Rick Shory

Offering a little something you might not otherwise have


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Germinating mimosa seeds

I thought that the main germination inhibition for mimosa (Albizia julibrissin) was the water impervious seed coat. This is an experiment to check that.

I found some mimosa pods that had just fallen from the tree. Their structure was papery valves (the flat sides), with wiry reinforced edges.

20151124_080445_mimosa_pods

Mimosa pods

It was evident their dispersal mechanism is to be blown about till the wiry edges wear out, allowing the valves to peel apart and drop the seeds. This goes along with the idea that the seeds are blocked from germination until their hard coats are breached, either from erosion by gritty soil, or long rotting in humus.

I took out ten seeds.

ten mimosa seeds

Ten mimosa seeds

I put them in water to soak.

ten mimosa seeds soaking

2015-11-24 08:10

About 24 hours later, two of the ten (20%) were imbibed with water.

20 percent imbibed by 2015-11-25 06:46

2015-11-25 06:46

This verified the seed coat was impervious enough to water to prevent absorption.

seeds, imbibed and not

Compare imbibed to not imbibed.

Breaching an impervious seed coat is called “scarification”. There are various ways to do it to bulk seeds; but for individual seeds you can use a file, knife, or sandpaper.

metal file

metal file

Here, I scratched seeds on a file.

scratching a seed on the file

scratched seed

I rubbed till the lighter colored interior showed through.

seed coat filed through

Seed coat filed through

I also nicked some seeds with a utility knife. I avoided the very tip of the seed, in case I might damage the embryo root, though seeds like this often protect their incipient root by embedding it somewhat back in the embryo.

Here is a scarified seed beginning to imbibe. This seed was both scratched and nicked. The flap towards the top is the nick.

seed beginning to imbibe

2015-11-25 09:19

The water absorption is a chain reaction. As the interior swells, it disrupts the seed coat from the inside, and allows still more water to enter.

Here is the same seed fully imbibed.

same seed fully imbibed

2015-11-25 12:05

The water absorption goes quickly after the seed coat is breached. Here, the seed has become fully imbibed after only a few hours. Many of the intact seeds were still dry inside after twenty-four hours soaking, and could have remained so indefinitely.

In order to closely observe the seeds, I put them in a standard germination test setup, rather than planting them in soil.

Here they are along the top of the folded, wet paper towel.

seeds on wet paper towel

I close the fold, and rolled this up on a chopstick.

seeds rolled up in wet paper towel

I held this, in light, at warm room temperature, about 80 degrees F.

seeds rolled in paper towel, standing in jar of water

2015-11-25 12:15

Within 48 hours, I had 100% germination.

ten mimosa seeds germinated

2015-11-27 09:01

close up of germinated seeds

close-up

This demonstrates that mimosa seeds’ germination requirement is primarily imbibation with water, and warm temperature. There is no inhibition by light, and no chilling requirement.

This explains why mimosa seldom volunteers in Portland. The time of year when temperatures are warm enough is also the driest weather. Seedlings that germinated in early summer would fail from drought later.

 

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The way through the snow

People tell me I’m lucky to have a job where I get paid to go hiking.  Well, luck is not always what you think.

All winter, on Tuesdays, I’ve been going in with Jack to the weather station in Rocky Mountain National Park.

A week ago Tuesday it felt like spring was finally coming.  It was about 50°F, sunny and warm.  Holes were melted through the snowpack to the creeks in some spots.  There had been bare rocks where I could lie in the sun for a moment. You don’t realize what a treat it is to have a solid dry surface to sit on, when the world is all melting snow. But that was last week.

Yesterday, it was back to winter.  About a foot of new snow had fallen overnight.  More was coming down.  It snowed all day.

It was soft, loose snow.  It was on top of a collapsing, mushy base.  That made for slow snowshoeing.

Our route in starts on a Park trail.  It’s a popular short day hike to a waterfall.

Before the waterfall, we veer off the real trail and go up a small canyon.  All winter, it’s filled with deep snow.  While the weather’s still cold, it’s easy to snowshoe.  But the trail’s melting out now.  The snow bridges across the little creek are a bit dicey.

The overnight dump of snow had obliterated all tracks.  We were first in that morning.  I took advantage of this to “put the trail back” where it was supposed to be.

In the course of the winter, people make shortcuts across the snowpack.  This doesn’t matter as long as the snow is deep.  You couldn’t find the real trail anyway.  People tend to follow the tracks they see.  So the trail gets shifted to a winter route.

But some of the shortcuts go across places that in summer would be meadows.  There are rivulets and pools.  These were slowly coming back into existence with the ending of winter.  I figured it was just a matter of time till somebody punched through.

So I carefully stomped tracks following the “true” route.  I hoped this would avoid someone getting wet feet, and save wear-and-tear on the meadows.

Some of this stomping was over big snowdrifts.  The casual tourist would have no way to guess there was a maintained trail underneath.  The more people walk there, the faster that snow will erode.  The faster it erodes, the sooner the trail be clear.

So we slowly slogged up our canyon to the pass.  With the new snow, everything looked different.  We even got lost at one point.  We went several hundred yards up a side slope before we found a way through the forest back to the trail.

We’d been going this route all winter, even in blizzards.  How could we get lost?  The featureless overcast hid most of the distant landmarks.  And heavy, snow-laden brush sagged into the tracks.

We learned to thwack the brush with a ski pole.  The snow would shower down, the branches spring up, and there would be the trail again.

We didn’t want the snow to shower on us.  It was barely below freezing.  Therefore, it was sticky.  It would melt and get us wet and chilled.

After the pass, we detoured around lower Icy Brook.  It was showing open water in some places.  The snow was surely thinning in many more.  We could hear the rushing creek underneath.

We climbed the snow ramp up over the rockfall at the lake outlet.  It was mushy and soft, though still substantial.  We crossed the lake, possibly for the last time this spring.  We stayed far up on the drifts under the north-facing cliffs.  These cliffs drop straight into the water in summer.  There was open water at both the inlet and outlet of the lake.

At the weather station, I dug out the solar panels and equipment boxes while Jack tended the gages.

Precipitation in the past week had amounted to an incredible three inches of water equivalent. One inch per foot of snow is the rule of thumb.  I wondered if some of it had fallen as rain, to make the snowpack so mushy and difficult.

On the way out, each of our packs was 10 to 20 pounds heavier — the full precipitation bottles.  At each step, the snow would crush down.  Then, as you put your weight on that foot, it would often punch in another inch or two.  It was an exhausting way to walk.

Hidden holes under the new top layer would wrench our feet sideways.  At least we’re on snowshoes, I thought.  In regular shoes, we’d be posthole-ing at every step.  We probably traveled about one mile per hour.

It was late afternoon.  We were hours behind our usual time as we started down the little canyon.  It crossed my mind we had not seen another hiker all day.

All other Tuesdays, even in the heart of winter, there would be at least one or two.  They would snowshoe in, or ski, to see the frozen lakes.  I guess not today, in this weather.  Wet, mushy snow, and more coming down without a break.

Then about the middle of the canyon, we met — the Donner Party!  I couldn’t believe it.  Two little kids were in the vanguard, wearing light shirts.  Their footgear was only sneakers and athletic shoes.

More people were struggling up below me, similarly attired.  It looked like maybe two sets of parents, and about ten kids altogether.  Some of the girls were in long skirts, and bare-legged.

They were obviously following our tracks.  We had packed the snow into some semblance of solidity on our way in.  A yard either side, they would have sunk in up to their knees.  They would have been drenched by wet snow from the laden branches.

Even though this is not a “real” trail, people come up.  Whatever their reasons.  Gamely, I advised the lead kids, “When you see two tracks up ahead, that’s where we’d got lost.  Keep to the low track.”

The kids looked at me like I was in their way.

Then Jack happened to casually inquire where they all were headed.

“To the waterfall.” one of the parents smiled.

Of course.  With no knowledge of the real trail, they would have wandered right off it, following our tracks!

We got them started back down, ahead of us.

That was kind of nice.  All those passing feet ahead of me crushed the snow more solid.  I could almost walk normally, when it was my turn to step on it.

We picked up at least two more groups, similarly misguided, before we reached the real trail.  There, we pointed the way to the waterfall.

What were these people thinking?  Hiking into the woods, in the snow, so late in the day?  How far would they have gone, if we hadn’t turned them back?  We were only there to turn them back because we were so long delayed.  Pure luck, for them.

I think luck must be genetic.  Everybody who’s not lucky, like those people, died out millions of years ago.