[ Lost in the Landscape ]

the experiment begins

The pointleaf man­zanita seeds I ordered ended up being from one of the many plant species (not only man­zan­i­tas) that depend on fire to per­pet­u­ate their species. In nature, a brisk fire might wipe out many of the exist­ing plants, but the fire also cre­ates an oppor­tu­nity for the seed­bank to come to life. With­out the nec­es­sary fire, the seeds just lie on the ground–that’s if they don’t get eaten by critters.

The sub­jects in this exper­i­ment exhibit really really hard shells that pro­tect the embryo inside. Get­ting word from a hos­pitable out­side world to the swad­dled seed germ is the chal­lenge. The seed packet I received rec­om­mended soak­ing them in sul­fu­ric acid for six to fif­teen hours. That’s one way to break through the seed coat to get mois­ture and nutri­ents inside.

Doing research on sim­i­lar man­zan­i­tas, some sites rec­om­mended scratch­ing the seed coat, mak­ing sure not to dam­age the germ inside. Some papers rec­om­mended build­ing a four-inch pile of com­bustibles above the seeds and set­ting the pile on fire. And yet another rec­om­men­da­tion was to boil the seeds for fif­teen to thirty sec­onds (one source) or one to two min­utes (another source).

No mat­ter which of the above meth­ods was tried, the seeds also required cold-stratification to con­vince them that they had endured a near-freezing win­ter and could begin growth. Which seed-torture method to try was the question.

Sul­fu­ric acid: Where can a non-chemist get it eas­ily? And it sounded a tad dangerous.

Scratch­ing the seed coat (some­times called scar­i­fi­ca­tion): Tedious for more than a cou­ple seeds, and how could I be sure I didn’t scratch off too much? Or not enough?

Build­ing a fire over the seeds? This method also sounded dan­ger­ous, but poten­tially fun.

Boil­ing the seeds (a vari­ant on scar­i­fy­ing seeds): Sounded safer than acid or fire, but do you go for fif­teen sec­onds or two min­utes? Wouldn’t too long kill off the lit­tle embryos?

I think that tem­pera­men­tally I’m part mad sci­en­tist. I thought an exper­i­ment to test out all the rec­om­mended meth­ods might be instructive–and at least a lit­tle entertaining.

I found some weak sul­fu­ric acid in a lit­tle squeeze bot­tle at a pool sup­ply store. At a con­cen­tra­tion of less than 1%, it was meant for test­ing water, not for play­ing with the acid bal­ance. Pretty weak excuse for acid, but worth a try. I soaked some seeds for 18 hours overnight, adding a lit­tle time to the end because the stuff was so dilute. (A day after doing this I encoun­tered an old bot­tle of drain cleaner in the garage, some­thing labeled sul­fu­ric acid. I’ll try another soak with the real stuff later on.)

The next method was to scratch the seed coat. I used a steel file to break the seed coat and a pair of pli­ers to hold the seed. I scraped vary­ing amounts off the seed coat, from a mod­er­ate amount to a fairly aggres­sive amount. This was hard, slow, del­i­cate work–way more dif­fi­cult than I thought it would be.

I said ear­lier that build­ing a lit­tle fire might be fun. It was, though I smelled like smoke for hours after­ward. The flames burned brightly with the aid of a fire­place lighter, then the embers hung around for a good ten more min­utes or more.

Some­how this approach seemed to make the most sense to me. If the plants rely on heat, this solu­tion would pro­vide it. If they rely instead on some secret ingre­di­ent that emanates from burnt wood, this method would give them that. And if the burn­ing helps break through the hard seed coat, this method could do that, too.

It goes with­out say­ing: You need to use a non-flammable pot to do this!

And my last method was boil­ing the seeds. I brought water to a boil, threw in a few seeds, and picked a forty-five sec­ond time period to leave them on the heat. The boil­ing seemed to soften the seed coat­ing, and I tried to pull off what I could.

No proper sci­en­tific exper­i­ment is com­plete with­out a con­trol group, so there were some addi­tional seeds that I tor­tured in no way. I was run­ning out of seeds pretty quickly.

Each of the groups of seed were then pot­ted up, labeled, watered, cov­ered with a bag, and then put in the low veg­gie drawer next to where I store the film for my cam­eras. Now I keep them moist–not wet–and wait for two months. At the end of Novem­ber I’ll take the pots out and move them to my unheated green­house or maybe a warm win­dowsill, for tem­per­a­tures higher than in the fridge. After their var­i­ous tor­tures and a proper period of strat­i­fy­ing, maybe I’ll be crowded with so many man­zan­i­tas that I can give them away to every­one I know in the spring. Or not.

I’ll post the progress as I go along…

October 01 2008 | Categories: gardening • my garden • plant profiles | Tags: Arctostaphylos pungens • fire ecology • germination • Mexican manzanita • pointleaf manzanita • scarification • seeds • stratification | 3 Comments »