Day length sensitivity is an important factor to consider when scheduling your fall plantings of ornamental grasses. This can vary in intensity between grass species and can have a huge impact on whether or not your fall plantings finish on time.Long-day grasses (such as Panicum virgatum) will grow and flower when days are long, and short-day species (like Muhlenbergia
As day length decreases, long day grasses will finish flowering and move toward dormancy, while short day grasses will initiate flowering. It should be noted that it’s actually the length of uninterrupted darkness that truly controls this response in plants, which is why night interruption works. With that said, we’ll still call it day length because everyone else does.
Day-length sensitive grasses
Day-length sensitive grasses like P.
You can help extend this period by extending day length with supplemental lighting. This can be done by reducing continuous night length by lighting at the end of the day or by providing a night interruption somewhere near the middle of the night. This might not work as well with strongly sensitive grasses such as P.
Grasses that aren’t as sensitive
For species that are not as sensitive, such as Pennisetum sp., extending day length can give you a little leeway when trying to get plants finished before they shut down or even keep them growing through the winter. Keep in mind that grasses like P.
At the other end of the spectrum, you have other grasses that don’t really seem to care if the sun is out for eight hours or 14 hours. Some crops don’t have a dormancy photoperiod response to speak
The bottom line: You want a finished plant with a solid crown and good root mass that shifts its energy stores into its root system as it moves into dormancy. Whether the grass you’re growing does this in September or December, your goal is the same—have well-rooted finished pots. This will improve overwintering success and help plants come out in spring with vigor.
When to pot
Adjusting your potting schedule to account for the different finish times based on dormancy gets rid of a lot of these problems. I’m a big fan of designing problems out of systems. Potting crops up on a schedule that gets them finished at the correct time solves a lot of problems before they start.
One way to control crops with a strong photoperiod response, such as P.
If you have potting schedules or other constraints that force you to do all of your potting at once, changing your liner size can also help control finish times. Starting with a larger liner can shorten finish times and get your crops finished on time.