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Don’t Panic, It’s Organic: Brix: What is it, and why is it important?

Andy Lopez, Contributing Columnist/Invisible Gardener
9:11 am PST February 16, 2017

Relative density scale indicates the percent of sucrose by weight (grams per 100 milliliters of water) in a solution or juice of a plant measured in degrees Brix. 

A refractometer is used for measuring solids dissolved in water; it corresponds directly to the refractive index scale. A refractometer allows you to accurately measure the percentage of sugar or Brix in any liquid with just two or three drops.

You can use a refractometer to measure the health of all plants, vegetables, flowers, trees and lawn. Experiment for proper Brix levels for the type of plant you are testing. Just press a liquid sample of either the fruit or the leaf down against the glass plate. Point it toward a light source and look through the eyepiece to view the reading. A refractometer is a “must have” for anyone growing their own food.

For most vegetables, flowers, etc, a good Brix level to maintain is 18 or higher (get to 22 and you will be singing).

The refractometer was invented by cook/scientist, Ernst Abbe, who wanted to know how sweet his fruit was. Gardeners soon found out that you can not only measure the “sugar” levels of wine and beer (it is used mainly for beer or wine making) but also fruit, vegetables, lawns and flowers, as well as plants’ levels of minerals and complex carbohydrates.

A refractometer device measures sugar concentration in plants both from the fruit and its leaves. Refractometers are also used for drug diagnosis, in gemology, in veterinary medicine and in aquariums to determine proper pH. 

A refractometer uses refractive light passing through plant sap or fruit or vegetable juice to take a reading of nutrient (sugar, mineral, carbohydrates) levels. The higher the Brix, the healthier, disease and pest free (more resistant) is the plant, and the higher nutritional (dense) value the plant will have.  

A low Brix means that your crop will not grow to its potential due to some external limiting factor, such as: low levels of nutrients, low mineral levels or mineral imbalance in the soil which allows weeds to grow and compete for food and light,  low calcium content in the soil or deficiency in boron and other exotic minerals (which usually indicates other problems with the translocation of sugars). This happens when you get a low Brix reading in one part of the plant and a higher Brix reading in another part. For gardeners, a refractometer will tell you if your plant has watery cells. Watery cells indicate that the plant is very low in the sugars it needs to function. You want your plants to have lots of dissolved solids like sugar. 

Using a refractometer on a regular basis to keep track of your plants’ health over a period of time will help you to determine problems before they crop up, as you can tell if what you are doing is working or not.

If you test your tomato plants with a refractometer and you notice a declining Brix reading, then you can correct it by either foliar applications or soil applications to raise it before it translates into a serious problem. 

Healthy plants will have a very high Brix reading. 

A plant with a high Brix reading means a few things to me:

1. The higher the Brix, the higher the complex carbohydrates. Insects can’t eat complex carbohydrates (but they do love simple carbohydrates!). 

2. The higher the Brix, the higher the minerals. 

3. The higher the Brix, the higher dissolved solids.

4. The higher the Brix, the less the pests. 

5. The higher the Brix, the less diseases it will have.

6. A plant with a high Brix reading is that way because the soil is alive with mycelium. Mycelium provides all plants with the minerals they need.

Brix levels are important to know if you want to be able to detect problems early. Knowing that a Brix level is low — low enough to attract insects — is an important warning sign to know, and one can use this information in order to control and the problem, and eventually not have it at all.

It has taken me over 55 years to understand that low Brix levels usually mean trouble for your plants. So, now, I pass this knowledge to you. 

Living in such a wonderful year-round climate, one can see from my location that I have developed into a very specific niche and within that niche grow only specific plant varieties and have done so forever. In Malibu, we do not have to worry about snow, and our plants show it.

Using a refractometer to measure the Brix level of your plant (not the juice) will reveal the minerals and complex carbohydrates the plant has available to it. A good gardener can tell if a plant is getting all its minerals or not by the way the plant looks, but sometimes it is helpful to have a tool that can guide you in the right direction.

EBay offers analog and digital models, but the digital ones usually cost more and are harder to use; however, they are well worth it once you get good at using it. You can expect the cost to range from $50-$200. If you buy one that is too cheap, don’t expect it to last. I would buy an analog refractometer around the $100 mark.

Refractometers and charts are also available from: Pike Agri-Lab Supplies Inc., RR2, Box 710, Strong, ME 04983 (207-684-5131); and Rex Harrill, PO Box 6, Keedysville, MD 21756 301-432-2979.

Once you obtain your refractometer, here’s how to get a reading. First, you must get the juice from either the fruit, the leaf, or whatever part you want to read. You can also use it for carrots  and other below-ground crops.

This can be done by placing a small amount of the juice onto the glass and then looking through the eyepiece to read the Brix level. The Brix level is the point (line) where the dark part on top meets the white solid bottom. Where the two meet, you read the Brix number next to it. That’s it!

Any questions? Email me at