Invasive Bulbs

[Diane Whitehead]

Fifty years ago, a generous neighbour gave my little daughter a dozen Spanish bluebells (Hyacinthoides hispanica).  They proliferated so much that I have been digging them out every spring.  I compost the leaves, but the bulbs go in the garbage - buckets of them.  Despite years of effort, there are still thousands.  The bulbs have put themselves under the thick roots of camellias and fruit trees where they can't be reached.

This picture shows how they might get themselves out of reach of my fork.  The young bulbs sprout a thick white root.  Do these contract to draw the bulb down?  Does a new bulb form at the bottom?  Or do they move sideways into new territory?  If I weren't so busy digging, I might experiment, but after being photographed, these went into the garbage can.

[MarcR]

Diane,

I planted 6 from Brent and Becky's 3 years ago. I still have 6 flowering faithfully. Perhaps you have a location that encourages their spread.

[janemcgary]

Hyacinthoides hispanica is one of the most invasive introduced plants in western Oregon. Almost every garden in the Portland area that has existed for more than a few years has it, thanks to people sharing "bluebells." It had already infested my current lot long before I bought the place, and I've given up trying to eradicate it. I let it flower for a couple of weeks and then pull up the scapes and all the leaves. The bulbs, as Diane suspects, do draw down deeply, and they increase like mad. Even a "trenching spade" I bought to attack this plant has failed to reach all the bulbs. In addition, it spreads readily by seed if not controlled. In more addition, it can be transferred from place to place when soil or compost is moved. Never, ever plant this on purpose -- but that may not save you, either.

[ksayce]

I concur, roots pull bulbs down and sideways both. As Diane and others do, so do I--pull the flowering shoots before seed set to reduce spread. I have 1000s, one of several legacy bulbs from a prior gardener more than 100 years ago. The shoots do go into the garbage, not compost, to keep down seeds spreading in the garden. Despite my vigilance, the seeds still pop up in new beds and under shrubs, where I can't easily dig to get at them. 

[Diane Whitehead]

I just checked Brent and Becky's website, and this is how they describe the blue hyacinthoides they are selling:

rich deep blue flowers form luscious naturalized woodland meadows and rivers

[MarcR]

I don't in any way doubt that they tend to naturalize and become weedy. That doesn't change the fact that mine have not done so. I bought 3 blue and 3 pink and planted them in a clump. I still have 3 blue and 3 pink flowering from early February until May.  Portland  winters tend to be 5-10 degrees colder than what I get. Perhaps the extra winter chill encourages them to proliferate.

[Rdevries]

Invasive bulbs in my gardens in Kentucky include:
Crocus tommasinianus
Allium sphaerocephalon,
Allium amethystinum and several other weedy alliums
Oxalis obtusa ( 1 from the BX is now 1000s of plants in the semi protected sand beds)
Notholirion thompsonianum came from BX as something else and shows up everywhere.
Gladiolus tristis

In protected areas and Under lights in garage
Gladiolus with very long and very narrow 2-3mm leaves that never bloom (G trichonemifolius?)
Melasphaerula graminea Just arrived as an imposter and it reported to be a greenhouse weed. 


Most older lawns in the Mid South are made up of
Ornithogalum umbellatum (Star of Bethlehem).
Muscari armeniacum
Wild onion
No matter how much you dig up the clumps you always miss some

[Robert_Parks]

Currently being annoying:
Zantedeschia aethiopica - tiny tubers will send up leaves from a foot or more buried...with years of attention I only pull a few a week.
Oxalis pes-caprae - after scorched earth methods, and 5 years of attention, I think there are only half a dozen eruptions a year.

Bulbs that are on track to be invasive:
Oxalis purpurea, obtusa, brasiliensis - I planted some of each in the ground along with other bulbs...then the gophers came and ate them all...or so I though. Actually they ate most of the bulbs, but they also carried some to food caches spotted around the garden (and into the neighbors yard), now I grow all my oxalis in pots (with those pots set in wire baskets as the gophers will eat through pots), but those three species are out of the barn. O. obtusa does poorly here without a hot dormancy, so most clones will likely dwindle away.

So far, nothing else has spread or seeded...now if some of the blue Ixias wanted to go wild, that would be hard to resist. I. polystycha Baby Blue divides vigorously and blooms quickly, and would make a delightful mass planting, we'll see how I. viridflora performs (lots of seedlings) the one blooming now is very much a light blue shade.

[janemcgary]

I second the opinion on Oxalis obtusa. It got loose in my old bulb frames, and apparently hitched a ride to the new bulb house by secreting its tiny bulblets inside the tunics of desirable bulbs. I've found them in such places when cleaning bulbs. Fortunately, it's only marginally hardy here in Portland, Oregon, so the few that get into the garden in discarded soil don't proliferate. Its tiny, glaucous foliage and large, soft pink flowers are much admired by people who don't know it's a thug. It sends out stolons that emerge up through the drain holes of plunged pots, too.

[Martin Bohnet]

Jane has made a good point: there is a difference between invasive in pots and invasive in open ground. as for pots I'd like to add Freesia laxa

, pops up everywhere for me.

[Uli]

Dear All,

Any climate may have invasive bulbs, in my case it is Oxalis pes-caprae, in other algarvian gardens there is a small white flowered Allium and along the roadside is Watsonia bulbifera in some areas.
To get rid of them I strongly recommend not to try to dig them, this may break up clumps and distribute bulbils. I cover the affected area with woven black plastic which lets air and water through but not the light. The plastic can be covered with mulch. Taking away the light is extremely effective but for the vigorous ones may need more than one growing season. Cut flat compost bags work well, too. For Oxalis pes caprae one season is enough because it has to renew its bulbs every season.
Bye for now 
Uli 

[Diane Whitehead]

The best advice, other than "don't plant them", is to remove invasives (or cover them with black plastic) before they flower .  I have continued digging my Spanish bluebells every day, but now they are in full flower - several shades of blue, with flowers of slightly different sizes and heights, plus some pinks. They are so beautiful that today I felt wicked as I consigned them to the garbage bin.

Perhaps I could select a superb form that would be willing to remain single. 

[David Pilling]

Or...

A "wonder weevil" has been introduced to fight the invasive floating pennywort weed that grows 20cm a day in rivers. The non-native South American weevil has been released into waterways in a world-first effort to tackle the highly invasive plant, which is making Britain's waterways inaccessible to canoes and anglers.

I have friendly pests that have rid me of horrors like fritillaries.

Now what do we set to catch the wonder weevil.

[Steve Marak]

Most older lawns in the Mid South are made up of
Ornithogalum umbellatum (Star of Bethlehem).
Muscari armeniacum
Wild onion
No matter how much you dig up the clumps you always miss some

In NW Arkansas, a number of non-native bulbs persist for many years around old home sites; a few of them (Narcissus, Muscari, Leucojum, Lycoris x squamigera and L. radiata) will slowly naturalize into larger clumps but I don't consider them aggressive or invasive. The one that is, and a real nuisance here is Ornithogalum umbellatum.

Arum italicum is about to make my list too. I had one clone which stayed put for years. When I got a 2nd, I began seeing seedlings everywhere.

Steve

[MarcR]

Or...

A "wonder weevil" has been introduced to fight the invasive floating pennywort weed that grows 20cm a day in rivers. The non-native South American weevil has been released into waterways in a world-first effort to tackle the highly invasive plant, which is making Britain's waterways inaccessible to canoes and anglers.

I have friendly pests that have rid me of horrors like fritillaries.

Now what do we set to catch the wonder weevil.

Your post brings back memories of the old nursery song "There was an Old Lady Who Swallowed a Fly."