astilbe. The tiny flowers are then clustered in large "feathery" or "cloud-like" plumes above the leaves, mostly upright, but there are also cultivars with more cascading flowers. Some cultivars are heavily scented and typical colours are white and pink tones. Leaf shapes vary a bit, from very narrow and serrated to more broader types and smoother rims, a lot of hybrids were created over time.

Astilbes like damp (semi-)shade, e.g. along ponds and can tolerate heavy clay. They multiply and spread easily if they like the conditions.