Tag: pawpaw

Post G23-032: Paw-paws 1, Gardener 0

 

Last fall I put aside some pawpaw seeds, to see if I could grow pawpaw seedlings  (Post G22-062).

Pawpaws have a reputation for being difficult to propagate.  They don’t much like to be transplanted, so it’s better to grow from seed.  But pawpaw seeds have a reputation for having a low germination rate.

Putting these seeds into storage last fall was quite a process.  Apparently the seeds are quite picky about the conditions they will tolerate.  So I devoted an afternoon to extracting, cleaning, sterilizing, and packing up pawpaw seeds.  In particular, they cannot be allowed to dry out, and require lengthy refrigeration in damp sterile medium if you are to have any hope of germination in the spring.

Or so they say.

Continue reading Post G23-032: Paw-paws 1, Gardener 0

Post G22-065: Round, brown, and slightly moist most of the time.

 

But few people have one.  And that’s a situation I’m trying to change.

A couple of months ago, I put away some seeds from the pawpaw trees in my yard, with the idea of starting and giving away pawpaw seedlings in the spring.  Preserving viable seeds turned out to be quite a process (Post #G22-062).  After a thorough cleaning, the seeds need to be kept moist, and kept cold over the winter.  So a couple of plastic bags of seeds-in-damp-potting-soil have been living at the back of my fridge for the past two months.

Today it was time for a mid-season checkup. 

They’re still brown (no evidence of mildew or fungus).  And they’re still damp, though it’s clear that they have dried out somewhat, so I’m going to top them off with a bit of fresh water.  (In hindsight, I should have weighed them before I tucked them into the fridge.)

But, in general, things are proceeding according to plan.

Except that I don’t actually have a plan.  I started this in response to a request for pawpaw seeds.  I noted how difficult it seemed to be to come by pawpaw seedlings locally. And pawpaws are the only known host of the zebra swallowtail butterfly.

So when you get right down to it, my entire rationale for doing this is butterflies (aw!). 

And thus I have fallen into the classic charismatic megafauna trap.  As humans, we focus on saving animals that are attractive (pandas).   Or noble-looking (elephants).  Or have cultural context (bald eagles).  Or, in this case, cute, and the Virginia state insect (zebra swallowtail butterfly).

The dead of winter is the perfect time to step back and take a more objective look at this effort.  Given that we’re in the middle of the great insect apocalypse, and given that growing trees in suburban yards is more-or-less a zero-sum game (if not a pawpaw, then some other tree), what is it, exactly, that I’m hoping to accomplish.

Is propagating pawpaws the smart thing to do?   Aside from the technical gardening challenge of doing this, and helping one insect (because it’s so cute!), is this really the best use of my time?

A summary of expert advice for an insect-friendly urban environment.

As my first attempt at being somewhat more systematic, let me use Google to find seemingly-serious websites offering advice on how to create an insect-friendly urban environment.

To frame that properly, I need to state clearly that urbanized areas constitute only a tiny fraction of U.S. land area.  So, from the outset, this list is going to be oriented toward personal actions that residents of urbanized areas may take.  My little survey clearly is not going to have the right “weighting” in terms of global impact, because those urbanized areas constitute such a small part of the entire U.S. insect habitat.

You can look at that any number of ways, and arrive at the same conclusion.  The U.S. Census has a formal definition of what it considers to be an urbanized area:

Source:  Census data via University of Texas.

Bloomberg has a nicely detailed summary of U.S. land use.  You reach much the same conclusion from that as you do from the map above.  Urban areas account for a few percent of the total land area of the U.S.

Source:  Bloomberg, Here’s How America Uses Its Land,By Dave Merrill and Lauren Leatherby,

So, almost beyond a doubt, policies or actions applicable to the other land categories will have a much larger impact than what gets done in urbanized areas.  Pasture/range, forest, cropland, and parks (and other special-use lands) vastly outweigh urban areas in terms of insect habitat.

The easiest way to quantify that is to focus on the diagram above.  Roughly speaking, there’s one acre of crop land and two acres of pasture/grazing land for every resident of the U.S.  Most of the production from that land is consumed domestically.  Adults consume more than kids.  If I had to guess, I’d guess that growing a year’s food for two U.S. adults takes up at least six acres of land.  Compare that to my suburban lot, and, arguably, what I choose to eat is going to matter a lot more than how I landscape my yard.

But you do what you can.

For urbanites.

That said, below I have tabulated the advice most commonly offered to Joe and Jane Urbanite, to help protect and preserve the insect population.  This is literally the first nine reputable sources that showed up in a simple Google query of best things to do to help insects.  The full tables may be a bit tough to read, so scroll down for just the good parts.

Just the useful bit:

When I start from this perspective, I’m pretty sure that displacing other species of backyard trees, in favor of pawpaws necessary for a single butterfly species, is probably not the most effective thing I can be doing to help beneficial insects survive in my yard.

#1:  Overwhelmingly, the first piece of advice is to reduce the area of your lawn, in favor of … well, just about anything else.   Eight of nine sources said some version of that.  Minimally, don’t mow it.   Maximally, return it to more-or-less a wild area.  Maybe plant it with wildflowers.  Maybe plant it with insect-friendly plants.

I think I’m going to take this one to heart next year, as I have a large section of my back yard currently covered in black plastic, trying to kill the weeds.  And a whole lot of saved flower seeds.  I think that’s all going to become a flower bed next year.

#2:  Skip the pesticides and herbicides.  I think I have that one knocked.  The more I grow in my vegetable garden, the less inclined I am toward any type of insecticides.  Herbicide?  I spell that h-o-e.

#3:  Address your outdoor lighting. I had no idea this was quite so much of an issue.  Everyone gives the same advice.  Minimize outdoor lighting.  And if you use outdoor lighting, go toward the red/yellow/amber spectrum, not white.  Apparently, there is some truth to the idea that old-fashioned yellow bug lights attract fewer bugs.  What also appears true, however, is that the switch to LED street lights. however good that is from the standpoint of reducing energy consumption, is a step backward in terms of harm to the insect population.   Apparently, those old fashioned yellow high-pressure sodium lights were reasonably benign, compared to the white light issued by LED or mercury vapor/halide lamps.

For me, this is fixable.  I have exactly two small outdoor lights.  Both have white bulbs in them.  I’ll swap those for bug lights, and problem solved.

#4:  Create bee nests, bug hotels, and other protected habitats.  Or, alternatively, just leave the edges of your yard looking like crap all the time.  That works for me.  I now have a great excuse for leaves, branches, pine cones, etc. along the margins of my yard.  It’s not sloth, it’s environmentally sound policy.  Plausibly the wilder it looks, the more insect-friendly it is.

But you can also buy bits of made habitat.  I bought one of those solitary-bee or mason-bee nesting boxes in Spring 2016.  Never touched it.  Here’s how it looks this morning:

To me, that looks like an underwhelming amount of new-bee production for six years.  A lot of the tubes remain untouched.  Maybe a half-dozen have clearly released a live bee, as evidenced by the hole in the end of the mud.  A few more might hold bees that will emerge this spring.  That said, those bees will re-use those tubes, so it’s not clear exactly how many bees this investment produced. Or, for that matter, whether those bees would simply have laid their eggs elsewhere, absent this cute little device.

That said, I already own a couple, so I guess I’ll get the refill tubes, clean them up, and re-hang them.  What could it hurt?

I’m going to stop there, except to note that planting native plants (such as pawpaws) is pretty far down the list.  And so, as I had begun to suspect, it’s likely that going to all this effort to produce pawpaw seedlings is not very efficient.  Laboriously saving the seeds, to produce the seedlings, so that others may displace some trees in their yard with pawpaws, so that the zebra swallowtail has a place to lay eggs … that’s a positive thing to do, but it should hardly be first on the list.

Best guess, after fixing my outdoor lighting, the single smartest thing I can do is transform large portions of the edges of my yard to wildflowers.  Around here, it takes considerable effort to keep “wild” patches of yard from being overgrown with less desirable plants.  So it’ll take some doing to get a setup that has any hope of maintaining itself, even if I mow it once a year to keep the trees down.

After that, it’s probably a question of being pickier about what I eat.  I’m not sure about the extent to which eating organic produce actually avoids use of pesticides, rather than merely substitutes some classes of pesticides for others.  But I am pretty sure that foods vary widely in terms of the average amount of pesticide and herbicide used per edible calorie.  I think my next step is to see if research can generate any reliable information on that.

Post G22-062, notes on trying to grow pawpaw from seed

 

Update, July 2023:  Near as I can tell, none of these saved seeds germinated.  So this ended up being a lot of work for nothing.  This fall, I’m going to try something easier, such as tossing whole fruit into pots of soil and seeing what comes up the next year. 

I have a couple of pawpaw trees in my back yard.  Well, two big ones, pictured above.  And then what amounts to a growing pawpaw patch all around them.

Near as I can reconstruct from old emails, these were planted in the spring of 2009, and they are:

  • Stark Brothers Mango Grafted Pawpaw.  This is a large-fruited, late-ripening variety with particularly tasty fruit.  Here’s their ad.
  • Edible Landscaping Select Pawpaw.  This is just a normal, native-to-Virginia pawpaw, that the folks at Edible Landscaping selected for better-than-average fruit.  This is a small-fruited, early-ripening variety. Here’s their ad.

I have, on occasion, eaten some of the Mango Grafted pawpaws, and they are delicious.  I no longer eat pawpaws, though — see Post G24.

Propagating pawpaws

I’ve now been asked to supply some fruit to people who want to try growing pawpaws.

I naively said, sure, I’ll just pick up some of the remains of the rotting fruit that are still on the ground.  I figured, seeds are tough, a seed is a seed.  Just pick them up, let them over-winter, and plant them next year.  Give it some time, and you too can have a delicious Mango Pawpaw.

But, as is my habit, I decided to do a little research.  And the answer is nope.  Everything I just said is incorrect.

First, from the Home Orchard Education Center, I learned one key fact:  Pawpaws do not grow true to seed.  They are like apples in that regard.  Plant a seed from a Granny Smith apple, and you’ll get an apple tree.  But it’s not going to be a Granny Smith.  Same with pawpaws, apparently.

In particular, seeds from that delicious Mango Grafted pawpaw are not going to produce Mango Grafted pawpaws.  The only way I could get more of Mango Grafted pawpaws would be to .. wait for it … graft a cutting from that tree onto some pawpaw rootstock.  Which, I now realize is probably why grafted is part of the name.  (Duh.)

Second, there’s a recommended process for saving the seeds. Apparently the seeds are fairly fragile, and require significant special treatment.  (Which, to be honest, does not quite square with the dozens and dozens of little pawpaw trees I mowed down this year.  Fragile or not, mine seem to be quite happy to sprout after falling on the ground and overwintering there.)

I’ve now started looking into what you’re supposed to do to save pawpaw seeds.  And there’s quite a bit more to it than than just picking them out of some old rotted fruit and chucking them in a paper bag until next year.

By far the most surprising recommendation is that you’re supposed to keep the seeds moist. That’s a new on on me.  Decades of growing stuff, and the advice has always been the opposite:  Keep saved seeds dry.  But for this one, nope, you have to keep it moist.  “If seeds are dried for 3 days at room temperature, the germination percentage can drop to less than 20%.” (From Peterson’s Pawpaws).

That makes any that I gathered from truly well-rotted fruit suspect.  They weren’t exactly dry, as we’ve gotten a fair bit of rain in the past few weeks.  But they aren’t guaranteed to be moist, as would be the case for seeds from intact fruit.

Separately, you have to chill them.  Commonly, they spend the winter in your fridge, inside something that will keep them moist.  I see recommendations of keeping them on damp paper towels, moist sand/peat moss mix, moist sphagnum moss, moist potting mix, or some similar sterile medium.  Inside a zip-lock bag seems to be the most common technique.

But you can also plant them outside, keep their planted area moist, and let the winter chill them for you.

Third, the common recommendation is to remove all traces of pulp and membrane from the seeds.  Apparently, there’s something in the pulp that inhibits growth.

Finally, if you plant in containers, for eventual transplanting into the ground, those containers need to be deep, as these produce a long and fragile taproot.  That much I already knew as these are reputed to be almost impossible to transplant out of the ground.  I’ll be using my paper bag technique from Post G22-012.

References also say that a) the seeds need high (75F to 85F) temperatures to germinate, one source specifies a soil temperature of 70F to 75F, b) they typically take a month to germinate in any case, C) they can do with a 24-hour warm water soak to speed germination, and d) you don’t get much foliage for the first couple of years.  All told, this seems like a project for somebody with more patience than I have.

One source — and only one source — says that wild pawpaw seeds need to be planted in soil taken from around the parent tree.  Something about microbes.  Not sure I believe that one.  That same source — and only that source — says to store them inside in a paper bag for a couple of months, then moisten and refrigerate.

References vary on whether or not you can freeze them.  Some say yes, some say absolutely not.  I am dead sure that these would freeze over the winter, naturally, so I find it hard to believe that freezing them would kill them.

Finally, the “float test” to separate viable and non-viable seeds does not appear to work on pawpaws (reference).  Which, to me, goes hand-in-hand with having to keep them moist.  This is just not a normal seed.

In any case, here are a few internet references on what you are supposed to do.

The plan

At this point, given that I want to try this, my plan is to prep a large number of seeds for overwintering in the fridge, and give away bags of prepped seeds.  If I do this again next year, I’ll know enough to collect the whole fruit before they rot, to ensure that the seeds do not dry out.

So, the plan is:

  • Start with whole fruit where possible.
  • Scrub the pulp and membrane off the seeds
  • Give the seeds the recommended soak in dilute bleach solution.
  • Bag them up in ziplock bags of moist potting soil.

Then they go into the fridge until next spring.

Edit:  Addendum

These are now done and stored away in the fridge.  All told, it took me maybe an hour and a half to process about 100 pawpaw seeds for storage over the winter.

I took the advice of several internet sites and “scrubbed” the seeds and pulp against a piece of hardware cloth, set over a bucket.  This was the most time-consuming step, mostly because I didn’t quite grasp just how hard you had to scrub, to part the seed from the surrounding membrane.  It went a lot faster once I decided to put more effort into it.  And it was obvious when I had managed to get a seed out of its membrane jacket.

I soaked the mostly-clean seeds a few minutes, then cleaned off any remaining pulp one-by-one.

Five minutes in a weak bleach solution (10-to-1 dilution of standard laundry bleach), several rinses to remove the bleach, and the seeds got tossed into Ziplock bags filled with damp potting soil.  And the bags got tossed into the back of the fridge.

The next challenge will be planting them in the spring.  As I understand it, pawpaw seedlings really don’t like to be transplanted.  They grow a long, fragile tap root before they even begin to break the surface of the soil.

Direct-sowing into the soil is preferred.   But I’m planning to raise seedlings to give away in next spring.  So I need to find or make some suitable containers.

You can find any number of very tall plant pots and containers specifically designed for growing tree seedlings.  But it is far harder to find very tall biodegradable pots, so that you can plant the seedling without disturbing the plant roots.  In particular, rumor has it that pawpaws can put out a one-foot tap root before you even see any leaves.  So I was looking for slender biodegradable pots at least one foot tall.

The best of the bunch seemed to be the lightweight Zipset (r) plant bands, 14″ x 3″ (reference).  These are more-or-less open-ended un-waxed lightweight milk cartons, and should degrade in less than a year.   They seemed to have the exact right combination of size, stiffness, and biodegradability.  They are cheap if bought in bulk, but the smallest quantity I could buy was a carton of 500.  That was far too many.

Instead, I’m going with 17″ tall biodegradable fabric grow bags (reference).  I can pick up 50 for $15.  The big unknown there is whether or not they really will degrade once planted.  I’ll bury a few this winter and dig them up before I decide whether or not to start my pawpaw seedlings in them.

In any case, at that price, the cost of the potting soil to fill them will far exceed the cost of the grow bags.  So it’s not like the bags represent a big money gamble in the overall scheme of things.  .

I decided against several varieties of home-made pots, just because I didn’t think they would be sturdy enough.  I could, in theory, make a foot-tall paper pot, out of newspaper.  Or use grocery bags, cut up and re-glued.  Maybe wrapped with jute netting, for strength. And so on and so on.

But all of those seemed to be a risk, and none of them seemed to be worth the trouble when I appear to be able to buy usable containers for 30 cents apiece.  After going to all this trouble, it didn’t seem very bright to take a gamble on the containers used to grow the seedlings.

So, tall grow bags it is.  We’ll see how this all turns out, next spring.