The buzz around short-day liners is most likely accompanied with confusion regarding their necessity and proper usage, but they are helpful for many reasons. The importance of short-day treatment is to delay the onset of blooming in perennials. This extends the selling season by allowing finished growers to offer a second round of flowering plants.
With short-day treatment, flowering Echinacea purpurea and Rudbeckia fulgida can be late summer or fall crops. The same protocol works for both genera. Short-day treated starters have lots of pent-up energy, which makes them a natural addition to the finished grower’s toolbox and a great way to take advantage of the limited window fall provides in most of the country.
With this in mind, short-day liners could add value and provide some great additional opportunities your operation isn’t currently capitalizing on during shoulder season.
HOW IT WORKS
In late spring to early summer, day length triggers the plant to bud naturally, which results in big, beautiful Echinaceas and Rudbeckias that sell so well. But, if they’re grown for the fall, day length tries to trigger the plant again. Unfortunately, the plant isn’t ready — it’s too immature. Without a pause in the development of the plant, it wants to bud prematurely. If that happens, there will be irregular buds and small plants.
With short-day liners, the plant is tricked into thinking it’s earlier than it is. Flowering is controlled (i.e., delayed) via day length manipulation. Essentially, it’s replicating what happens naturally in the spring. It sounds simple, but it’s anything but, as evidenced by the fact that few growers try it, or once they do, they give it up.
Because it’s so rigorous, growing short-day liners is not something everyone can or will do. It requires hands-on management with emphasis on providing well-branched plants. Echinacea don’t always break evenly, so when you’re growing short-day liners, focus on ensuring that.
Light exclusion must be very thorough. Shaded isn’t good enough; it has to be dark. These plants get ready to bud at about 14 hours day length. So, you must limit the day to less than 12 hours.
Just as important: that darkness must be consistent. Every day, you have to provide blackout. It must be done seven days a week. The cover has to be open in the morning and closed in the evening. That needs to happen every day, even on the weekends — which means that unless you’re highly mechanized (and sometimes even if you are), someone has to be at the greenhouse very early and very late each day.
Covering them every day is a challenge because if too much moisture is trapped early, it can present a host of issues. Heat buildup can be a killer too. We all know what happens when plants get too hot and moist, and it isn’t pretty.
So what happens if total blackness isn’t provided, and/or isn’t consistent with your blackout? It’s not going to work. It will result in small plants and uneven bud initiation. There will be some flowers, but the flowering wouldn’t be consistent.
With Echinacea ‘Cheyenne,’ for example, there will be late summer to fall colors, so you don’t want a bloom here, a bloom there. That irregularity would completely take away from the salability of the plant. Not to mention, it wastes all the labor and time spent growing those special liners.
WHAT TO DO WHEN YOU GET YOUR SHORT-DAY LINERS
It’s very important to plant promptly. It’s advised to plant short-day liners as soon as possible after receiving them. That’s because when they arrive at your greenhouse, they’re being exposed to natural day length, so they’re being told it’s time to react. That makes it critical to get them transplanted in a timely manner.
Plant in June or July to finish for late summer or fall. And transplant them into a well-drained media, such as a perennial nursery mix. If you’re buying short-day liners of an Echinacea like Cheyenne, which is a mix, it’s recommended to plant three or more plants per 2-gallon pot or deco container. Even three to five per pot is good.
Then, treat them as you would any Echinacea. Bud initiation will be noticeable in approximately three to four weeks after planting. Keep plants well-spaced and they should finish in eight to 10 weeks.
Feed with a balanced fertilizer containing at least 150 ppm nitrogen in a slow release or liquid. Maintain soil pH at 5.8 to 6.2 and soil EC (electrical conductivity) at 1 to 1.5 mS/cm using the 2:1 extraction method.
Make sure a good growing spot is chosen if they’re placed outside. It’s recommended to be in a place with lots of light — ideally full sun. Place in full sun outside or provide a minimum of 5,000 foot candles inside. Using a negative DIF will help prevent stretch.
They’re much more likely to stretch in the greenhouse, so PGRs are recommended if they are being finished indoors. Utilize a PGR application, approximately 2,500 to 5,000 ppm of Dazide or B-Nine. The nice thing about Dazide is that it’s a short-lived effect, so you don’t have to worry as much about over-applying. No pinching is necessary.
If the foliage is wet, foliar diseases may arise, so try to keep water off the leaves. Drip irrigation, if available, is safer than overhead watering. A routine foliar application of fungicide should help with prevention. Prevention is the real key here. Don’t wait until there are spots on the leaves to treat.
This is an actively growing plant, so it doesn’t like to wilt. But also, don’t let it sit in water or it’ll get root rot.
If you’re growing outside, watch for pests like caterpillars and spider mites, but you shouldn’t encounter anything too unusual. Keep an eye out for aphids, whiteflies, thrips and aster yellows as well.