Tag Archives: invasive plants

seed bomb controversies

October 8, 2010 James 13 Comments

Someone has declared tomorrow, October 9, 2010 as International Tulip Guerrilla Gardening Day. [ Here’s the Facebook event. ] I won’t be discussing tulips, but this post does have a few things to say about guerrilla gardening.

The local native plant listserv lit up a few weeks ago over a story in the local paper about seed bombs that ran on August 30.

If you’re not up on seed bombs here’s a little background: The idea of rolling up seeds and clay to make little balls that could be lobbed into an area to sow the seeds probably goes back centuries. But the technique was revitalized in Japan by Masanobu Fukuoka during the last century as part of a low-disturbance style of planting. Instead of tilling the ground, these lumps of seed and clay could be spread out on the earth’s surface, reducing ground disturbance and the resulting need to weed so intensely. Up to that point the little round seed delivery devices were known as seed balls, earth balls or even clay dumplings.

With the rise of the militant guerrilla gardening movement, the little seed ball became one of the weapons of choice against what was perceived as urban blight. An untended vacant lot could be showered with with these little projectiles, and a few good rains could see the seeds sprouting and taking over what might have been invasive weeds. In the testosterone-soaked guerrilla garden movement the friendly seed ball quickly became rebranded a “seed bomb.”

Now we return to current times and the article I started out mentioning: The original cut of the article touted how these particular seed bombs contained native species, including–cue the scary music–sweet alyssum! While the definitely-not-native sweet alyssum isn’t one of the top two or three most invasive plants, it’s undisputedly a problem and has no business in a seed ball that could get hurled into an wild area by a well-meaning guerrilla gardener. In my own garden, a sowing of the stuff twenty years ago has led to a situation of seedlings still popping up every time it rains.

The article generated all sorts of comments, and several people wrote directly to the maker of these particular seed bombs mentioned in the paper, Jim Mumford of GreenScaped Buildings. One thing led to another and it was revealed that the newspaper got hold of a bad list of ingredients, and that sweet alyssum had never been a part of the mix. The newspaper ran a sidebar correction to the story. (The species used to me looks like the California native wildflower mix offered by S&S Seeds.)

Still by that point the damage had been done, and the creator of these particular balls felt like he needed to show up last month at the lion’s den of the the native plant society meeting to do some damage control. He brought us all a big bag of free seed balls. He ran down the real list of species that were really in the mix. He reiterated that sweet alyssum had never been part of the mix.

When it was all over, several in the audience were saying they had no trouble with the species used to make the seed balls. The plants were all from California and weren’t considered invasive. But this was a tough crowd to please and there were still a few lingering concerns.

Within the state there are distinct forms of many of the plants in the mix, and each region’s flora has a particular balance of local plants. If you bring in a non-local strain of a “native” plant you might do something to mess up that balance. Really the only way to make a safe seed bomb that you might lob into a wild area would be to use seed from local plants. Seed bombs are fun, but keep them confined to urban gardens away from wildlands and don’t go tossing the balls into your neighborhood canyon thinking you’re doing the earth a favor.

The story of the San Diego seed bombs has a relatively happy ending. But over the last couple of months I’ve run across a seller who offers “West Coast seed bombs” on Etsy and through a number of boutiques. The vendor lists the ingredients as “Cornflower, Siberian Wallflower, Garland Chrysanthemum, Shasta Daisy, Farewell-to-Spring, Plains Coreopsis, Sulphur Cosmos, Wild Cosmos, African Daisy, Sweet William, California Poppy, Blanket Flower, Baby’s Breath, Tidy Tips, Mountain Phlox, Blue Flax, Sweet Alyssum, Annual Lupine, Lemon Mint, Red Poppy, Rocky Mountain Penstemon, Desert Bluebell, Mexican Hat, Gloriosa Daisy, None-so-Pretty, Prairie Coneflower, and Black-eyed Susan.” Not only does this mix include sweet alyssum, it contains garland chrysanthemum, one of our local scourges. Some parts of the country also have problems with the baby’s breath.

The issue of invasives aside, it makes me wonder about people’s definitions of what constitutes a wildflower. Siberian wallflower on the West Coast? African daisy?

I got in touch with the makers of these seed bombs, and they were quite responsive, saying “we are continually developing this product. Your feedback will help inform our product going forward and is much appreciated. We will gladly include information about the danger of invasive species in our product from here forward.” And they asked for suggestions for plants that would be better citizens in a West Coast wildflower mix. Off the top of my head I referred them to the list accompanying the article, and added just a few ideas of California natives not on the list: baby blue eyes, fivespot, coast sunflower, desert marigold. What others would you recommend?

If the makers of these seed balls drastically change their mix we could have another relatively happy ending. Most of us probably have non-native plants in our gardens. If what happens in the garden stays in the garden, then it’s not quite a doom and gloom scenario. But we definitely have a problem if people start throwing seed bombs into the wilds.

In this case, accompanying the seed balls with a note about the potential threat of invasive plants could do as much good as reformulating the mix.

gardening, my garden

a new weed

June 20, 2010 James 10 Comments

This past winter I was noticing a weed popping up all around the yard that I hadn’t noticed before. I was mentioning it to John, and added, “I’m not sure what it is, though think it could be some sort of euphorbia.”

Then in the gently tactful way spouses have of correcting you and pointing out your blind spots he quietly cleared his throat and pointed to one of the four young potted plants we have around the garden of Euphorbia lambii, one of my dry garden-adapted plants from the Canary Islands. “Maybe it’s that?”

Uh, like duh. What else would it be?

Last year was the first that these plants bloomed, and this spring they bloomed with a vengeance. During sunny weather over the last few weeks I’ve heard little popping noises from the direction of the plants, and have come to the conclusion that the sounds were that of seed pods exploding and jettisoning the dust-like seed everywhere.

I may come to regret the day I introduced these to the garden, which according to my records is March 9, 2008.

Speaking of weedy plants, here’s another surprise seedling from the garden, a little baby red fountain grass, one of three seedlings I noticed this year. In recent years the related green fountain grass, Pennisetum setaceum has become a noxious (though stunningly beautiful) weed and has landed high on virtually every thou-shalt-not-plant list issued for California. But many people gave a by to this related red plant. It was often pushed as being sterile and incapable of reproducing by seed, a piece of misinformation even I relayed in this blog. (I’ve corrected that earlier oops in case anyone reads that earlier post.) As you can see here it can reproduce by seed, though this form doesn’t spawn the same way regular fountain grass does. Nor is it immediately the same monster pest that feather grass (Nassella tenuissima) can be.

Poking around the web I found an updated plant description at San Marcos Growers that includes some interesting background on this plant:

Recent work in preparation for the grass sections of the Flora of North America, which will include naturalized and cultivated grasses, indicates that the name chosen for this plant will be Pennisetum advena or perhaps P. x advena. Dr. Joseph K. Wipff, previously with Texas A&M and now a turfgrass breeder, wrote the section on Pennisetum and has indicated that Red Fountain Grass is most likely a cross between P. setaceum and P. macrostachys (AKA ‘Burgundy Giant’). As a hybrid the name would most appropriately be Pennisetum x advena ‘Rubrum’. The latin word advena means “newly arrived” or “stranger.”

So is it safe to plant this form of fountain grass? Here’s my thinking: Hybrids between species are often sterile. (Think of mules, the offspring of a horse and a donkey.) But every now and then something happens that allows the hybrid to reproduce. Sometimes the seedlings will be just as nearly sterile as the immediate parent, but other times a mutation could render the seedling entirely fertile. In that latter scenario the nearly-sterile fountain grass could turn into something with the ugly invasive potential of its Pennisetum setaceum ancestor.

In other words, today I would be cautious and not plant it. Unfortunately, almost twenty years ago, we designed the front yard around a big mound of the stuff. The plants look stunning and move graciously in response to the breezes. Their size is perfect for the spot, and their red color is unmatched among other grasses. Every now and then I look at other options, like those recommended in the Don’t Plant a Pest brochure put out by the California Invasive Plant Council. But these lists often fall short in the alternatives they offer and end up reading like, “Cheesecake is bad for you. Would you like to eat this delicious raw rutabaga instead?” So…I’m still looking for the perfect replacement plant–hopefully some sort of native, but in the meantime I’m pulling the occasional seedlings.

gardening, my garden

plant it once, have it forever

April 3, 2010 James 10 Comments

There’s a prominent Northern California nursery* that advertises on its website that a variety will self-sow and naturalize. Or in its peppy, enthusiastic way: “Reseeds!” One of the plants so listed has a followup note: “Due to agricultural restrictions, we cannot ship this plant to Arkansas, New Jersey, New York, Oklahoma, South Carolina, and Texas.”

Read between the lines: This plant, under the right conditions, might just run wild, out of control, and take over your garden or an ecosystem! (Not all plant restrictions are based on their invasive potential, however. For instance, some might be controlled because of known pests or diseases the species may harbor.)

Over the years I’ve added interesting plants to the garden, only to have them sow and propagate themselves all over the garden. For most of these, I don’t worry huge amounts that they’ll escape to the nearby wilds because they’re wimps when not pampered in a garden, but with regular watering they’re aggressive thugs. Pretty thugs, to be sure. But still thugs.

Here are a few of my mistakes. Some are merely annoying. Others require multiple hours of labor every year to keep under control. Colder areas might not have the same problems with these that I do, but I’m sure you have your own monsters. (My apologies in advance to the fine nation of Mexico. I just noticed that four of my selections have “Mexican” in their common names…)

Mexican petunia (Ruellia brittoniana). Pretty, tough. Also pretty tough to eradicate in my garden once it got a foothold. I should have paid attention when the guy at the plant sale warned me that it might spread. According to Floridata, “Mexican petunia is listed as a Category I invasive species by the Florida Exotic Pest Plant Council. This means that it is ‘altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives.’ This warning applies to all parts of the state of Florida (and other areas with similar mild climates). Where hardy, the Mexican petunia excels at invading wetlands.” It also can be a nuisance in a dry garden like mine where it spreads underground and via exploding seed pods.

Mexican fan palm (Washingtonia robusta). Maybe it’s a uniquely California thing: You go out to the garden to pull weeds, and along with the crabgrass and spurge, you end up pulling up little palm trees. Folks in colder climes might be thrilled to have some of these, but here they’re a nuisance. Our Mexican fan came with the house, and it took us a few years to finally remove it. All that time we were yanking baby palms all over the front yard, and the seedbank remained viable for several years afterward.

Mexican feather grass (Nassella tenuissima). I’ve dinged this plant several times before. I won’t add anything more here other than to note that I’ve probably pulled up a hundred seedlings this season. At least this is down from the orgy of seedlings that I had when there was a harem of adult plants in the garden that apparently had nothing on their mind except sex and reproduction.

Mexican evening primrose (Oenothera species, I think it was O. speciosa). I was on vacation at the Grand Canyon in 1991. Innocently I bought a packet of seeds of these that were sold as a “wildflower.” I was thrilled when they came up the first year and I had a gregarious patch of delicate bright pink flowers where there’d been a patch of dirt previously. Little did I know they’d resow and spread by underground runners and continue to annoy me to this day. Wild flower, indeed.

Sweet alyssum (Lobularia maritima). Don’t let the “sweet” in its common name fool you. I continue to weed alyssum seedlings popping up around the garden from a single packet of mixed colors I planted in the late 1980s.

Fortnight lily (Dietes iridioides). A few clumps of these came with the house. The tough, hard seeds lay dormant in the ground for years and plague you with unwanted seedlings long after you’ve removed their source.

Calla lily (Zantedeschia aethiopica). I’ll have to admit that I have a soft spot for these plants and don’t pull them out the same way I pull out other unwelcome plants. My parent’s house came with a fifty-foot foundation planting of them on the north side of their house. The way the plant can spread, however, now makes me think the previous owners might have started with just a half dozen plants. Feral callas are plants of concern in some California wetlands. A couple well-watered garden spots seem to generate calla lilies out of thin air.

Epazote (Dysphania ambrosioides). I won’t quite call planting this Mexican herb a mistake, since I use occasionally in cooking. It does spread about the garden a bit, however, and pops up in unexpected places. There are reports [ including this one ] that it’s colonized parts of New York’s Central Park–though that’s not my doing. I popped over to Wikipedia and learned this pretty interesting detail I’d never heard before: “Epazote essential oil contains ascaridole…; in pure form, it is an explosive sensitive to shock.” Botanical TNT–Wild!

To my mistakes, I’ll add some native California annuals and perennials that have been really successful in reproducing themselves in my garden. Currently, my plants are wandering around an area where they’re desired and haven’t escaped far. I won’t call them mistakes at this point, but I can see that they could become unwelcome in some situations.

California poppies (Escholzia californica). What? Our sacred state flower?! Well, there are some unwelcome escaped colonies in Chile and Australia. And the seeds regularly find their way into cracks in the pavement.

Baby blue eyes (Nemophila menziesii). Not really what I’d call a thug, though these seem to be pretty successful at reproducing themselves. It’s easy to pull out the occasional unwanted plants, but who’d want to?

Clarkia (Clarkia spp.). I haven’t grown many clarkia species, but the one that seems to wander around the most for me is C. rubicunda ssp. blasdalei.

*There’s a good chance you’ll have guessed the identity of this well-known nursery if you’ve spent any time at its website. I don’t mean to diss them at all. You can get potentially rambunctious plants from virtually all nurseries, including those dedicated to native plants.

gardening, landscape

our gardens after we’re gone

February 2, 2010 James 26 Comments

Ever wonder what your garden would look like if the human caretakers just vanished?

Maybe I’ve been inspired by all the disaster flicks like 2012 or the History Channel’s Life After People series. But envisioning gardens after gardeners is an interesting intellectual exercise that might help us answer that pesky question: What is a garden?

Would all the invasive species take over? Would the native plants reclaim their turf? For how long would you still be able to tell that a garden existed in a spot in the first place?

I looked at parts of my back yard and tried to imagine what would happen.

Within the first month, in Southern California’s dry climate, most of the potted plants would perish for lack of water. Some of the succulents might hang on longer, but without an extensive root system in the ground, they’d be doomed.

This little frog would be staring at a bog garden where all the bog plants have died back, once again for lack of water.

Within two or three months the fishponds would be dry: no waterlilies, no cattails, no sedges, no water for the local birds.

This pathetic patch of grass would go through boom and bust cycles, turning green with the rains, dying back to brown other times of year. Seeds of other plants better adapted to the conditions would eventually take hold. Maybe some plants from the local canyon. Maybe some hardy exotic or invasive species.

Behind the back fence of the house is this slope dominated by rampant iceplant. The the neighbor behind me and I haven’t been able agree on what to do with the space. I’ve planted a small collection of native plants to help stabilize the slope. These are species that with only once exception can be found within a five mile radius of the house, and include plants like this nightshade, Solanum parishii…

…and Del Mar Manzanita, Arctostaphylos glandulosa ssp. crassifolia, an extremely rare plant that’s on the Federal endangered species list. The neighbor, however, loves their iceplant and can’t imagine of a slope without this gawdawful invasive species clamoring all over it. The local chapter of the California Native Plant Society has prepared a great pamphlet on getting rid of iceplant that you can view [ here ]. It goes into some great reasons to get rid of the stuff:

Planted on hillsides of thousands of homes in San Diego, it has since crawled off the original site and into neighboring Open Space parks, endangering unique plants by smothering them. Iceplant provides little habitat value compared to the plant community that it is replacing. Compared to the native shrubs, iceplant has very shallow roots that do not hold soil well; close inspection often reveals gullies underneath the twisted mat of vines. After rain, Iceplant engorges with water, substantially increasing its weight. As a result, iceplant can cause the deterioration of steep hillsides by encouraging slumping – potentially endangering the house above.

For people in suburbia, “habitat value” might mean plants that harbor scary wild animals and bugs, so that’s not always the most compelling reason to go native. The fact that iceplant might endanger their property values could be more persuasive.

So, returning to my main topic, the iceplant would probably overrun most of the native plants in a very few years and form a deep pile. Once we neglected the slope for a few years and found that the mat of iceplant was starting to push the back fence over. Within ten years the fence would begin to fail and the iceplant would begin its descent into the lower garden.

These plants along the back fence would stand a chance of surviving without water. The yucca, palm, protea would be tall enough to survive an onslaught of marauding iceplant from behind. They’re plants that don’t require much maintenance, and this wall of foliage would probably look unchanged for a number of years. But the lower aloes and other succulents would likely be smothered by the iceplant.

This apricot against the back fence never looks great without summer watering, but it survives. It’s tall enough that it would probably survive the iceplant invasion. Some of the adjacent native plants do great with the natural conditions. They might not cope so well with the marauding iceplant.

The neighbor on the side has Algerian ivy that requires constant clipping to keep it next door. Within two years it would begin to establish itself in the back yard. Taller plants that might survive the iceplant invasion might have ivy crawling up and smothering them.

This raised bed near the house is where veggies and irrigated plants live. Most of the exotic plants wouldn’t make it without water. The Dr. Hurd manzanita, the bougainvillea vine and maybe the Garrya elliptica would probably hang in there, however, maybe for decades, maybe for much longer.

Fifty to seventy-five years out the house would start to fail. Plants might begin to move in. The surrounding garden space would be overgrown with the hardiest drought-adapted species. I almost never plant in rows, but the mixed origins of the species–South Africa, South America, Europe, as well as from all over California, not just local species–would clue an investigator into the fact that a garden existed on the site. The relationships between the plants would be dictated by nature, not a gardener preserving order between plants with mismatched levels of vigor.

Chances are excellent that one hundred years out, maybe two hundred or more, the most persistent invasive species would still be here. Iceplant and ivy, plus fennel and black mustard that have invaded the local canyons, would feature in the neighborhood landscape. But while many invasives bask in the newly disturbed earth of a garden or the re-engineered grades around roads, they don’t always do so well long-term. Biologists have suggested that many native plants would return to a place where they’re not being pulled out or constantly mowed. My yard might be colonized by the local Mexican elderberry, or toyon, or lemonade berry, or prickly pear. And maybe some of the plants I’ve already introduced to the yard will persist and reproduce. The restoration of nature might spread from my house and from the wild edges of nature just a few houses away.

Even after nature returns, the occasional hardy exotic plant surviving amidst the natives, along with some of the neighborhood’s plantings of trees and shrubs in rows will make it obvious: There used to be gardens here.

gardening, my garden

out with the old

November 22, 2009 James 8 Comments

This will be the year that I finally win the battle against Mexican feathergrass, the blogger said optimistically. I doubt that I’ll be seeing the end of this beautiful but wildly overprolific grass any time soon, but I’ve completed pulling all the parent plants in the garden. With the source of seeds removed, the hundreds of unwanted seedlings that I have to pull up every year should diminish.

So how bad was the feathergrass problem? Here’s a shot underneath a black sage in the back yard, no closer than seventy-five feet from the nearest adult feathergrass plant capable of setting seed. The seed just blew downwind and set up household in the sheltered germinating conditions in the shade of the sage. Other areas of the garden will look like this when the rains begin again and all the banked seed begins to germinate. I hate to think that these might get to the local urban canyon, four houses away.

My relationship with Mexican feathergrass (Nassella tenuissima or Stipa tenuissima) started off in the early 1990s. Like most people who’ve planted it, I saw it at the nursery with its stalks weaving delicately in its beguiling come-hither way and fell in love. I bought two.

At first things between us went well. The grasses spread a bit, but the thought of free plants were a real bonus. I even gave plants away.

Though prolific, the plant isn’t currently listed as an invasive species on the master Cal-IPA inventory, but appears on a 2007 list of nominated species. It’s clear from some of the comments on a Fresh Dirt posting that it’s a growing problem in some areas, my neighborhood included.

Yes, the stuff is gorgeous. But too high maintenance and potentially problematic in my area. It’s time for us to part ways.

So how will I get my fix for delicate, feathery grasses? This year has been my first time growing the native Aristida purpurea, purple three-awn, a species that’s found locally. The plant is shorter than the common feathergrass, which might be a bonus, depending on your garden situation. And unlike the nassella it has a decidedly purple color to it while it’s growing–very nice. I’ll post photos once my plants get a little bigger. I have no idea if it’ll be the same issue of the plant volunteering all over the garden, though I doubt it. Even if it escapes to the wilds, it’ll be in the company of others of its species. Not a problem.

landscape, plant profiles

the chrysanthemum problem

May 13, 2009 James 6 Comments

All around town, both roadside and trailside, the garland chrysanthemums have been blooming.

The perky spawn of plants that have been grown for centuries in China and Japan for their tasty young green leaves, Chrysanthemum coronarium has come to be a big nuisance in many disturbed areas of Southern California.

But rather than getting all negative and cursing the plant, let me try a different tack to try to encourage everyone to rip it out by its pretty little roots:

Did you know that 100 grams of boiled garland chrysanthemum provides 51% of your recommended daily requirements of vitamin A, 40% of vitamin C, 21% of iron, and has only 20 calories? (That’s according to healthalicious.com.)

OregonLive.com offers some kitchen ideas for garland chrysanthemum: “Lightly saute the leaves and stems or whole 4- to 6-inch seedlings with sesame seeds, garlic, ginger and soy sauce… Eat raw in salad, add to soups containing fresh ginger, or dunk in fritter batter and deep-fry.”

(Be sure your greens come from a site other than a roadside that might have been sprayed with herbicides by the city. And be sure you’re eating garland chrysanthemum instead of the somewhat similar bush sunflower (encelia) or San Diego sunflower (viguiera).)

There are of course other reasons to pull up this plant. The Tijuana River National Estuarine Research Reserve site puts it succinctly: “[C]hrysanthemum forms fields that overtake native plants such as California buckwheat and sagebrush–both these plants provide food and shelter for native birds, insects and other animals.”

So in the end garland chrysanthemum is the perfect weed. Whether you respond to thoughts of a healthy snack or to appeals of doing what you can to make the world a better place, you can get out your weeding tools and go to town.

A final thought: Wouldn’t it be great for green-conscious restaurants to offer tasty and hip entrees on their menu that contain locally-harvested garland chrysanthemum greens that otherwise would have been damaging the ecosystem? Or maybe we could stock stalls at farmer’s markets with piles of the stuff? Why not turn this over-abundant invasive plant into a resource that could be cropped, improving the local landscape at the same time?

Eat up, everyone!

This post is dedicated to Outofdoors, who first thought up the idea of dedicating the 13th of the month to posts on invasive species.

gardening, landscape, landscape design, places, plant profiles

…and some not so garden-worthy

March 13, 2009 James 4 Comments

You could probably gather together six gardeners and get six different opinions of what would make a plant garden-worthy. But I suspect there might be somewhat more agreement on certain other plants that probably shouldn’t be included in a garden. Here are some encounters from Sunday’s trip to Tecolote Canyon that would fall easily into most people’s less-than-desirable category.

I’ll have to admit to actually liking this plant to the right. During the winter it drops its leaves and is an attractive thicket of upright or sprawling branches. This time of year it starts new growth that has this warm red-brown coloration. It’ll flower soon, and then set some loose clusters of white berries. Pretty, yes, and native, and important to wildlife. But this is poison oak. Maybe not the best choice for small backyard gardens…

Most of the rest of my list below is comprised of exotic plants that have staked a claim for themselves at the expense of the native species. Different locations have their own list of invasives, so what you see below is tailored to Southern California. Some of these plants could be good choices for other locations. Others would be trouble almost anywhere you grow them.

[ At this point I’d like to dedicate the rest of this Friday the thirteenth post to Outofdoors, who last month devoted her Friday the thirteenth post to invasive plant species. ]

I won’t go into too much detail about this troublesome trio. People have been working hard to get the word out on pampas grass, green fountain grass, and iceplant. The grasses, in particular, can be gorgeous things in gardens, waving in the breeze and lending their dramatic form to groups of softly mounding landscape shrubs. You can see why people want to grow them. But are they garden-worthy in Southern California?

All three of these quickly check out of people’s gardens and make for the wilds. I found both grasses and plenty of iceplant escaped into the canyon, here on this hillside and in other spots. So, as pretty as they can be–and I consider this drift of fountain grass in the second photo to be particularly poetic–these three would be better left in their native lands, or grown in climates where the weather might limit their spread.

This is the first flower I saw this season on the local plants of onion weed (Asphodelus fistulosus). The first time I saw it I thought it was a wildflower and wanted some for my garden. In full bloom the stalks of white flowers are an impressive sight. But they do spread like crazy. Not a good choice for the garden.

This combination of plants looks as impressive as any planting assembled by practitioners of the New Perennials garden movement. But once again, the plants aren’t really welcome additions to the canyon. In the foreground is teasel (Dipsacus sp.), a plant with excellent year-round architectural structure but having invasive tendencies that are considered “Moderate” by the California Invasive Plant Council (Cal-IPC). Here it’s set against a background of last season’s black mustard, a problem in these parts since it was introduced by the Spanish in the eighteenth century. The Cal-IPC only considers the mustard’s ranginess to be of “Moderate” concern, but also states: “Primarily a weed of disturbed sites, but can be locally a more significant problem in wildlands.” I’d say it’s a more significant pest locally.

Fennel can be attractive in the herb garden, but like the rest of the invasives in this post, this is another plant that gets around. Its overall undesirable impacts are considered “High” by the Cal-IPC. If I see fennel offered in the local nurseries it’s usually the bronze colored strain. It’s less vigorous, but all forms are considered invasive. I do wish this were a better choice for gardens because it hosts swallowtail butterflies, but at least there’s plenty of swallowtail food out in the local canyons. The butterflies won’t starve. Okay, I’ll pass.

Say “Old California” to anyone who’s lived in these parts for long, and this plant will probably come to mind. The ~~Brazilian~~ Peruvian pepper tree forms a gorgeous tree with long, delicate leaves that move any time there’s a breeze. But unfortunately the plants develop berries that the birds find irresistible. While the Cal-IPC considers their threat to California to be only “Limited,” there are plants that would be better choices.

The Australian peppermint willow (Agonis flexuosa), although not a native plant, is a good drought-tolerant substitute that looks a bit like the pepper tree but doesn’t share its invasive tendencies. If you must have a delicate weeping tree that says “Old California” but don’t mind a lilting Australian accent, this would be a better choice–and you can get varieties with either green or dramatic black foliage. Or you could give up altogether on the colonial look and go in for any of the truly native trees. It doesn’t get any more “old California” than that.

As I reread this post I’m struck that I’m probably not doing a particularly good job of discouraging people from growing these plants. I keep going back to the beautiful redeeming qualities of these invasives, and I guess that’s why they continue to be such a problem. The mind tells you they might be bad news, but sometimes it’s hard to say no.

With this last image I leave the plant kingdom and turn to another species that’s native to the local canyons. This one I think you’ll definitely agree you wouldn’t want around. I won’t assume that you like snakes any more than I do, so if you want to see the picture you’ll have to click HERE.

Still, who among you doesn’t think baby animals are just the cutest things? Now, everybody, say “awwwww”… This is a little baby southern Pacific rattler, probably no longer than my forearm and too young to rattle. I’m deathly afraid of snakes but managed to fend off the fear to snap the picture and watch the snake as it coiled itself defensively and make like a sidewinder, sliding backwards into the grasses.

I have to respect these animals since they do wonders to keep down the rodent population. And they’re every bit as native as the poison oak I showed earlier. But after having had one of these in the backyard facing off against my cat, I’ve definitely decided this is another species that’s not garden-worthy, at least in my enclosed little space.

I admit it, I’m a wimp. Nature isn’t always convenient is it? But throw out the rattlesnakes and pampas grass and black mustard and fennels and you’re still left tens of thousands of cool and friendly selections to invite into the garden.

gardening, places

the long brown season

July 29, 2008 James 4 Comments

When you spend your time in San Diego’s well-watered burbs it’s easy to forget that you’re living in the middle of a desert. The last significant rainfall in town occurred in February, and the unirrigated natural lands around town have long ago begun their transformation into the long brown season.

My recent little excursion to Los Peñasquitos Canyon, a local open-space preserve between San Diego and Del Mar, gave me a chance to see what the natural world is doing in these parts.

Not everything is brown, of course. Some plants are tapped into locations with residual moisture. Others have adapted to the climate and have the stamina to stay green year-round.

Here are a few of the plants still showing colors other than brown:

Flat-topped buckwheat (Eriogonum fasciculatum) a native plant.

Wild rose (Rosa californica) a native.

Fennel (Foeniculum vulgare) an exotic, invasive species. This is the culinary plant from the Mediterranean that has escaped into the wilds.

Poison oak (Toxicodendron diversilobum) a native–one of the few plants that turns blazing red in the fall. Even now, it’s showing some of that red color.

Thistle in bloom. I’m not sure if this is native or not, but it’s not the hyper-nasty Russian thistle (the dried flowers of which are shown in the large photo above). [Correction/edit August 1: This is actually a teasel, not a thistle. Like the escaped fennel above, this too is a renegade exotic species. Pretty, though…]

It’s a condition of our consumer culture and times to want what we don’t have. Living in San Diego, most of the plant materials that people expect to find in their home gardens fall outside of the category of what occurs naturally or is well-suited to the area.

It’s always instructive to visit the natural preserves to see plants–even the nasty invasives–that are supremely well-designed to live in this climate. Some of the plants in these parks would do extremely well in gardens. But it’s hard letting go of plants that many of us associate with places we’ve lived in and even people we’ve known.

My own yard has several areas that I consider my guilty pleasure zones. I have pieces of a bromeliad and a kahili ginger that I was given in the 1970s, as well as the green rose from that I dug up from the house where I grew up in the Los Angeles area. And I’m a natural born collector who has a hard time saying no to interesting plants. These plants all require some water and tending beyond what nature brings.

But they’re counterbalanced by garden areas planted with drought-tolerant species, local and introduced, that receive almost no water and attention over the summer. As time goes on, I’ll be expanding those areas. Don’t expect me any time soon, however, to plant poison oak, as pretty and hardy as the plant is. I have my limits as to how much true nature I want in my garden…

[ Lost in the Landscape ]

Tag Archives: invasive plants

seed bomb controversies

a new weed

plant it once, have it forever

our gardens after we’re gone

out with the old

the chrysanthemum problem

…and some not so garden-worthy

the long brown season

an artist loosed in a garden