Host an Event Volunteer Join Tickets

Support the plant database you love!

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
See a list of all Smarty Plants questions

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

 
rate this answer
Not Yet Rated

Wednesday - March 18, 2009

From: Newburgh, NY
Region: Northeast
Topic: Pruning, Seasonal Tasks, Herbs/Forbs
Title: Cutting back achillea in New York
Answered by: Barbara Medford

QUESTION:

Last summer I planted three gorgeous hearty achillea with flat, yellow tops, about 3 feet high or more each, in my sunny garden. But after they were done flowering, I left those very pretty brown stems and heads right where they were. It's still cold up here in upstate New York. Should I cut them back and if so, how far?

ANSWER:

You can certainly cut back the perennial Achillea millefolium (common yarrow) in the fall or early spring. It was a good idea to leave the stalks and heads where they could add some interest to the winter garden. Care of most herbaceous perennials suggests cutting back the stalk after it dies back, and cleaning up the area around the plants to prevent mold, insects overwintering and disease. We like to leave about a 6-inch stalk when we trim back perennials to mark their place so, when the first leaves start coming up from the roots, you will not think it's a weed and pull it out. The yarrow in our Image Gallery are all white, but we found this Magnolia Gardens website with a picture of the "Moonshine" cultivar in yellow. 

 

From the Image Gallery


Common yarrow
Achillea millefolium

Common yarrow
Achillea millefolium

More Pruning Questions

Pruning lower branches of Cordia Boissieri from San Antonio
December 08, 2013 - My Texas Wild Olive Tree is about 6 feet high now. I bought it at the 2012 plant sale. This past summer it put on new branches near the base of the tree which I would like to cut off (to encourage u...
view the full question and answer

Pruning Wax Myrtle trees & bushes
February 28, 2016 - When is the best time of year to prune Wax Myrtle trees & bushes.
view the full question and answer

Lilies not blooming from Austin
May 03, 2013 - Last December 8, you published a letter in the Statesman that I had written to you regarding Rain Lilies, Oxblood Lilies, and Copper Lilies. The were sprouting in my garage in a bag. You recommended...
view the full question and answer

Questions about care and pruning of Mexican Plum and Mountain Laurel in Austin, TX.
January 24, 2012 - I have a couple of questions regarding tree care and pruning. I have a Mexican Plum (Prunus mexicana), about 10 years old or so. I would like to prune it. Is it ok to prune now in late wi...
view the full question and answer

Care for penstemons in South Jordan, UT
June 21, 2009 - I have Firecracker Penstemons and they bloomed beautifully this year. How do I trim them and when? Will they continue to bloom throughout the summer?
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.