How to Grow with a Load of Brix

Want Bigger, Sweeter, Healthier Crops?

You may not know it, but every grower should be trying to grow their plants with a high level of Brix! However, it tends to be something that not many growers concern themselves about. In this article we're going to investigate what Brix is, and how it can make a big difference to the size and quality of a crop.

Exactly What is Brix?

Degrees Brix is basically a measure of the sugar concentration of a liquid. The higher the Brix level, the more sugary the liquid is. By definition, 1 degree of Brix is the sweetness of 100 grams of liquid which has 1 gram of sucrose (normal table sugar) dissolved in it. Degrees Brix is often abbreviated to °Bx, much in the same way that degrees Centigrade is frequently abbreviated to °C.

There are a few other scales for describing the sugariness of a solution. There's the Plato scale (°P), and the Balling scale (°B). The strange thing is that 1° Brix pretty much equals both 1° Plato and 1° Balling. There are actually very, very slight differences between the scales but you would need some very expensive equipment to be able to measure them. For our purposes we can consider the 3 scales to be the same and interchangeable.

You might wonder why there needs to be 3 different names for what is essentially the same scale. The reason is mostly historical and usage dependent. For example, the °Balling was the original scale invented in 1843 and has now largely fallen out of use. The °Brix was introduced by Adolf Brix in the 1900s and includes tiny corrections to the very slightly inaccurate °Balling scale.

The Brix scale is the usual scale of choice for industries involved in products such as wine, sugar, fruit juice and honey. The °Plato scale is the one used most often in the brewing industry to measure the sugar levels in wort (the liquid produced after the extraction of sugars from malt) which gives the brewer an indication of the likely alcohol content after fermentation.

As mentioned above, the Brix scale is the one which is generally used in the wine industry. Vineyard workers will often keep an eye on the Brix levels in their grape vines as they grow. This is why Brix is usually the scale of choice for growers of other plants too.

Why the Brix level in Plant Sap Matters - A Lot!

Plant sap contains the sugar that has been created by photosynthesis in the leaves. The plant shuttles the sugar-containing sap from the leaves to the other parts of itself where it is needed. It is this sugar level in the sap that is of interest to us growers. It gives us an insight into the health and vigour of our plants and even the likely eventual crop size and sweetness of the produce. Basically, it is a way of measuring recent photosynthetic activity, and that has a whole host of implications. Plants with a high Brix level have the following advantages:

  • Better frost damage resistance
  • Greater resistance to insects
  • Greater resistance to diseases from pathogenic fungi, bacteria and viruses
  • Rapider carbohydrate production
  • Higher lipid production (for long-term energy storage)
  • Sweeter, higher quality produce containing more sugar, essential oils, terpenes etc.
  • For organically grown plants, more sugar is available for the beneficial microbes in the root zone. This creates a healthier and much larger microherd. This helps to protect the roots and makes more nutrient available.

One of the most interesting of all these advantages is the increase in pest & disease resistance as Brix levels go up. Out in the wild, plants that have good genetics, good soil and a good location will generally have very good Brix levels. The high Brix levels mean that the plant can afford to spend plenty of it on building its own immune system and structural integrity. Pests and diseases will mostly leave these uber-healthy plants alone and instead attack weaker plants which are growing in poor soil and/or in a poor location. This is one of the ways that nature whittles out the genetically weak and favours plants growing in the best places.

Why Measure Brix Levels?

Clearly, with the wealth of benefits brought by having high Brix levels, it makes a whole lot of sense to try to increase the levels in your plants as much as possible. For this we need some way of measuring it. We can then monitor the Brix level occasionally through the course of a grow and see how well the plants are doing. We can also see what effect something has when we try to increase that level.

As a side note, it is important to know that the Brix level in plants rises through the day and drops again as night-time approaches. When the daytime begins, plants begin to photosynthesise to make sugar and so the Brix level begins to rise. As night-time gets closer the plant begins to shuttle sugar down to the roots to feed beneficial organisms and this causes the Brix level in the plant to fall. Therefore, it is important to test the Brix level at the same time every day

How to Measure Brix

Most humans can taste the difference in sweetness of just 1 °Brix. Of course, this would be just a subjective test and only really of use for comparative purposes. However, there are devices which can measure the sugariness of a solution. Brewers can test the sugar level in their wort (the fermenting brew) with a simple glass "float" device called a hydrometer. The higher the sugar level in the brew, the higher the float sits in the liquid.

This is because the more sugary a solution is, the denser it is. The measurement is read off on a scale on a thin neck at the surface of the solution. Unfortunately, this method of measuring sugariness requires a lot of liquid (several hundred millilitres) which is far more than we can get out of a leaf or 2:

Fortunately, the Brix level in a plant can also be measured with something called a refractometer. Brewers sometimes use refractometers as well as hydrometers. The great thing with refractometers is that they only require a couple of drops of solution. These devices actually measure to what degree light is bent as it passes through a liquid. The higher the sugar content (and to some extent the mineral content) in it, the more that light is bent (refracted).

There are various different types of refractometer on the market and price varies a lot depending on accuracy, and also on whether they are optical or electronic. For general use the optical hand-held type is more than adequate and with a quick hunt on the internet you'll find they can be had for as little as £20 or even less. This is the type that we'll describe how to use here.

There are various different types of refractometer on the market and price varies a lot depending on accuracy, and also on whether they are optical or electronic. For general use the optical hand-held type is more than adequate and with a quick hunt on the internet you'll find they can be had for as little as £20 or even less. This is the type that we'll describe how to use here.

To use an optical hand-held refractometer to measure the brix level of your plant you will need to snip off a leaf or two. The sap within the leaves can be extracted by chopping them and using a garlic press or a pestle and mortar to squeeze out the juice. Only a few drops are needed. The juice is dropped onto the testing plate on the refractometer and a clear lid is flipped over onto it which makes it spread out into a uniform film. The user then looks through the eyepiece located at the other end of the device. Light shining through the test slide (and the test solution) is bent (refracted). The extent to which it is refracted depends on the sugar content in the solution (the degrees Brix). The greater the sugar content, the greater the light is refracted.

There is a vertical scale in the viewfinder and the refracted light lands upon it. The Brix level can be read off by seeing where the white area and the blue area meet on it. To ensure accurate readings, always calibrate your refractometer before use and clean the test plate afterwards. If you decide to get a refractometer for yourself, make sure you get one with a 0-32 scale. This is the type with the most appropriate scale for measuring plant sap.

What the Brix Level Reading Means

So, what does the reading mean? Well, different plants have different ideal Brix levels. There are plenty of charts around on the internet which will list the ideal Brix levels of the plant you want to grow. They will generally tell you the poor, good and excellent Brix levels for various different types of plants and fruits. Let's just take a look at the ideal Brix level for Cabbage. A poor Brix level for a cabbage is considered to be 6. An Excellent Brix level for a cabbage is considered to be 12. Fruit will usually have a higher Brix level. For example, a poor Brix level for grapes is considered to be 8 while an excellent Brix level for grapes is considered to be 24. It is frequently noticed by growers that if a plant has a Brix level of 12 or above then it is much less likely, or even highly unlikely, to have any pest problems.

One other thing to look for when taking a reading with a refractometer is how clear and sharp the dividing line is. A fuzzy line indicates a high mineral content (particularly calcium) in the sap. If the line is clean and sharp it could indicate a calcium deficiency.

So, How Do I Increase the Brix Level in my Plants?

It is important to get environmental factors such as light, temperature and humidity right so that your plants are happy and unstressed. There are also a few nutrients and additives that can make a difference too:

Carbohydrate Additives
As mentioned previously, plants send some of the sugar that they manufacture through photosynthesis down to the root-zone during the dark period. This is to feed beneficial microbes. Plants have evolved to perform this action, and they will still do this even if the root-zone is sterile. Unfortunately, by secreting some of the sugar out through their roots, their own Brix level is reduced. By adding a quality carbohydrate additive to the root-zone, your plants will reduce the amount of sugar that they transport down there to feed the beneficial microbes. In fact, in most cases the loss can be reversed and the roots will absorb sugar instead which will actually increase the Brix level within the plant. However, the right type of sugars need to be added - household sugar will not work very well at all. Among the very best carbohydrate (sugar) additives is Advanced Nutrients CarboLoad. However, Advanced Nutrients Bud Candy contains a wider variety of sugars and does an even better job. Other quality carbohydrate additives are:
The Brix level in a plant has a lot to do with nutrient availability and balance. If the nitrogen to potassium ratio is too high, then the Brix level is likely to be low. This is because it takes energy (sugar) for a plant to use nitrogen and this then reduces the Brix level. Also, adequate potassium is required for optimum Brix levels. An imbalance can be corrected by reducing the amount of nitrogen in the feed and increasing the amount of potassium. Remember that nitrogen is required for solid vegetative growth and some is still required during flowering so don't reduce it down too far. If the leaves turn yellow then most likely your plants are nitrogen deficient. A potassium additive can be used to alter the nitrogen to potassium balance without reducing the nitrogen level too far. An excellent example of a potassium additive is Aptus K-Boost.

Calcium plays a big part in a plant's internal transport system. It also helps with the uptake of other nutrients from the rootzone. A calcium deficiency will almost certainly have a detrimental effect on Brix levels. Calcium can be added to soil with lime, or a calcium-containing supplement (such as a calcium-magnesium product) can be used. Although it is important to avoid a calcium deficiency, it is also important not to provide an excess. Too much calcium will lock out several other vital nutrients such as potassium, phosphorous and boron. Some great cal-mag products are:

Particularly in soil, organic matter provided by humates makes nutrients more available to the plant and it is a sign of quality soil. If the natural level of humates in the soil is low, then this can be corrected by the addition of quality compost or peat. It can also be added with a humic acid containing product such as:


Kelp Extracts
Kelp, or seaweed extracts contain all sorts of good things - micronutrients, natural plant hormones and natural sugar (mannitol). Mannitol is a natural chelation agent for micronutrients and is therefore helpful for the transport system. Boosting the availability of micronutrients helps to ensure that there's no plant deficiencies in them (particularly boron) which could cause low Brix levels. There are several additives on the market made from kelp. It is well worth using one. Some of the high quality kelp extract additives are:

Amino Acids
Plants use amino acids to make proteins which are then used to build plant matter. Providing amino acids to the plant means that it doesn't need to expend its sugar-energy in order to make them. Amino acid blends are in several additive products. If you can, try to use one that contains the full array of them. Various products contain amino acids such as:


A good Brix level is very important for optimum growth & abundant flowering/fruiting, as well as pest & disease resistance. Along with environmental conditions (light, humidity, temperature, vapour pressure deficit) it is one of the most important aspects of successful growing that the grower has some control over. Get your environmental conditions and the Brix level optimised and your plants will flourish, giving you the biggest and highest quality crops possible.

Expert tips