Gardening in Hawai’i is typically considered the Garden of Eden, but when it comes to growing Zucchini, you may as well be in the pits of hell. Most gardeners in Hawai’i give up on the plant. It’s prolific reputation does not hold up in the land of pickleworm and melon fly.
That’s not to say that it can’t be done. On the contrary, people are able to grow zucchini successfully in the islands and there is even a farm on Oahu that produces tons of zucchini. They most likely use tons of chemicals though.
For the average backyard grower in Hawai’i, zucchini is going to be a novelty plant that will take more than the average amount of work to get it to produce. But some of us just have to have zucchini. If you’re one of those people, let’s give it our best shot.
Related: I’ve noticed that the zucchini that can handle the pests is the one that is grown in the healthiest of soils. I have one secret weapon that I have to thank for my zucchini harvest, year after year and it’s this product from Amazon.
The Problems with Growing Zucchini in Hawai’i
Zucchini loves warm climates, but it does not love excessive moisture or too many pests. Unfortunately for us, a lot of places in Hawaii have those exact problems. I want to address the pest & disease issues first because that is the main reason most people are unsuccessful with growing zucchini in Hawai’i.
POWDERY MILDEW
Powdery Mildew is a fungal disease that wreaks havoc on zucchini plants in Hawai’i. Powdery mildew thrives in moist, humid climates. If you live on the dry side of the islands, consider yourself lucky that this may not be such a problem for you. But for the rest of us it is something we must mitigate.
The vector for Powdery mildew are aphids and other sucking insects. If you see aphids but don’t see any problems on your plant, just wait, it’s coming. Try to get rid of them as soon as you can.
If infection is noticed, believe it or not, milk can help solve the issue. Make a mixture of milk to water (1:10) and spray it on plants at the first sign of infection. Repeating weekly. Studies have shown this to be more effective than chemical fertilizers!
PICKLEWORMS
Pickleworms (Diaphania nitidalis) have only arrived recently (2003) to the islands but they have left a lot of damage in a short amount of time. They can be found on all islands destroying your squash, cucumbers and melons.
Exclusion is the best way to manage Pickleworms. The pickleworm moth is only active at night when they lay their eggs, so if you can cover your zucchini at night with mosquito netting or remay cloth and take it off in the morning to allow pollinators in during the day, you can keep the pickleworm larvae from invading your plants.
You must be vigilant though, forgetting for just a night or two may be all the pickleworm moth needs.
You can also choose a zucchini variety that is parthenocarpic. These varieties do well in indoor production and do not require fertilization from insects.
You can tell you have pickleworm by the small holes they leave in the fruits and flowers of the zucchini. To control them you can use sticky traps to catch the moth at night, but you tend to also catch plenty of beneficial insects as well. I prefer to keep them covered.
MELON FLY
The Melon Fly (Bactrocera cucurbitae) is a major pest in the Hawaiian Islands. They are most common from sea level to 1500ft and love squash, tomatoes, cucumbers, papaya, peppers and more.
The best way to manage the fruit fly is by sanitation. Bag all infected fruit and dispose of it at the dump or bury at least 18” into the ground. You can also feed the infected fruit to animals, but don’t leave it sitting around for more than a day.
Fruit fly traps can also help keep the numbers low and allow you to find out the population of fruit flies in your area.
If the population is just out of control, you can apply a foliar spray such as GF-120 Fruit Fly Bait Concentrate®, a combination of protein bait and spinosad insecticide that is very safe to humans. It is approved for organic production. Just spray it once a week on affected plants and host plants such as cassava, castor bean, corn, & ti until they are under control.
Related: Perennial Vegetables: Edible Plants for a Hawaiian Garden
Best Varieties of Zucchini to grow in Hawai’i
It is important to choose varieties of zucchini that are resistant to Powdery Mildew and parthenocarpic, meaning able to self pollinate. These are the best ones that I have found.
- Partenon – This is a medium green straight zucchini that does well in greenhouses. It is parthenocarpic and resistant to powdery mildew. I have found it to produce some zucchinis, but powdery mildew did become a problem over time.
- Dunja – My favorite zucchini variety for Hawai’i. I have found this variety to be a good producer while under cover. It also had minimal problems with powdery mildew. I found it to grow well in pots or a raised bed. If I were to choose a zucchini variety to start with, Dunja would be the one.
- Noche – Another good zucchini for our Hawai’i climate, it is resistant to powdery mildew, but its dense leaf cover does create favorable conditions for powdery mildew to develop, so it does not last as long as the Dunja variety. I would plant this for diversity in case it just isn’t the year for the other 2 varieties.
Best Way to Grow Zucchini in Hawai’i
Zucchini is recommended to be started in the months of March thru early May, but you can get away with planting them as early as January in Hawai’i. If you can get them planted earlier the better. WAY fewer pest issues to have to worry about in the plants that got a good head start.
Zucchini is best grown in a medium loam soil that is rich in compost, they are heavy feeders. A lot of backyard growers in Hawai’i achieve optimum soil conditions simply by planting zucchini in pots or raised beds with amended soil. Growing directly in the ground in many places has proved troublesome.
If you are growing directly in the ground, a spacing of 20”-30” between plants and 2’-3’ between rows is recommended as these are very large plants. Amend with a high phosphorus fertilizer and a little extra nitrogen just as fruit starts to come in to enhance vigor of the plant.
In my opinion, the best way to grow zucchini in Hawai’i is in raised beds or pots that can control access to insects. That means by creating a covered bed or pot with mosquito netting or remay cloth. This will help keep the pests out that wreak havoc on your zucchini crop.
I like to build a frame out of PVC that is the size of my growing bed or pot and wrap it in mosquito net or remay. It is light enough to take on and off with ease. If you have the space, a well ventilated greenhouse that has a clear roof up top and screen everywhere else is a great option as well.
In fact, an additional control measure would have you growing your zucchini plant under cover if you are in a super rainy part of the islands. I have an outdoor space that has a clear roof where I put all of my more finicky plants that don’t do too well here. That way I can control the irrigation.
You can also achieve this by growing zucchini in a pot and moving the plant in or out depending on the rainfall.
If you haven’t been deterred yet and are just as determined than ever to grow zucchini, following these control methods can help you have a successful crop.
Caring for Zucchini While it Grows
If you haven’t figured it out yet, Zucchini takes a lot of care in order to grow it here in Hawai’i. By keeping access to the plant away from all of the pest insects that want to attack it, you are doing pretty good, but sometimes they do get in.
Remove infected fruit and bag it up and dispose of it as soon as you see signs of infestation. A spry of insecticidal soap can help but has limited effectiveness. Most of the pests live inside the fruit or flowers and do not get affected by pesticide spray.
If you begin to see powdery mildew, keep water off the leaves and spray with a milk solution as mentioned earlier in this article.
When the plant is young, cultivate carefully to remove weeds as the roots of the zucchini plant are very shallow and can be disturbed if you are too rough when weeding.
If you are able to take all of these precautions, you may begin to find yourself some zucchini to harvest. Try to pick the fruit when they are about 6” long, don’t leave them there for as long as you have to. This will minimize the chance of insect infestation.
Related: Building Soil In Hawai’i
Either Success or Miserable Failure
So by now, you probably have a zucchini plant that is well fortified. After all this work, you stand the chance of having an incredible zucchini harvest that will make you the envy of your Hawaiian neighbors or you’ll get totally skunked.
The trick is to never give up. I really like zucchini. I love making zucchini pancakes or curry/stir fry with zucchini. Because of that I try a little harder when it comes to growing out the plant.
However, due to its difficulty in growing, I have been moving more towards crops that have an easier time growing in our Hawaiian climate. Kombucha Squash or chayote are good substitutes and grow way easier. Sometimes I wonder why I go through the struggle.
I guess I like the challenge. I hope this article helps get you prepared for the challenge of growing zucchini in Hawai’i. After all, what’s life without a little challenge.
Happy Gardening!!
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