Variety glauca with lots of prickles and almost none (Nearly-prickle-free photograph courtesy of Matthew Kahokuloa Jr. CC BY-NC 4.0.). As you can see here, variety decipiens (against the sky) has many more prickles on its fruit capsules than var. glauca (Photograph courtesy of sea-kangaroo CC BY-NC-ND 4.0.). Don't be fooled by the Mexican prickly poppy (Argemone mexicana) with its yellow flower, which has naturalized (now grows wild) in Hawai‘i (Photograph courtesy of Dinesh Valke CC BY-SA 2.0.). Several pua kala decorate a home walkway. Seedlings can pop up in the most unlikely places. Pua kala's odd-looking seedlings in the header photograph.

Growth Requirements

General 

    Argemone glauca, with its otherworldly colored foliage and bright flowers, is a fascinating addition to any landscape. And, we believe, any negatives attributed to its prickles are overstated. Yes, the prickles are painful to the touch, but they are also much less dangerous than the thorns of popular landscape plants like cacti, roses, and bougainvillea. Perhaps, the only true downside to pua kala is its very short lifespan, but we offer a partial solution to that below. Use a lone pua kala as a landscape accent or plant several together to more clearly attract attention. Creative gardeners can even use pua kala's prickles to discourage or direct foot traffic. You can also keep pua kala in a container where it will flower, but will likely become root-bound and stunted. 

    Plant your pua kala in a site with lots of full sunlight for the best growth, color (i.e., maximum blue-silver), and most flowers. Avoid windy sites because pua kala tends to get blown over. This normally doesn't kill the plant, but could place it somewhere you don't want, like across a walkway. Secure a bamboo stake along the plant's central stem to prevent it from toppling or to straighten a fallen plant. 

    Pua kala is extremely heat and drought tolerant. Therefore, once established in the ground, water it very little or not at all. Too much watering can result in top-heavy plants, which tend to fall over. If you do water your pua kala, do so with infrequent (e.g., once a month) long deep waterings rather than short frequent showers; the surface soil should be dry most of the time.

    Pua kala will grow in anything from cinder/lava to clay, provided the soil does not become waterlogged for more than a day. In a container, use a media mix with a lot (50% or more) of black cinders or perlite.

    We have not found it necessary to fertilize pua kala, and actually discourage it because it can result in excessive growth (and toppled plants). After a primary stem has aged and begun to wither, prune it back to the plant's base to encourage new shoots. You can also try removing the top half of the primary stem to encourage new shoots (i.e., more stems and flowers). Removing young fruits (capsules) and old flowers regularly also seems to extend blooming.

    Eventually — about a year in our experience — your pua kala will die, and then the question becomes, "What to do next?" If you enjoy propagating plants, try collecting seeds early and sowing several in a pot filled with clean well-draining media — then wait. Pua kala seeds can remain dormant in the soil or media for many months. Scarification or pre-soaking might speed germination, but there is also some evidence that sprouting is influenced by day length, with the shorter days of November and December being the trigger [Culliney & Koebele 1999]. Alternatively, you can dedicate a spot in your landscape to pua kala, permit (or help) your plants to scatter their seeds within this spot, and water the area regularly AFTER the adult plants have died. Hopefully, each year, some of the seeds will sprout, and you will have a recurring patch of pua kala to always decorate the space. Depending on the number of sprouts, you may want to do some thinning or repositioning. Fortunately, the tiny seedlings normally survive any early transplanting. 

Pests and Diseases

    Other than an occasional spider mite infestation, few pests bother pua kala. Refer to the Pests & Diseases page for treatments. 

Special Features and Information

General

    The Poppy family (Papaveraceae) contains about 42 genera and approximately 775 known species worldwide, occurring in temperate and subtropical climates mostly in the northern hemisphere [WikipediA;Papaveraceae]. Pua kala is the only poppy native to Hawaiʻi and is closely related to the Mexican poppy (Argemone mexicana), which has naturalized (grows wild) in the Islands. A spontaneous hybrid between the two species was collected in upper Pāʻia, Maui, but did not produce seed [Wagner et al. 1990].

    Pua kala is one of the few truly toxic native Hawaiian plants. We could find only one limited study that investigated the chemistry of the sap of Argemone glauca. This study by Stermitz et al. [1971], along with other more comprehensive studies of the closely related Argemone mexicana, determined that the two species contain an assortment of alkaloids that are likely responsible for their toxicity and medicinal uses. However, neither species appears to contain the well-known opioids such as morphine or codeine extracted from the sap of their more-distantly related cousin species, the opium poppy (Papaver somniferum). 

    According to Scott & Thomas [2000], the alkaloids in pua kala supposedly taste extremely bitter (neither of us has been brave enough to taste it), thus limiting the number of reported poisonings. The alkaloids also reportedly irritate the stomach and intestines. This acrid taste is likely the reason cattle (and, possibly, other ungulates) find pua kala unpalatable; it is one of the few native plants left untouched in cow pastures. Perhaps, pua kala's unpalatability could be used to create a natural behavioral barrier to prevent unwanted grazers from entering fragile native areas.

Hawaiian Name

    Pua kala translates to "flower" and "rough" [Pukui & Elbert 1986]. This is also the name of a native lobelia (Cyanea solenocalyx) with prickly leaves endemic to Molokaʻi. The name pōkalakala is also used for Polyscias lallani [syn. Munroidendron racemosum], an endangered tree endemic to Kaua‘i.

Etymology

    The genus name, Argemone, is derived from the Greek word argema, for cataract, in reference to the use of the sap of a poppy-like plant with the same name reputed to cure cataracts [Wagner et al. 1990]. The species and variety name, glauca, is from the Greek word for "sea-green, bluish or with a waxy bloom," referring to the color of this poppy's leaves. The subspecies name, decipiens, is from the Latin word deceptum, which means "deceptive or misleading" [Gledhill 2008].