Choosing the rightnutrients for your marijuana growing is a crucial decision. Get it right and you’ll be enjoying strong, healthy plants. Get it wrong and you could suffer with yellow leaves, a reduced harvest or, in the worst case, dead plants.
Rather than recommending any one particular nutrient solution for your growing needs, this article will cover the basics of what your plants require to help you understand what nutrients are and why you need them.
We will follow this up with a further article discussing specific requirements depending on your growing medium. Our follow up article will include recommendations for nutrients for both soil growers and hydroponic growers.
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- Nitrogen (N) : Your plant needs nitrogen because it is used in all growth processes. It is the major component of amino acids, which are used in plant cells as building blocks for enzymes, protein and the green chlorophyll pigment.
- Phosphorus (P) : The phosphorus element plays a key role in energy transfer and storage within the plant. IN essence, it is the power station that your plant needs in order to accumulate and use energy from nitrogen.
- Potassium (K) : Potassium is required by cannabis plants for a number of critical processes. These include the development of cell walls, flowering and water uptake.
- Sulfur (S) : Sulfur is used in plants for the formation of many essential amino acids as well as some of the proteins and vitamins needed for chlorophyll production. It also plays a part in reducing stress from environmental fluctuations, diseases and pests.
- Calcium (Ca) : Just as we need calcium for strong teeth and bones, so plants need calcium to build strong cell walls, healthy root structures and strong growing points. Overuse of potassium can sometimes cause a calcium deficiency, particularly if your soil has a low pH.
- Magnesium (Mg) : This element is an important component in chlorophyll and is needed to move phosphorus around the plant. It moves around the plant and any deficiency is usually seen in older leaves first.
- Trace Nutrients : These nutrients are required in trace amounts, but should also be considered when choosing nutrients for your marijuana plant to ensure they get a healthy mix overall.
- Humboldt’s Secret : This California based nutrients company have developed an incredible marijuana grow formula which is having astounding results with growers worldwide. Developed through 20 years of hands on growing experience with some of the most experienced growers in Humboldt
- Power Feeding : If you prefer a hydroponic set up, or indeed soil based set up but with more control over the feeding regime, then Powder Feeding have some great products to help you produce perfect plants.
- Germination and Rooting : Germination usually takes place for around the first week of the plants lifetime. Depending on whether you are growing from seed or from a cutting, this time may be more or less and nutrient needs will be lesser or greater.
- Vegetative Growth : Your marijuana seedlings should stay in their starter pots or Rockwool segments until you start to see roots protruding from the bottom, at least 3 inches long. This will signify it is time to transfer your seedlings into their main growth medium.
- Flowering : The flowering stage requires a significant increase in phosphorus, in order to give your plants the energy and resources to make nice, big, sticky buds. It can be a good idea to prepare your plants for the changeover from vegetative to flowering by feeding an equal mix of all nutrients for around a week.
- Fox Farms : Lots of growers have had great success with Fox Farms. The nutrients are incredibly concentrated, so it is very much a case of ‘less is more’ with this one.
- Botanicare : The Botanicare Pure Blend for Soil is highly recommended for beginners, and offers easy use and a relatively inexpensive method of feeding your plants.
- General Organics : The GO Box contains everything you need in one box, and offers a workable solution if you are looking for a chemical free grow without the hassle of some organic fertilizers.
- For Water Based Systems : A tried and tested success in water based systems has to be the General Hydroponics Flora Series Nutrient Trio
- For growing in Coco Coir : When growing in coco coir, problems with calcium and magnesium deficiencies are common, so it’s worth supplementing your nutrients with additional Ca and Mg.
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Choosing and Using Nutrients for Marijuana Growing – Part 1
What are nutrients?
There are three main nutrients which need to be considered when you are growing cannabis. They are:
- Potassium (K)
- Nitrogen (N)
- Phosphorus (P)
Almost every nutrient product you find will specify these three elements in the format N, P and K and will display numbers showing the ratio of one to another. For example, if you see a product listed as containing 15-15-15, this means the nutrient content is 15% potassium, 15% nitrogen and 15% phosphorus. The rest of the mix will be made up of secondary elements which, while helpful to growth, are not the main focus of the mix. These will include:
And in trace quantities:
The balance of these different nutrients and the amount that you give to your plants will differ throughout the growth cycle. As a general rule, rooting and germination requires more P nutrients with less N and K, vegetative requires lots of N and in the flowering phase you will be looking at a mix with more P and K plus extra calcium.
However, the amounts, balance and method of delivery is different depending on whether you are growing in soil or using hydroponics. This will be discussed more thoroughly in part 2, although you can read more on the N-P-K ratios here. Do bear in mind that you should stop using all types of plant food at least two weeks before harvest in order to flush out the chemicals from the marijuana plant. If you don’t you could end up with weed that tastes like fertilizer at best. At worst, you could end up with levels of toxicity that could cause sickness in humans.
Why are nutrients so important for cannabis plants?
Just as animals need to eat to survive, so plants need to ‘eat’ to live well. Nutrients are their food of choice, and will make the difference between your plant just surviving and your plant truly thriving. Getting the balance and quantity of nutrients right is the key to healthy plant growth.
Understanding the main uses of various nutrients for your plant, as well as how to spot the early signs of nutrient deficiency, is the first step in choosing and using a healthy, well balanced feed.
- Nitrogen (N)
Your plant needs nitrogen because it is used in all growth processes. It is the major component of amino acids, which are used in plant cells as building blocks for enzymes, protein and the green chlorophyll pigment. Chlorophyll is critical to plant growth, as it is this which converts the energy from light into usable energy for the plant, in the form of carbohydrates and sugars.
Nitrogen deficiency can usually be detected in a plant by:
- – Stunted growth, or slower growth than expected
- – Yellowing of leaves, usually the oldest first
- – Purplish tints on the stems and underside of leaves
- Phosphorus (P)
The phosphorus element plays a key role in energy transfer and storage within the plant. IN essence, it is the power station that your plant needs in order to accumulate and use energy from nitrogen. Without phosphorus, the nitrogen you are giving your plant is useless.
Inadequate supplies of phosphorus are typically characterized by:
- – Slow or stunted growth
- – Smaller leaves, often with blotchy spots
- – Leaf stems may turn reddish or purple
- – Older leaves turn dark colors and curl downwards
- Potassium (K)
Potassiumis required by cannabis plants for a number of critical processes. These include the development of cell walls, flowering and water uptake. Potassium keeps the sap stream flowing freely, moving other nutrients and water around the plant. It can also help plants to resist insects, diseases and environmental stresses.
Potassium deficiency in marijuana plants is characterized by:
- – Dark green healthy looking foliage in the newer sections of the plant
- – Older leaves turning dull, yellowing and eventually developing rust colored spots
- – Stems becoming weak and brittle
- – Leaf tips curl up, leaf edges look burned
- Sulfur (S)
Sulfur is used in plants for the formation of many essential amino acids as well as some of the proteins and vitamins needed for chlorophyll production. It also plays a part in reducing stress from environmental fluctuations, diseases and pests.
Sulfur deficiency can be spotted in its early stages by:
- – All over yellowing of the leaves
- – Buds dying off
- – Yellowing a starts at the back of the leaves and moves forward
- – Leaves become stiff and brittle before dropping off
- Calcium (Ca)
Just as we need calcium for strong teeth and bones, so plants need calcium to build strong cell walls, healthy root structures and strong growing points. Overuse of potassium can sometimes cause a calcium deficiency, particularly if your soil has a low pH.
You can spot calcium deficiency by:
- – Spotting or mottling of the leaf surface
- – Crinkling of leaves, curled tips and leaf die off
- – Stunted growth and smaller or deformed new leaves
- Magnesium (Mg)
This element is an important component in chlorophyll and is needed to move phosphorus around the plant. It moves around the plant and any deficiency is usually seen in older leaves first.
Watch out for the following telltale signs of Magnesium deficiency:
- – Light green or yellowish coloring of the veins and edges of older leaves
- – Yellow or bright green edges to leaves
- – Brittle feeling leaves
- Trace nutrients
These nutrients are required in trace amounts, but should also be considered when choosing nutrients for your marijuana plant to ensure they get a healthy mix overall.
- – Molybdenum (Mo): Involved in nitrogen metabolism
- – Copper (Cu): Needed to produce chlorophyll and for plant respiration
- – Zinc (Zn): Associated with chlorophyll production and protein synthesis
- – Manganese (Mn): Involved in growth, germination and new tissue production
- – Iron (Fe): Helps carry oxygen around plant cells and involved in chlorophyll production
- – Boron (B): Moves sugars around the plant and is involved in the uptake of calcium
- The important thing to note with all these nutrients is that they work together. Often the over or under feeding of a particular type of nutrient can cause the plant to be blocked against taking up or using another type of nutrient. This is why it is crucial to maintain a healthy, balanced diet for your plant that offers it all the right ingredients for the growing phase it is in.
Do marijuana plants require different nutrients than other plants?
Essentially, no. All plants need these same basic building blocks of life in order to germinate, to grow and to reproduce. In fact it has been known for some growers to produce perfectly adequate harvests from marijuana plants using regular houseplant food mixes.
However, as your investment in your cannabis growing is likely to be substantially more than Aunty Jeans’ investment in her potted geraniums, we would recommend you steer away from off the shelf plant foods and stick to the specialist marijuana nutrient solutions for the best results.
- If you are growing hydroponic marijuana you need to consider using alternative nutrients such as Powder Feeding. Do not be discouraged if the nutrients websites you visit do not talk about growing marijuana on their sites. Unfortunately some nutrients websites if they mention marijuana they risk losing their merchant account and then they can not take credit card orders. Hence they talk about growing vegetables, in reality most of their customers use their nutrients to grow marijuana.Although marijuana is a plant like any other, with nutrient requirements that are very similar, one key piece of information to realize is that nutrient use in cannabis is unique in when and how it requires certain nutrients. The skill in growing big, healthy plants with large harvests is all about the grower understanding the nutrient requirements at different stages of growth, and how to best manage the nutrient input to maximize health and growth.
What happens if you grow without nutrients?
In our current culture of embracing all things organic, natural and green, it is understandable that some growers may want to extend these ethics to their cannabis growing too. Whilst it is commendable to want to grow your plants in the most natural and chemical free manner, growing without nutrients is really only an option if you plan to grow in soil.
Plants are living organisms, and in the same way our bodies need food to fuel our various functions, so plants need nutrients to grow, to flower and to survive in a healthy manner. If you were to deny yourself the use of any added nutrients, then you will immediately make hydroponic growing impossible.
Soil growing is possible, and with a quality soil with a good mix of pre-existing nutrients already in it you may get your plant to grow and flower, but it really is a case of getting lucky. The most likely scenario, if you do get your plant to grow at all, is that it will show signs of nutrient deficiency and will end up being short and stubby, with a much lower yield than expected.
If you would like to try growing without nutrients, there are really just two situations which would allow you to do this with success.
- In the case of outdoor growing where you know you are planting in very fertile soil you can get away with no added nutrients. If you pick a plant designed for free, easy outdoor growing, something like Guerillas Gusto, you should be able to just plant and run, leaving it to acquire nutrients from the surrounding environment.
- If you purchase a specialist soil, designed for growing cannabis. There are some products available which use advanced chemistry, microbiology and a superior stimulant to create the best possible environment in which to grow a marijuana plant.
The second part of this article will discuss recommended nutrients in more detail. However, we would like to bring to your attention two major specialist suppliers who offer products for both the hydroponic and soil based grower:
Humboldts Secret: This California based nutrients company have developed an incredible marijuana grow formula which is having astounding results with growers worldwide. Developed through 20 years of hands on growing experience with some of the most experienced growers in Humboldt, the Golden Tree formula is a secret recipe designed to achieve higher yields, bigger buds and a better quality product overall. Field testing has shown that Golden Tree gives an average of 60 per cent increase in root growth, giving growers a stronger, bigger plant every time. This all in one nutrient solution comes with satisfaction guaranteed, and is available in a variety of sizes to suit all growing needs.
Powder Feeding: If you prefer a hydroponic set up, or indeed soil based set up but with more control over the feeding regime, then Powder Feeding have some great products to help you produce perfect plants. Their powders are incredibly easy to use and are designed to help you tailor your mix for your plants needs without having to invest in multiple products and complicated nutrient strategies.
The company motto is ‘Keep it simple’, and that’s exactly what they’ve done with their powders. Their patented ‘grow’ formula has been designed to support a big, bushy mother plant as well as providing balanced nutrition for young plants and rooted cuttings of any genetics. For older, crop plants, you can choose from ‘short flowering’ for your 60% plus Inidca varieties or ‘long flowering’ for 60% plus Sativa, or even their ‘hybrid’ mix for those complex hybrid plants that range from 40% to 60% Indica.
What about over feeding?
Of course the flip side of growing without nutrients is over feeding your plants, and another situation you should be acutely aware of. Overfeeding is much more common than underfeeding, and can cause all sorts of problems in marijuana plants. For this reason it is important to be able to spot the telltale signs before they become irreparably damaged.
Look out for these signs of nutrient overdose:
- Drooping leaves and branches
- Erratic leaf sizes
- Yellowing of leaves, or in some cases leaves turning a deep, deep green
- Lack of typical serrated edges on new leaves
- Chemical ‘burn’, characterized by spots, edges with a burnt appearance and brittle, browning leaves
You will notice that many of the symptoms of overfeeding have similar characteristics to those of nutrient deficiency. This makes for a pretty tough call if you are unsure whether your plants need more or less food. In this situation, often the best tactic is to revert to a nice, balanced soil pH of around 6.5 and give your plants nothing more than some good old H2O for a few days. If they start to look healthy again, chances are you were overfeeding, whereas if the problem persists or gets worse, it should now be easier to determine which nute your plant needs.
Organic vs non-organic nutrients
There is a lot of talk about growing organic marijuana, and it is possible. In fact, in a survey by MMJ Business Daily, 43% of medical marijuana patients said having organically grown marijuana was critical to them. This could be in part due to the general desirability of having fewer chemicals in anything we are putting into our bodies, but is more likely to be because of the significantly better taste achievable through organic growing methods.
Organic nutrients are naturally occurring rather than man made. This means they could really be any organic matter that has some nutritional value, although the most popular ones among experienced growers are things like guano, fish meal and worm casts. There are some interesting discussions on growing marijuana organically in our forum, including some links to homemade organic nutrient ‘teas’ in this post here.
The benefits of organic growing:
- Improved aroma and taste of final product
- Plants grown organically cannot be over fertilized
- Organic nutrients do not require flushing before harvesting
- Can be even easier than soil growing, and much more simple than hydroponics
- Nutrients remain in the soil after use, so you can grow another plant in the same medium, whereas chemical nutrients are taken up so quickly it leaves the soil nutrient poor after harvest.
The downsides of organic growing:
- Usually more expensive than using chemical nutrients
- Impossible to precisely control the various nutrients being given to the plant
- Nutrients taken up more slowly, so more difficult to correct deficiencies if they occur
- Not possible to use if growing hydroponically
Overall the choice between organic or non-organic nutrients comes down to personal preference, budget and how much it matters.
Your own organic fertilizer?
There have been some interesting threads on our forum in regards to using human urine to fertilize cannabis plants. It is true that human urine is sterile and contains many useful chemicals such as nitrogen, urea, creatinine and others. However, taking a pee on your plants directly is not really recommended, as undiluted urine is rather strong and almost certain to give your plants chemical burn. Apart from anything else, you’re going to be smoking that plant pretty soon. Yuck!
Another reason not to urinate on your marijuana plants is that human urine contains a range of salts. Depending on your specific diet, the salt content in your urine can be as much as 2.2%. These salts can be harmful to plants, and can build up in your soil over time, making for a poor growing environment for your plants.
Having said that, some growers have reported success with using urine as a fertilizer, but if you plan to do so you must dilute it in a ratio of 1 part urine to 10 parts water to make it weak enough for the plants to tolerate. Some hydroponic growers have found this solution a good additional nutrient source, alongside powders and specialist mixes. Outdoor growers have also found that urinating near to their guerilla grow site will keep inquisitive wildlife at bay.
The last word
Hopefully you now know what the main and most important nutrients for your cannabis plants are, and have an understanding of the functions they perform. Next we will look at what nutrient requirements are in various stages of the growing cycle, and how things differ when growing hydroponically as opposed to growing in soil.
In the meantime, there are lots of useful threads on our forum to help you find out more about nutrients, nutrient companies and your plant’s needs.
Choosing and using Nutrients for Marijuana Growing – Part 2
We have already discussed what types of nutrients marijuana plants need to survive, as well as some of the problems that can be encountered if they are deficient in certain nutrients. However, as well as giving a good supply of mixed nutrients throughout the life cycle, there are still considerations to be made regarding the mix of nutrients used at various stages in the life cycle, as well as variations in nutrients depending on your growth method.
The essential information
However you decide to grow and whatever nutrient mix you use, there are a few key pieces of information to keep in mind:
- Follow manufacturer’s instructions: Don’t overfeed in the hope of growing bigger plants – it won’t work!
- Feed quarter doses to seedlings: Start your seedlings off on ¼ of the normal dose, increasing it to ½ as they become more established.
- Store nutrients correctly: Follow the guidance on the manufacturer’s website or product packaging to ensure you don’t put yourself at risk.
- Start simple: Novice growers should stick to pre mixed of ‘off the shelf’ formulas until they become more experienced, rather than experimenting with organic or homemaderecipes.
- Ask the experts: If your plants become sick or you feel confused, talk to our growing marijuana community at our grow forum.
The different nutrient needs of the life cycle
pp>Marijuana plants require different nutrients at different stages of the life cycle. The life of a marijuana plant can be split into three main stages:
- Germination and rooting
- Vegetative growth
There is also a less well defined fourth stage, which is the harvest time. We will discuss the different nutrient needs of each of these stages, as well as whether changes should be made prior to harvesting the plants.
1. Germination and rooting
Germination usually takes place for around the first week of the plants lifetime. Depending on whether you are growing from seed or from a cutting, this time may be more or less and nutrient needs will be lesser or greater.
Growing from a seed usually does not require any additional nutrients. Marijuana plants store nutrients in the seed husks, and so this tough outer layer serves as a packed lunch for your seedling, giving it all the nutrients it needs to begin to grow. It is important to determine when your seed has grown enough to be classed as a seedling, at which time you should be ready to start feeding it regularly.
You can choose to grow your seed directly in soil, in which case no additional nutrients should be needed until you start to see a shoot popping through the soil surface. If you choose to germinate your seeds before sowing them, you should wait until the taproot has developed to sow them in soil or a hydroponic solution and can start feeding shortly after this.
If you are growing from a cutting, you should take care to clone and bring on your plants carefully, then once roots are formed should treat your cutting like a seedling.
2. Vegetative growth
Your marijuana seedlings should stay in their starter pots or Rockwool segments until you start to see roots protruding from the bottom, at least 3 inches long. This will signify it is time to transfer your seedlings into their main growth medium. Whether this is soil, coco coir or something else, the stress and shock experienced by the plants during the transplantation process can be lethal. To help them cope with being transplanted, you can feed them with a suitable nutrient mix which will help ease the shock.
As discussed in the first part of this article, marijuana plants require a diverse mix of nutrients to stay healthy. However, the most important nutrients to get to grips with are nitrogen (N), phosphorus (P) and potassium (K), also known as macro nutrients.
During the vegetative growth stage, your plant will require a good amount of nitrogen, as well as some phosphorus and potassium. Throughout the growth cycle, this requirement can fluctuate significantly, so it is a good idea to vary your feeding regime depending on the age and size of your plant.
- Seedlings: It is suggested that a ratio of 2-1-2 for NPK is ideal.
- Early vegetative: When the plant is starting to look larger, around week 3 – 4, switch to a higher amount of nitrogen. The ratio 4-2-3 is suggested as a good balance.
- Mid vegetative: Around weeks 5 – 6, you can boost the nitrogen even more to give your plant the necessary energy to bush out. Go for something in the region of 10-5-7.
The ratios of these nutrients is far more important than the actual numbers. A mix of 8-4-6 or even 16-8-12 are both the same as 4-2-3 in terms of the relationship of one nutrients to the other, so the results will be largely the same.
As a general rule of thumb, during the vegging stage, keep phosphorus at around half that of nitrogen, and potassium at around half to two thirds of the nitrogen. Nutrient requirements vary from one plant to another, so keep in tune with your plant’s needs and vary your feeding regime accordingly.
For those growing in coco coir or hydroponics is achieved with the products from Power Feeding, which are tailored to the type of plant you are growing for optimum results. Also Golden Tree is proving to be popular with growers as they offer a 4 month gurantee, so you can get a refund if you are not happy with the nutrients.
The flowering stage requires a significant increase in phosphorus, in order to give your plants the energy and resources to make nice, big, sticky buds. It can be a good idea to prepare your plants for the changeover from vegetative to flowering by feeding an equal mix of all nutrients for around a week. Some farmers recommend a mix of 7-7-7 for this phase, but again the ratio is much more important than the numbers.
Once the plants start to flower, you need to switch to phosphorus as your main macro nutrient. As a rough guide, you should aim to take nitrogen down to about half the amount of phosphorus, and potassium at around a half to two thirds. Recommended N-P-K mixes through the flowering period are:
- Early flowering: 5-10-7
- Mid flowering: 6-15-10
- Late flowering: 4-10-7
You will notice that in both the vegetative and flowering phases, potassium is maintained at around half to two thirds of the level of the lead nutrient. Keeping close to this ratio will help you to avoid nutrient lockout and other problems associated with over or under feeding your plants.
Before you harvest…
Before you can harvest your beautiful buds, it is highly recommended to perform a nutrient flush to rid your plant of any unused nutrients which could spoil the flavor or compromise the product in any way.
- Why flush: No matter how careful you are with you nutrient balances, there will invariably be some leftovers when your plant has finished its meal. Over time, these leftovers build up in the plants tissues, which in large quantities will harm the plant. Even if your plant looks super healthy, excess nutrients in the bud can cause a harsh chemical taste in the final product.
- When to flush: Some farmers recommend flushing once or twice during the flowering phase, but the most important time to perform a flush is just before you harvest the plants. Sometimes a flush can also help in the case of a nutrient lockout.
- How to flush: You can either use plain water, or a specialist flushing product like Clearex. Empty your reservoir and refill, adding 20 – 30ml Clearex per gallon as per the instructions. Run this mix through your plants generously – you’re looking for around 80% to 90% runoff here. If you are growing hydroponically, simply saturate the system for around 15 minutes then allow it to drain back to the res.
It really is that simple. If you have a ppm meter, then you can get into measuring the runoff to see how well your solution is draining the nutrients from your plants, but it’s not entirely necessary.Taking the time toflush the plants of excess nutrients can make a huge difference to the taste and quality of the final product, so don’t be lazy at this stage of the process.
Nutrient advice for different growing solutions
- Growing in soil
- Growing in soil is perhaps the simplest way to cultivate marijuana plants, and can be more forgiving when it comes to nutrients. If you are growing in soil, it is important to either use a soil that is designed for growing cannabis, or to purchase nutrients designed for in soil growing.
- Most nutrient manufacturers know that you need to vary your mix with the growth cycle, and offer different products or additives to their main nutrient mixes so you can tailor the product to the needs of your plant. Some of the most positively recommended products include:
– Fox Farms – Lots of growers have had great success with Fox Farms. The nutrients are incredibly concentrated, so it is very much a case of ‘less is more’ with this one. The Fox Farm Trio which includes Big Bloom, Grow Big and Tiger Bloom provides everything you need for a successful grow.
– Botanicare – The Botanicare Pure Blend for Soil is highly recommended for beginners, and offers easy use and a relatively inexpensive method of feeding your plants. The two bottles supplied contain everything you’ll need to take your plants from germination to flowering, and come with simple instructions for getting the best results.
– General Organics – The GO Box contains everything you need in one box, and offers a workable solution if you are looking for a chemical free grow without the hassle of some organic fertilizers.
- Growing using hydroponics
- Growing hydroponically covers a multitude of sins, including growing in coco coir, deep water culture, soilless growing medium and bubbleponics – basically anything which is not soil. If you have chosen to grow this way, then your plants will be entirely reliant on you to supply the nutrients they need to grow and thrive.
- One benefit of this is that you will be able to provide nutrients in much more precise quantities than would be possible in soil, but that does mean you need to know what you are doing at every stage of the process. And it’s not just the N-P-K here, because you’ll need to ensure they are getting the right micro and trace nutrients too.
– For water based systems: A tried and tested success in water based systems has to be the General Hydroponics Flora Series Nutrient Trio. This product does not contain any particles which clog up your tubes and pumps, but still achieve outstanding results time after time. Botanicare also do a great hydroponic nutrient solution, known as the KIND trio. Less pricey than the GH option, this one is recommended by lots of growers and well worth considering. Both products also contain the trace and micro nutrients your plants need, so no additional products are necessary.
– For growing in coco coir : When growing in coco coir, problems with calcium and magnesium deficiencies are common, so it’s worth supplementing your nutrients with additional Ca and Mg. There are plenty of supplements around that provide these nutrients, a popular one being Cal-Mag by Botanicare. You can use this in conjunction with a range of other products, but a real crowd pleaser with coir growers has to be Canna Coco A&B, a solution of Dutch origin which has be tailored to perform well on coco substrates.
- There are many other nutrient mixes available for both hydroponic and in soil growing, and every grower has their own favourite among them. Check out our A – Z of nutrient reviews for an overview of the main players, or join in the discussions on the forum to find out what other growers are favoring right now.
Problems to watch out for
Feeding your plants is not rocket science, but it does take a bit of care. It’s quite easy to get it wrong, but thankfully marijuana plants are quite good at letting us know when things aren’t going so well, giving us a chance to put it right. Here are a few of the most common issues when it comes to nutrients, and what to look out for in your plants.
- Over or under feeding
Believe it or not, it is far more common for plants to be overfed than to be underfed. Overfeeding can cause problems with nutrient burn, nutrient lockout and can result in very sick plants. You will typically notice ‘burn’ at the edges of the leaves, and will require a flush to put things right. Underfeeding can cause slow growth or the leaves to become a lighter green, but will not usually kill the plant.
- Nutrient lockout
Nude lockout occurs when unused nutrients are stored up in plant tissues, making it impossible for the plant to get the nutrients it needs. Overfeeding for extended periods can cause this, but it can also be caused by:
- – Incorrect or fluctuation of the pH
- – Build-up of salts in the plant
- – Chemical reactions between two nutrient solutions mixed together
- – Incorrect use of single pack hydroponic solutions
- – Use of aged nutrients
- Signs of nutrient lockout are similar to signs of nutrient deficiency. Test your pH and ppm of run off to establish what’s going on with your plant. If you suspect nutrient lockout, then perform a flush using a leeching agent, then start to feed at quarter strength until you see signs of growth again.
- Overwatering and under watering
Overwatering plants is a common mistake by novice growers, so stay tuned in to the amount of water your plant needs to avoid this problem. Too much water will slow growth, and can cause problems with mold and fungus. The only solution to this is to cease watering until the plant has used up all the moisture in your growing medium, and then start slowly until you see healthy growth again. Under watering is easy to spot, as the plant quickly starts to droop. Marijuana plants need the odd dry period for potency and optimum growth, but ideally you should never let the leaf wilt excessively. Read more about optimum watering strategies here.
- Imbalancesin pH
Fluctuations in the pH of the water or growing medium you are using can cause problems with nutrient lockout, poor growth and discolored leaves. The optimal pH for a marijuana plant is between 5.5 and 6.5 when growing hydroponically or 6.5 to 7 for soil growth. Signs of an imbalance include yellow or brown leaves, stunted growth and wilting. Both hydroponic and soil growers can use pH balancing products like pH Up and Down from GroWell to correct this problem.
Getting the temperature wrong will cause your plant to become stressed, which in turn will affect the uptake of nutrients. Check the optimum temperature for the variety of plant you are growing as well as our guide on temperature and ventilation to help get this right.
Again, getting the lighting regime incorrect will cause your plant stress and therefore affect nutrient uptake. Not only this, but your plant requires light to photosynthesize, which is where a lot of the nutrients are used, so achieving the right lighting cycle for your plant is crucial too.
- Pests and other problems
As with any growing of marijuana, you’ll need to be vigilant for pests, fungus and other damaging infestations. Check our guide on pests and diseases here for advice on prevention and treatment of these types of problems.
Let us know your tips and advice for choosing and using nutrients to grow marijuana, and keep in touch with the friendly growers on our forums for personal help with your plants.