I don’t know about you but when I visit a garden and I see large fruits, I get excited! Well, cucurbits such as Pumpkin and zucchini are offering this experience. They are producing large and numerous fruits under a rich foliage. I actually love to look around below the leaves to find the fruits. I feel like a kid at Easter day!
Cucurbitaceae are very common and not so difficult to grow. Here are 3 points to keep in mind when you want to grow them in aquaponics:
A mature aquaponics system is required for zucchini
They are large fruits and as we have developed it numerous times, they need a wide variety of minerals and nutrients. This points make them unadapted to young aquaponics ecosystem as they would miss crucial elements and not develop properly. In a mature aquaponics system (6 months – 1 year and more) they will grow very well and be very productive.
Keep space for other species…
The foliage is very generous and spread very widely. For this reason we will avoid to grow them in the center of an aquaponics grow-bed. We will prefer to grow them in a corner where the roots will develop but the foliage will fall on the side of the grow-bed and leave the surface to other crop. Some species of cucurbits are very good climbers and can be grown in height. This technique will also help to leave the grow-bed surface available to other plants.
The trick to get them fertilized
Zucchini flower in aquaponics
Cucumber develop both male and female flowers. The female flowers must be fertilized in order to give fruits. In nature insects are going from one flower to the other which therefore fertilize it. Unfortunately with the number of insect decreasing significantly it is very frequent to find unfertilized female flowers. In some cities or in a closed greenhouse it is almost impossible to get natural fertilization. If you are in this case you will find some little baby cucumbers on the plant but they will not grow. Instead, they will dry or rot after a few days. This is typical and very frustrating for the gardeners who don’t understand what is going on.
In this case we can artificially fertilize the flowers. To do so you can pick a little brush or tick and gently brush the center of the male flower. Once done you can repeat this process on the female flower and the flower is fertilized. After few days you will notice the little fruit at the base of the flower will grow to form a nice cucumber.
A challenge in aquaponics
In Aquaponics we grow our vegetables in a grow-bed. The depth is generally 30 cm. Therefore, the conditions are very different to a classic garden. Where animals such as worms are able to go deep and mix the deep soil full of minerals with the surface. In aquaponics the only source of minerals is coming from the fish food. However, if you grow a large variety of demanding fruit plants, the minerals available may not be enough… In this case we can observe severe mineral deficiencies on the plant leaves.
Some consequences for your courgettes.
Slight deficiencies will simply tent your squash leaves. Nevertheless, more advanced deficiencies will decrease the leaves efficiency. In other words it will affect the zucchini growth in your aquaponics system. The outcome will be a lower fruit production.
Aquaponics zucchini deficiency
The solution to zucchini deficiency in aquaponics
As explained on my video about mineral deficiency in aquaponics, in this situation we must act. The cucurbit need a blend of minerals but it is difficult to know exactly which one and which quantity. In this case I recommend to add rock powder which is a mix of crushed stones. It is rich in essential elements. It is recommended to add approximately 20 g per square meter of grow-bed but those values vary. It really depends on your plants need. I mix the powder with some water and empty it into the bell siphon cage. In this area, the water flushes before reaching the fish tank and the growbed. It allows a good dilution of the powder.
Iron is one essential mineral to the plants. however, in presence of water and oxygen, it goes through an oxydation. The result is rust but plants such as zucchini are unable to absorb rust. The solution is to add an iron encapsulated into a protective molecule. It is called chelated iron. I am not going through all the types of chelated iron here but there are many of them. The only recommended one is the DTPA iron. Other types will color your water and can be toxic.
the essential minerals are now available in your grow-bed. Your zucchini can grow and develop their full potential in your aquaponics system.
Fungus on Zucchini in aquaponics
Zucchini are subject to a variety of fungus. Some of them (Phytophthora spp) will make the fruit soft and wet. It will become non-consumable. Those fungus can develop on any type of gardening but they like wet environment. In aquaponics I recommend keeping the 3 first cm of your media dry. In this case it will slow the fungus progress. If your media is completely wet, the fungus will find a good environment and spread.
What quantity of zucchini can we expect?
If we take an average of 2 zucchini plant per square meter of aquaponics grow-bed. Remember that we plant them on the side of the grow-bed and let them fall away from the other plants. We can expect between 3 and 8kg of crop per square meter. This is a great outcome. We don’t use much space from the aquaponics grow-bed and we can grow plenty of other plants.
Freshly grown aquaponics zucchini are delicious. They are crunchy and full of flavor. You can’t compare them to the ones bought from the supermarket. You will be proud to feed your family with very healthy courgettes.
The optimum pH for zucchini is slightly acidic, around 6.2. If you grow them in hydroponics, you will target this specific value. However, they accept a large range. In aquaponics we generally aim for a pH around 7. They will grow well in those neutral conditions.
Zucchini are growing fast and they require a high quantity of nitrogen. The optimum nitrate level is around 100ppm. In aquaponics we take in consideration our fish. As an ecosystem we try to maintain the nitrate value below 50ppm. This value will still allow a very nice growth to your courgettes.
I highly recommend this crop if your system contains a high level of organic material. Indeed, you may be struggling to keep your nitrate low, in this case few zucchini plants will help. They will transform the excess nitrate in nice fruits.
Watch out! The original plants can have a high level of a toxin called “cucurbitacins” so be careful if you produce your own seeds. The toxin taste bitter and is easy to detect so don’t eat your crop if you feel a bitter taste.
You will probably be interested to discover Jonathan’s six steps to build and manage an Aquaponics system. Click here to access for free! Thanks and good reading 🙂