Oxalis, how I loathe thee

I’ve heard people say that weeds are just unloved flowers; plants whose virtues have not yet been discovered; or perennials that haven’t been educated yet.

Common yellow oxalis sprouting with abandon
in our succulent bed

I don’t agree. What I do agree with is the Danish proverb “Weeds never die”. When everything else is on the wane, weeds are busy laying the groundwork for next year’s invasion.

Oxalis growing between the stems of a sea urchin sedum
(Sedum lineare ‘Variegatum’)

My biggest enemy in the realm of weeds is oxalis, or wood sorrel. There are many oxalis species grown as ornamentals, and yes, they can be beautiful. The one I’m having a beef with is the common yellow wood sorrel (Oxalis stricta). It grows everywhere and at any time of year—the photos in this post were taken just now, a few days before Christmas—and it seems to prefer places where I would have to sacrifice skin and blood to get to it, like the base of prickly succulents. It prefers alkaline soil, which is pretty much all we have, and it loves the sun, of which we have plenty as well. Its roots go straight down and its stems are weak, making it impossible to pull out neatly. If you leave any of the root behind, the plant will happily make a comeback.

Roundup (glyphosate) is an effective weapon, but for every oxalis you kill, ten more are waiting in the wings—and it’s all to easy to damage desirable plants growing nearby. Plus, the environmental impact of herbicides is something that does concern me, so I only use Roundup when I absolutely have to.

Newly sprouted oxalis at the base of a potted Bambusa dolichomerithalla 'Silverstripe'. This is fresh soil that we had brought in a month ago; I doubt that the oxalis seed was in the soil. It somehow landed on the soil after I potted up this bamboo.

So, what to do about this noxious devil with the pretty yellow flowers? I’ve read of people using the wand of a steam cleaner to literally cook weeds in situ. I was going to give this a try but our steam cleaner is for mopping floors only and doesn’t come with a wand. If any of you have successfully employed this method, please let me know. I like the idea of it, but I’m not entirely convinced that it would destroy the roots of oxalis, too, and unless you kill those, the leaves will grow back in a hurry.

Another solution I’ve heard about is using a portable flame thrower, or “weeding torch”, that public works departments often use for weed suppression in parks. While I don’t have one of those, I do have a chef’s torch—the kind you use to caramelize sugar on top of crème brûlée. Being the curious mind that I am, I decided to give it a try.

My trusty chef’s torch, never used for anything this crude

Chef’s torch in action—will the oxalis survive the blaze?

Before…

…and after

The chef’s torch certainly worked. It burned the oxalis to a crisp in a matter of seconds, creating a pretty nasty smell in the process. Since our succulent bed is criss-crossed by drip lines, I had to be careful not to get too close. That severely limits the usefulness of the chef’s torch, or any other fire-spewing implement, in this bed and all others that are on a drip system.

But this was just a quick experiment anyway. I’ll keep a close eye on the areas that I torched to see if the oxalis will come back. I have no idea how deep into the ground the heat penetrated so I don’t know if the roots are dead or alive.

To get rid of the rest of the oxalis, I’ll resort to my tried-and-true methods. Old-fashioned weeding implements work, at least in easily accessible places. Smothering the seedlings with newspaper plus a layer of mulch does the trick as well. And as last resort there’s always a well-placed squirt of Roundup for the areas that I just can’t get to easily, combined with a quick plea for forgiveness from Mother Nature. But no matter how many minor battles you walk away from victoriously, it seems that you simply cannot win the war against oxalis.

A few stalwarts still blooming

During a break in the rain I took a quick stroll through the garden and snapped a few photos of what’s still in bloom. It was good to see how much color there still is. Aside from the cold spell over Thanksgiving, our weather has been fairly mild, prolonging the flowering season of these late bloomers.

Wouldn’t it be nice it we made it through the winter without any more frost? Or is the mere act of expressing that wish asking for trouble?

Butterfly ginger (Hedychium coronarium)
I bought 10 rhizomes from an eBay seller in Hawaii
a few years ago and this is the first year they’ve bloomed.
In fact, I didn’t see the first blossom until mid-November.
I have high hopes for next year!

Cape balsam (Bulbine frutescens)
This succulent native to the grasslands of South Africa does very well in our climate—almost too well. I bought three plants in 4-inch containers a few years ago and I’ve divided and re-divided them many times since then. All you have to do is break off a piece of the plant along the rhizome that grows very close to the surface (sometimes even above ground) and stick it in the soil. Like aloes, the leaves contain a gel-like substance used to alleviate burns, cuts and rashes.

Lavender (Lavandula sp.)
Lavender blooms almost year round in our climate.

Bog sage (Salvia uliginosa)
Like most sages, an indefatigable bloomer for us.

Rose leaf sage (Salvia involucrata var. puberula)
5 feet tall now and blooming non-stop since late summer.

Grass aloe hybrid (Aloe 'Grassy Lassie')
A typical winter blooming aloe.

Echeveria (Echeveria imbricata hybrid)

Giant farfugium (Farfugium japonicum giganteum)
One of my favorite shade perennials.

In addition to these late bloomers, I spotted a few plants about to start blooming.

Flower stalk of Aloe microstigma
Another winter-blooming aloe.

Calla lily (Zantedeschia aethiopica)
We have about 10 clumps of calla lilies in our back yard that survive the summer without much supplemental water. Their foliage dies off by mid-summer and comes back in the fall. In a month, we’ll have dozens of blooming callas, provided we don’t get any hard freezes.

Not all plants love the rain

Northern California is being pummeled by a series of wet winter storms. The Sierra Nevada is expecting as much as 10 feet—yes, feet!—of snow by Wednesday, and the Sacramento Valley up to 5 inches of rain. 5 inches of rain may not sound all that impressive to some readers, but that’s almost one third of our annual precipitation, which averages between 17 and 18 inches (430-460 mm) a year.

This is what you see when you stare too closely through a wet window screen.

I had quite a few things I wanted to do this weekend but because of the weather I had to scale down my to-do list. I did take advantage of a break in the weather on Saturday and cleaned up the succulent bed next to our driveway. The cherry plum tree planted between our house and our neighbor’s has been dropping leaves for the past few weeks and this succulent area was covered in a sea of red. With perennials I wouldn’t worry too much about the leaves because they break down relatively quickly and act as insulation against the cold. However, succulents don’t like wet feet, and a thick layer of leaves keeps the soil soggy far longer than it otherwise would. The biggest dangers our succulents face in the winter aren’t prolonged sub-freezing temperatures as much as prolonged periods of wetness.

Driveway-side succulent bed covered with leaves from our cherry plum tree (Prunus cerasifera 'Krauter Vesuvius')

Same area after I cleaned out most of the leaves

Using a rake isn’t practical in this area since it would be too easy to damage the plants, so I simply scooped up the leaves with my hands. A thin stick proved useful in cleaning out between agave and aloe leaves. I didn’t try to remove every single leaf—that would have been a Sisyphean undertaking anyway since the cherry plum tree still has some foliage left—but the result is a much nicer-looking bed and hopefully an improved chance of survival for the succulents planted there.

Agave attenuata x shawii ‘Red Margin’
As I was removing the leaves around the base, I saw a new baby poking its head out of the ground. This is one of my favorite agaves and It’ll be nice to have offsets to share.

Resin spurge (Euphorbia resinifera) after I cleaned out most of the cherry plum leaves

You can’t really see it in the photos above, but this succulent bed is mounded in the middle, and the most xeric plants are on top of the mound. In addition, we added sharp sand and pea gravel to the soil when we built this bed so drainage is excellent.

However, in spite of these precautions, some succulents will still rot, especially if planted at the base of the mound rather than higher up. This happened to an Aloe brevifolia (common but beautiful) a couple of years ago. I replaced it with Sedum rupestre 'Blue Spruce' (the bluish-green groundcover on the far left in the photo above) because it doesn’t mind the extra moisture.

The most water-adverse succulent I have is an Agave utahensis var. eborispina. Its native habitat are dry, stony outcroppings in the Mojave and Great Basin deserts of Nevada, Arizona and Utah, which get very little rainfall. In contrast to many agaves which don’t mind regular irrigation—some actually thrive on it—this agave is so touchy about water that some collectors grow it in pure pumice instead of soil to ensure perfect drainage. My specimen is still very small. It lives in a 4-inch pot on our front patio and gets watered once a week in the summer, not at all in the winter.

 

Mature Agave utahensis var. eborispina
Photo: http://www.xericgrowers.com

If you have succulents that are particularly prone to rotting during the wet season—like some cacti and aloes—you may need to take extra precautions in the weeks to come, especially if this winter turns out to be much wetter than normal. If they’re relatively small and in pots, the easiest thing would be to move them to an area where they are protected from the rain, like under the eaves of a roof or on a covered porch.

If they’re in the ground, the ideal solution would be to build a tent-like shelter that keeps the area dry. However, I realize that most people won’t go to that length so I’d suggest you simply cover them with a lightweight frost blanket or similar fabric; some water will penetrate but most of it will simply run off. Frost blankets let light and air through and won’t hurt plants even if left in place for longer periods of time.

Clear plastic sheets are OK as well as long as it doesn’t get down to freezing at night; otherwise the plant parts that touch the plastic might get damaged from the transferred cold.

I wouldn’t recommend opaque tarps, such as the ubiquitous blue ones, because they block too much light and hence aren’t suitable for more than a day or two of use. But in a pinch if you have nothing else and a heavy rain is imminent, you can use just about anything that will keep your sensitive succulents dry. Just make sure that whatever cover you use is anchored or weighed down because our winter rainstorms are often accompanied by strong winds.

Trees of the year

Nature photography has been a passion since my teen years. One of my favorite subjects are trees, and 2010 was a very good year indeed as far as taking pictures of trees is concerned.

We started out the year in Australia, and I’ve only just begun to mine the 2000 images I took during our 3-week trip. In May, we spent a weekend in Yosemite, which is paradise for nature photographers. This was followed by a trip to the Olympic Peninsula in Washington State in mid-summer as well as camping getaways to Samuel P Taylor State Park and Bodega Dunes, both north of San Francisco. Thanksgiving spent at my in-laws in Mount Shasta in far Northern California brought not only snow, but also some lovely photographs.

As fellow gardeners, you love nature as much as I do, and I hope that you will enjoy this compilation of my favorite tree images of 2010. If only we had enough room in our yards for all of these beauties!

Moreton bay fig (Ficus macrophylla), Sydney, Australia

Western dogwood (Cornus occidentalis) in bloom, Yosemite National Park, CA

Western dogwood (Cornus occidentalis) in bloom, Yosemite National Park, CA

Summer forest along the Quillayute River, WA

Red alders (Alnus rubra), Forks, WA

Tree skeletons, Rialto Beach, Olympic National Park, WA

Monkey puzzle tree (Araucaria araucana), Forks, WA

Morning mood, Bodega Dunes, CA

Coastal redwoods (Sequoia sempervirens),
Samuel P Taylor State Park, CA

Monterey cypress (Cupressus macrocarpa),
Point Reyes National Seashore, CA

Snow globe fantasy, Mount Shasta, CA

My favorite book of fine-art tree photos is Listen to the Trees by John Sexton. Trees have never been photographed more sensitively or more evocatively. Sadly this book is now out of print, but you may find a copy in your local library.

If you’re interested in seeing more of my photography (anything but trees), please visit The Photo Continuum.

The other kind of white

Looking out over the neighborhood from upstairs this morning, I saw white, lots of it. No, not snow, but frost. All the roofs were covered, as were fences, lawns and cars. Magic!

The temperature was right around 32°F so I knew this wouldn’t last long. I grabbed my camera and tripod and took a quick series of photos. As I’m writing this, a couple of hours later, the frost is gone, the sun is out, and we’re having a picture postcard winter morning.

Special moments are so ephemeral.

Pear tree leaves and dandelion in our lawn

Catmint (Nepeta x faassenii ‘Six Hills Giant’)

Jerusalem sage (Phlomis fruticosa)

Lavender (Lavandula sp.)

Miscanthus plume (Miscanthus sinensis ‘Rigoletto’)

Mexican bush sage (Salvia leucantha)

Canna Tropicanna (Canna x generalis 'Tropicanna')

Echeveria with ice in the center (Echeveria imbricata hybrid)

Ice on car window

Frost on fence top

To see more photos of the gossamer beauty of frost, jump over to the site of fellow garden blogger Alan Lorence.

Nocturne in the mist

 
Fog at night transforms even the most familiar surroundings.

 

 

 

 

 

 

 

A quiet hush settles over the neighborhood.

 

 

 

 

 

 

 

Sounds, while muffled, seem paradoxically intensified.

 

 

 

 

 

 

 

What is mundane by day appears mysterious under the cloak of darkness.

Welcome, Sacramento Bee readers!

As of December 14th, my blog is being syndicated on the Sacramento Connect site operated by the Sacramento Bee. All my posts can be found under Interests > Garden.

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Don’t call me Moss, sir!

The other day, I wrote about moss popping up in our yard. In my original post, I had a photo of something that superficially looks like a moss, but really isn’t. Instead, it’s a lichen.

Lichen on rock in our back yard

Moss, lichen—they all grow on rocks and trees, so how big can the difference be? To my amazement, I realized that the difference is fundamental.

Mosses, even though they don’t have roots or flowers, are real plants with tiny stems and leaves. They prefer moist and dark areas and form mounds or mats that are soft to the touch. When no water is available, mosses dry up and can survive in that state for quite some time.

Tree moss (Isothecium myosuroides) in the Hoh Rain Forest, Olympic National Park, Washington

Lichens, on the other hand, are composite organisms consisting of a fungus living in a symbiotic relationship with a partner that is capable of photosynthesis (either an algae or a cyanobacterium). I like how lichenologist Trevor Goward describes it: “Lichens are fungi that have discovered agriculture”.

Green and red lichen, Cradle Mountain National Park, Tasmania

Unlike mosses, likens are less dependent on a steady supply of water and hence look more or less the same year round. They can survive in climatic extremes, like arctic tundra and hot deserts, but are also found in more temperate environments, sometimes even in the same place as mosses. (For a fascinating article on lichen, check out this post by fellow garden blogger Alan Lorence.)

Lichen and moss on boulder and tree, Yosemite National Park

For a layperson (like me), it’s sometimes difficult to distinguish between lichen (fungi + algae) and straight algae. I wasn’t sure if the orange-red in the next two photos is from lichen and algae, but it seems to be algae (specifically a green algae with “abundant orange secondary pigments forming a shaggy coat”).

The entire side of this house is covered by algae; this is actually the fog signal building at Point Reyes National Seashore north of San Francisco

Lichen (white) and algae (orange-red), Point Reyes National Seashore, Northern California

The green stuff covering the rocks and pilings in the next photo is algae as well.

Algae-covered rocks, La Push, Washington

It’s safe to say that the only place most gardeners will ever encounter algae in their yard is in a pond or other body of standing water. Unless they have water-front property, that is.

Another plant often confused with moss is “Spanish moss” (Tillandsia usneoides). Not a big surprise considering that “moss” is part of the name. Actually, Spanish moss is an epiphytic bromeliad. “Epiphytic” means that it grows on another plant, such as a tree, and extracts all its nutrients from the air and rain. Bromeliads include house plants such as billbergias and guzmanias; dyckias and hechtias popular in xeriscaping; as well as the common pineapple.

Spanish moss (Tillandsia usneoides) in Louisiana
Photo from Wikipedia

Spanish moss only grows in areas where the climate is sufficiently warm and humid, such as the southern and southeastern U.S. In fact, when I think of Spanish moss, pictures of stately antebellum mansions with oak-lined avenues come to mind. Spanish moss prefers southern live oak (Quercus virginiana) as well as bald cypress (Taxodium distichum), another iconic tree of the South, because the leaves of these trees leach minerals that serve as nutrients for Spanish moss. It hangs from trees like a long silvery beard and can form quite a sizable mass.

I think Spanish moss looks utterly beautiful; it creates a wistful and brooding atmosphere that brings to mind Gone with the Wind and other tales of days long gone by.