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Is It Too Late to Plant Squash?

Recently our pastor's wife approached me and wanted to know: Is it too late to plant squash?  Their farm had recently been hit by the storm that produced the Greenfield tornado and while their house was spared, the garden and outbuildings were not so lucky.  With the gardening season in full swing, she was left wondering what she could do to salvage this year's garden.  If you're reading this, you probably have your own reasons for getting a late start on your squash. Hey, life gets ahead of all of us.  But rest assured, I'm here to put you at ease.  To let you know that, no, it's not too late.  In fact, there are some pretty good reasons why planting squash late might actually give you an advantage over those go-getters next door who got their squash sown as soon as the last snowflake had melted off the garden.

First Some Encouragement

If you've read our About Us story, you've probably heard about our gardening mentors Bob and Colleen who nearly twenty years ago taught me my first lessons in gardening.  Bob was a masterful gardener who probably had 50 years of gardening experience under his belt by the time my exuberant hands first touched a garden hoe.  Colleen, who was raised on a farm in Missouri, had spent most of her life tending gardens and canning, carrying on the traditions of her mother, who by this time was in her late nineties and still driving (a testament to the lifestyle, I think.)

Anyway, one year we had a particularly tough spring, and for reasons I can't remember I found myself needing to replant zucchini in late June.  I lamented to Colleen that it would probably be October before I had anything to harvest.  "No, you're just in time" she exclaimed, "My mother never planted zucchini before June 21st!"  

Well, wouldn't you know my zucchini did produce a crop, a bumper crop in fact, and in less time than I thought.  What's more, it seemed like they were healthier and had fewer bugs.  It wasn't the first time I'd been enlightened by Colleen's gardening wisdom, and it certainly wouldn't be the last, but nevertheless I was amazed at how well it worked.  

Boy holding a climbing zucchini fruit

Advantages to Planting Squash Late

In the twenty or so years since Colleen first told me about this tradition, I've heard numerous old-timers confirm that the 21st is indeed the day to plant squash.  I'm not entirely sure, but I suspect this particular date is favored because it typically coincides with the summer solstice.  For generations, gardeners paid great attention to the signs and seasons, a practice which has fallen out of favor in recent decades, but which was once a way of life.

I'm no expert on planting by the signs, but I have replicated this experiment time and time again, sometimes planting in late June and sometimes even later.  And over the years, I have come up with a few observations and subsequent theories about why planting squash late works so well.

Acorn squash

1. Fewer Bugs

The most bothersome pest to affect squash is the all too common and universally despised squash bug.  If you've been gardening for some time, I'm sure you share my disdain for this creature.  I know God created everything with a purpose, but is it not possible that these things crawled up from the bowels of the earth?

Seriously though, squash bugs can be a nuisance if you're trying to grow squash, which is one reason you might want to try starting your squash late if squash bugs are a persistent problem.  Colleen told me that she figured the bugs were less of an issue when you plant late because, by that time, they'd already settled in on the neighbor's plants (You know, Mr. and Mrs. Go Getter that I mentioned earlier).  I chuckled initially at this suggestion, but as time goes on, I think she might be onto something.

Excepting northern climates, squash bugs will typically undergo multiple generations in a single season with each generation taking 5-7 weeks to mature.  The first generation typically emerges in April or May, depending on your climate, and begins searching for mates. 

If you don't have squash plants out until late June, the emerging generation is not going to be laying their eggs in your garden.  As Colleen suggested, they're probably going to settle in someone else's.  In fact, you might not have to deal with them at all until the second generation emerges (and takes flight), lays eggs, and those eggs mature into nymphs that are able to feed on plants.

adult and nymph squash bugs

Adult and nymph squash bugs on a leaf.  Although nymphs present in the fall will not overwinter, they are often responsible for the most damage owing to their overwhelming numbers.

So, the first benefit is that you're delaying the onset of terror that they're about to unleash, but there's another benefit here and it's mathematical, so bear with me.

Let's say you plant your squash in early May.  A single pair of lovebugs mate and begin raising their brood on your squash plants.  This is pure fantasy, by the way, because there are surely more than two squash bugs lying in wait beneath the leaf litter in your dormant garden but let's run with it.  That female likely just laid around 250 eggs on the undersides of your squash leaves. If they all hatch, the law of averages would have it that 125 of those larvae are female. 

Six weeks later it's mid-June and those young ladies are ready to start their own families.  So they go off, mate, and lay eggs, 250 eggs remember?  It's a baby boom!  You potentially have 31,000 squash bug eggs on your plants and its only June.  I don't think I need to continue with this hypothetical to illustrate that by August, you've got a serious infestation on your hands.

By contrast, imagine now that you sow your seeds the last week of June, missing entirely the first egg-laying generation and possibly part of the second.  Sure, you're not entirely squash bug-free come fall, but they're more manageable than they would have otherwise been, and harvesting is a lot more pleasant.

Healthy summer squash plant

2. Faster Growth

There's a misconception about the days to harvest number you see printed on seed packets.  The fallacy is that a variety will mature in the same number of days every time, regardless of when it's planted.

But the truth is that a plant grows a lot faster in July than it does in May.  Why?  Because it's warmer in July than it is in May and perhaps more importantly, because the nights are warmer in July than they are in May.

Let me explain.

Plants, and particularly heat-loving plants like squash, grow best when the air is warm.  This is because the enzymes responsible for performing photosynthesis and facilitating cell division and expansion (otherwise known as growth) perform most efficiently when the temperature is warm.  

Depending on the plant, these processes work most optimally in temperatures between 60 and 95 degrees.  While you will often see daytime temps squarely in the middle of this range early in the growing season, nighttime temperatures will often fall below the minimal temperature.

But plants don't photosynthesize at night anyway, so what's the big deal?

Ah, this is true.  But they do respire, which is important because respiration is the actual step where the photosynthesis product, glucose, is converted into energy.  Energy that is used for growth.  Therefore, if plants can't respire optimally, they can't grow optimally.

Try this out and see it for yourself.  You may notice that a zucchini variety with an 8-week maturity actually matures in less than 7 weeks when planted in July.  Likewise, you may find that a winter squash planted later in the season matures a full two weeks ahead of its stated maturity.

Healthy, late-sown squash plant

3. Less Disease

There's a little bit of carryover from the last point here.  It's a simple fact that plants that are actively growing are a lot less prone to disease compared to plants that are petering along.  They are making lots of glucose and thereby lots of energy and they can use those resources to ward off disease.

But there are additional benefits to growing squash later in the season when the temperatures are warmer.

First of all, rain becomes less frequent as the season carries on.  This may mean that you need to run irrigation or string out the hose on occasion, but it also means that there is less opportunity for diseases to spread.

Secondly, because both the daytime and nighttime temperatures are higher, any rain that does fall is less likely to remain on the leaves for long periods.  Another reason why disease is less likely to take hold.

And for reasons previously discussed, bugs are less of a problem when you plant later in the season which means that they are going to be less likely to pass along disease.

Interior of a cheese squash


So, there you have it.  Three reasons why sowing your squash seeds late just might be the way to go.  They'll grow faster, and therefore mature faster, and they'll be less prone to insect pests and disease.

But there's one more thing.

I don't want to sound like a freeloader, but consider this: About two weeks after harvests begin, Mrs. Go Getter is going to be ditching her excess zucchini on your porch, so you won't be missing out on much of the summer squash season anyway.  Don't feel bad.  Later in the season, when her garden is overrun with squash bugs, you can return the favor by ditching some of your zucchini on her porch.  After all, the Go Getters are actually pretty nice folks.

Freshly harvested zucchini

Other Considerations:

I think this goes without saying, but if you're trying to decide if it's too late to plant zucchini or other squash, you're going to want to take special notice of the type of squash you want to grow and its intended purpose. 

Although the vast majority of squash belong to one of the four major Cucurbita species, the time to harvest will vary depending on the variety and its intended use.  Zucchini, yellow summer squash, and scallop or patty pan squash, for example are typically harvested young.  The days to harvest for these varieties typically range from 50 to 70 days. 

Winter squash, on the other hand, typically require at least three months to mature.  As previously discussed, your late-planted squash are probably going to finish ahead of their maturity date, but you'll still want to ensure you have enough frost-free days remaining to be able to fully mature.  After all, fully matured and properly cured winter squash will have the longest storage potential.

Blue skinned pumpkin

Final Thoughts

Look, stuff happens.  A rabbit chomps off the plants you've been carefully nurturing for the last month.  Your toddler decides to surprise you by "weeding" the garden.  Your spouse suddenly asks why you didn't plant any of that vegetable they never liked or showed interest in before.  Sometimes you find yourself arriving to the party late and in need of a game plan.  But take heart in knowing that these experiences sometimes are the ones that provide the most opportunity for learning.  I hope you've found this article useful and if you're on the fence about sowing a round of squash seeds this late in the season, I hope I've given you enough encouragement to try.  After all, what have you got to lose?

Becky Weeks

Becky Weeks

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