Category: Garden

 

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.

 

Post G22-012. Continue reading Post G22-017: Wordless workshop followup.