Perennial Season Extension Trial

This research grant was started in 2008. At the time of the grant award, some of the sought-after varieties were unavailable. The 2008 drought caused much of the planting to be pushed back to 2009. We also ran into space limitations as some of the field areas where they were to be planted, were overrun with pernicious, perennial grass.

2009 was another tough year in our area with almost constant rain until September. Spraying, fertilization, weeding and even harvest were often delayed. 2009 started out with a deep late May freeze that nipped some of the heleniums in pots.

Our farm is in the mountains of North Carolina in zone 6. We have been experimenting with several perennial varieties, using pinching as a means of lengthening their bloom period. We chose the varieties because they are relatively easy to grow and we wanted these varieties to have bloom periods long enough for our customers to get to know the flowers. We especially wanted the orange and red heleniums to bloom later when those colors are “in” for fall.

The varieties used were: Phlox ‘David’, ‘unknown late pink’, and ‘Blue Paradise’; Helenium ‘ Coppelia’, ‘Mardi Gras’, ‘Flamenspiel’, ‘Kanaria’, and ‘Tiny Dancer’. That’s how it all started anyway. Helenium autumnale species was unavailable so we substituted Helenium ‘Red Shades,’ which was started from seed in 2008.

Some important notes on what we learned right away: Helenium should be planted in the spring, not the fall. Helenium flexuosum ‘Tiny Dancer’ rotted in pots over the winter. All of the Helenium and Phlox varieties get powdery mildew, even when sprayed with organic solutions. Other pest problems that now limit our interest in these varieties include red spider mites and (possible) downy mildew on Phlox ‘David’, aphids on the yellow ‘Kanaria’ helenium, and worm issues on either the buds or flowers of all the Helenium and Phlox varieties. Starting in 2008, we had deer eating the phlox as they reside in our rented field where we aren’t allowed to operate our electric fence during the summer.

During 2008 many of the heleniums were kept in pots due to their size and our lack of prepared bed space. Most were planted in the fall of 2008.

The phlox fared much better. ‘David’ was divided in spring of 2008 but all were cut to the ground due to red spider mites and (possible) downy mildew. They were full and ready to pinch in 2009. ‘Late Pink’ was divided in spring of 2009. However, it was not established long enough to give accurate results. ‘Blue Paradise,’ my new favorite phlox, overwintered well and bloomed shorter than normal during the 2009 season.

Each variety was divided into thirds: one-third for the control, one-third for the first pinch in mid-May, and one-third for the later pinch in mid-June. We followed this fairly well, leaving only the ‘Kanaria’ unpinched as it was taken over by (and survived) a massive infestation of running mustard.

Given the 2008-2009 data limitations, we will continue our experiment into 2010, when we will hopefully have comparable sizes of mature perennials, to establish more accurate results. So far, there is great variety in initial bloom time, as well as response to pinching.

The following charts list pinches and bloom times as well as notes and comments on each variety.
Helenium ‘Kanaria’: All were soft pinched late due to major weed, then powdery mildew issues. It bloomed 7-10 days later than normal and we sold several bunches to a florist. The soft pinch did not change the bloom period. It was available August 10 to September 5 in both 2008 and 2009.

Helenium ‘Coppelia’: These were lost over winter for the third time. We used our nursery stock quarts, planted in spring 2009 for the trial. One of our earliest to bloom most years, this flower is deep red. Pinching did not change the height on this one. All were only 12-18″. This weak variety should be taller at maturity if we could get it to overwinter.

Helenium ‘Flamenspiel’: The most vigorous of the red heleniums. I suspect this ‘Flamenspiel’ is really another variety altogether. It is not blooming red like past ‘Flickering Flame’ stock.

Helenium ‘Mardi Gras’: This robust, early helenium needs another year for results. We didn’t plant it until July 15th. It may require netting or staking.

Helenium ‘Red Shades’: Pinching delayed this variety’s bloom into September, like we were hoping. However, it needs a full year in the ground for accurate results. It is easy and inexpensive to grow from seed. It substituted for Helenium autumnale.

Phlox ‘David’: I have been surprised by the disease and pest problems on this one. In 2008, we cut them all to the ground in midsummer. 2009 was a bit better, with more mature divisions. They should be worth the extra effort to extend the bloom period.

Phlox ‘Late Pink’: We chose this seedling selection for its late disease resistant nature. So far, it’s continued to overachieve. 2010 will allow us to get more accurate results from the younger divisions.

Phlox ‘Blue Paradise’: Pinching may not be necessary, as this one reblooms readily. This is our favorite variety of Phlox and the customers love it too.

This grant was supported by the ASCFG Research Fund.
To learn how you can apply for an ASCFG Grower Grant, go to and click on Research.

Susan Wright Shady Grove Gardens & Nursery Vilas, North Carolina