Skip to content
opens in a new window


Mar 15, 2023

Q & A: Why Summer Perennial Production?

Darren Barshaw
Product Representative

When does summer production start and for how long? Many Spring blooming perennials require prior year Summer bulking/growing and a vernalization for maximum flower power.

tall purple flowers in the landscape

Which perennials benefit from bulking (i.e., strongly rooted and mature)? Some popular Summer-blooming perennials benefit greatly with a prior year bulking and overwintering. See chart below for examples. (links open in new window)

Class What they are used to growing Newer varieties Improvements Special Forms
Alyssum Basket of Gold-seed Golden Spring Stronger vigor, improved foliage
Armeria Splendens seed


Larger flowers and longer blooming, strong heat tolerance & summer performance

Callused Cuttings
Iberis Purity Snowsation Longer blooming with better branching, larger flowers Callused Cuttings
Spanish Lavender Anouk Primavera Greater heat tolerance, larger & darker flags, continuous flowering Callused Cuttings
Lithodora Grace Ward
Phlox divericata Blue Moon & May Breeze
Phlox subulata Drummond's Pink, Emerald Blue, Fort Hill

Eye Series from Walters,

Eye Candy (top seller)

Improved habit and better vigor
Salvia nemerosa May Night, Caradonna Blue by You, Rose Marvel Better habit in the landscape, cleaner foliage, stronger colors, easier to finish
Viola Seed varieties Halo Series Better heat tolerance throughout season Callused Cuttings

Why are high light levels important for cost-effectiveness? High light levels can be cost effective. Overall, it’s free heat. Most perennials grow best under high light levels and long days. Labor availability is also much better.

Why are long days important? You will have a fully rooted container with foliage to at least the edge of the container. This will ensure your perennials will overwinter with great success. Roots are the key to success. I would rather have more crop time on a perennial crop that is going to be overwintered, then not give the crop enough time to root out.

Summer production of perennials

For Fall sales and overwintering for Spring sales, this usually starts in week 20 through 35 in the north with a goal of week 42 to have a fully rooted plant and foliage covering the pot. For the south start week 30 through week 44.

Please make sure you have your liner orders or URC orders booked by week 14-16 for best availability. By placing your orders now for weeks 20-36 planting, we can ensure that URC supply is good coming out of our Darwin Colombia stock farm.

Also, if you use liners as your preferred inputs our rooting stations can plan to have liners ready when you need them. If our spring selling season is strong, we will have supply to meet your needs.

Contact your local supplier for availability and happy planning!

chart for summer perennial production

Reader Comments
Be the first to comment! Share your thoughts using the form below.
Post a New Comment



Click to confirm:

NOTE: Comments are moderated

Return to Blog Home
Don't miss a thing! get blog alerts in your inbox

Sign Up Now