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One of our favorite “trouble plants” is the lovely buttercup oxalis, Oxalis pes-caprae. It is a fascinating little herb originally from South Africa. Above is a patch of lantana that has been completely smothered in a lush carpet of buttercup oxalis.

Yes, it is a noxious invasive that can overwhelm many other kinds of plants. Despite what some gardeners may say (Oh, that stuff never dies. It will be there forever!) it can be tamed, controlled and even completely eliminated. But without the use of icky chemical toxins (please, don’t!) it could take a bit of persistent work.

140519-0733In South Africa it’s a native surrounded by local herbivores that eat it. Here in California it can spread rapidly through underground runners and bulbs. Many gardeners hate it because it is very difficult to remove. Directly pulling up the plant almost always leaves the bulbs behind, which can be as deep as six inches or more. Yikes!

 

it can be done!
The good news is: They can be cleared by persistent, complete plucking of all new rosettes every few weeks during the winter growing season.

But you really will have to keep after them! Do not allow any rosettes to get to the blooming stage because that is when they send out dozens of tiny underground bulblets. Each bloomer will be surrounded by a six-inch radius of tiny new plants next spring. You must pull out all rosettes, no matter how tiny.

It is enough to pluck out the stems if you are patient and persistent, but the biggest ones can come back four or five times before they give up. Fortunately, we can move faster. Just keep plucking.

You can eliminate them faster if you get the bulbs. Use a long, thin, sharp tool like a weeder, screwdriver, or thin trowel to shove down deep under each rosette. Your goal is to break open the soil without breaking the lowest stem of the plant. It can be tricky, especially if your soil is dense, but there is a certain joy in gently shaking off loosened soil to find a bulb clinging to the thin thread at the bottom of the root. That one will not come back!

 

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you can eat all of it
Not everything about buttercup oxalis is bad. Not only is it exceptionally pretty, it is also edible. The sweet-sour yellow flowers and flower stalks are great in salads, and the bulbs are said to be good for getting rid of tapeworms. I haven’t had a chance to test that claim yet.

As invasive as they are, we love these little plants. But we keep them in their place. Where is that? Several places, actually.

 

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a drift in the leaves
Natives-only gardeners may cringe, but there can be a place for these little beauties in a deep nature garden. There may be a spot in the semi-shade with deep leaf debris, where buttercup oxalis can poke up through the leaves. The best place for such an oxalis drift is under a deciduous bush or tree, so that they can enjoy some filtered sun during the winter growing season. The annual leaf drop from above can challenge them and help to keep them under control.

In the picture above there are lemon-yellow buttercup oxalis flowers under the blooming wisteria vine, and spilling out into a sunny meadow of california poppy, wild strawberry, and English violet.

If you want a big harvest of the sweet-tangy flowers you can create a more robust and productive drift of oxalis. Just let the little cuties grow in some likely place. In the picture below is such a drift among some beautiful rocks. If it is strictly removed from other garden areas it can be a gorgeous and tame part of the ecosystem. But it will definitely need to be controlled around the edges.

 

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tame, beautiful, delicious
The best place of all for a wonderful, edible little invader like buttercup oxalis is a container. As you might imagine, they are fairly easy to grow. We’ve been growing some in our eco-packs. Want one?

Read more about buttercup oxalis at Wikipedia.

 

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Did you miss the previous episode in this series? You can also jump back to the beginning.

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December 19, 2012. Morning sun slants across the garden at little yellow house. There was some serious rain, and now thousands of sprouts are popping up in every blank space. The garden is greening up!

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Above: An odd little corner of the front strip features a variety of fascinating plants including petty spurge, groundsel, mallow, cut-leaf geranium, English violets, buttercup oxalis and more, plus a few pretty autumn leaves. Here’s a closer look:

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Right now, our most important task in this garden is thinning out extra sprouts of anything that is too abundant, plus removal of certain plants like buttercup oxalis that we generally prefer to restrict to selected areas because of their invasive nature.

Below: An area shadowed by a purple lantana in the street strip shows a bit of frost on leaves of English violet.

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Above: On the left side of the front walk the daisy bushes enjoy the sun while the wisteria bush behind it is still in shade. It leaves are turning yellow and dropping down. There’s frost on the neighbor’s roof in the background. Under the daisy bushes in front there is a carpet of violets and decorative strawberries, still filling in. Like almost every other plant in this garden they were there to begin with, not deliberately planted.

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Above: Skipping forward to Christmas eve, 2012 the garden continues to grow in rapidly. In the front strip is a drift of blooming buttercup oxalis, pushing up between the frost-burned stems of lantanas. In spite of the frost damage, some stems of lantana still bear pretty purple flowers.

This is one of two areas where we are allowing the oxalis to stay. Here it has to compete with the vigorous lantanas, and it is also quite difficult to extract from this zone without damaging the lantanas. The other oxalis drift is under the big wisteria bush, where they look pretty pushing up through the carpet of fallen leaves.

Below: Closer looks at the buttercup oxalis. The beautiful yellow flowers are edible and excellent in a tart-sweet, tangy way. Try them in salads!

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Below: A few more sweet little scenes from the garden at little yellow house on Christmas eve, 2012. We see English violets, sweet alyssum, a cute mushroom, and some autumn color.

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Next: Wisteria drops its leaves, the owner begins a stone patio, and there’s lots more thinning to do.

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One of the most fascinating projects here at deep nature central (my city apartment!) is the eco-packs, which are essentially very small container gardens. Each one includes one or more kinds of interesting seedlings or small plant starts. They are intended to be diversity enhancements for distribution to local gardens.

Most eco-packs start with a rich 50/50 mix of ultra compost and ordinary cheap planting mix. This is a mostly seed-free mix. In the center of that is deposited just a pinch of eco-mix, which contains something like 300 different kinds of seeds, including natives, domestic flowers and vegetables, and of course a wide assortment of what many people might call “weeds.”

The containers are generally either small traditional plant pots, or plastic containers harvested from our recycling bins. The container must be large enough to stay moist through a sunny, warm day, which means at least a pint or so of volume.

Once the sprouting begins, a successful eco-pack can quickly become rather crowded. Below, the lid of a container that once held a roast chicken from Safeway shows a dense collection of seedlings, many of which are ordinary invasives that need to be thinned out:

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This container is actually not an ideal choice for an eco-pack because it isn’t really deep enough. I’ll transplant this one into a larger pot soon.

Let’s thin out those weeds out-of-place plants:

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What’s left? Dominating the center in the picture above are two seedlings in the solanaceae (tomato / potato / nightshade) family. These are probably nightshade, which is very common and generally thinned out, but there are also some wonderful seeds of jimsonweed in the eco-mix, so I am keeping these until I can determine their exact identity. At the upper left are two sweet little Kenilworth ivy seedlings, one of my favorite small moisture-loving vines. Another one is at the top margin, and another one in front between the two probable nightshades. Also visible, two tiny sprouts in the carrot family, with their finely dissected leaves.

Here are more eco-packs with various kinds of interesting plants:

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This one (above) features two beautiful sprouts in the mint family, possibly lemon balm. At upper left, another little Kenilworth ivy. In the shady upper right is a scarlet pimpernel sprout, another highly invasive plant but one that is really quite pretty. It is a great ecosystem builder in young deep nature gardens, but one that must usually be cleared out as the garden matures.

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One of my favorites in the current collection is this vigorous plant on the left, sharing space with another Kenilworth ivy. This eco-pack has already been repotted once from a much smaller container, and it won’t be long before it gets repotted again. What is this beautiful young plant? It’s much too soon to be sure, but it could be statice or dock, or any of many other plants. I can’t wait to see it bloom!

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Not every eco-pack contains more than one kind of plant, or grows from seed. Here (above) are two little pots with sunchoke starts, growing from tubers. Also known as Jerusalem artichoke, these plants are in the sunflower family and will grow into 4-6 foot stalks bearing happy yellow flowers. In the fall, the stalks die back and the delicious edible tubers can be dug from the ground. Naturally, we’ll save a few for some new eco-packs!

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I can’t resist another picture of my favorite tiny vine. By now I’m sure you know what this is called!

The small white rectangle is a chunk of egg shell, one of the most visible ingredients in the ultra compost. Egg shell is a source of valuable calcium and a potent slug deterrent.

One of the best things about container gardening is how easy it is to control plants that otherwise can become incredibly invasive and unwelcome in an in-ground garden. Below: a gorgeous young buttercup oxalis grows rapidly, well on its way to sending up its beautiful, edible, tangy and delicious yellow flowers. Here in this container (and soon to be moved up to a larger one, where it will spread and grow further) it is completely under control and will provide lovely flowers and salad garnish for years to come, but in the ground in the garden it is extremely difficult to control.

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Local folks (including my garden clients and anyone else who’d like some new diversity in their garden) are welcome to receive eco-packs. Just get in touch, and I’ll tell you where I live and we can set up a time for you to stop by!

For now, all the eco-packs are free (although not all of them are available yet), but once I begin to accumulate some rare and especially interesting ones there may be a money price for those special ones.

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Deep nature gardening in containers can be challenging because there is a lot less room, and water and nutrients can be quickly depleted. Above is a container with some strawberry plants and a little holly sapling. It is late March 2012, and this container has just been thinned of annuals from the previous winter’s growing season. A little white clover has been left at the rear to help enrich the soil and there are a few small creeping oxalis and other small seedlings.

All of these plants came up from random seeds present in the eco-mix that was used to start this container several years before the above picture was taken. Here, the container has already been through a few cycles of growth and thinning.

It is not always necessary to do this severe degree of thinning in a container but in this case I want to encourage the strawberries to grow lushly and bear fruit, so most competition has been removed. A sprinkle of extra-rich eco-mix was added to encourage new growth.

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Above: By May of 2012 the creeping oxalis has spread and now bears cute purple flowers. There are many new seedlings, including a grayish cudweed just left of center. The strawberries have also become lusher, and the holly has a crown of new leaves. Behind the holly are some brownish clover seed heads. Also present (but hard to see): chickweed, lamb’s quarter, and more.

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By late June, even more growth. The cudweed has sent up flower stalks taller than the holly, and the white clover has intruded into the front of the container. It will need to be limited back very soon! But even with the competition, the strawberries are doing great, blooming and setting fruit in the depths of the leaves.

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Early October, and beautiful ripe strawberries dangle over the edge of the container. More are ripening all through the micro-jungle. The white clover has been completely removed, along with cudweed and some others. A tiny new tomato plant pokes up at right front.

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By early December the tomato has grown up a bit more and now bears one humble, green fruit. To its left another cudweed has sprouted up, and in the far back another creeping oxalis has filled in with pretty leaves. The strawberries have become dormant, and just hold on to a few green, yellow, brown and red leaves. At the far right a few sow thistle plants have sprouted and behind them are two stems of lamb’s quarter. Despite the lush appearance, this container is now growing very slowly in the cool winter weather.

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Mid-February 2013 brings us right around again, after a fairly drastic late winter thinning.The dormant strawberries are now fully freed of competition, once again ready for the next growing season. The holly in back is now about twice as tall. After the thinning, a generous layer of seeded eco-mix was strewn everywhere.

In the far background at the extreme upper right (beyond the neighbor’s deck) a blooming magnolia tree drops its petals onto the ground.

Just a few weeks later the container was, once again, lushly filled with interesting new sprouts.