Category: Garden

 

What I don’t know about garden irrigation could fill a book.   Or at least a blog post.

And that’s what the next post is about.  All the things I thought I knew about irrigation that were wrong.

That’s probably going to be a lot more interesting than this post.  Here, I describe the irrigation system I just put into place this morning.  But be warned, the actual, currently-functioning drip irrigation system is boring.*    Its basically a hose that drips.

* Not that “plumbing project” and “excitement” are things any sane person wants to see in the same sentence.  Try:   “I had a little excitement fixing the leaky toilet”, or “I was halfway through changing the faucet washer and that’s when all the excitement started”.   I don’t know about you, but for me, “excitement” in that context does not conjure thoughts of pleasant events.

Sure, it’s a high tech hose creating beautifully uniform drips.  I’ll describe it below in excruciating detail.  But it’s basically a hose with little holes in it.  Plus enough other stuff to get water from the outside tap to that hose.

The more interesting piece of this is everything that wouldn’t/couldn’t/didn’t work.  The system I just put in place is nothing like what I started out to do, outlined in Post G22-016.  My original plan did not survive even the most casual brush with reality.  That process is far more interesting than the finished product.  But that’s for a separate post.

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What I did.

Above you see the last bit of my newly-installed drip irrigation system.  The brown hose is 1/2″ drip emitter tubing (a.k.a. dripline).  It has a couple of holes (“emitters”) every foot, carefully constructed to drip one gallon of water per foot per hour, at water pressure of 25 pounds per square inch (PSI).  (For a simple metric-compliant reference, that’s about 1.7 atmospheres).

It’s pinned to the soil with standard steel garden staples (the sort you would use to hold down agricultural cloth or row covers.)  Eventually I’ll cover all that with mulch.

Not seen, that brown “emitter” tubing above connects to solid (no-holes) 1/2″ black distribution tubing.  Irrigation distribution tubing is more-or-less cheap, thin, UV-resistant hose.

Three additional brown drip emitter lines are tee’d off that black tubing, one for each raised garden bed.  That all eventually connects back to the outdoor tap on the back of the house.

All-in, there’s almost 100′ of 1/2″ black distribution tubing now pinned to my lawn, distributing water to four garden beds.  There it connects to pieces of 1/2″ emitter tubing (dripline), which then distributes the water to the soil, one drop at a time.

The furthest end of the system is about about 125 tube-feet from the tap, there’s about 150 feet of emitter tubing total.  All of it appears to be functioning correctly.

There are really no details of construction worth noting.  As constructed, the whole thing just sits on top of the ground, held down by the occasional steel garden staple.  Two 1/2″ emitter tubes, spaced about 2′ apart, seem adequate to water the surface of a 4′ wide raised bed.  The 1/2″ pipes all fit together with fittings made for this exact purpose.  Lay out the tubing, cut it with a knife, slide one end over the fitting as far as it will go, tighten up the locking cap.  That’s it.

Well, maybe there’s one pro tip, but it’s standard advice for anything of this sort:  Tubing, extension cords, rope, and so on.  The tubing comes in a roll.  Unroll the tubing onto the ground, by rotating the coil of tubing about its axis, just as if it were a car tire.  Ideally, pin one end of the tubing to the ground and literally unroll the coil by rolling it on the ground.  Do not uncoil it, that is, do not put the roll of tubing on the ground and pull out what looks like a big, long coil spring made out of tubing.  If you uncoil it, you will almost surely end up kinking the tubing as you handle it, and that is double plus ungood. 

Why:  While it superficially looks the same, unrolling is completely different from uncoiling.  When you uncoil it, each original loop on the roll leaves one rotation along the axis of the tubing.  If you had twenty loops on the original roll, and you uncoil it, sure, it’s laid out in a line, but now it’s as if you’d taken one end of the tubing and given it 20 360-degree twists in a row.   And that high degree of twist along the axis will almost inevitably manifest itself as a kink in the tubing.

Basically, a monkey could do it.  The only tool needed is a knife (or scissors) to cut the tubing.  This took me under two hours this morning, and most of the time was spent maneuvering the emitter tubing around my already-existing plants.  If I’d done this while the beds were still bare, I doubt it would have taken me an hour.

Arguably, shopping for the parts was harder than assembling the system.  In the end, to cover four beds, each maybe 4′ x 25′, I bought/used:

• 200′ of 1/2″ emitter tubing (“dripline”, with weepholes)
• 100′ of 1/2″ distribution tubing (no holes).
• Four figure-of-eight fittings to close the ends of the driplines.
• Three 1/2″ “tee” couplings and one 1/2″ straight coupling to connect the first three and the last driplines to the distribution line.
• One in-line pressure reducer
• One drip irrigation female adapter (to convert the end of the distribution line to garden hose thread).
• Some garden staples.
• Optional:  One charcoal filter (see chloramine, below).

I still need to add a timer.

For what it’s worth, if you go with this form of drip irrigation — using emitter tubing or “dripline” instead of individual water emitters — your main choice is between using 1/4″ and 1/2″ emitter tubing (dripline).  I ended up using 1/2″ emitter tubing, and I am glad that I did.  That’s explained just below.

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A few details worth noting.

Half-inch versus quarter-inch irrigation tubing: Quarter-inch line is tiny.  

Above you see the ends of two pieces of irrigation tubing.  The small stuff is the nominal 1/4″ tubing.  The larger one is the nominal 1/2″ tubing.

If you are like me, you probably heard the terms “quarter-inch” and “half-inch” and just fuzzily thought, oh, that’s about twice as big.  But even in theory, if the internal diameters were as described, the half-inch line would have four times the internal cross-sectional area.  And in practice, it looks like the half-inch line has around eight times the internal cross-sectional area of the quarter-inch line. 

Which, roughly speaking, means that the half-inch line has eight times the water-carrying capacity, or conversely, can carry water eight times as far before the water pressure in the line gets too low to be usable.  The manufacture recommends limiting runs of half-inch dripline to 240′ or less, compared to limiting runs of quarter-inch dripline to 33′ or less.   Or about one-eighth the distance.

That has a lot of benefits.

First, you can cover a garden bed just by running one long piece of 1/2″ emitter line back-and-forth.  That’s less work that cutting and connecting many short pieces of 1/4″ emitter line.  In my case, my 4′ wide garden beds required just one piece of emitter line, twice the length of the bed, run up one side and down the other.  Basically, it’s no different from running a soaker hose up and down the length of the bed.  That means need to make just one cut in the supply line, and insert one “tee” connection to connect the emitter line to the black supply line.

Second, the 1/2″ emitter line also serves to distribute the water, in addition to dripping it into the soil.  This adds considerable flexibility down the road.  It carries enough water that you can easily tap into it.  So, for example, if I now wanted to add some additional emitters in the same garden bed, or add a stretch of 1/4″ drip line, I could just add those directly onto the existing half-inch emitter line.

I see just four downsides to the 1/2″ emitter line.  First, it’s stiff, which makes it harder to install (particular, as here, installing it in beds where the plants are already growing).  Second, it provides a less-even distribution of water.  It appears to come with a minimum emitter spacing of one foot, and emitters that release one gallon per foot per hour, whereas the 1/4″ emitter line is commonly available with emitters spaced every half-foot, emitting a half-gallon per hour.  Third, you have to connect it to the supply line with a tee fitting that costs about $3, whereas the 1/4″ emitter line connects to the supply line with a little push-in “spike” fitting that costs maybe $0.25 each.  Finally, it costs slightly more per foot than the 1/4″ emitter line.

Chloramine filter.

I added a a high-volume activated charcoal filter to remove chloramine from the tap water.  These days, no matter where you live, if you rely on public utilities for your water, chances are that your water is treated with chloramine, not chlorine.  And that makes a big difference to some plants.

Once upon a time we had chlorinated water in the DC area.  They literally used chlorine gas.  And that’s volatile.  Spray that on your garden, or put it in a bucket, give it a little time, and most of the chlorine would simply evaporate right out of the water.

But volatility is a liability if you want to maintain a safe water supply with old pipes.  Now our water is treated with chloramine, not chlorine.  Chloramine is persistent, and does not produce as many by-products as chlorine.  The upshot is, it stays in the water unless you take extreme measures to remove it.

Some plants do not tolerate chloramines well.   In the garden, for example, I find that my peas bleach and die if I water them with straight tap water.  It seems to be immediately toxic to the ground cover “sweet woodruff”.  Many seeds are reported to germinate poorly if watered with water containing chloramine.

So when I water with tap water, I do my best to filter out the chloramine.

It costs a bit, but only a bit, to take this extra step.  The high-throughput charcoal filters like the one linked above are good for somewhere around 10,000 gallons.  At that rate, removing the chloramine adds about $3 per 1000 gallons to the cost of city water.  I currently pay about $17 per 1000 gallons (combined water and sewer rate) for municipal water itself.  So if I’m going to water my garden with city water, chloramine removal only adds modestly to the resulting financial pain.

Pressure regulator.

The manufacturer of this line recommends putting a pressure regulator in-line, to restrict pressure to 25 PSI.  That regulator cost about $10, but it seemed like a good idea to follow the directions despite the cost.  It just screws into the overall assembly using standard hose threads.  So I added one.

I don’t think the strength of the tubing itself is the problem.  It looks to me like the various connectors (tees and such) are a little iffy for high-pressure use.

In any case, given that this was the first time I’d ever done one of these, I figured I ought to follow the manufacturer’s directions.   And that includes putting a pressure regulator in-line.

Other manufacturers use “pressure balance” lines and such.  That struck me as being unnecessarily complicated and possibly prone to clogging.  Here, I have one pressure regulator and large-diameter lines to carry the water.  It’s hard to see what could go wrong with that.

Possible conversion to using raw rain water.

There is some possibility that the large-diameter 1/2″ emitter line could be used with a gravity-fed low-pressure (“rain barrel”) system.  I’m skeptical that would work well, but I see people on YouTube who appear to have functioning irrigation set up that way.  For sure, given the low pressure of a typical rain-barrel system (maybe 1 PSI), there’s a far greater chance that will work over a distance with the larger-diameter emitter tubing compared to the 1/4″ tubing.

The point is that there is some possibility that I could just hook up my rain barrels to the installed system and (slowly) water the garden that way.  Either purely gravity-fed, or using a small submersible pump.

I’m definitely going to have to test that before I declare that works.  At the minimum, that’s going to be a slow process, for sure.  These emitters let out one gallon per hour at 25 PSI pressure.  At somewhere around one PSI, what takes the current tap-water system an hour to deliver should take a gravity-fed system at least a day.

If it will work at all.  Some forms of water distribution simply don’t work at all at such low pressures.  Most timers require at least 10 PSI.  Soaker hoses require 8 to 10 PSI.  And, of course, anything designed to spray water at 25 PSI will only dribble it, at best, at 1 PSI.

Winterization remains a mystery at this point.

I’m pretty sure it’s a bad idea to leave plastic pipes full of water out to freeze over the winter.  And I’m too lazy to bury them.

From what I gather, the emitter lines will take care of themselves, slowly emptying out as long as one emitter on the line is at a low point.  The problem is the black distribution piping, where I have multiple low spots between my various raised garden beds.

Tentatively, I’m planning to hook my shop vac up to one end of the distribution line, open up the ends of the emitter lines,  and let ‘er rip.  Basically, blow the water out of the system at the end of the year.

If that doesn’t work, well, with 1/2″ tubing throughout, this really is no different from a bunch of garden hoses.  I’ll winterize it as I winterize my garden hoses.  Just pull them up, empty the water out as I roll them up, and store my irrigation system in a corner of the garage.

 

 

 

Visualize!

This year I planted nine short-season/cold tolerant tomato plants, three each of Glacier, Fourth of July, and Stiletz. These varieties tolerate cool nights and so can be set out in the garden about a month earlier than most tomato varieties.  They produce ripe fruit quickly, with two of the three advertising less than 60 days to maturity.

That combination gives you the promise of having some ripe tomatoes quite early in the year. And this year, I am pleased to report that this promise has been fulfilled.  I ate my first ripe tomato out of the garden today.  And it’s not even officially summer yet.

I think that’s pretty good for gardening in Zone 7 without a greenhouse.

So, how did that first ripe tomato taste? Eh, pretty much like a tomato.  Not bad, but nothing to write home about, either.  I’m sure that in the days before decent grocery-store tomatoes became available, I’d have thought it a miracle on a vine.  But now, with (e.g.) Campari tomatoes available year-round, that first fresh tomato was nice, but nothing you couldn’t buy at Safeway.

Above:  A couple of ripe Glacier tomatoes, the winners in this year’s short-season tomato race, 6/20/2022.

Above:  Some almost-ripe Fourth of July tomatoes, on 6/20/2022.  These came in second, but they are clearly going to live up to their name.

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For Mature Audiences Only

Now that I have have my first ripe tomato, with the promise of more to follow, I can finally address a question that has been nagging me ever since I decided to try this.

What does “days to maturity” actually mean?  From what starting point, to what end point, under what conditions?  I’ve seen this on seed packets all my life.  I’ve never been quite sure what it means. 

Let me use these two short-season tomato varieties to illustrate the issue.  I planted these in the garden on 4/10/2022.  I started them from seed about a month earlier.  Here’s how the actual days to first ripe fruit compare to the “days to maturity” on the seed packets:

As you can see above, in this case the actual elapsed time between sowing the seeds and the first mature fruit was about twice the stated “days to maturity”.

Is that typical?  I can’t even ask that question until I figure out what seed sellers mean by “days to maturity”.

As with so much of home gardening, I see a lot of folklore and wrong answers along with the correct information.  But even with that, and putting aside all the variations that might arise due to the weather, the soil, the length of the day, and so on, I believe that there is literally no standard definition of what “days to maturity” actually measures. 

So, at the end of the day, its no wonder that I don’t know what it means.  It’s not really a well-defined term.

Let me now summarize, as best I can, kind of the gist of what it is supposed to mean.  This is based mainly on the information found in these three sources:

• A detailed discussion of the entire “days to maturity” issue on a blog titled Garden Betty.
• A more compact explanation on The Spruce Eats.
• Oregon State University extension service.

For plants that are traditionally started indoors, in pots, then transplanted to the garden, days to maturity is defined as the number of days between:

• the time that a seedling that is ready to be transplanted is put into the ground, and
• the time the first fruit is ripe enough to be picked for eating,
• under optimal conditions (temperature, day length, water, fertilizer).

For plants that are traditional directly sown into the soil, days to maturity is defined as the number of days between:

• the time you plant the seed …
• or maybe the time the planted seed sprouts …
• or maybe the time the sprouted seed shows its first true leaves, and
• the time the first fruit is ripe enough to be picked for eating,
• under optimal conditions (temperature, day length, water, fertilizer).

No matter how you slice it, there’s a ton of ambiguity in those definitions.  At what point is a seedling ready to be transplanted?  What does ripe mean (e.g., for cucumbers that can be used either small, as pickling cukes, or larger, as slicers).  Does the clock start when you plant the seed, or a couple of weeks later when you see the first true leaves?

On top of that, planting at the times where this figure really matters — early spring or late fall — guarantees that you won’t have optimal growing conditions.  There’s a nice discussion of this point in the Garden Betty blog cited above.  So, these figures will be the least reliable just when you’ll be counting on them the most..

Finally, it almost goes without saying that different seed vendors are going to define and measure “days to maturity” differently.  So while “days to maturity” might give you some general guidelines as to what will ripen first, within a given seed vendor, you probably can’t compare them across vendors.  Likely this explains why my actual observed days to maturity above, under identical growing conditions, are in the reverse order of the vendor-stated days to maturity.  Plausibly one vendor uses a more aggressive definition than the other.

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A practical takeaway from a novice gardener

I get the fact that YMMV.  I did not expect to see mature fruit appear exactly “days to maturity” after I set out my plants.

What I didn’t understand — before focusing on this — is that your mileage may vary a lot.  When you see a “days to maturity” number, you can’t reliable expect to see ripe in that time, plus or minus a few days.  Instead, I’m guessing that there’s never a “minus” — that those day counts are under absolutely ideal conditions.  And then, you can’t be surprised if the actual day count is several weeks longer than the days to maturity figure, even if you’ve started the seeds weeks before you planted the seedlings in the ground (and thereby started the “days to maturity” clock).

This explains, I think, why I totally failed to grow summer squash last fall, after the squash vine borer (SVB) left for the year.   Planting a late-season crop is a commonly-mentioned strategy for avoiding the SVB.  So, after I observed my last SVB last year, I put a few summer squash seeds into the ground.  I had far more than 60 days of growing season left, which is the approximate “days to maturity” of the varieties I was growing.  But I got no squash.

Let me do the math, in light of this new-found knowledge.  Typical first frost date in this area is October 15.  Stated days to maturity is 60.  But in that cooler, short-day climate, I can count on it being at least 90.  But that’s measured from the time you have a pot-grown plant that is ready to be transplanted into the garden.  So chuck on another 30 days to raise the seedling from seed to “ready to transplant”.  But that’s from the time the very first squash appears.  So add at least another 21 days if you want to get a mere three weeks of actual production out of those squash plants. Now add that up.  And, of course, put it all in a spreadsheet.

The upshot is that for a fall crop of summer squash: a) I should have planted the seeds weeks ago, but more importantly, b) I can’t actually grow a fall crop of summer squash, out in the open, in this climate, that avoids the SVB.  I’d have to set the plants out in the garden squarely in the middle of SVB season.

The bottom line is that if I want a fall crop of summer squash, without pesticides, I’m going to have to start out by growing my squash seedlings under insect-proof netting.  Which is exactly what I’m doing with my parthenocarpic varieties now.  The only difference is that I’d be able to take that netting off after the first six weeks in the garden.

It’s possible that I’ve overstated the fudge-factor here, given that I’d have to start these in the garden pretty much at the start of summer anyway.  But even if I completely removed that 30-day fudge factor, I’d still have to put these plants in the garden weeks before the typical end of SVB season.

The ultimate takeaway here is that if you use “days to maturity” for estimating the last viable planting date for a fall crop, you need to add a lot to the raw number.  You need to add in the minimum number of days over which you’d like the plants to be productive.  You need to add a fudge factor for what are likely to be sub-optimal growing conditions.  And then, for plants traditionally started indoors, you need to add in the time to produce your garden-ready seedling from the seed.

And when I do that, for summer squash and Zone 7, it turns out that I can’t dodge the squash vine borer by aiming for a fall crop of summer squash.  If you don’t want to use pesticides, the only thing the fall crop gives you is the ability to remove the insect netting from the squash some weeks before the plant is due to begin setting fruit.

 

Source:  Clemson University, original photo credit David Cappaert, Bugwood.org

I saw my first Japanese beetle of the season today.

Is it really that time already?  Yep, sure is.  The Japanese beetles are out, which means more garden pests are soon to follow.  In particular, this means that the squash vine borer should be arriving more-or-less now, in this region.

Insects emerge almost like clockwork, based on the cumulative springtime warming of air and soil.  In particular, Japanese beetles emerge right around 1000 growing degree days of warmth.

Growing degree days in a year are calculated as the cumulative time during which the air temperature exceeds 50F.  In Virginia,  Virginia Tech would be the place to get information.  A nice general reference is available from the American Public Gardens Association.  The most commonly-used basis is 50 degrees because that’s the temperature at which most plants and insects begin to grow.

Last year, in Northern Virginia, we passed 1000 growing degree days on or about June 11, 2021 (Post G21-033).  And this year, we passed that mark on June 11, 2022, per the Cornell University degree-day counter.

Source: Cornell University degree-day counter.

In short, the only thing that’s surprising about this is that I’m surprised.

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To trap or not to trap?

For me, it’s now time to buy and hang a couple of Japanese beetle traps.  I use the Bag-a-Bug brand.  It’s not that I think these are necessarily more effective than any other.  It’s just that, as an economist, I get a chuckle out of the carefully-calibrated prices of the traps, lures, and bags.  All the parts are available, so, technically, it looks like you could keep re-using the same trap year after year.  In practice, the prices are such that ever-so-slightly cheaper to chuck everything and buy new traps every year.  There’s no way that could possibly be coincidence.

There is considerable controversy over whether or not to use Japanese beetle traps. 

The controversy isn’t really about environmental impact.  This is, after all, an invasive non-native species.  To the best of my understanding, birds around here will only eat the adults if there’s absolutely nothing else available.  So I don’t think anybody sheds a tear for a dead Japanese beetle.

Nor are the traps toxic.  These are lure-and-pheremone traps.  They attract Japanese beetles, then physically trap them.  As far as I have ever seen, they are absolutely specific to Japanese beetles.  Nothing else gets killed, and there are no pesticides involved.

Instead, the controversy is all about how smart (or dumb) it is to have these in your yard.  Maybe all you do is lure even more Japanese beetles into your garden, and so increase your beetle damage.  Completely respectable sources of gardening information urge you NOT to use Japanese beetle traps.

And yet I persist.  I looked at the research showing that traps increase crop damage, read up a bit, and decided that putting Japanese beetle traps directly in your garden is, in fact, not very smart.  To me, that’s what the research seemed to show.  Hanging widely-spaced traps in the middle of an orchard (which is the method used in the research typically cited) turns out to be a fairly bad idea.  That did, in fact, increase beetle damage relative to adjacent areas without traps.

Instead, I think you want to place the traps downwind and away from your garden.  Not in your garden.  Not upwind of your garden.

The idea is to place these so as to intercept beetles flying upwind, lured by the smell of your delicious garden plants.  At this latitude, prevailing winds are out of the northwest, so my traps get placed south-east of the garden itself, as far away as I can place them in my back yard.

You don’t use these traps to lure beetles away from your garden, or away from your plants.  (Which would mean placing them upwind of your garden — don’t do that.)  Instead, the idea is to intercept beetles that are flying upwind, toward you garden.

In any case, I know what the scholarly research says.  I just happen to disagree with their blanket conclusion that these traps increase damage on your plants.

My observation is that, placed downwind and away from the garden, Japanese beetle traps work exceptionally well.  It seems to take about a week to go from beetles everywhere, to nary a beetle in sight.  Maybe that’s just by chance, but that observation — plus a couple of quart bags full of dead beetles — says otherwise.

Finally, there’s a reason that I’m on the lookout every year.  As soon as everybody realizes the Japanese beetles are here, the stores (and even Amazon) will sell out of Japanese beetle traps.  Snapped up by all the people who, like myself, ignore the expert advice on this issue.

So I’m off to the local big box store to pick up a couple of traps.  If this year is like last year, in another two weeks there won’t be a trap left on the shelves.

It is now time for the fourth and final phase of my 2022 tomato strategy, heat-tolerant tomatoes. 

I outlined the overall approach in Post G21-001.  There, among other things, I listed the varieties I’m planting.  To recap, the goal is a continuous supply of tomatoes all summer long, with a large batch of paste tomatoes for producing dried tomatoes. Continue reading Post G22-022: Heat-tolerant tomatoes

Source:  University of Kentucky

I saw my first striped cucumber beetle of the year, at the end of last week.  It feels like it’s too early in the season, but I’m reasonably sure I didn’t hallucinate it.  Last year, they showed up in my garden at the end of May (Post #G21-027, Cucumber Beetles).  So they’re right on time. Continue reading Post G22-021: First cucumber beetle of the season.

 

 

 

This is a quick followup on my last gardening post, where I answered the question “where do seedless cucumber seeds come from?”.

The short answer is that most of them are first-generation hybrids.  Thus, seedless cucumbers seeds come from the fruit that results from crossing two carefully-chosen seeded cucumbers.  The resulting fruit has seeds, but those F1 seeds are then sterile, in the sense that the plant grown from that will not  produce viable seeds. Continue reading Post G22-020, seedless cucumber germination rate.

 

The question.

Recall Post G22-013, where I proposed to bypass last year’s troubles with cucumber beetles and squash vine borer by growing parthenocarpic varieties of both plants.  A parthenocarpic plant is one that produces fruit without fertilization, that is, without pollination.   No bees needed, which means I can grow them inside an insect-proof enclosure, excluding the bees along with the pests.

The resulting fruits are sterile and lack fully-developed seeds.

I have to admit, as I ordered up a few packs of seeds for various parthenocarpic cucumbers and squash, I did have this nagging little question:  How do they produce viable seeds from parthenocarpic plants?  Isn’t “seedless cucumber seeds” an oxymoron?

I stifled that question and ordered the seeds anyway.  The seeds I bought were offered by a presumably reputable seed merchant.  And I know that greenhouse-based farms produce plenty of produce from parthenocarpic varieties.  Didn’t seem like much of a risk.

That said, buying seeds for seedless cucumbers does seem like a bit of a Catch-22.  Or maybe a chicken and egg problem.  Perhaps my local nursery stocks the seedless cucumber seeds right next to the dehydrated water.

At the time of purchase, I noted a seemingly unusual percentage of purchasers’ comments complaining of low or no germination rate.  But you see comments like that on the sites of any seed vendor.  I chalked up the squawking to the relatively high cost per seed.  These parthenocarpic varieties seem to sell for anywhere between 25 cents and 50 cents per seed.  A poor germination rate is not much different from mulching your plants with ground-up dollar bills.

And now, of the 20 seeds planted (five different varieties, three cucumber, two squash), in peat pellets, exactly four seeds appear to have sprouted.  These are from two cucumber varieties.  All the rest of my new whiz-bang parthenocarpic seeds appear to be duds.

But is that normal?  And is it true that they failed to sprout, or is there some other explanation?  Because if that’s really the germination rate, I paid somewhere around $1.75 per viable seed.    For cucumbers and squash.  Which feels more akin to mulching your plants with $20 bills.

So that gets back to the main question of this post:  How, exactly, do seed vendors produce seeds for parthenocarpic varieties?  (Or, more simply, where do seedless cucumber seeds come from?) And is there usually a low germination rate for parthenocarpic varieties?

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The answers.

As it turns out, there are several ways in which you can get viable seeds for “seedless” parthenocarpic plants.   But as far as I can tell, the most common parthenocarpic varieties are F1 (first-generation) hybrids.  So, by and large, you don’t get seedless cucumber seeds from seedless cucumbers.  You manufacture them by crossing two seeded varieties that generate the parthenocarpic (seedless) first-generation hybrid offspring.

Of the five varieties I planted, four of the five ( Diva Cucumber, Sweet Success Cucumber, Easy Pick Gold II squash, and Golden Glory squash) are either explicitly marketed as F1 hybrids, or simply as hybrids.

For those, there’s no fundamental reason they would have any lower germination rate than any other F1 hybrid.  These same varieties are planted by commercial farmers growing produce in greenhouses and poly tunnels.  Presumably, they wouldn’t put up with extremely low germination rates.

The sole exception to the F1 rule is Little Leaf cucumber.  As it turns out, that is an open-pollinated variety, not a hybrid.  But that’s also a gynoecious variety — that is, it produces all (or nearly all) female flowers.  Thus, you can get a Little Leaf cucumber with seeds, in the rare event that a male flower is produced that fertilizes one of the many female flowers.

So the upshot is that of the five seedless varieties I’ve chosen, four are F1 (first-generation) hybrids, so the seeds for them are actually produced by crossing two non-parthenocarpic varieties.   I don’t think they’ll produce seeds under any circumstances.  And the last one is seedless, but only because the plants are rarely fertilized owing to its gynoecious nature.  It’ll produce either seeded or seedless cucumbers, depending.

Now that I know how this works, I’ve done what I should have done from the start, and dissected the peat pellets that I planted these in.  Mystery solved: There are no seeds inside.  Plausibly, some birds came by and pecked the seeds out while I had these sitting outside.  So all I need to do is replant, and be a bit more careful, and I should be able to proceed according to plan.

I’ll report back on the actual (bird-free) germination rate in a couple of weeks.

 

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