Q: Our garden beds were taken over with a plant that grows from a white bulb and has purple bellflowers. Last year I dug down a foot and pulled out all the bulbs I could find. This spring, thousands of new shoots are growing from deep tubers, bulb connectors or tiny mini-bulbs. Is this a stick-with-it-obsessively-pull-up-every-bulb-yousee situation? Or should I do as my husband says and be thankful that there's something I can't kill.
Tess Trethewey,
Coquitlam
A: You've got Creeping Bellflower (Campanla rapunculoides) and it's a gardener's nightmare. It's a good-looking plant so you could try learning to love it, but it usually spreads into a dense mat that out-competes everything else.
There's no quick trick or magic potion to remove this. Weed-killers remove only the upper growth. Those fat, deep-down tubers have lots of reserves that put up more stems.
It's crucial to deadhead the flower spikes so that they never get a chance to seed. But the real key to removing it is to dig up the tuberous roots. It sounds as if you didn't dig deep enough for the big roots. You may need to dig down about 45 centimetres.
I'd recommend a Lee Valley Tools drain spade because it has a longer blade than ordinary spades. It's heavy but helpful in retrieving many bulbs (such as snowdrops, camas, bluebells) that work their way down to China!
Trying to tackle all the garden beds at once is probably impractical. You could select one war zone for digging and move your most precious plants somewhere else that's hopefully bellflowerfree. Wash their roots. Don't move any soil over.
After deep digging, cover that area with black plastic. Then weigh down the plastic with something heavy enough to flatten any upthrusting shoots and nicelooking enough to be a patio for a container garden. Any remaining mini-tubers should die out in a couple of years.
Before reclaiming the bed, put a seven-centimetre mulch on top. This should prevent any old bellflower seeds from germinating.
With the other beds, deadheading the clumps, weeding seedlings and continuing to sieve soil to remove mini-tubers should hold the situation static until you can begin a deep-digging battle in another conflict zone. I wish I could help you more. This is a very difficult plant to eradicate.
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