Mendocino--Coast Botanical Garden
Mendocino--Coastal Walk

Gardening Up Close--Managing Self-Sowers, Plants with Runners, and Bulbs

Gardening: Up Close   What to do about plants that crowd eachother and themselves. 

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Garden plants do not just stand still and look pretty. Not only do they grow taller, but they also leap wildly from place to place, creep stealthily outside their allotted area, and sometimes bunch up until they are so close together they can barely breathe, let alone bloom. So one of the tasks of the gardener is to serve as a plant referee. This photo shows three plants that are competing for the same space. Not only that, but one of them is competing with itself! These plants also illustrate the three main ways plants reproduce: seeds, runners, and bulbs, and how a gardener might referee their competition.   

            The blue-flowered lobelia is an annual, a plant that grows only from seed, blooms in a couple of months, and dies in under a year. It spreads in a garden by dropping seeds. They might grow where they drop or may roll or be moved by water into new places. In my garden, dropped lobelia seed doesn't grow very often, resulting in only a few random plants a year, so it doesn't make a pest of itself. I watch for the  small lobelias with their first blue flowers, and either leave them unmolested where they choose to grow, or move them to a place I prefer. I left the one in the photo alone to grow where it voted to put down its roots. I thought it a nice touch at the base of the broken concrete retaining wall next to the creeping fern.

            Then the fern began to creep toward the lobelia. Its rhizomes crept forth, forming new plantlets every few inches. OK with me, since it makes a nice backdrop for the tiny sapphire blossoms. The fern is Blechnum penna-marina, a South American species that in cool moist locations, in mild winter gardens, makes a tidy perennial patch of low, leathery leaves.This one survived in a neglected corner of my garden for several years, just getting by, but has been growing happily in the new spot to which I moved it about five years ago. It has filled in its space and slightly enlarged the area it covered.

            As this past spring progressed, the lobelia got bigger, and then the fern began to creep under and past it, into the area where I have been growing some Babiana. Babiana is from South Africa, where it blooms after winter rains and can survive the  long dry summer. The leaves that emerge with my California autumn rains grow to about eight inches tall. Then in late winter flower stems reach a foot or so tall, each bearing about a half-dozen rosy-purple flowers. Very nice on an early spring afternoon with the sun shining through.

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            Spring passes, summer comes, I cut the browning flower stems, then the dying leaves. Soon there is only a tidy brown stubble, awaiting another chance to grow. The bulbs, or in this case, the similar structures known as corms, have stored up food enough to send down fresh roots when the rains begin again, to start the process over.

            Babiana has been the perfect choice for this tiny strip of rather sandy soil between the brick patio and the retaining wall. It turned out that strip was so narrow that it was very difficult to keep moist all through the summer, but since Babiana is dormant all summer, it needs zero summer water.             

            As the fern runners continue their reach, fern roots are going to tangle with the perennial Babiana corms. I have no way of knowing if the Babiana will survive this overrunning of its territory, so I must consider taking out some of the competing fern growth.

            Mediating further in the direction of fern control now is the fact that the Babiana corms, have been multiplying in their appointed spot for several years. This plant, as is the case with bulbs generally, doesn't move around, it just becomes more crowded. The plant is fighting with itself to find more room. There are more and more leafy plants each year. At first, the stand just produced more flowers, but in the past couple of years, the number of flower stems has held steady, or maybe even decreased. The Babiana is succeeding so well that it has begun to fail.

            At this point, I need to dig up all the corms and divide them. This just means separating them--they are loosely connected--and resetting the largest of the bulbs with a bit of room among them. If there are too many large ones for the space allotted, I'll have the choice of giving the planting more room or giving some of them away.

            There will also be small ones that won't bloom for two or maybe three years. These can be interplanted with the large corms in a larger area, or can be grown in an out-of-the-way place until they bloom, when you can decide where you want a new bed of Babiana. Or, they can be given to someone who wants to wait while they reach blooming size, or added to compost.          

            The questioning mind might wonder: If bulbs that grow from year to year crowd themselves up until there are few blooms, what happens in nature? In the case of Babiana, I have been told that they got their scientific name from the fact that baboons like to eat them. They dig up the corms and chomp them down, probably in the dry season when it is easier to wipe them clear of soil and they provide a welcome bit of moist food. I imagine baboons eat the biggest corms first, but miss some and especially miss the small ones, naturally thinning the lot.

            In some cases, as with Watsonias, the corms eventually form a large circular mound. If some animal begins to bite or kick out a corm here or there, and some that become detached might don't get eaten, they might roll off to a new location to start a new stand of Watsonias.

            The same goes for plants like my fern that grow from rhizomes or runners. Some foraging animal might break some off and not do a thorough job of munching all the broken plant bits, so some broken bits could roll or blow to a new place and send down roots.

            But a garden is not part of an intact ecosystem, with an equilibrium between animals and plants, so when plants are fighting it out, the gardener must step in. I now need to legislate the locations of the running fern and the clumping Babiana. Where do I want to let them be? And do I want to let the innocent lobelia, which grew from a randomly dropped viable seed right between the fern and the Babiana live out its short life in peace?

            First, I will dig up the part of the fern that has overtaken the Babiana bed, pot it up and save it for a friend who wants to grow some. Then I will dig up all of the Babiana corms and see what I have there. I will probably dig some fertilizer, a bit of earthworm compost, into the place they have been growing. Then I'll replant some of the larger corms 4 inches deep and 4 inches apart. (I looked the best depth and spacing up in a book.)  What if there are more large ones than I need for my tiny space? Hmm. Then a decision needs to be made.

            I will not disturb the part of the fern under the lobelia right now, because it is such a cheerful spot of blue! Only when it begins to fade will I decide if I have taken out enough of the fern.  

            But for a while longer, I will simply enjoy the battle, letting visitors to the garden think that this handsome plant grouping is an intentional and stable garden arrangement, created by nature and my careful planning.

I'll show that first photo again and if your eyes are sharp, you will see two other situations developing that will need attention one day.

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Did you notice the different kind of fern, the one with the larger fronds, at the base of the broken concrete, just above the lobelia? There seem to have been fern spores in the crannies of the used concrete we got through Craigs List, and some of them have germinated. Chances are this wll be a large fern, too large for the space. I may not be able to priy it out to move it either, so when it starts to overwhelm the spot, I may have to just rip it out. Sigh.

And arching up into the cracks of the concrete above and to the right of that fern, you will notice the leaves of some creeping campanula that has reached down from the top of the wall. Nice now; it made a few blue flowers that were very winsome in the wall in June. But if the wall were to be covered with it you'd lose the charm of the wall. You got it, more ripping out in the offing.



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