Thursday, July 24, 2008

Native Water Garden

I rarely see a variety of Hawaii’s native plants being used for landscaping outside commercial buildings, so I was pleasantly surprised with the recently installed plantings outside Kawaiha’o Plaza, the administrative offices of Kamehameha Schools in downtown Honolulu. This multi-level raised planter seems to be designed as a miniature ahupua’a.

Mauka plants such as naupaka kahuahiwi, palapalai, and koa were planted at the top level...

Kalo was growing in a tiny lo'i at midheight along with native sedges...

Even 'ihi'ihi was there, an unusual endangered native fern that resembles a four-leaf clover. In the wild it grows in vernal pools, so naturally it's a good plant for the water garden...

At the very bottom were plantings of makai plants such as alula...

hala pepe and 'ae'ae...

As the landscaping matures it will be interesting to see how many of the plants will have to be removed or replaced, if any. The koa seemed planted too close to the building, and I was surprised to see the naupaka kuahiwi was still thriving even though it was at this low elevation. Nonetheless, I have much to learn from this landscaper -- I’m impressed! I’ll have to revisit in the future to check up on this very akamai and inspiring native water garden.

Monday, July 14, 2008

A Bittersweet Tale

Bittermelons look like what hedgehogs would be if they fell under a wizard's spell and became vegetables.

Once in a great while I like bittermelon Chinese-style with furu, fermented tofu. My Filipino neighbor loves bittermelon. Birds love his ripe bittermelon fruit and scatter the seeds, so occasionally I find vines growing in the middle of the lawn, which I mow anyway. However, now there's a bittermelon vine growing on the fence between me and my other Filipino neighbor. I'm sure neither of us planted it, but I'm not entirely sure if he's eating from it. He hasn't sprayed it, and usually he sprays the fenceline. It's actually my fence, so I guess I could just rip the vine out. But I don't want to spoil my neighbor's enjoyment, that is, in case he is in fact enjoying it. I suppose I could ask him, but he never answers the door when I go over.

So the vine just grows. Is it a weed? Some people would say if someone has found use for a plant, it isn't a weed. So I guess it isn't, because for me right now it serves as a reason to get to know my neighbor a bit better.


Look! Is this Drymaria a half-dead or a half-alive weed?

Does limonene work as an herbicide? Two weeks after spraying I've decided the answer is yes...and no.

The label on the pesticide says that it is most effective on annual weeds shorter than 6 inches. I wanted to see what difference weed whacking would make before spraying, so I used a string trimmer to cut most of the weeds to ground level. I also left one patch uncut.

I found that the herbicide appeared to affect the foliage of some weeds that were whacked that weren’t affected when left intact. However, weed whacking before spraying didn’t seem to make any difference for hardier weeds. Limonene appeared to cause foliage to burn on some weeds but it didn’t outright kill them; the affected weeds put out new growth within 2 weeks.

For example, garden spurge greater than 6 inches that was sprayed looked healthy and unaffected, however buttonweed foliage burned though the stems seemed unharmed. Nutgrass sedge seemed to be unaffected by any of the treatments.

Limonene seemed to affect foliage of some weeds quickly. Oxalis turned yellow immediately upon spraying, as did Drymaria. I mowed sleeping grass (Mimosa pudica) in the lawn, then sprayed it; the weed and the grass surrounding it turned brown, but new growth appeared within 2 weeks.

Okay, so all of this is anecdotal and not so scientific, but you’ve read this far so you might as well read the rest of this half-baked report.

Unless someone convinces me otherwise, I’m not using limonene as a weed killer again. I’m sticking to my electric string trimmer and propane flamer for weeds that aren't kept in check with mulching and hand-pulling. Spraying limonene was a pleasant, fragrant exercise in weed abuse, but certainly not worth $21.99 as a weed control strategy. My conclusion: When life gives you lemons, don’t make weed killer.

Thursday, July 3, 2008

De-lovely, De-weeds & D-limonene

A couple of weeks ago I happened to be wandering the “organic” aisle of my local hardware store, as I do every now and then to see what’s been added to the store’s inventory. In the past 6 years I’ve watched this section grow from one or two products to more than a dozen different ones filling half the length of the aisle, which I’d say is an indication of consumer demand. And on this most recent perusal I found something I’d never seen before: “organic” weed killer based on D-limonene, a citrus oil extracted from the rinds of oranges.

I’ve used other natural, earth-friendly limonene-based products: adhesive remover/solvent/degreaser, household cleaner, ant killer. Sounds like powerful stuff, doesn’t it? Since it’s OMRI-listed, of course it’ll be killing those weeds softly, shouldn’t it? However, if something says it’s “worryfree” I start getting skeptical. Is it safe, and does it work – really? I had to try it.

I usually pull weeds by hand or use a propane flamer to burn them. So a 32 oz bottle of concentrate for $21.99 nearly took my breath away – this is not cheap stuff, but then it wasn’t locked up like the Roundup was. On the way home I stopped to visit a friend. When I got back to my truck and opened the door, my sinuses were blasted with a familiar odor from small-kid time: Lemon Pledge. An oily scent, not entirely beckoning, like a crateful of Meyers with an industrial undertone. Apparently the bottle tipped, and even though the cashier had tightened it, it leaked into the plastic bag and a tiny bit spilled on the floor mat. Even a week later, each time my visiting niece got into my truck, she’d inhale deeply and sigh, “Mmm, auntie, your car smells so nice.” Not your typical reaction, but keep it out of reach of children anyway – read the label, there are some warnings.

The label says this weed killer takes care of “annual weeds” and that “perennial weeds may need more than one treatment.” I’m not sure what annual weeds are in Hawai'i though, since many plants perennialize here. When I bought the weed killer I did not know that even though it is a concentrate, 32 oz makes only 1 gallon of spray! I’ve decided that if this 70% D-limonene pesticide proves to be effective I’m going to use it only in areas next to the house where I don’t want to use flame.

Have a look at some of the weeds I’m trying it on.

(Warning: the following pictures may be disturbing to those with obsessive tendencies.)

garden spurge, koko kahiki, Chamaesyce hirta

Phyllanthus amarus

partridge pea; lauiki, Chamaecrista nictitans

bubble gum plant; root beer plant, Polygala paniculata

buttonweed (Spermacoce assurgens) oxalis and some assorted grasses and sedges.

Stay tuned for the results in the next couple of weeks!