pH and PPM: Knowing What Your Plants Are Eating and How Much They Can Handle

There are a lot of factors involved in having your own indoor garden. You could be doing everything right — from grow lights to feeding cycles to temperature control — but you might still notice your yields suffering.

That could be because your plants pH and PPM levels aren’t where they should be. This makes it difficult for your plants to eat, which in turn causes underdeveloped growth.

If you’re wondering what pH and PPM are and how they pertain to the plants in your grow room, here’s an easy-to-understand explanation:

• pH refers to the potential of hydrogen ions in your water, which will determine if your water is too acidic or has too much alkaline in it.
• PPM (parts per million) refers to the concentration of minerals and soluble matter in your watering solution.

Correct pH and PPM levels are the backbone of any grow room or grow tent. Making sure your plants' levels are balanced often means the difference between a healthy harvest and weak, unhealthy plants.

Table of Contents

1. pH Levels
   1. Different pH Levels Explained
   2. Adjusting pH Levels
      1. Premade (Store Bought) pH Buffers
      2. Homemade pH Buffers
2. PPM Levels
   1. Common PPM Readings
   2. Adjusting PPM Levels
3. Understanding Your Plants’ pH and PPM for a Successful Harvest

In this article, we’ll get into the importance of balanced pH and PPM levels in your plants. We’ll also give you tips to adjust your plants’ levels if they’re off, and recommend the best solutions for fixing any pH or PPM-related ailments in your grow.

pH Levels in Plants

Simply put, the right pH level will create an environment where your plants can absorb nutrients quickly and easily. This means your plants will be able to take in all the nutrition they need, leading to a better harvest.

Nutrient-rich water is filled with elements that are helpful to your plants. That said, if those elements aren’t broken down properly, they could cause potential harm to your grow.

The right pH level will determine the quality of helpful bacteria in your water. This bacteria helps break down elements, increasing the metabolic rate of your plants.

Here’s what to watch out for when factoring the pH level of your plants:

• Low pH Levels — A pH level of around below 5.0 can be considered low. At this level, heavy metals like iron and aluminum change and can become toxic to your plants.
  • Symptoms of Low pH Levels in Plants — Plants affected by low pH levels typically suffer from yellowing leaves. They also experience stunted growth, wilting, and decreased update of nutrients.
• High pH Levels — A pH level of around 7.0 or higher is usually considered too high. Elements like calcium and phosphorus can’t be broken down completely when pH is high, which will hinder the overall growth of your plants.
  • Symptoms of High pH Levels in Plants — High pH levels often cause plants to suffer from chlorosis, which is an iron deficiency that results in yellow-white foliage. In addition, plant growth suffers due to the plant's inability to take in nutrients.

The acidity in the water you use in your grow room determines the properties of your plants and grow medium. You'll want your plants' nutrients to be a little acidic — otherwise they can't break down. Too much acidity, though, and your nutrients can become toxic.

So always keep in mind:

• A pH that’s too low will be toxic to your plants.
• A pH that’s too high means stunted growth.
• The ideal acidity you want in your water is between 6.0 to 6.5.

What's the Best pH Level for My Plants?

If you’re still unsure as to what will or won’t harm your plants as far as pH is concerned, we’ve broken down the general pH levels and their effects on plants. That way there’s no room for error, and you can ensure your plants are healthy throughout their growth cycles.

• Below 4.0: Root Damage
• 4.0 to 4.9: Nutrient Leaching
• 5.0 to 5.9: Good pH Level
• 6.0 to 6.5: Ideal pH Level
• 6.6 to 7.0: Acceptable pH Balance
• 7.1 to 8.5: Poor Nutrient Uptake
• Above 8.5: Root Damage

It’s also worth mentioning that different plants thrive in varying pH levels. Some plants might thrive in levels that would be harmful to others. This is due to their acidity needs. Let’s take a look at some examples.

• Tomatoes: 5.5 to 7.0
• Cucumbers: 5.5 to 7.0
• Blueberries: 4.5 to 6.0
• Lettuce and Cabbage: 6.0 to 7.0
• Sweet Peppers: 5.5 to 7.0
• Hot Peppers: 6.0 to 6.8
• Honey Locust Trees: 6.0 to 8.0

As you can see, finding the right pH balance also depends on what you’re growing. As such, it’s worth it to do a bit of research so you know exactly how to keep your plants healthy, especially if you’re growing different types of plants that require their own unique pH balances.

In addition, it’s important that you keep in mind that soil-grown plants tend to need a slightly higher pH than hydroponics. This is because soil retains and releases certain elements to your plants at different times. As such, take note of the following:

• Optimal pH levels in soil range between 5.5 to 6.5.
• Optimal pH levels in hydroponic systems range between 6.0 to 7.0.

Once you know exactly what the sweet spot is for your plants, be sure to measure the soil periodically using a pH meter or monitor to ensure its pH is balanced.

• Prestige pH Meter (Price: $19.99): Using a pH meter is the most cost-efficient way to check your grow room’s pH levels.
• Autopilot Digital pH Controller (Price: $317.10): A pH controller is a much more sophisticated way to both monitor your plants’ pH levels and ensure they’re consistently regulated. With a controller like this, you can set the ideal pH range and let the device do the rest of the work for you. If the controller registers a change in the pH, it will automatically adjust it by either raising or lowering the acidity in your grow medium.

How to Adjust pH Levels

If your plants’ pH balance is too low or too high, it doesn’t necessarily mean your harvests are doomed. As far as solutions go, there are both premade and homemade options available for you to consider.

The Best Way to Adjust Your pH

By far the simplest solution if your plants are suffering from a pH imbalance is a premade pH buffer. As its name suggests, a premade pH buffer is a solution that has already been prepared for you. All you have to do is buy it and you’re good to go.

• X Nutrients pH Up/Down Set (Price: $19.95): This set of pH solutions includes both pH Up and pH Down. So whether your plants are suffering from a pH deficiency or too much acidity in their grow medium, you’ll be able to adjust their levels accordingly.
  • This type of solution is designed to raise and lower the pH of your water while keeping pH levels balanced.

How Do You Make pH Buffers?

You’d be surprised what you can do with everyday household items. If you’re trying to remedy a pH imbalance quickly, or if you need something while you wait to restock on a premade pH adjuster, you might have a quick solution around your house.

• Citric Acid and White Vinegar Help Lower pH Levels: If pH levels are too high, either citric acid or white vinegar should do the trick and lower your soil’s pH.
• Baking Soda Helps Raise pH Levels: When your plants’ pH levels are low, you can use a bit of baking soda in your solution to bring those readings up.

In addition to being readily available, solutions like these are cost-effective and mostly easy to use. We say “mostly” because, unfortunately, it’s possible to misuse an ingredient like baking soda and see a severe spike in pH if not handled properly. As such, we recommend these as temporary solutions only. For the most part, it’s best to stick with a premade pH solution.

PPM Levels in Plants

PPM (parts per million) refers to the concentration of the particulates in your feeding solution. This includes everything from minerals found in tap water to natural elements found in your nutrients. You want to make sure that the PPM levels in your watering solution are on point so you’re not underfeeding or overfeeding your plants.

pH plays a huge factor in PPM levels because while you may have the correct PPM reading, some particles — and the concentration of those particles — can be harmful to your plants. For example:

• Let’s say your plants need to be at a PPM level of 700.
• You mix your solution and get a PPM reading of 700, but your pH is around 4.5.
  • This means the majority of the available food for your plants likely contains a lot of heavy metals in it, which will quickly toxify the plant.
• You’ll need to adjust the pH level of your solution to make sure you’re not toxifying your plants.

You might be wondering if adjusting your pH solution will affect your PPM levels. Well, it definitely can, which is what’s sometimes tricky about pH and PPM levels.

Remember: When you adjust either pH or PPM, you’ll typically have to adjust the other, as well. This can be pretty simple and stress-free, or it can be troublesome depending on the water and nutrient solution you’re feeding your plants.

What Is a Good PPM Reading?

Understanding PPM readings can be overwhelming if you don’t have a reference point. Let’s take a look at optimal PPM readings depending on your plants’ stages of growth. Like pH, the values will vary slightly between a soil grow medium and a hydro system.

First, let’s take a look at PPM readings in soil.

• Early Growth: 400 to 500 PPM — You won’t see too many particles aside from what’s in your grow medium.
• Seedling: 500 to 600 PPM — The information above applies here, though any starter nutrients will affect the readings.
• Early Vegging: 800 to 850 PPM — This is when you typically transplant. At this stage, not a lot of particles are needed.
• Mid-Stage Vegging: 850 to 900 PPM — You’ll start giving your plants more nutrients at this point.
• Late-Stage Vegging: 900 to 950 PPM — Nutrient intake increases as your plants prepare to flower.
• Early Flowering: 950 to 1000 PPM — As your plants grow, they need to eat more. PPM readings will reflect the particles in the increased nutrients.
• Mid-Stage Flowering: 1000 to 1100 PPM — Your plants’ nutrient intake continues to increase at this stage.
• Late-Stage Flowering: 1100 to 1150 PPM — This is when your plants are eating the most, especially if you provide additives.
• End of Flowering/Flushing: 0 to 400 PPM — At this stage, you’ll be flushing your plants. Ideally, you don’t want too many leftover particles at the end of flowering.

If you’re growing with hydro, PPM readings will be slightly different. It’s important to understand the exact PPM you’re looking for. So let’s break that down PPM readings in a hydroponic system.

• Early Growth: 350 to 400 PPM — You won’t see too many particles aside from what’s in your grow medium.
• Seedling: 400 to 500 PPM — The information above applies here, though any starter nutrients will affect the readings.
• Early Vegging: 650 to 750 PPM — This is when you typically transplant. At this stage, not a lot of particles are needed.
• Mid-Stage Vegging: 750 to 800 PPM — You’ll start giving your plants more nutrients at this point.
• Late-Stage Vegging: 850 to 900 PPM — Nutrient intake increases as your plants prepare to flower.
• Early Flowering: 900 to 950 PPM — As your plants grow, they need to eat more. PPM readings will reflect the particles in the increased nutrients.
• Mid-Stage Flowering: 950 to 1100 PPM — Your plants’ nutrient intake continues to increase at this stage.
• Late-Stage Flowering: 1100 to 1150 PPM — This is when your plants are eating the most, especially if you provide additives.
• End of Flowering/Flushing: 0 to 400 PPM — At this stage, you’ll be flushing your plants. Ideally, you don’t want too many leftover particles at the end of flowering.

Plant growth can be pretty dynamic, and as a result, PPM meters will change during different stages of growth. You’ll want to make sure you’re keeping up with any changes in your plants’ PPM levels so you can adjust them as necessary.

• Prestige PPM Meter (Price: $19.95): With a PPM meter like this, you’ll get accurate readings of your plants’ PPM levels. This means you’ll be able to make the necessary changes and removes any guesswork on your part!

Adjusting PPM in Water

If you notice your PPM levels are off, you’re going to want to add more water to correct those readings. Keep in mind: The water you use to adjust PPM should be filtered.

• NU Aqua Platinum Series 7 Stage Alkaline and UV Ultraviolet 100GPD RO System (Price: $255.95): With a reverse osmosis water filtration system like this, you’ll ensure the water you provide for your plants doesn’t have excess minerals.
  • While some minerals are helpful to plants, standard tap water often carries additional particles and contaminants that could be harmful if PPM levels are too high. As such, with an RO system, you’ll filter out the unnecessary minerals.

You’ll want to adjust the PPM of your base water before you start feeding it to your plants. Now, any time you add anything into your watering solution, you'll be adding more particles into it, so keep an eye on your PPM levels at all times.

Here are a few more tips to keep in mind when monitoring your grow’s PPM levels:

• PPM Requirements During and After Vegging — In these stages, your plants will require more out of their feedings so filtering isn’t too necessary. We recommend mainly using filters at the beginning of a plant's life when low PPM readings are needed.
• If PPM Is Too High — For a quick fix when PPM readings are high, just add a bit of fresh water with a good pH level.
• If PPM Is Too Low — When readings are low, it’s usually time to feed your plants. When you add nutrients to your feeding solution, your PPM readings will go back up, which means your plants are going to be happy and healthy.
• PPM Requires Constant Adjustment — It’s absolutely important to keep a close eye on your grow’s PPM readings. Be on the lookout for any changes and irregularities so that you’re able to adjust as needed.

Understanding Your Plants’ pH and PPM for a Successful Harvest

By now, you should have a good understanding of what pH and PPM levels in your plants and grow medium mean and how they can affect your harvest.

Beyond that, you also know how to address any pH imbalances your plants may experience. Thankfully, you shouldn’t feel discouraged if you notice any changes in pH. The best thing you can do is act to prevent any harm to your grow.

It can be scary at first to see pH levels dip or rise a bit too much, but with the tips and solutions provided here, you should be equipped to handle any changes in your grow room!