Friday, March 13, 2015

What a Creep!

Creeping raspberry not looking its best. Unfortunately, I've found this mass of dead stems to be a common sight in back-to-back Tennessee winters. Would the plant look prettier in a warmer climate? No doubt. But it would also probably expand faster, and that's a somewhat scary thought for a non-native species with few obvious wildlife benefits. I'd be especially wary of planting this next to any wild areas where it could expand and try to outcompete native vegetation. Oh and notice how despite its rampant growth, it has failed to block out all the love-in-a-mist seedlings poking through in the foreground.

I'm not talking about the iconic Radiohead song from the 1990s, but rather the creeping raspberry (Rubus rolfei, a.k.a. R. calycinoides or R. pentalobus).

I've reported on this plant twice before:

- In October 2013, I was over the moon with anticipation that I'd found the perfect groundcover. I waxed rhapsodic about its merits - the scalloped crinkly leaves, its supposed evergreen foliage, its rapid growth rate and its reported wildlife value (flowers for pollinators, berries for birds and mammals - including people).

- By April 2014, I was singing a different tune after the creeping raspberry died back to the ground in the winter of 2013-14 and took a long time to emerge in the spring. My dreams of a trouble-free evergreen groundcover disintegrated as I clipped back tough raspberry stems with dried dead leaves.

Now it's March 2015 and I've permanently broken up with creeping raspberry. After another colder-than-average winter (8th coldest February on record in Tennessee), creeping raspberry once again had lots of unsightly, dead stems.

After three growing season in the garden, the biggest plant had rooted all along its runners to establish a thick multi-layered patch that spilled out of a bed and onto a sidewalk. All the new plantlets grew so fast that they created maintenance work in the garden as I had to trim back the runners pretty frequently to prevent them from covering the sidewalk. (I'm pretty sure that left on its own, creeping raspberry would have crept right over the sidewalk and rooted into the grass on the other side.)

Creeping raspberry roots all along its nodes. These rooted sections send out their own runners, so the plant self-propagates and expands with ease. Too much ease for my comfort, especially when we're talking about a non-native plant with little obvious wildlife benefit and limited aesthetic appeal.

Those berries and flowers I'd hoped for to give the groundcover wildlife appeal (and provide a handful of fruit now and then for me)? Never saw them. (Well, I saw a single flower the first year I had the plant in the garden, but nothing ever bloomed after that. Perhaps creeping raspberry only blooms on old wood and thus can't flower or fruit in a climate where it keeps getting killed back to the ground?)

Creeping raspberry is a conundrum. Despite its wild and wandering ways, despite its multi-layered foliage, it still doesn't do that great a job of blocking weeds. In fact, I'd say it's least effective at blocking weeds than any of the other groundcovers I'm trialing in my garden (such as lamb's ear, perennial geraniums, creeping veronica, epimediums, ajuga or lady's mantle).

This is a Cambridge geranium (Geranium x cantabrigiense) called Biokovo. So far, I'd say it makes a much better groundcover than the creeping raspberry here in Tennessee. As you can see, it's stayed mostly evergreen through the winter with some nice reddish highlights in the foliage. Unlike the creeping raspberry that forms tough and wiry stems, I've never needed to cut back Biokovo. The last year's foliage slowly fades away and is superseded by fresh new foliage, plus Biokovo gives you weeks of white flowers with pink centers. The dense foliage does an excellent job of blocking weeds and the clump has expanded at a measured pace while staying dense in the center. 

So yesterday I decided it was time to give creeping raspberry the heave-ho. It did not go without a fight. That main clump which had only been in the garden for around three years had set some serious roots. In some ways, it was like trying to dig out a small shrub. To give you an idea, I had a much easier time digging out three (less-established) clumps of Amsonia hubrichtii (Arkansas blue star), no shrinking violet itself, than I did prying creeping raspberry out of the ground.

The trouble I had removing the plant convinced me that I'd made a very good decision to remove it when I did. Given another year or two, I fear this non-native groundcover would have insinuated itself throughout my planting bed, making it much harder to remove it without doing damage to some of the other perennials and shrubs nearby.

So what do I plan to put in its place? I have a couple of ideas. One possibility is Gaillardia x grandiflora (a hybrid between two North American species - G. aristata and G. pulchella - both of which are primarily native to the western United States, although G. pulchella's range does extend naturally into Southeastern coastal regions). Gaillardia x grandiflora has a reputation as being a short-lived perennial, especially on the sort of heavy clay soil that predominates on my property, but I have a few clumps that have fared very well on the other side of the driveway for a couple of years and I like the fact that it flowers profusely for many months during the growing season, attracting bumblebees and other pollinators. It's a very cheerful plant. Even the spent flower stems are attractive, so I leave them up through the winter and then cut the plant back to its basal foliage in early spring.

I may go with gaillardia as a replacement, but I do have a few other options I'm mulling over. Stay tuned!