There are two common complaints I hear from gardeners about their zucchini plants. One is that their zucchini plants just produce massive fruit with large seeds and tough skin. The other is that their zucchini plants are taking over their garden. Since I've grown more than my share of zucchini in the last decade in a variety of ways, I thought I'd take some time this month to relieve you from these two common problems.
Before I get into the details of managing your zucchini plants, here's a quick video that summarizes the main points of harvesting, pruning, and staking. Read on for more specifics.
Harvesting Zucchini
When you put a zucchini plant in the ground, you're likely thinking that you want to harvest and eat a bunch of homegrown zucchini, but that zucchini plant is thinking that it needs to produce the biggest possible fruit possible with lots of mature seeds so that I can pass on its genetics to the next generation of zucchini. These two goals do not align, but we can use this knowledge to understand how a squash plant will behave.
One summer, my neighbour invited me into his backyard garden to inquire about a problem he had with his zucchini plants. They had stopped producing fruit.
"I see you harvesting your zucchini almost every day," he said, "but my plant just has this one massive fruit."
"Why don't you pick it?" I asked.
"It's too big! I just want the small zucchini," he replied.
By allowing his zucchini plant to produce one massive fruit, my neighbour had helped his plant accomplish its primary goal of making seeds for the next generation. Consequently, the formation of new smaller fruit was significantly slowed.
The lesson from this short example is if you're going to plant zucchini (or any other type of summer squash), you need to harvest it regularly. That's the deal. It's not the kind of crop that you can plant in spring, ignore most of the summer, and return in fall for your harvest. That works with winter squash. Summer squash requires your attention throughout the summer as the name implies.
Sometimes, I see novice gardens refrain from harvesting their fruiting crops because they don't want to use it up right away. They think that leaving a fruit on a plant can preserve the food for a later date and help them a void wasting their harvest. If you've had similar thoughts, then I have some good and bed news for you. The bad news is that fruit doesn't remain in good condition when you leave it on your plants past its ideal harvest window. Something about that fruit is going to get worse. It may become overgrown. The skin could split. It may become bitter. That list could continue and the consequence of a late harvest really depends on the fruit, but hopefully you get the idea. Let's move on to the good news. Thankfully, when you harvest a fruit at the right time, you actually encourage the plant to produce more fruit. It no longer has the burden of enlarging or ripening the fruit you just harvested and it can turn its attention toward growing another piece of fruit. As evidence of this concept, check out the graph below which shows our summer squash harvest this summer from just 3 plants. Our first harvests were back in early July, but those harvests didn't stop production. In fact, it looks like the rate of production increased a little into August as the plants became more established.
In my books, the highest quality zucchini fruit are those less than 7 inches in length. Once they reach this size and larger, seeds start to develop and the quality of the flesh near the centre of the fruit becomes less desirable. You might miss the ideal harvest window for some of your fruit allowing them to grow past their prime, but don't make the mistake of my neighbour and leave the fruit on the plant. Be sure to harvest any overgrown fruit even if its only to throw them in your compost pile or sneak into your neighbour's mailbox. This will open the door for the plant to produce more high quality fruit.
Pruning Zucchini
As much as I encourage regular harvesting, it is not the only key to ongoing squash production. I also prune the leaves of our summer squash regularly and there are a number of benefits of this practice.
What first led me to prune my squash was the science, because trials have shown that pruning actions can significantly increase yield. The authors of this study compared two simple pruning methods with no pruning, and in their pruned summer squash plants, they recorded "increased flowering, fruit number per plant, fruit length and diameter, and ultimately increased yield compared with no pruning."
What the science doesn't mention is that pruning also makes it more pleasant to navigate a squash patch and a whole lot easier to see and access the fruit. With more space to walk and a clear line of sight to the growing fruit, I'm much less likely to let overgrown fruit escape my grasp and slow down my production.
I said that the pruning in this study was simple because they only removed the first branch 20 days after transplanting and the second branch 30 days after transplanting. A limited amount of pruning is easier to execute for a controlled trial like this, so I can see why they stopped the pruning here. We've taken things one step further though. We now prune our summer squash continuously throughout the summer, because after experiencing the benefits of pruning, it's hard to stop. While I don't have a scientific study to support my continuous pruning routine, I can say that over the last decade of regular squash pruning, my plants have continued to thrive throughout our entire growing season, right until they meet their frosty demise in late September.
In the past, I would have said that pruning off older leaves helps slow down the spread of powdery mildew as well, and there may be some logic to this, but pruning isn't the only factor impacting the presence of powdery mildew. The squash variety you select and the growing conditions you give your plants are also really big factors. Since we now select the varieties with the most resistance to powdery mildew and always focus on giving our plants the conditions they need to thrive, powdery mildew just doesn't seem to be showing up anymore.
Of course, there are limits to how much you can prune, because your leaves are still necessary to drive photosynthesis. Two rules of thumb that I've been using to guide my own pruning are to never prune above the lowest forming fruit and to never leave less than 12 leaves on a plant. Regular pruning is also less of a shock to a plant than one big overhaul in the middle of summer, so make it a routine to cut off a couple of lower leaves every time you harvest.
Staking Zucchini
If you've pruned your zucchini as I have described above, then quite a long spine will eventually develop between the base of the plant and its newest leaves. This spine has to go somewhere. When I operated my market garden, I laid these spines along the ground. This works just fine for the plants and it's easy to organize as long as the spines of all of the plants in a squash bed are leading in the same direction. In my larger market garden beds, I had room for this.
However, when we scaled back our squash production to fit in our smaller kitchen garden beds, something had to change. I no longer had the extra space to allow the long spines to sprawl along the ground. I'm happy to provide my plants with enough resources to meet their basic needs, but I'm not going to let them have free reign over my garden space! In the kitchen garden, the sprawling squash would have encroached on other crops or started to cover up walkways, so it was clear that the only direction they could travel was UP!
To support our summer squash plants I turned to stakes. The vines and stems are too stiff to wind through the netting that we use for peas and beans, and the leaves are far too big to easily wrap around supporting twine like we use for tomatoes and cucumbers. I did consider using tomato cages for a short time but imagined that the squash would become lopsided inside the cage with no real central support to which I could tie the spine of the plant. A supporting stake seemed like the best option.
Over the next few years, I tried one stake per plant, then two, and then changed up the material used for the stakes. The method of support that I've landed on now is working really well, so I'll skip the details of the less than ideal trials and jump right to the setup that we're using today. Each zucchini plant now gets two personal supporting posts installed right after transplanting. I really like using two stakes instead of one because it allows space for the leaf stems to branch out in all directions from the central spine. The small diameter of our stakes also helps to allow space for the splaying leaves. In previous years, I had used 2x2 wooden stakes and these take up a lot more air space when placed right next to the plant.
Our thin metal posts today are made from 1/2 inch metal conduit. It looks like they are just pounded into the ground, but that's not the case. I've done that in the past, but if I want a 5 foot high conduit stake, I need a 7 foot long piece of conduit to pound into the ground with a sledgehammer. That requires the assistance of a ladder or 7-foot-4 Victor Wembanyama, and at the end of the season these pounded posts can be challenging to remove. So to make the setup and cleanup tasks a little quicker and easier, I use a couple of extra components. First, I insert a 3 or 4 foot length of 1/2" rebar (which can be pressed into the soil with my own bodyweight) and slide a large fender washer over that rebar. The fender washer falls down to the surface of the soil and prevents the conduit from sliding below the surface when it is added on top of the rebar. This trick becomes much more important when using conduit staking for really heavy trellised crops like beefsteak tomatoes. Anyways, that's the first trick shown below.
At the top of the conduit posts, I use two 1 inch poly pipe elbows held together with a really short piece of 1/2" poly pipe inserted between the elbows as shown in the next image. These components fit together snuggly so I haven't bothered to fasten them with screws. If I didn't use this top spacer, the posts would be squeezed together by the tie bands that use to hold the spine in place below.
Putting it All Together
I'd classify summer squash as a high needs crop because of the ongoing attention it demands, but your ongoing attention will certainly be rewarded. When you commit to the practices of of regular harvesting and pruning, and possibly even staking your zucchini plants, you can look forward to many months of steady production and always remain in control of your squash patch. Thankfully, not every crop demands this level of attention, but each crop you grow in your vegetable garden is guaranteed to have some unique needs that are important to get right. If you're tired of learning the hard way and you'd like to accelerate your progress, it could be time for you to join our Seed to Table course community.
