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invasives

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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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One of our flagship deep nature gardens is called “birch corner.” It has been taking shape since late summer of 2013. With the help of some good tree work from our licensed friends and some power tools wielded by the client, we took out a dead old lawn under a big pistache tree, pruned the tree back to let in more light, and drastically limited a birch (the garden’s namesake tree) that was also stealing light from the garden area below.

The ground under the pistache was shaped into hills and valleys, and a lot of beautiful rocks were added to create a walking path and many step-able access points.

In the past year the garden has grown a wide variety of interesting plants. Some, like several varieties of blueberries, spreading patches of bidens, and yellow lantanas were deliberately planted. But many more, like the fluorescent orange zinnias, burgeoning arums, and drifts of small tree saplings emerged on their own from seeds already present in the soil.

Let’s have a look around!

 

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Above: Viewed from the street, the right (west) side of the garden includes the namesake birch tree at the far right. At the extreme right side of the picture is a wooden fence shading that side, with a climbing rose on it. In the spring and summer this fence is also covered by sweet pea vines, deliberately planted and just now sprouting back up from last year’s dropped seeds.

In the middle of the picture are two large clumps of yellow-flowering bidens, which will soon be limited back before they take over even more space. A clump of hair grass stands at the top of a low berm, and in the back against the fence is a young apricot tree. Also visible are a few rocks and some logs slowly decaying into the ground (trimmed from the pistache tree above).

Below: A closer look at a spreading patch of bidens, with an orange zinnia peeking in at the right.

 

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Below, a patch of cyclamen that was planted last winter near the shady base of the back fence is still thriving and blooming. The base of the apricot tree is at left. A closer look shows many little sprouts of new cyclamen. It looks like it is naturalizing nicely.

 

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In this first year at birch corner we are still encountering a variety of vigorous volunteers that will need to be either limited or removed completely. Among these are the many sprouts of variegated arum, almost all of which will have to go.

There are two (non-chemical) ways of removing arums. The first requires patience – simply pull out all the leaves as they appear, until the tubers below run out of steam. But that method takes some persistence. In coming weeks and months we’ll use the faster approach which is to dig down and actually remove the tubers.

Below, a sampling of the arums at birch corner. Each one has its own particular pattern of leaf variegation. We’ll save a few of the most interesting ones, but they will be kept under control. Some may be moved into containers, where their invasive nature will be tamed and we can enjoy their beautiful leaves, flowers, and the seed heads with their bright red seeds.

 

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Birch corner is a forest floor ecosystem, heavily influenced by a dense drop of leaves from the pistache tree every autumn. Those leaves contribute to a gently acidic soil type, which favors plants like the blueberry showing its fall colors in the picture below.

 

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Here in California, autumn marks the beginning of the winter growing season. At birch corner, one sign of the coming winter is thousands of tiny sprouts of petty spurge and a few other low growing annuals. These will fill in, forming a beautiful green carpet that competes with leaves falling from above.

 

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We leave you with a few more of the many interesting new kinds of plants coming in. How many of these can you identify?

 

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Is it a “weed?” You may have seen it by a roadside or in some disturbed area. A basal rosette of thin, iris-like leaves and knee-high stalks bearing composite flowers with spiky green sepals behind the purple rays. It’s a biennial, with just the rosette in the first year.

 

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Once you know it, it’s unmistakeable. It is purple salsify, also known as oyster plant or Jerusalem star, Tragopogon porrifolius, native to Mediterranean Europe and now found all across the US. It is a beautiful herb that is edible and full of good nutrients.

There is another plant called salsify. It is black salsify, Scorzonera hispanica, more commonly grown for food in Europe, but I have not seen it in our area. It has wider leaves and looks a bit like broadleaf plantain or dock.

While it can be invasive if it is not controlled, purple salsify is fortunately easy to clear. Pull out all the rosettes, using a weeder or other long, sharp tool to cut the root. Most plants won’t come back if you cut deeply enough.

141121-0711Those lovely flowers may not last long in our gardens because they are edible. Even the leaves and flower stems are edible, but the real prize is the crisp, carrot-like root, which has a nutty, earthy flavor something like oyster. The best time to harvest the root is just as the first flowers open. After that the root begins to become woody and loses its nutrient value.

Purple salsify spreads by releasing large dandelion-like, windblown seeds, so the responsible thing to do is deadhead any flowers you don’t eat. Or you can do what I do… cut that seed head as soon as it matures and save the seeds for planting as food plants in containers. Be sure the container is deep enough for the delicious root!

There is no place for purple salsify in a California natives-only garden, but this is one of those “friendly invasives” that we sometimes allow in controlled deep nature ecosystems. Like many other aliens, it must be carefully limited or it will spread. If you can’t keep it limited, remove it completely!

But with its edible roots and flowers and its simple, elegant beauty, it is one of those aliens we love to grow in safe, escape-proof containers.

There’s more about purple salsify at Wikipedia.

You can also read about black salsify.

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Large bunch grasses can be among the most challenging plants to prune. Every year they send up dozens of flowering stalks, which quickly turn into seed-heads shedding vast numbers of tiny potential grass sprouts all over the nearby landscape. Many gardeners resort to heavy weaponry to simply shear them right down to the ground, leaving behind an ugly, unhealthy, flat-topped “tuffet” of cut stems and leaves. Definitely not naturalistic!

I was recently faced with just such a challenge. Large clumps of perennial grass had gone to seed and grown out into unruly pompoms with long leaves (blades) trailing out across nearby plants. The client agreed that another annual shearing was not wanted, but could these grasses be limited back without sacrificing a natural look?

Of course they could! But it involved three different pruning methods, two of which were invented on the spot. Let’s start in the back garden, where a large grass looked like this in the “before” picture:

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First, the seed stems. They all had to come off. I reached in and clipped the seed stems way down among last year’s sheared-off stems. That worked to invisibly remove them, but there was a problem: I was also removing a lot of the green blades clinging to the stems. This was not good because those leaves made up about a third of the overall density. I was thinning too much!

I invented a new method just for this kind of grassy seed heads, clipping about half way up each stem, just a tiny bit above the node where the largest live blade was attached. Most of those blades were left in place, and the overall density was preserved. I call this new style of pruning “partial grass deadheading” because it leaves the lower half of the seed stalks in place while removing the business ends.

The second kind of pruning was also brand new. Unlike the leaves of broadleaf plants, grass blades elongate as they grow. This is an adaptation to herbivores that bite off the ends of the blades. Such shortened blades can still grow longer. But there are no grass-eating herbivores in most suburban gardens, and the blades of the bunch grasses tend to grow longer and longer. I realized that for these grasses to be trimmed in a healthy way I had to become that herbivore.

Having recently experienced a haircut, I realized that I could use a method similar to what my friend Janice had done to my head. I swept my hand across the ends of the over-long blades, scooping up a manageable handful and gently tugging outward. Then I clipped off the ends of all the blades in that handful, depositing the cut off bits into the debris bin. By repeating this operation all around the outer parts of the clump, I was able to reduce the lengths of the blades without creating a sheared off look. I call this pruning method “bunch grass haircut pruning.”

With the seed heads gone and the blades shortened all around, the bunch already looked much better. But the overall size of the bunch was too large and there were lots of old blades and stems around the base. It needed to be smaller without sacrificing the naturalistic look. I used a variant of undercut pruning. Reaching deep under at the base, I grabbed a small tuft and clipped it right at ground level, repeating and carefully observing the results all around the base of the plant. The density near the base was reduced, creating more of a fountain appearance and less of a pop-pom.

Here is the result on the bunch grass in the “before” picture above. Notice how much more visible are the small silvery plants near the base:

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Out in front of the house at the base of a tree, there are three more clumps of the same grass. Applying the same three pruning methods, these clumps were rapidly tamed. There is a “before” picture at the top of this post; here is another:

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Let’s have a closer look at the rightmost clump before pruning. See how dense are the seed stems, and how long the blades:

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This is how these grasses looked after the pruning. What do you think?

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I love pruning as much as I love creating deep nature gardens. I am available to prune almost anything in your garden (except mature trees, for which we bring in a licensed tree surgeon). If you are not near us, I am also available through online media (email or real-time video) to coach you on how to prune your plants.

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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Growing a deep nature garden is not about planting a whole lot of different plants. It’s more about creating a blank slate (or, if you are lucky, a healthy starting ecosystem!) and then allowing the garden to “grow in” from there.

Most patches of ground already contain seeds of hundreds of kinds of plants, including rare natives. One of the basic principles is to start with what you have — within reason, of course. It might be necessary to perform massive triage at first, in which most or all of the plants are physically removed, and some landscaping is often a good idea. Seeds can be added if there’s not much in the ground to begin with.

A deep nature garden does not happen overnight, or even over several months. It’s a serious, long-term relationship between the garden and the gardener. The gardener’s goal is to remove what diminishes beauty, diversity, and productivity while occasionally adding new diversity in various ways.

Over the course of many months, it evolves.

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There may be an early surge of vigorous fast growing plants. These are not “weeds” — we don’t recognize that word. These early pioneers are valuable contributors, quickly building up a new, rich, diverse soil ecosystem. In this group (in the SF Bay Area) are prickly lettuce, sow thistle, petty spurge, grasses, California poppies, lamb’s quarter, purslane, and many more.

As each of these pioneers matures it is pulled out or clipped neatly at the base. Many are strictly deadheaded as their blooms fade. Most pioneers are not allowed to go to seed. Although some of these vigorous early residents are wonderful edibles (purslane, lamb’s quarter, etc), they are best grown for food in containers or farming areas. In the deep nature garden their presence is almost always temporary because they are gradually replaced by slower-growing perennials.

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Among all of these early sprouters are hundreds of other seeds and seedlings, of many different species. As the pioneers come out, these other plants begin to grow. Some are well adapted to their microclimate, and out-compete others. Those might end up dominating, but no species will be allowed to take over.

For a passionate deep nature gardener, a large part of the joy of deep nature gardening is the excitement of waiting to see what new kinds of plants will sprout up.

At any point we can guide the ecosystem’s development in several ways.

  • We can increase diversity in the form of new plants. These can be store-bought or they can be our special eco-packs.
  • We can increase diversity by scattering seed mixes.
  • We can prune plants as they grow, for best artistic, naturalistic appearance.
  • We can actively thin out plants that are limiting the beauty, diversity, or productivity of the garden.
  • We can handle overgrown areas though various forms of local triage.
  • We can scatter soil amendments to improve fertility or nutrient balance.

Gradually, the garden shifts. The big, fast, showy annuals are replaced by slower but more diverse long-lived plants that are more precisely adapted to the particular part of the garden where they grow. Shade plants will grow in the shade, and the dry summer sun lovers will eventually take over in the dry, summer sunny places.

All along the way we gently guide the ecosystem, aiming for that special aesthetic “ah!” moment, over and over again.

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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.