Ornamental grass bomb

Ornamental grass bomb

Author:

Judith Adam

Variegated 'Morning Light' is a clump-forming ornamental grass. (Photo by Brendan Zwelling)
Variegated ‘Morning Light’ is a clump-forming ornamental grass. (Photo by Brendan Zwelling)

We’re down to the last week or two before the ground freezes, and there’s one job I’ve saved for last, because it’s the most frustrating. Several years ago I planted three small pots of silver feather grass (Miscanthus sinensis ‘Silberfeder’, Zone 5) in front of a cedar hedge. The five-foot (1.5-m) silvery plumes were beautiful against the dark green conifers, and stood out prominently in autumn. I was pleased with the planting, and noticed in the second year there were more silvery plumes. In the third year there was so much silver feather grass that it was overwhelming other shrubs and perennials in the bed; in the fourth year it was coming up in the lawn. The original three clumps had sent roots in all directions, and I began to understand how prairie grasses travel.

I’ve never heard a similar story about this grass, and wonder if I was unlucky enough to get three pots of some renegade that isn’t ‘Silberfeder’ at all. I started digging out the grass roots, and was surprised to find a deep system of tough, resistant woody runners. It was impossible to get all of them out, and each autumn I have a major digging initiative to work on removing grass runners that have spread during the summer. The runners have gone into and through the cedar root balls, so I must excavate around the cedars and then actually get tools into their roots, trying to drag out the grass runners. This is not a happy situation for the cedars, and even less so for myself.

Because of this experience, I now make a point of planting only non-running grasses. I have another Miscanthus cultivar behaving a bit out of character, and that is Miscanthus sinensis ‘Morning Light’ (Zone 6). This is a gorgeous variegated green and cream grass, and everything I’ve read about ‘Morning Light’ says it’s clump forming and non-running (I made sure of that!), and doesn’t set seed. However, it has made a baby offset, about five feet (1.5 m) away. I don’t know if it got there by runner or by seed (I suspect it’s a seedling). So far, there is just one baby that survived last winter and went on to grow a bit this past summer. If I see a second baby, I’ll rip them both out right away. But for now I’m keeping my eye on this singular offspring. ‘Morning Light’ is so beautiful, I wouldn’t mind a second clump—but I don’t need enough for a prairie!

 

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Comments

8 responses to “Ornamental grass bomb”

  1. Judith Avatar
    Judith

    Hi Tracey,

    That’s a good idea and I certainly recommend it to anyone contemplating planting this miscanthus. If I were starting from scratch, that’s exactly what I’d do——plant it in a container sunk into the ground. But as things stand, I’m done with it! Except, of course, for the remains I’ll be digging out every year forever.

    — Judith

    Reply
  2. Tracey Avatar
    Tracey

    Hi Judith
    Miscanthus sinensis is considered an invasive species in North America, mainly due to its ability to spread so quickly. It’s such a popular plant with gardeners that it won’t ever be eradicated (I have it in my own garden), but as long as we educate people and take measures to keep it contained, I think we’ll all still be able to enjoy it. I keep mine planted in a pot buried in the ground and every year dig up any runners coming from around the root area.

    Reply
  3. Judith Avatar
    Judith

    Hi Vera,

    Ah, yes, the moat system of restraint! I hope this continues to work for you, but don’t be surprised to find ‘Silberfeder’ popping up beyond the trench. It’s determined to get its way. You may someday be struggling to remove it. I think we should be looking for a substitute, another grass with pretty silvery plumes, but no desire to explore new territory.

    — Judith

    Reply
  4. Judith Avatar
    Judith

    Hi Ann,

    And I was surprised to read you have the same problem with ‘Silberfeder’! I was beginning to think I was cursed, or had a mystery grass, or that the miscanthus had reverted back to some ancient genes. I was out again today, digging into the cedars, try to get bits and pieces of ‘Silberfeder’ roots out (this practically requires dental tools). I’ll never get it all, but I set it back substantially. It really is a mistake to market a grass with such aggressive roots. I’m amazed at how woody the roots are, and with sharp points to drill through anything in their path. Looking at sources selling this grass, none mentions the aggressive spreading characteristic; and in fact, they give directions on when to divide it to make more clumps! ‘Silberfeder’ was selected from seedling ornamental grasses growing at the Munich Botanic Garden in the 1950s.
    — Judith

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  5. Judith Avatar
    Judith

    Hi Leonore,

    You’re right, chameleon plant (Houttuynia cordata, Zone 5) is a devil of a plant to get out once established. But the very pretty leaves catch a lot attention, and its most aggressive growth is in areas of wet soil. There are indications this plant has allelopathic properties–certain chemicals that inhibit seed germination and growth of nearby plants–a feature that ensures no competition for nutrients and moisture. Black walnut trees are another allelopathic plant. It’s best to treat Houttuynia like mint, and grow it in a container sunk into the ground. Thanks for reminding me about Houttuynia cordata, I haven’t thought of it since I got it out!
    — Judith

    Reply
  6. Ann Fraser Avatar
    Ann Fraser

    Hi Judith,
    I was so surprised to read that you have had a similar experience as I had with a Miscanthus sinensis ‘Silberfeder’. It was beautiful the first few years. It then sent out runners all through my perennial garden. I spent a lot of time trying to get rid of these aggressive runners and the plant. Many years later I still find a new plant starting in that garden. I only use clump forming grasses, so I was quite surprised and I wondered if I had planted a mislabelled grass. The Zebra grass I planted in its place is much more friendly with the other plants and looks great in the winter as well (does not collapse after first snowstorm). I enjoy reading your posts every week and they are so timely.

    Reply
  7. Vera Paul Avatar
    Vera Paul

    Since I did not want to totally eradicate the miscanthus variety with the resistant woody runners, I dug a trench around them to keep them at bay. They were becoming extremely invasive. A yearly project of hard work to keep them back.

    Reply
  8. Leonore Avatar
    Leonore

    Judith: The same case applies to the beautiful, but invasive Chameleon Plant. The leaf colours are glorious, two-colour green, cream and pink, but it spreads vigorously. And there is some chemical(?) in its roots that stunts the growth of neighbouring plants – especially miniature roses. The plant should come with a warning label.

    Reply

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