Why Is TDS Important For Your Cannabis Plant

They say too much of a good thing is bad — just like adding extra cheese to your pizza until it’s basically soup. The same goes for cannabis nutrients. You don’t need to give your plant a lot of it — the right amount will do the trick. 

That’s where TDS (Total Dissolved Solids) comes in. Understanding it helps you balance nutrients, avoid overfeeding, and grow strong, high-quality buds. Learn all about TDS in this article below. 

What are Total Dissolved Salts?

Total Dissolved Solids or TDS is a measure of everything dissolved in your water — both organic and inorganic substances. In other words, it’s a number that tells you how concentrated your water is with minerals, salts, and other compounds.

When growing cannabis, TDS gives you an idea of the nutrients and minerals in your water or nutrient solution. It’s measured in parts per million (PPM), which indicates how many solid particles exist per million parts of water.

There are two ways to measure this: TDS and EC (electrical conductivity). While both methods measure the nutrient concentration, they do so differently. TDS gives you a direct reading of the dissolved solids, whereas EC measures how well the water conducts electricity, which indirectly indicates nutrient levels.

However, EC has a limitation — it doesn’t detect non-saline elements in your solution. That’s where TDS comes in handy, as it provides a more complete picture of what’s in your water.

Now, why does this matter for your cannabis? TDS helps you figure out whether your nutrient solution is too weak or too strong. 

If your water’s TDS is too high, it can overwhelm your plant, leading to issues like nutrient toxicity, lockout, or even nutrient burn. On the other hand, if it’s too low, your plant might not be getting enough nutrients to thrive.

For cannabis, anything over 1000 mg/L of dissolved salts can be harmful. Excessively high TDS levels can cause stunted growth, plant diseases, and lower yields.

Factors That Influence Your Water’s TDS

Total Dissolved Solids (TDS) isn’t just one thing — it’s a mix of different elements that come from natural sources, municipal treatment, and even the pipes your water travels through. While some of these components are beneficial, others can throw off your plant’s nutrient balance. Here are some of them.

• Minerals and Salts

Your water naturally contains minerals like calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K). These are essential nutrients for your cannabis plants, but too much of a good thing can be harmful, leading to deficiencies or toxicity.

• Carbonates and Bicarbonates

If you’ve ever dealt with hard water, you’ve encountered these. Carbonates and bicarbonates raise alkalinity, which can mess with your pH balance. And as you probably know, unstable pH means your plants can struggle to absorb nutrients properly.

• Sulfates

Sulfates are another factor that influences TDS. While they’re not necessarily bad, they can alter the taste of water and impact how well your plants absorb nutrients. If you’ve ever had water with a slightly bitter or metallic taste, sulfates were likely the culprit.

• Chlorides

Most tap water contains chlorides, and while your plants need them in small amounts, too much can be harmful. High chloride levels can lead to toxicity, affecting plant health and even altering the final flavor of your buds.

• Organic Matter

Water can also contain dissolved organic compounds, including acids, sugars, and remnants of decaying plant material. While some organic matter can be beneficial, excessive amounts can promote bacterial growth or clog hydroponic systems.

• Metals

Trace metals like iron, manganese, copper, and zinc are naturally found in water and act as micronutrients for plants. However, excessive concentrations can throw off your plant’s nutrient balance, leading to deficiencies or toxicity.

The Role of TDS in Cannabis Growth

TDS is important because it affects how your plants take in nutrients and stay healthy. As cannabis depends on specific nutrients for best growth, understanding TDS levels helps growers balance them just right in cannabis to offer the plants what they need.

How TDS Affects Nutrient Absorption

The TDS shows the concentration of minerals like nitrogen, phosphorus, potassium, calcium, magnesium, and trace elements dissolved in water in every stage of the plant’s growth. If you don’t maintain it properly, TDS levels cause the plants to suffer due to a lack of nutrients.

Effects of Low TDS on Cannabis Plants

When TDS levels become too low, it means the nutrient concentration in the water or soil is insufficient to support healthy growth, which can lead to various issues, including:

• Plants that lack nutrients do not develop properly. Also, their leaves will lose color and turn yellow.
• If the plant does not get enough nutrients, cannabis plants will be stunted in growth and will have smaller leaves.
• If a plant lacks nutrients, it becomes more prone to diseases, pests, and environmental stress.
• Low TDS levels can give you small buds that have lesser potency due to low cannabinoid and terpene content.

Effects of High TDS on Cannabis Plants

In contrast, high levels of TDS can create an imbalance and cause problems too, and they are:

• A nutrient lockout happens when excessive minerals are present, causing other nutrients to become unavailable to plants. Consequently, plants will show deficiencies even when there is an abundance of nutrients in the growing medium.
• A high concentration of salts in the growing medium will stress the roots. Ultimately this will prevent the plant from absorbing water and nutrients.
• When a plant receives excessive nutrients, it develops brown tips that curl. Excess nutrients burn the plant tissues, which can itself be unpleasant for the plant. 
• The pH levels vary a lot when there’s high TDS, which stops nutrient intake which can further lead to deficiency or toxicity.

TDS For Cannabis Plants

The right TDS levels can make or break your cannabis grow, but the ideal range depends on your setup, water quality, and growing medium. Whether you're working with tap water, soil, or hydroponics, understanding TDS can help you dial in the perfect balance for healthy, thriving plants.

But before that, here’s what you should know about TDS based on your setup. 

• Tap Water TDS

Tap water is the go-to for many growers, but its TDS can vary wildly. If the PPM is too high, your plants may already be getting a hefty dose of dissolved minerals, meaning you’ll need to adjust nutrient levels accordingly. 

Ideally, tap water should be under 500 PPM. If it’s not safe for drinking, it’s probably not great for your plants either.

If your water source has a high TDS, a reverse osmosis (RO) system can reduce it to around 10 PPM, allowing you to build a nutrient solution from scratch. RO filters aren’t cheap, though, so alternatives like carbon filtration or distillation can also help improve water quality without breaking the bank. 

Not sure what’s in your tap water? Reach out to your local water supplier for a breakdown of its contents.

• TDS For Growing in Soil

If you grow your cannabis in soil, TDS isn’t something you need to stress over too much. Soil naturally buffers nutrients, making overfeeding less likely than in hydroponics.

However, if you’re using low-quality soil, testing your runoff can give you a clearer picture of whether your plants are getting enough nutrients. If levels are too low, you may need to supplement with organic fertilizers to keep your plants happy.

• TDS For Hydroponics

Hydroponics is a different game altogether. Since plants get their nutrients directly from the water, TDS management is critical. 

Get it right, and your plants will thrive. Get it wrong, and you’ll see the effects almost immediately. Too many dissolved solids can cause salt buildup and nutrient lockout, while too few can leave your plants starving.

Impact of TDS on the pH 

TDS (Total Dissolved Solids) doesn’t work alone, much like pH and EC (Electrical Conductivity). These two work together with TDS to restrict the availability of nutrients. Thus, knowing how these three things relate to each other will help you provide your plants with the perfect environment.

The Role of pH in Nutrient Absorption

pH is a measure of how acidic or basic (alkaline) a solution is. This is measured on a scale of 0 to 14 with 7 being neutral. In cannabis growth, pH plays a role in the uptake of nutrients by cannabis plants.

Optimal pH Range for Cannabis

Hydroponic and Soilless Systems: 5.5 – 6.5

Soil-Based Growing: 6.0 - 7.0

If the pH level goes outside of this range, certain nutrients may not be available to the plant, even when the TDS levels are right. This is known as nutrient lockout which can cause deficiencies and poor growth.

Effects of Incorrect pH Levels

1. Too Low (Acidic pH < 5.5)

• Limits the availability of essential nutrients like calcium, magnesium, and phosphorus.
• Leads to weak stems, slow growth, and yellowing leaves.

2. Too High (Alkaline pH > 7.0)

• Reduces iron, zinc, and manganese absorption, causing deficiencies.
• Results in slow growth, discolored leaves, and poor bud development.

How to Use EC to Calculate the TDS?

EC indicates how well a solution can conduct electricity. Basically, the higher the conductivity, the more salt (nutrients) dissolved in the water. And, the higher the EC, the more dissolved ions are present. As nutrients are in the form of salts, which dissolve in growing mediums, EC is a measure of nutrient strength in any hydroponic or soil-based growing system. 

What is the difference between TDS and EC?

• TDS shows the total salt that exists in the water.
• EC, measured in mS/cm or µS/cm, is the electrical conductivity of a solution.
• TDS is derived from EC by using a conversion factor, which varies depending on the measurement scale used. 

Since TDS meters measure in PPM, you can also use an EC (electrical conductivity) meter for better accuracy. Here’s what different EC readings indicate:

• Stable EC: Your water-to-nutrient ratio is balanced. Just top up the reservoir with a solution of the same strength.
• Low EC: Your plants are absorbing more nutrients than water. Add a slightly stronger nutrient solution to compensate.
• High EC: Your plants are drinking more water than nutrients. Dilute your solution by adding more water.

Watch for signs like burnt leaf tips (nutrient burn) or slow growth, as these indicate your nutrient mix is too strong. Also, factor in weather — on hotter days, plants tend to drink more water, which can shift EC levels.

Most high-quality nutrient brands provide a TDS chart — compare it with your water’s TDS to determine if you need additional nutrients.

Ideal EC Levels for Cannabis Growth

Seedling Stage: 0.4 - 0.6 mS/cm

Vegetative Stages: 1.0 - 16 mS/cm

Flowering Stage: 1.6 to 2.2 mS/cm

• If the EC is too low, it means the plant is deficient in nutrients.
• If EC is too high, the plant may burn its nutrients, damage its roots, and stunt its growth.

How Monitoring EC & TDS Together Improves Growth

Because TDS and EC are related measurements, measuring both gives growers the ability to fine-tune their nutrient solution for plants.

• High EC but Low TDS? Adjust this as per the scale used. It’s likely due to an incorrect conversion factor.
• High TDS but Correct EC? Check nutrient balance to avoid salt buildup. 
• Correct EC but pH is Off? pH imbalances can create nutrient deficiency even with proper EC or TDS.

When you regularly check the pH, EC, and TDS, you can make a more accurate adjustment to supply your cannabis plants with the right nutrients at the right time to maximize yield and potency.

How to Measure the TDS of the Water?

Measuring TDS is easy, though it may take time to master. The best tool is a TDS meter, but if you only have an EC meter, you can convert the readings:

1. Use a calibrated EC meter to measure the water’s EC.
2. Multiply the reading by 1000, then divide by 2 to get an approximate TDS value.
3. Keep in mind there’s usually a 10% discrepancy between EC and TDS readings, but it’s negligible for most growers.

Measuring Runoff TDS

Checking runoff water also helps check how well your plants are absorbing nutrients:

• If runoff PPM is lower than the water you're providing, your plant is effectively absorbing nutrients.
• If there’s a big drop in PPM, you might need to increase nutrients.
• If runoff PPM stays the same, your plant isn’t taking in nutrients properly, possibly due to pH issues or nutrient lockout.
• If runoff PPM is high, salts are building up in the medium — flush your plant with clean water to prevent nutrient toxicity.

How to Adjust the TDS Levels?

If your water or nutrient solution has the wrong TDS levels, here’s how to fix it:

• Lowering TDS: Use filtration methods like reverse osmosis (RO), carbon filters, or distillation to remove excess minerals and salts.
• Increasing TDS: Simply add more nutrients to the water to raise the PPM.

For growers dealing with high natural TDS in their water source, alternative options like bottled water or rainwater might be worth exploring. Test different sources to see what works best for your setup.

Best TDS for Cannabis Plants

Now, for the big question — how much TDS does your cannabis plant actually need? The ideal levels vary depending on the growth stage and keeping them in check ensures your plant gets the right nutrients without overfeeding or deficiencies. To ensure a balanced nutrient supply, make sure you monitor and adjust TDS levels based on your plant’s stage of growth. 

If you're growing in a hydroponic system, always check your reservoir’s TDS. As your plant absorbs nutrients, the PPM will drop over time, so regular monitoring is key. If the TDS levels are kept within the perfect range, you can achieve robust rooting, lush green foliage, and dense and potent buds. Regularly measuring TDS with a digital meter and adjusting nutrient concentrations will help you optimize cannabis plant health and yield.

1. Seedling Stage (500-600 ppm)

Time Frame: First 2-3 weeks after germination

The seedling stage in cannabis is one of the most delicate phases of its life cycle. All through this stage, the plants develop roots and early leaves, requiring not too many nutrients or optimal environmental conditions. Proper management of TDS ensures that the young plant does not get overloaded by minerals.

Why Is Low TDS Important for Seedlings?

1. Delicate roots are more susceptible to nutrient burn

• Small and weak roots can’t handle high-concentration nutrients.
• Just like your body loses water when you sweat, so do the roots to balance the salt around them. When there are too many salts (nutrients), the roots end up losing more water than they should, leading to dehydration.
• Keep TDS levels between 100-300 ppm to prevent that from happening.

2. Seedlings Rely on Stored Nutrients

• The seed has enough nutrients stored to sustain initial growth.
• Too many nutrients cause problems for the plant instead of helping it at that time.
• During the first 7 to 10 days, plain filtered or distilled water is essentially all you need as the seed has enough to grow roots and leaves.

3. Low TDS promotes strong root development

• Instead of pushing for rapid growth with high nutrient levels, the focus should be on establishing a healthy root system.
• A mild TDS solution ensures roots grow steadily without stress, setting the foundation for vigorous vegetative growth later on.

Tips for Managing TDS in the Seedling Stage

1. Use clean or filtered water

• Don't use tap water as it has chlorine and fluoride which raises TDS unnecessarily.
• Using distilled or RO water can help you control the TDS correctly.

2. If you are using nutrients, then begin at 25% strength

• Nutrient solutions at full strength are too harsh for seedlings
• Start with ¼ strength and raise it as the plant grows its first true leaves.
• Many growers use light and well-balanced fertilizers to ensure early growth (e.g. 1-1-1 NPK).

3. Check pH and TDS regularly

• TDS should stay between 100-300 ppm for best results. 
• Make sure that the pH level is 5.5 to 6.5 for hydroponics and 6 to 7 for soil. 

4. Avoid Overwatering

• Overwatering can wash away nutrients, disrupt oxygen flow to the roots, and lead to root rot.
• Water only when the topsoil is dry and ensure proper drainage.

5. Increase TDS Gradually as the Plant Matures

• Once seedlings grow their first set of true leaves, slowly increase TDS to 400-600 ppm as they transition into the vegetative stage.
• By carefully managing TDS and nutrients during the seedling stage, you’ll build a strong foundation for robust, high-yielding cannabis plants.

2. Vegetative Stage (800-900 ppm)

Timeframe: Weeks 3-8 (or longer, depending on strain)

The vegetative stage is very important as it sets the stage for the flowering stage where the plant can develop buds. During the vegetative stage, the plant focuses on developing a strong root system, broad leaves, and thick stems so the plant is strong and won’t topple even if the buds are heavy. This stage typically lasts 3-8 weeks, depending on the strain and growing conditions. Proper nutrient management and TDS levels ensure vigorous growth, so pay attention to the plant carefully during this phase. 

Why Is TDS Important in the Vegetative Stage?

1. The plant shifts focus to leaf and root development

• Compared to seedlings, which have soft roots, plants in the vegetative stage quickly develop their roots, branches, and leaves for flowering.
• With abundant roots, the plant absorbs ample moisture and nourishment to grow rapidly.
• Adding more TDS ensures the plant receives plenty of nutrients to grow quickly.

2. Higher nitrogen levels are essential for photosynthesis

• Nitrogen (N) is the most important macronutrient during this phase, as it fuels chlorophyll production and enhances photosynthesis.
• With more nitrogen comes bigger, greener leaves that absorb more light, allowing the plant to store energy for flowering.
• When nitrogen is too low, yellowing of leaves (chlorosis) and stunting of growth will begin.

3. More nutrients are needed to support larger stems

• During the vegetative stage, cannabis plants can get bushy and tall. They require more phosphorus (P) and potassium (K) to strengthen the stems and also help in transporting more nutrients.
• As plants get bigger, they consume more energy. This may cause them to not develop well without adequate TDS levels. They may get weak branches and other deficiencies. 
• As PH levels drop, TDS levels must rise as a beneficial way to provide proper probabilities.

Tips for Managing TDS in the Vegetative Stage

1. Start with 600 ppm in Early Veg, Then Gradually Increase

• Weeks 3-4: Keep TDS between 600-700 ppm as the plant establishes its root system.
• Weeks 5-6: Increase TDS to 800 ppm as plants grow larger and more nutrient-hungry.
• Weeks 7-8 (Late Veg): Push TDS up to 1000 ppm, ensuring the plant is fully prepared for flowering.

2. Keep an Eye on Nutrient Burn & Deficiency

Nutrient Burn (Excessive TDS):

• Brown, crispy leaf tips, slow growth, dark green leaves.
• To resolve this, mix in fresh water with low TDS in your nutrient solution.

Nutrient Deficiencies (Low TDS):

• Symptoms include brown, crispy leaf tips, slow growth, and dark green leaves.
• To resolve this, slowly increase the TDS to achieve a balanced nutrient solution.

3. Adjusting pH will help in uptaking nutrients

In hydroponics, keep the pH between 5.5 to 6.5 whereas it should be between 6.0 to 7.0 on soil to avoid lockout. 

4. Train your plants for optimal growth

• Low-stress training (LST) is when you bend branches to create an even canopy.
• Topping and pruning the main stem allows the plant to grow wider and create more buds.

5. Gradually Raise TDS Prior to Switching to Flowering

• As the plant begins to flower, change your nutrients to increase phosphorus and potassium and reduce nitrogen a bit. 
• Your TDS should be 800-900 ppm by the end of the vegetative stage to start transitioning to flowering.

By managing TDS during the vegetative stage, you help the plant to strengthen the root and increase its size so that it directly helps in the yield and strength of the buds in the next phase.

3. Flowering Stage (1000-1100 ppm)

Timeframe: Week 8 to harvest.

The flowering stage is the last stage of growth, but don’t underestimate it as it’s the most important. After all, you’re doing everything so you can grow buds, so it makes sense to take care of your plant like a baby during this final phase. It is also the most important stage of growth. In this stage, the plant changes from the vegetative state to growing buds. The average duration of this stage is 8-10 weeks, depending on the strain. We must manage nutrients properly to maximize yield, potency, and flavor.

Why Is TDS Important in the Flowering Stage?

1. Buds require more phosphorus and potassium (P & K)

• As cannabis plants flower, they shift energy away from growing leaves and stems and towards the production of thick buds.
• Phosphorus promotes the formation of flowers, while potassium helps to strengthen cell walls and improve the bud structure, size, and overall disease resistance.
• If P & K levels are too low, buds will grow small, airy, and less potent.

2. The plant’s need for nitrogen decreases while overall TDS increases

• Make sure to reduce nitrogen in the nutrient solution gradually and increase phosphorus and potassium to promote resin and larger bud production.
• Unlike in the vegetative stage, where nitrogen (N) is essential for leaf growth, too much nitrogen in flowering can lead to excessive leafy growth instead of bud production.

3. TDS management directly affects yield and potency

• If TDS is so low that it is just above the lower limits, then there are no nutrients available to the plant and it will not develop bud properly and yield will be small.
• When TDS is excessive, it can burn nutrients, lock nutrients out, and produce harsh-tasting buds.
• Raising TDS slowly will make sure the plant gets the balance of nutrients necessary for maximum potency and resin.

TDS Levels by Flowering Phase

Tips for Managing TDS in the Flowering Stage

1. As the buds grow, you should increase the TDS slowly

• Start at about 1000 ppm in early flowering and work your way towards 1400-1600 ppm in mid-to-late bloom.
• Adding too much nutrients too fast can shock the plant, so adjust slowly.

2. Keep an eye out for nutrient burn and deficiency

Nutrient Burn (Excessive TDS):

• Symptoms include brown, curled leaf tips, and stunted growth.
• The solution is to add more water to the nutrient solution or flush.

Nutrient Deficiencies (Low TDS):

• Symptoms include weak bud formation, chlorosis, and stunted growth.
• To counteract this, increase the TDS by adding more bloom nutrients in small increments

3. Adjust pH to prevent nutrient lockout

• Hydroponics: Keep pH between 5.5 and 6.5 to ensure all nutrients remain available.
• Soil: Maintain pH around 6.0-7.0 to prevent deficiencies.

4. Flush in the final 2 weeks for a better flavor

• High TDS levels near harvest can leave behind harsh-tasting residues in buds.
• Reduce TDS to 300-500 ppm and use pure water or a flushing solution to clear excess nutrients. This enhances the flavor, smoothness, and overall quality of the final product..

TDS Adjustments & Troubleshooting

• If TDS is too low, gradually add nutrients and check EC (Electrical Conductivity) and pH to maintain balance.
• If TDS is too high, dilute with pure water or flush with a lower ppm water to remove excess salts.
• Incorrect pH can block nutrient absorption, even if TDS levels are ideal, so monitor the pH frequently. 

By closely monitoring TDS, EC, and pH, growers can optimize bud development, maximize resin production, and ensure a smooth-smoking, high-quality harvest!

The Importance of Monitoring TDS Regularly

Maintaining the right Total Dissolved Solids (TDS) levels throughout the cannabis plant’s life cycle is essential for optimal growth, nutrient absorption, and high yields. Regular TDS monitoring ensures plants receive the correct nutrient concentration, preventing common issues like nutrient deficiencies, lockout, and toxicity.

Summary: Why Is TDS Important For Your Cannabis Plant

Mastering TDS is like tuning a guitar — get it right, and everything works in harmony. It’s all about balance and figuring out the sweet spot, after all. 

Whether you're growing in soil or hydroponics, keeping an eye on TDS ensures your plants get what they need without the risk of deficiencies or burns. A little monitoring goes a long way in producing top-shelf cannabis.