Laidback Gardener Tip of the Day

Not Too Late to Save Your Purple Fountain Grass

Pennisetum x advena ‘Rubrum’

Even if you’ve already had a frost or two (I certainly have!), it’s probably not too late to save your purple fountain grass (Pennisetum x advena ‘Rubrum’, formerly P. setaceum ‘Rubrum’) from the cold.

This beautiful grass, with reddish-purple foliage and foxtail-shaped flower spikes that dance in the slightest breeze, is a very popular summer garden and container plant. However, nurseries offer it as an annual, so most gardeners simply leave it to freeze in the fall, assuming it’s doomed to die anyway. But it is not in fact an annual, but a tender perennial grass (zone 8 or 9) you can easily overwinter indoors.

And, as mentioned above, it is probably not too late to save your plant, as it will tolerate quite a bit of frost: down to about 15?F (-10?C). So if you act quickly, before the real winter cold sets in, you ought to be able to bring it indoors while it is still in good shape.

Easy to Overwinter

Container-grown purple fountain grasses are simple to bring indoors: just clean off the pot and carry them in. If yours are planted in the garden, you’ll have to dig them up and put them in a pot.

Like most ornamental grasses, purple fountain grass does best when you cut it back drastically to remove old leaves. Do this when you bring it indoors, cutting back both flowers and leaves to about 2 or 3 inches (3-5 cm) high. Place the plant near a sunny window in a heated room. Normal room temperatures are fine as are cooler rooms with night temperatures down to about 40?F (5?C).

Water the plant like any houseplant, when the potting mix is dry to the touch. Don’t fertilize it for now, though: you don’t want to encourage rapid growth while the sun is so weak: that will only give floppy, etiolated leaves. So put the fertilizer away and let slow and steady be your motto, at least until the longer days of spring.

Plant resprouting after a harsh pruning. Note the leaves indoors are green, not purple.

Note that though the foliage will grow back fairly quickly after the plant’s severe pruning, its new leaves will probably entirely green or only slightly reddish: that’s because the plant’s purple coloration only truly comes out when the plant is exposed to intense sunlight, as in outdoors. Indoors, your plant will look more like a pot of ordinary lawn grass than the splendid purple fountain grass it becomes in summer!

In March, divide the clump and repot the divisions. This will give you more plants to put outside for the summer!

When there is no longer any danger of frost, gradually acclimate the divisions to outdoor conditions and pretty soon you’ll have striking purplish red grasses with swaying flower spikes to brighten your garden all summer!

No Seeds

Do note that you can’t grow purple fountain grass from seed: it’s a sterile hybrid, P. advena ‘Rubrum’, resulting from a cross between African fountain grass (P. setaceum) and P. macrostachya ‘Burgundy Giant’. That’s good news for Southern gardeners (zones 8 and above), as the species P. setaceum is highly invasive and growing it is illegal in many areas. Since it is sterile, however, purple fountain grass can be grown in tropical to subtropical climates without fear that it will escape and become a menace.

Other Tender Pennisetums

Pennisetum x advena ‘CHerry Sparkler’

Purple fountain grass has given rise to a few cultivars with variegated foliage, like P. advena x ‘Fireworks’ (red, pink and white), P. advena x ‘Cherry Sparkler’ (pink, white and green) and P. x advena ‘Skyrocket’ (green and white). All require the same winter treatment as purple fountain grass.

Pennisetum x First Knight™

There is also a group of pennisetums with purple foliage but that share a different background. Derived from crosses with Napier grass (Pennisetum purpureum), they are grown as perennial grasses in zones 9 to 12 and as annual grasses in temperate areas. They are popular for their dense clumps of fairly broad, deep purple leaves. Napiter grass hybrids don’t bloom in short season climates (actually, they rarely flower even in the tropics). This group includes such cultivars as ‘Prince’, ‘Princess Grace’, and First Knight™. Like purple fountain grasses, since these varieties are not true annuals, they can be kept indoors over the winter. Just treat them the same way you would purple fountain grass.

Pennisetum glaucum ‘Red Baron’

On the contrary, another ornamental pennisetum, pear millet (P. glaucum), which has given several cultivars with colorful leaves, like ‘Purple Majesty’, ‘Purple Baron’, ‘Jade Princess’ and ‘Purple Jester’, usually is grown an annual, even in the tropics. It’s normally multiplied from seed that you then resow the following spring. If you have one of these in your garden, you can then collect its seeds now… if the birds haven’t already eaten them all!

Hardy Fountain Grasses

Pennisetum alopercuroides

There are hardy fountain grasses, too, Chinese fountain grass (P. alopecuroides) being the species most often grown. It has provided many worthy cultivars (‘Hameln’, ‘Moudry’, ‘Foxtrot’, ‘Little Bunny’, etc.), all with the attractive arching foxtail flower spikes that give purple fountain grasses such grace. Chinese fountain grass cultivars are hardy to USDA zone 5 (AgCan zone 6) and will grow in even colder zones with a little winter protection.

Oriental fountain grass (P. orientale) is just a lovely and about as hardy, with pinkish foxtail spikes. ‘Karley Rose’ is the best known cultivar.

Hardy fountain grasses don’t need to be brought indoors over the winter.

8 comments on “Not Too Late to Save Your Purple Fountain Grass

  1. Milton C. Craighead, Jr.

    how do I maintain First Knight Napier Grass during the cold Michigan winter? Last winter the plant died and I had to dig out and plant new purchases of the same plant.

  2. Pingback: Why Is My Purple Fountain Grass Not Purple? 27 Most Correct Answers -

  3. I was happy to find this article and would love to overwinter my 8 large Fountain Grass. But I don’t have much light for them in the basement where I would need to store them and there is no room for any of them upstairs all winter. I see online there is another approach: Also to cut them back and keep them lightly watered and alternatively to store them in a dark space in a cool room until March. In March you bring them into the light for new growth and once there is new growth and warm enough, you then harden them off outside. Note: My space is not cool, but not as warm as upstairs. That approach will be easier for me because there is little light in the basement. Will that approach work as well here in eastern Canada? Also, I am a bit concerned about bringing insects into the house. If I continue to leave them outdoors for some frosty weather (above – 10 C) will that kill off all the bugs? It was -1 deg C yesterday and the plants still look great. Thank you!

  4. Hi Larry,

    I recently purchased Pennisetum ‘Burgundy Bunny’ (Hardy Fountain Grass). I don’t really consider them hardy for my area (Gatineau). What would be the best insulation material to ensure winter survival? I’m thinking garden soil (similar technique used for hybrid tea roses). What do you think? As insurance, I could take a small division in October to ensure I get succession following spring.

    • It’s essentially tropical: whoever prepared the table simply goofed: the word “hardy” doesn’t belong there! You’d have to overwinter it indoors.

  5. Can I leave my
    Purple Fountain Grass out for the winter & cover it with something? Ive just planted it this spring & I don’t want to dig it out because I have laid landscaping material down to keep the overload of weeds out & being fairly crippled up, makes it very hard to tend to. I was told when I purchased it that it was perennial, If I can cover it with something, Please tell me what to use. Thank-You ever so much, have a good day……

    • I’m assuming you live in a very mild climate, hardiness zone 8 or 9, and if so, you can without using any protection, or in zone 7, where you should be able to keep it alive by covering heavily with a mulch like chopped leaves. In colder areas, I don’t think any kind of mulching will help. It’s just not a hardy enough plant.

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