Indoor Garden | Preliminary Researches

Today, I wanted to talk about a project I have for a very long time, growing fruits and vegetables in my flat. I'm going to approach this project differently this time, because I haven't yet made my choice on all the methods I plan to use, so I'm taking advantage of this article to expose my criteria and the different possible solutions with their advantages and disadvantages and discuss them with you in the comments.

It's not the most STEM article I've written so far, but I think it has its place here, because for any project there is a research phase at the beginning, used to make the state of the art of the studied domain, to learn about the methods used, and I think that it can be interesting to share with you this process.

You can read this article in French here

Origin of the project

Some time ago I came across an advertisement from the company Click & Grow which sells autonomous indoor gardens that allow you to grow various plants that you buy in the form of pods containing the seeds and substrate (which replaces the soil). Simply place the pods in their devices, fill the water tank and plug it into an electrical outlet, the system is then fully autonomous for several weeks, it will automatically water the plants and provide the necessary light using the integrated lamp. They provide for the essential needs of the plants.

Click & Grow offers a subscription to receive the pods of your choice every 2 to 4 months at a reduced price.

Advantages of Click & Grow

• Easy to use
• Reliable pods
• Completely autonomous (up to 4 weeks for the 9 pods version)
• Only need water
• The lamp doesn't consume much power (13W)

Disadvantages of Click & Grow

• Ready to use solution (no modifications possible)
• Only a few plants simultaneously and per year (18 to 36/year)
• Expensive device and pods
• Long growing time and harvesting periods constrained by the pods
• One company has the control over the pods and its pricing

Cost simulation for Click & Grow

The company offers 2 models of indoor gardens, Smart Garden 3 and 9, which as their name suggests have 3 and 9 places for pods. The first costs €80 ($88, currently €1=$1.1)and the second €150 ($165). The price of the subscription varies according to the frequency of sending and the number of pods, I left on a cost of €3 ($3.3) per plant, you can see a detail of the costs on the table below:

Summary table of the costs of a Click&Grow device

Criteria for the project:

The idea of growing fruits and vegetables has been on my mind for several years. Seeing these products gave hopes that it could be done without a lot of space. After learning more about their products, I started to look at the alternatives and to prepare specifications before making my choice.

Objectives :

• Growing herbs, fruits and vegetables
  • Start with salads and herbs to test
  • Then raspberries, strawberries, tomatoes and peppers
• Be able to adapt to different plants (manually or automatically)
• Be able to support perennial plants (plants that produce for more than a year)
• Have (a lot of) sensors to monitor the environment
• The size of the yield and the growth rate are not important, the goal is to find a balance between effort, number of products used and the plant health.

Constraints:

• Must work indoors, without a specialized grow room
• Must not disturb the occupants of the room (not too much noise or unbearable lights)
• Must prevent insect invasion
• Ideally with equipment that can be used in organic agriculture
• Be as stable as possible and require little or no maintenance
• As inexpensive as possible

As for seeds, you can find about 1600 salad seeds for €3 ($3.3), and the same price for 50 small tomato seeds. So even if only 10% germinate, the cost is negligible compared to the other expenses. I'm also considering starting with seedlings, depending on the growing time.

I took a horticulture light (also called UV light) to supplement the insufficient natural light I have, it represents about €20 ($22) per lamp (which consume up to 16W in full brightness from what I've been able to measure).

During my research I found many techniques, here are three of them :

Alternative #1: Growing in pots with soil

This one is pretty obvious, using potting soil and growing the plant in a regular pot or small planter. Then you just have to add water until the nutrients in the potting soil are exhausted and then replace the potting soil or use fertilizers. Both liquid and stick fertilizers exists. You have to add liquid fertilizer each time you water your plant and most of the organic ones can't be used with an irrigation system (or you have to flush with fresh water after each use), so I will maybe prefer the sticks that you need to replace after 6 to 8 weeks.

I find this method ideal for perennials such as thyme, raspberries and strawberries (just to name a few that I have on my wish list).

Advantages of growing in soil

• pH stable (big problem with the following solutions)
• No need for fertilizer during the first weeks
• Greater diversity of nutrients in some soils
• Possibility to add enzymes to protect the plants

Disadvantages of growing in soil

• Need a potting soil that can be used indoors to prevent the proliferation of insects and diseases
• Bag of potting soil are not very practical in a small flat…
• Liquid organic fertilizer cannot be used with an irrigation system
• Fertilizer sticks can damage plants if planted too close to the roots

Cost simulation of growing in soil

For growing in soil, I was interested in Plagron's products, they have a line of organic products and the other one not.

We find this soil at €10 ($11) for 25 L (this price and the ones in the rest of the article are from a French website where I'm going to buy the supplies), to which we must add this fertilizer at €12/L (enough for 250 L of solution). If we start with pots of 3 L per plant, we get 8 plants for 25 L, for the fertilizer, we can take 1 liter of water per week per plant, so we will use up to 250 L of water in 8 months. So we are going to need 1,5 L of fertilizer per year, equal to €18. With one repotting per year, we arrive at a cost of €28 for 8 plants that will produce all year, equivalent to €3.5/plant.

For fertilizer sticks, we find 32 sticks for €7 ($7,7), they last 2 months and we may need half to 2 sticks per pot depending on their size, for 8 plants, we will need a package every 2 years. This gives us €10 of potting soil plus half of €7 or €13.5/year and €1.7/plant.

Alternative #2: Hydroponics with the Deep Water Culture (DWC) technique

This method consists in placing the roots of the plants directly in a nutritive solution. It is simple to implement and perfectly adapted to the culture of leafy vegetables such as salads (even if it is possible to grow them in pots) and other fruits and vegetables without a lot of weight too high.

This method is generally used when you want to control all the parameters affecting a crop, so it is often accompanied by artificial lighting.

Advantages of DWC hydroponics

• "Easy to implement"
• Fast growth
• Easy to maintain (just a tray to clean)
• No soil required

Disadvantages of DWC hydroponics

• You need to replace the water every 1 to 2 weeks
• Need to monitor pH balance

Cost simulation of hydroponics DWC

If we start with a 6L tank for 6 plants (€16, or $18), we will need nutrients for the growth of the plant (€12,5/L), which has a dilution ratio of 1:400, we will have 400L of solutions. If we consider that we need 3 times the volume of the tank for salads (1 complete change + addition as we go along to keep the level), we should be able to make 22 cultures of 6 plants (that is 132 salads in 2 years with 1L of nutrients). In addition to the nutrients, we need to add something to stabilize the pH if it is too high or low, which costs €9 but ideally we will use them in very small quantity. We also need an enzyme to clean the substrate between cultures. We find a cost of €20/year (nutrients + pH regulators + enzyme) for 66 plants (if we harvest after 5 weeks) that is €0.30/plant.

It is also necessary to think about the medium that will replace the soil to support the roots, we often find rock wool, coconut fiber or clay balls. I chose the last option, because it seems to be the easiest to implement and to reuse, but also inexpensive (€22/45 L) and without any effect on the nutrients.

Alternative #3: Hydroponic Drip Culture

This method consists of drip watering the plants with a nutritive solution, either in a substrate capable of retaining water (coco) or not (clay balls). The water can be collected at the bottom of the pot and reused, or some industrial systems let the excess water escape (run to waste systems).

Advantages of drip hydroponics

• Suitable for larger plants
• Possibility to adjust the amount of water each plant receives

Disadvantages of the hydroponic drip culture

• Possible crystallization of the fertilizer in the tank and pipes
• More important maintenance
• All plants receive the same solution (same ingredients and same concentrations) unless you multiply the number of pumps and tanks.

Cost simulation of hydroponic drip culture

For this method, you can fill the pots with clay balls, coconut fiber, or a mixture like this one (€18/50L). The system to bring water to the plants consists of a container + water pump + air pump (€25, or $27), a watering hose (€6) and a drip watering kit (€12). Then we use the same fertilizers as for the deep water culture (€12.5/L). So the price of installation is higher, but it's the same as DWC afterward.

Conclusion

With all of this in mind, I'm going to start by testing a few plants in pots, some with sticks, some with liquid fertilizers to see if they produce fruits and vegetables easily. I will be able to manage the quantity of fertilizer each plant receive by adding more or less sticks in the pots.

Then try a few salads with a deep water hydroponic system, as it is the easiest hydroponics to set up, and the salads grow quickly.

We'll see in the next few posts how I set up this indoor garden and how I will monitor it.

What about you, do you have any experience growing fruits and vegetables indoors? Come and talk about it in comments!

All the references given in the article are to give an idea of the needs and the cost of the different techniques. None of the links are sponsored, and I have not yet made my choice, nor tested the different solutions proposed.

To go further

If you want to learn more about the different hydroponic systems, I suggest you take a look here:

• Home Hydroponic Systems
• https://hydropros.com/blogs/growers-corner/6-types-hydroponic-systems
• Everything you need to know about water testing

And to the many pages of explanations published by Plagron:

• Grow Topics | Plagron

Sources

• Click And Grow Website - https://eu.clickandgrow.com
• Cellmax - https://www.cellmax.eu
• pH and EC guide - https://okstate.edu
• List of Home Hydroponic Systems
• Grow Gardener - 8 Fast Growing Hydroponics Plants