Question
QUESTION: I bought two small penesetum rubra plants today for containers on my porch, (with ivy planted around them). I'm not sure if they're considered annuals or perennials. I had one a few years ago which died out in winter. I don't want that happening again, even if I must bring them in for the winter. They are too lovely to let die. Can you steer me in the right direction, i.e., annuals? Proper care? Anything else??? I live in NC, zone 7B. Thank you!

ANSWER: You're in luck.

Pennisetum setaceum 'Rubrum' is a perennial ornamental Fountain Grass hybrid, sold in some venues (like Burpee) as an annual. In fact, it is a warm-season grass.  Heat-loving and drought-tolerant, it would do best if you were to move closer to the equator, to Zone 9.  There and south, it never gets what we call 'cold' up here. You know where that is?  New Orleans.  Saint Augustine.  Houston.

Still, like other warm-season Grasses, this plant likes to go into hibernation when it temps get below 50 degrees F., even in Zone 9.  Once so afflicted, it turns brown, and appears dead as a doornail (doorknob?).  Trust me, you won't like it as much if that happens.  A few more zones south and it rests without receding.  Then in spring, when temps begin to rise, it purples-up and glows brighter than ever.  And it is beautiful.

Worth a lot of trouble, if you think about it.  If you contemplate bringing this plant indoors in North Carolina for the winter, however, you may not be so happy.

For one thing, this is a full sun plant.  That, my friend, is non-negotiable.  FULL sun, as in high-noon full-spectrum 5000 degrees Kelvin daylight.  Those deep purple pigments come from anthocyanins -- the same pigment you find in Red Onions and Black Currants.  Making anthocyanins requires steady, strong light.

Also, there is also this little matter of day length that may still ruin everything no matter hat you do.

You see, under low light levels, or with short days, there's less purple.  From what I've read, succeeding indoors with P. setaceum means providing a minimum of 13 1/2 hours of light.  This was spelled out by scientists six years ago, with results published as 'Relationship of light quantity and anthocyanin production in Pennisetum setaceum' in the Journal of Agricultural and Food Chemistry.

This is quite possible to accomplish -- in theory -- indoors.  Trouble is, these Fountain Grasses are tall plants.  If you got your hands on high-watt fluorescents (the kind they use in fish tanks), you would still need to get them close enough to the leaves for best results.  And you can't do that with Grass.  Orchids and Bougainvillea are more compact.

But if you're like any gardener I know, you won't care.  You'll do this anyway.  We always do. So here's my advice to you, gardener to gardener:

When the nights start to feel like you need a sweater at 5 a.m., at the coolest time of evening, waste no time in hauling these indoors to your most sunny window or skylight.  Set up a sodium vapor or similar superlight overhead, and always keeping day length at least 13 1/2 hours.  Alternately, you can keep them indoors in a bright window where it will not be cool, and watch them languish through the fall, the winter, and the spring.  Once you're sure the weather is warm, with no surprise cold spells, you can carry them outdoors, and watch them brighten up, which will be a matter of days if they have not been dormant.

This plant can take dry heat, so low humidity will not be a problem from central heating in the dead of winter.  You probably don't have much of that down there, anyway.

Failing that, try this:  Let your grasses go to seed, harvest the seeds and save for spring.  Results should be interesting.  They may or may not grow true.  This is not for everyone, of course.

Whatever you decide, remember that this, like all gardening, is a learning experience, and that is always worth the trouble.  Good luck.  And thank you for writing,

THE LONG ISLAND GARDENER

---------- FOLLOW-UP ----------

QUESTION: Can't thank you enough for your thorough, beautifully written answer. One more question, please:  Would it behoove me to cut the purple fountain grasses back when weather gets cool, almost to the ground level? Just wondering. I voted for you as "Expert of the month", your answer was so professionally written. (Have you ever considered writing a book)???
Thank you again!

Answer
Slice and dice 8 to 12 inches off the ground as nights grow longer and days cool down, almost like mowing Zoysia.  Here's the advice of the Proven Winners company, which sells plants to professional growers:

'Rubrum is a warm-season grass... In areas where Winter temperatures remain above 20 degrees F, it should be considered a perennial.... Their major growth and flowering happens when the weather is hot.  They will usually turn shades of brown for the Winter...

'Cut back Warm Season Grasses in Fall or by mid to late Spring. Warm Season Grasses turn shades of brown as the weather turns colder. Once your Warm Season Grasses turn brown you can trim them back at almost any time.  If you like to tidy your garden in fall or if you live in an area where fire can be problematic trim warm season grasses so they are just a few inches tall.'

The full lecture is available here:

www.pwcertified.com/grower

In the event that you attempt to harvest and sow seeds of this cultivar, you should know that this would be an unusual challenge.  Although the species is invasive, this particular cultivar is generally considered sterile, although experienced researchers have in some cases a very small percentage would be viable.  Work is ongoing, because the plant is so popular.  (Can you blame them?)  Still, sowing the seeds is most certainly not going to be any substitute for holding on to the clumps and saving them; even in a laboratory, your success rate could be a fraction of a percentage.  Save and divide the clumps you have -- or let go, and plan for more next year.

I appreciate your kind words.  Thank you.

L.I.G.