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Phosphorus Deficiency

Problem: A cannabis phosphorus deficiency generally appears on leaves from the lower/older parts of the plant. The lower leaves may turn dark green or yellow, and start getting spots or big splotches that look brown, bronze or even a little blue. The leaves may thicken and curl, and the affected leaves feel stiff. Sometimes the stems of the plant turn bright red or purple, but not always.

Sometimes accompanied by a Calcium deficiency, as Phosphorus and Calcium interact with each other in the plant.

A cannabis phosphorus deficiency usually appears with some or all of the following symptoms:

  • tends to affect the lower and older leaves of the plant
  • sometimes a phosphorus deficiency is accompanied by bright red stems (though not always), though if you have red stems but no other symptoms, it’s typically not something to worry about
  • leaves darken (turning a dark green, blue or grayish color) and may appear shiny
  • leaves may start turning yellow in places if the phosphorus deficiency is left untreated, or if the deficiency is combined with other nutrients deficiencies and/or pH problems. However, yellow leaves is typically not associated with the beginning of a phosphorus deficiency.
  • leaves get bronze, purple or brown spots and splotches
  • leaves thicken and may feel dry or stiff
  • stems sometimes turn bright red or purple, but not always
  • sometimes accompanied by a Calcium deficiency, as Phosphorus and Calcium interact with each other inside the plant
  • this deficiency is more common after buds start forming, when the plant is using a lot of Phosphorus

Phosphorus deficiencies in the vegetative stage usually appear at the bottom of the plant on some of the oldest leaves, and will progressively climb up the plant if left unchecked.

The progression of a cannabis phosphorus deficiency

A phosphorus deficiency tends to be more common after plants start making buds in the flowering stage. Cannabis plants tend to love phosphorus in the flowering/budding stage and it is unlikely for a cannabis plant to get too much phosphorus using standard nutrients formulated for a flowering plant like cannabis. Nearly all flowering nutrients will come with an abundance of phosphorus for your plants. So if you’re seeing a cannabis phosphorus deficiency while using standard cannabis nutrients, chances are you actually have a root pH problem (explained below in the solution section)!

Phosphorus (P) is used by your cannabis plant in all phases of growth. It is one of the 3 major nutrients (N-P-K) listed on the front of most nutrient bottles, and phosphorus will be represented by the second number that appears.

When there is a phosphorus deficiency, the lower (oldest) leaves turn dark green. Leaves occasionally get a bluish or bronze tinge, and may thicken or curl downward before exhibiting dark gray, bronze or purplish splotches. Sometimes the stems of the affected leaves will turn bright red or purplish, usually starting from underneath.

It’s common to see a Phosphorus deficiency accompanied by the symptoms of a Calcium deficiency, as those nutrients interact with each other in the plant.

Sometimes you will get a cannabis phosphorus deficiency, and the stems do not appear red or purple at all, or the coloring may not be pronounced.

The leaf below was at the bottom of the plant and turned dark green and shiny, with a bluish tinge. Cannabis phosphorus deficiencies usually appear on the lower/older parts of the plant. The leaf then started showing the spots of a phosphorus deficiency where it was being touched by light (the parts of the leaf working hardest). The leaf began to curl downwards and turn yellow.

Notice that the stems or veins never turned red or purple on this leaf, except for some parts that were actually affected by the phosphorus deficiency.

A common symptom of a cannabis phosphorus deficiency is bright red or purple stems, though it doesn’t appear on all affected plants. Red stems can also be caused by direct light exposure (like a “tan”)

Another example of bright red stems that may be the result of a Phosphorus deficiency, or possibly direct light exposure.

It’s important to remember that some cannabis strains naturally grow with red or purple stems even when all their nutrient needs are being fulfilled, so red or purple stems is not a symptom to worry about on its own.

Do not mistake natural reddish-purple colored stems for a phosphorous deficiency!

When you notice that stems are turning red or purple starting from underneath, it may be a sign of a phosphorus deficiency only if accompanied by other symptoms. If the only symptom shown by your plant is red or purple stems, and you are not seeing any other signs of splotches or unhealthy leaves, the red or purple stems are likely caused by the genetics of your plant. If that’s the case, you have nothing to worry about.

Phosphorus is used heavily by cannabis plants in the flowering phase to produce buds, and is a crucial component of photosynthesis (turning light into energy for the plant).

Some strains of cannabis use much more phosphorus than others, or be more susceptible to a phosphorus deficiency, and you may have many plants in the exact same setup with only some of the plants showing signs of a phosphorus deficiency.

Solution For Cannabis Phosphorus Deficiency

1.) Adjust pH to Correct Range

Your cannabis plant may show signs of a phosphorus deficiency if the pH at the roots is not in the right range. That is because when the pH of your root zone is off, your cannabis cannot properly absorb phosphorus through its roots. Therefore the first step is to ensure that you have the correct pH for your growth medium. Learn more about pH and cannabis.

Phosphorus is best absorbed by cannabis in soil at a root pH of 6.2 – 7.0. Phosphorus is best absorbed by cannabis in hydro at a root pH of 5.5 – 6.2. If you believe you have a cannabis phosphorus deficiency, it’s important to check the pH of your root zone to make sure the deficiency isn’t caused by the pH being too high or too low.

If you suspect your growing cannabis plant has a phosphorus deficiency, flush your system with clean, pH’d water that contains a regular dose of cannabis-friendly nutrients that includes phosphorus. This will remove any nutrient salts that may be affected the uptake of phosphorus and help restore pH to the proper levels.

  • In soil, phosphorus is best absorbed by the roots in the 6.2 – 7.0 pH range (in soil, it’s generally recommended to keep the pH between 6.0 – 7.0, but phosphorus specifically tends to be best absorbed above 6.2 and below 7.0)
  • In hydro, phosphorus is best absorbed by the roots in the 5.5 – 6.2 pH range (in hydro, it’s generally recommended to keep the pH between 5.5 – 6.5, but phosphorus specifically tends to be best absorbed below 6.2)

2.) Take Good Care of the Roots

Wet, compact soil or overwatering can trigger a phosphorus deficiency to appear even when all other factors are perfect. So make sure you water your plants properly every time to help prevent a phosphorus deficiency.

3.) Provide the Right Temperature

Cooler temperatures lower than 60°F (15°C), as well as large temperature swings, can make it harder for the plant to absorb phosphorus. Cannabis plants are therefore more likely to show signs of a phosphorus deficiency when the temperature drops too low, or if they go through a cold spell.

Cannabis likes a comfortable room temperature (they like about the same temperatures as we do).

4.) Give the Right Nutrients

Most growers have actually already given plenty of phophorus to their cannabis plants since it is found abundantly in quality soil and cannabis-friendly nutrients. However, even if you are giving phosphorus, it’s important to give your cannabis the right ratio of nutrients.

An excess of Fe and Zn may cause the symptoms of a phosphorus deficiency by preventing the plant from being able to absorb phosphorus properly. If you believe there may be a buildup of nutrient salts in your growing medium (or if you are growing in hydro and have not recently flushed or changed your reservoir) you should make sure it’s not an excess of other nutrients that is actually causing the phosphorus deficiency to appear. Flush your plant thoroughly with properly pH’ed water containing a regular dose of cannabis nutrients including phosphorus, or completely change your reservoir if you believe that an excess of nutrient salts may be causing the phosphorus deficiency.

Sources of phosphorus:

If you’ve tried everything else, then you may try adding a higher percentage of phosphorus to your feeding schedule and see if that helps clear up the problem for your plant. Cannabis plants love phosphorus, and therefore it is unlikely that you will give your cannabis too much phosphorus.

Most nutrient systems that are formulated for a plant like cannabis will carry and abundance of phosphorus, especially in budding/flowering formulas, so it is unlikely that you will see signs of a phosphorus deficiency before other nutrient problems when using nutrient systems formulated for cannabis (as long as you keep your root pH in the correct range and prevent the plants from getting cold or being overwatered). If you’ve got very high powered lights, or if your plants are growing in direct sunlight, they may be going through a lot more phosphorus in the flowering stage than average and may need you to provide extra phosphorus to make sure buds get as big as they could be.

Just remember that if there’s no actual phosphorus deficiency currently appearing on your cannabis plant, adding more phosphorus is probbaly not going to help plants grow better or make bigger buds – in fact adding too much phosphorus may actually hurt your plants by preventing the uptake of other nutrients! While it’s difficult to overdose your plants on phosphorus, adding too much compared to other nutrients will often cause other strange & unexpected deficiencies to appear.

5.) Take Good Care of the Roots

Phosphorus deficiencies can show up with the plant is having root problems or if the plant is overwatered, even if the pH is right and the phosphorus is there. Proper watering practices help plants grow healthy and avoid a host of problems!

6.) Watch for Recovery

After going through all the above steps, watch to make sure that the phosphorus deficiency starts to clear up within a few days to a week or so. After a phosphorus deficiency is cleared up, the problem (brown spots, unhealthy lower leaves, red/purple stems, etc) will stop appearing on new leaves, usually within a week.

Please note that leaves which have been damaged by a phosphorus deficiency will probably never recover or turn green, so you want to pay attention to other leaves for signs of recovery.

If you cannot get rid of your phosphorus deficiency, please consult our 7-Step Cure to 99% of Cannabis Growing Problems

Plant Symptoms

  • Bronze or brown patches
  • Brown or slimy roots
  • Brown or yellow leaf tips/edges
  • Buds dying
  • Buds look odd
  • Bugs are visible
  • Curling or clawing leaves
  • Dark leaves
  • Drooping plant
  • Holes in leaves
  • Mold or powder
  • Pink or purple on leaves
  • Red stems
  • Shiny or smooth leaves
  • Spots or markings
  • Twisted growth
  • Webbing
  • Wilting leaves
  • Yellow between leaf veins
  • Yellow leaves

This page is part of our Plant Doctor series. You can use our tool to filter by symptom and help diagnose your plant.

Phosphorus deficiencies cause dark splotches on leaves and can appear at the bottom of the plant on some of the oldest leaves. Learn to spot & fix the issue.

How to Grow Pink or Purple Cannabis Buds

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Would you like to grow colorful cannabis buds? You may have seen marijuana buds that are pink, purple, red, orange, or possibly even blue! But how do you grow colorful buds at home?

If you want to grow buds that are pink, red, or purple, you must choose the right genetics!

The tendency to turn colors is almost 100% determined by strain/genetics, so you can’t force any plant to produce colorful buds. However, you can purchase seeds of strains that naturally turn vibrant colors, and there are tricks to maximize their genetics and bring out the colors of your buds.

You cannot produce buds this purple without a strain that has been bred to makes purple buds. There are tricks to maximize the natural color of your genetics, but you have to start with good genes!

4 Different “Parts” of Cannabis Can Become Colorful

When people are talking about “colorful” buds, most people imagine brightly colored buds in their hands. But there are actually different parts of cannabis plants that can display non-green colors, and sometimes people will lump all them all together. Each one is a little different from each other, and some have a significant effect on the final looks of your bud, while others don’t make much difference.

Many different parts of a cannabis plant can turn purple, including the whole plant!

The parts of the plant that can become colorful are…

  • Pistils (Hairs) – some of the color remains after drying/curing
  • Calyxes (Buds Themselves) – very strong effect on final color
  • Leaves – relatively small effect on final bud color since many are removed by trimming
  • Trichomes – small effect on final color

Buds are made up of different parts and are usually more than one color

Colorful Pistils / Hairs

Most growers want the buds themselves to appear colorful, so the color stays even after the buds are dried and cured.

There are two parts of the buds that can turn color. One part is the pistils/hairs that stick out. There are several strains where the pistils turn pink or purple.

Sometimes just the pistils/hairs turn pink or purple, while the leaves and buds may still be green.

When buds are dried, they retain some of their pistil color, but you will still be able to see the color coming through underneath.

Colorful Calyxes (Buds Themselves)

Calyxes are what make the buds themselves. Cannabis “buds” are actually made of hundreds of calyxes stacked on top of each other, and some or all of them may become colors other than green.

This fantastic picture shows how the overall appearance of buds changes with the ratio of colorful vs. green calyxes.

Nearly all Smooth Smoke buds (by Tropical Seeds) produce at least a few pink calyxes here and there, and some plants in the right conditions can produce buds where almost every calyx is a deep purple.

Calyxes are what give the most color to your buds. Even a few purple calyxes can give the buds an overall purple tint, and when you break open the buds there will be some pieces that are completely purple.

This nug contains several purple calyxes.

After being ground up, you can see the purple pieces distributed throughout. The higher the percentage of purple calyxes, the more vibrant your final bud color will be.

Colorful Leaves – Sometimes It’s Not the Buds That Turn Color!

With some strains, the leaves may turn purple while the buds stay mostly green. This can make for absolutely gorgeous plants, but since leaves mostly get trimmed off after harvest, usually, a lot of the purple will no longer be visible on the buds after the trimming process.

For some strains, the leaves may turn purple while the buds stay green. This often happens after the plant gets exposed to chilly night temperatures (but not always). The leaves exposed to direct light are most likely to turn purple, while leaves in the shade often stay green.

Although the leaves have turned purple, the buds themselves are mostly green.

Only the tops of buds exposed to direct light have any purple left after trimming off all the leaves. Trimming removed almost all of the purple coloring.

Colorful Trichomes

In general, cannabis trichomes go from clear (not ready) to white (highest THC) to amber/yellow (more of a mellow effect) before they eventually wither and die. These color changes are often used to determine the best time to harvest cannabis.

However, sometimes, trichomes can turn purple or pink, making it difficult to know when to harvest. In that case, you want to also look at the pistils to determine the best harvest time!

Purple or pink trichomes can make it tough to know when to harvest, but they’re exotic and beautiful! The color of trichomes may leave a slight tint on the buds after they’ve been dried and cured, but the bud color underneath will be the dominant color.

Now on to making purple buds at home!

How to Maximize Color and Genetics

Before you do anything else, you need to begin with the right genetics. If the genes of your plant don’t make colorful buds, there’s nothing you can do! So, you must start with a colorful strain to get the best results with maximizing color.

  • Choose Colorful Strain (Most important!)
  • Choose Strain that Produces Very Dark Colors (if you want buds to maintain color after being harvested and dried)
  • Temperature – Warm days & cool nights
  • Bright Light – Strong light levels can help bring out color
  • PH at the Roots – Some strains may express colors at higher or lower pH ranges

Choose Strains with Brightly Colored Buds and Pistils If Possible – This maximizes the overall colorful appearance of your buds.

For the most significant final effect on your dried and cured buds, you want to choose a strain where as many parts of the plant as possible are colorful. So ideally, you want buds where the pistils and calyxes (which make up most of the final color) are both vividly colored. If the leaves and trichomes are also colorful, that will improve the effect even further.

In this case, the buds are purple, but the pistils are orange.

To maximize the final color, you want to choose a strain with brightly colored buds and pistils. For example, this bud has purple calyxes, mostly purple pistils and even some purple leaves. This combination makes the entire bud appear bright purple.

Choose Deep Purple Buds for Maximum Color After Drying/Curing – Deeply colored buds (sometimes called “black” strains) tend to be the most vibrant after drying/curing.

To produce the most colorful buds, you need to make sure the color goes all the way through the buds, and ideally, also through all the surrounding leaves. This level of color-penetration is most likely to happen with intensely dark colored buds. Buds that are paler in color tend to lose a lot of their vibrancy in the post-harvest processing.

These buds were mostly pink at harvest, but the color doesn’t go all the way through the buds.

There was still a lot of green on the parts of the buds that didn’t get direct light.

After they’re trimmed and dried, the pink color has become more subtle.

You will “keep” the most color after drying/curing by choosing strains that are dark purple through and through, from buds to pistils to leaves if at all possible. Deeply colored buds keep more of their color after drying and curing than pale purple or pink buds.

These buds were deep purple at harvest…

When buds are darkly colored, they tend to keep more color after being dried and trimmed.

Note: Your buds will naturally lose some of their overall vibrancy and color during the drying/curing process (but not any of their potency!). That’s why you will likely never run into neon purple buds that have already been dried and cured for 2+ weeks. Even green buds go from being bright green to a more muted green color by the time they’ve cured for a few weeks. When you see very brightly colored buds, it almost always means the buds are still relatively fresh.

Although color is determined primarily by genetics, there are a few things you can do to help your plant express its natural colors…

Temperature – Some Strains Express Colors When the Night Temperature is a Few Degrees Cooler than the Day

If you’re growing a strain that turns color, some strains will only show their colors when night temperatures are at least a few degrees cooler than during the day in the flowering stage, especially towards the end. However, some plants don’t react to cool night temperatures, and many strains (like Panama) nearly always turn color no matter what the temperature.

Certain strains like Querkle turn color more easily when the temperature is warm during the day as opposed to cool at night. So, it’s always a good idea to aim for nice warm days, and cool, comfortable nights, because that contrast seems to help bring out colors for many strains.

How to Maximize Color with Temperature

  • Warm Days (75-80°F / 24-27°C)
  • Cool Comfortable Nights (65-70°F / 18-21°C)

Note: Some strains turn color no matter what the temperature. You can sometimes contact the breeder and ask if they have advice on how to bring out colors for a particular strain. I’ve found that most breeders will get back to you quickly if you go to their website and ask questions!

Temperature makes a difference! Some strains need contrast between day/night temperatures for their buds to turn colors. For example, the buds of this Auto Frisian Dew turned bright purple after it started getting below 70°F (21°C) temperatures at night.

Strong, Direct Light may help bring out colors

In some cases, a plant may produce purple tones in response to intense, direct light (on buds and leaves). Although we’re not sure exactly why it’s possible this may act as a sort of sunscreen for the plant! The importance of light levels varies on a strain by strain basis.

The pH at the Roots may affect cannabis bud color expression

Outside the cannabis world, there are a few species of plants with flowers that are known to turn different colors based on the pH at the roots.

For example, the flowers of specific types of hydrangeas can turn blue in very acidic soil but may turn pink if exposed to neutral or only slightly acidic soil (though this type of variation is rare in the plant world).

Yet there have been occasional reports of cannabis strains that produce different bud colors based on the pH at the roots, though unfortunately, more testing is needed!

If growing multiple plants of the same strain, you might consider giving plants different pH ranges to see what effect it has on the final bud color!

Pictures and Examples of Colorful Strains

Here are some pictures of cannabis strains that sometimes grow colorful purple and pink buds.

Photoperiod (Regular) Strains

Frisian Dew

The next two pics are of the strain Frisian Dew, a popular strain by Dutch Passion, who specifically designed the strain for growing outdoors. It is exceptionally hardy, high yielding, and is also mold and pest resistant. About 50% of the time, Frisian Dew buds will turn bright purple instead of green!

The plant in the middle with the dark purple buds is Frisian Dew.

Purple Trainwreck

Purple Trainwreck buds are usually purple-tinted, with purple leaves or pistils.

This Purple Trainwreck plant is growing purple pistils.

For this Purple Trainwreck cola, it’s mostly just the leaves turning purple. In either case, the effects are the same!

This Purple Trainwreck bud turned particularly purple.

Panama

The following plants with pink pistils are from the strain Panama by Ace Seeds

This is what Panama buds may look like when they’re first growing in.

beautiful pink pistil pic by trippergreenfeet

As the Panama buds develop, the pistils and even the buds themselves may intensify their pink color

Smooth Smoke

Smooth Smoke buds (by Tropical Seeds) can become quite colorful, with colors from hints of pink to deep purple!

Auto-Flowering Strains

Auto Frisian Dew

Auto Frisian Dew by Dutch Passion (this is an auto-flowering version of the original famous marijuana strain) – Unlike the regular Frisian Dew which gets about 50% purple bud plants, the breeder claims only 10% of the plants from this strain produce purple buds. Still, some growers are getting far better odds than that. When purple does appear, the color is incredibly vibrant and spills out onto the nearby leaves!

This Auto Frisian Dew plant got a little stunted at first, but still ended up producing beautiful purple buds!

Auto-Flowering Bloody Skunk

Auto-Flowering Dark Devil

Dark Devil Auto is another fabulous auto-flowering strain by Sweet Seeds that turns a gorgeous purple or even a deep red.

This Dark Devil Auto bud turned completely purple from top to bottom.

Purple Kush Auto

Brilliant color on Purple Kush Auto plants! The buds turn almost black after being dried!

pics by kingkola1

Colorful “Duck” Strains (Stealth Leaves)

“Duck” strains are characterized by their oddly shaped leaves. The idea is that the plants look less like cannabis with 3-finger leaves. The bright colored buds also help make them look less like cannabis.

Frisian Duck

One of the most popular variations of the Ducksfoot (Ducksfeet?) strains is called Frisian Duck by Dutch Passion. This strain thrives outdoors and grows with the traditional stealthy leaves. This strain also often makes bright, beautiful purple buds (with cold enough temperatures) that have a fresh scent that is sometimes even a little fruity.

Frisian Duck plants react well to growing in a living soil that’s been composted and amended with slow-release organic ingredients.

This is a Frisian Duck plant in the vegetative stage.

This Frisian Duck plant was grown outdoors in a greenhouse. More than half of Frisian Duck plants grow bright purple buds!

Frisian Duck is based on the famous Frisian Dew strain which also produces purple buds and has been bred for generations specifically for growing outdoors. The Frisian genes thrive under sunlight, and buds are resistant to bugs and mold!

This Frisian Duck plant is just about ready to harvest!

However, even with stealthy strains, be aware that they still smell like cannabis in the budding stage!

Why Do Cannabis Leaves and Buds Turn Purple?

Sometimes you’ll see purple leaves because of a nutrient deficiency, but oftentimes purple leaves are actually caused by natural plant processes!

There are many species of plants that make purple leaves. The leaves appear purple due to high levels of a purple pigment called anthocyanin. Anthocyanin may act as a sunscreen for plant leaves because it protects against damage caused by UV-B rays. Anthocyanin is also known to help protect against cold or heat stress on the cellular level.

It’s not just cannabis plants that grow purple leaves. Here’s an example of a False Shamrock plant, which has glorious purple leaves from top to bottom!

With some cannabis strains, the leaves may turn purple while the buds stay green. Just like with buds, the leaves are more likely to turn color when the plants are getting cool night temperatures in the late flowering stage.

The leaves most likely to be affected are the top leaves and other leaves getting direct light. With this purpling, the leaves in the shade of the plant usually stay green.

For some strains, the leaves may turn purple while the buds stay green.

The leaves of this plant turned purple overnight after that plant was exposed to chilly night temperatures.

The leaves exposed to direct light are most likely to turn purple, while leaves in the shade often stay green

In this case, all the leaves that are exposed to the light have turned purple, including the sugar leaves. However, once the leaves are trimmed off, the buds will be mostly green.

Buds may still be purple-tinted from leaves that weren’t completely trimmed off.

If there’s a lot of purple leaves, there may be a lot of color left even after trimming.

Case Study – Super Purple Haze plant

The top leaves of this Super Purple Haze plant have turned a vibrant purple

Here are the buds from that Super Purple Haze plant drying – you can see that the parts of the buds that were exposed to the light have strong hints of purple

A closer look at those buds so you can better see how much bud is purple and how much is green after being trimmed and dried (click for a closeup!)

This cannabis plant has grown vibrant red and purple leaves.

This outdoor cannabis plant has turned purple everywhere it received direct sunlight. Splendid!

Cannabis sometimes has neat mutations, like this two-tone plant where only half the leaves turned purple!

These Swiss Cheese plants by Nirvana exploded with red, pink and purple leaves when it got cool at night right near harvest time, but the buds themselves did not change color. Unfortunately, when just the leaves turn color, the buds themselves will often look mostly green once they’re trimmed. But this beautiful picture lives forever!

Bright purple stems may be a sign of a phosphorus deficiency, but this “symptom” is sometimes actually caused by genetics, just like purple leaves, pistils or buds!

Blue Dream (rare deep purple phenotype)

Blue Dream buds usually don’t turn this deep purple, so if you want to see buds like this you’re better off with a strain that’s bred to always grow dark purple buds. However, the pictures were so beautiful I just had to share!

How can you grow colorful buds that turn purple or pink? Learn which strains to get, as well as what you can do to maximize color during your grow.