Start My Diary Login Sign Up

What Is Cannabis White Ash And How To Get It

Created by
JoshuaHolt JoshuaHolt
Added 7 November 2020

What Is Cannabis White Ash And How To Get It

Many claim that white ash is a sign of clean, chemical-free weed. On the other hand, dark ash is frowned upon for the unpleasant smoke it delivers. After much debate and testing, it could be said that the answer lies in the flush and cure. This article discusses white ash and how to get your joints burning smoothly.

What is White Ash?

Burning Cannabis Produces Ash

The definition of white ash is pretty self explanatory, but why is it important? White ash is the result of combusting cannabis buds that supposedly have been properly flushed and cured. In theory, the ash should be on the whiter side if the buds are clean.

It may be that you burnt some weed one day and the ash was dark, hard and crackled big time. The likelihood is that the weed was fed heavy amounts of chemical nutrients and not flushed or cured properly before harvesting. Of course, there are many affecting factors when it comes to determining the quality of your weed, but the colour of the ash can be one of them.

Bad Quality Weed

Dark Ash Is A Sign Of Bad Quality Weed

When the ash is dark and hard there could be something wrong with the bud. Growers use all kinds of chemical products to boost their weed. It may increase yields for them, but the final product is less than satisfying and potentially harmful for us.

When weed is very heavily fertilised, or even sprayed with chemicals (weirdly enough, some people do that), the ash will show it. Sometimes the tainted bud is so bad the ash goes solid as well as being on the dark side. Headaches and panic attacks are some of the reported effects of very overfertilized or sprayed buds. Fortunately, if you buy from a reputable source this is never really an issue, but just be careful where you get your weed from. 

Growing your own is often the best way to ensure the quality of your weed. If your buds do burn dark, it does not necessarily mean that is a sign of bad quality weed. However, it may mean harvesting was not completed correctly. In most cases the flush and cure do tend to make a positive difference to the final product. Let's take a look.

The Importance Of Flushing

Flushed Cannabis Plant

The topic of flushing has been widely discussed and there are growers who do not believe the process to be an important step in determining the quality of their weed. There are many variables when it comes to flushing and it does not always have to be performed in the same way. The important thing to understand is that flushing is more about cleaning the soil than literally taking out nutrients stored in the buds.

How heavily a grower chooses to flush depends on how the weed was grown. For example, an organic grow using compost and super soils does not benefit from flushing because there are no chemicals used in the growth process. There would probably be quite a difference in the colour of the ash if one was to burn an organic bud next to one that has been fed chemical nutrients until harvest day.

To give you a quick idea, flushing is performed with the intention to flush out any built up minerals, primarily around the root zone. Removing the nutrients from the soil prevents the plant from absorbing more and encourages it to feed off what is left stored in its reserves. 

Flushing normally involves giving plants a thorough watering at the beginning of the process to 'wash' out excess nutrients from around the roots. This is not entirely necessary but can help to kick start the flushing cycle.


Soil Flush (Days)

Hydro Flush (Days)













Alternatively, if you don't feel your plants need a heavy flush, one can simply stick to a watering schedule until harvest. That means just giving plants water as and when they need it. Cannabis plants tend to start drinking less as they mature. It's a good sign the plant no longer needs further external nutrients.

There are many arguments against flushing and many growers believe it does not make a difference to the colour of the ash. If you're still unsure whether flushing helps to achieve a whiter ash, why not put it to the test? Grow two of the same strain, one on a light feed and the other on a heavier nutrient schedule. Flush the first plant and not the second. Dry and cure them in the same way and see what the outcome is.

Curing For A Cleaner Smoke

Curing Helps To Improve The Quality Of Your Buds

White ash is also considered to be the result of properly cured weed. It is well known in the growing community that drying and curing is crucial to achieve a flavourful, potent product.

When we dry and cure our weed correctly, the remaining sugars continue being metabolised. These compounds break down slowly and are released gradually into the atmosphere. It seems without them, the smoothness of the smoke improves noticeably.

The key here is to not dry and cure your buds too quickly. When this happens, some of the heavier compounds may remain in the bud (such as chlorophyll and other sugars) as they do not have enough time to break down, essentially becoming locked in the bud. Because of this, buds that have been fast-dried may deliver a harsh smoke that has a grassy taste.

The moisture content in the bud could be linked to the colour of the ash. If the buds still hold too much moisture then they may not burn properly (and at a lower temperature) and the ash is likely to be darker unless the weed is heated for a longer period of time. 

Drying and curing does help to remove some of the impurities left in the buds, and in theory, results in a whiter ash when burnt. Unfortunately, we still do not know the exact reason for white ash and it is probably a combination of factors, but curing does show significant improvement in bud quality.

Burning Cannabis Buds

Your Materials Affect The Colour Of 'Ash'

The colour of ash may also depend on how the plant material burns. For example, when the material burns at a higher temperature for longer periods of time, the ash tends to be whiter. The drier the material, the hotter it will burn.

Pure white ash essentially means there is no carbon left. Carbon based plant matter burns dark when it combusts (think of charcoal) but if you keep burning it will eventually turn white. The carbon eventually breaks down, leaving just some basic minerals which form a light, white ash.

Charcoal Turns White Once The Carbon Has Burnt Off

It could be said then, that if the mineral content is still high in the plant when it is burnt, the minerals that remain in the ash could be higher if the burning temperature is not hot enough. Dark ash may be because the weed was not able to fully combust as it was burning.

You also need to consider :

  • What materials you use to smoke
  • How dense you pack your bowls or joints
  • The way you heat the weed
  • For how long the weed is heated

Resin and other substances may get left behind in the ash when the product does not burn correctly. That's why you can usually relight a bowl of 'black' ash and still get a hit.

Rainbow Chip by Rocksfarm from GrowDiaries

Tip: It is important to note that vaping does not combust the buds. If that happens then you are smoking and the plant material will turn to ash. Vaped weed is decarboxylated and looks brown and crispy afterwards.


In the end, there is no concrete evidence to suggest that white ash means the final product is of a higher quality than a bud that produces dark ash. However, it is very common to hear that dark ash is not pleasant. This is why we suggest taking the time to flush and cure your weed, because the difference is more than noticeable.

If you found this article useful or have any comments about white/black ash, please leave a comment down below!

External References

An Investigation Of Decarboxylation Of Acidic Cannabinoids: THCA-A, CBDA And CBGA. Planta Medica. - Wang, Mei & Wang, Yan-Hong & Avula, Bharathi & Radwan, Mohamed & Wanas, Amira & Antwerp, J & Parcher, J & ElSohly, MA & Khan, Iftikhar. (2016)

Heavy Metal Soil Contamination and Bioremediation. - Muzafar, Malik & Goyal, Pooja & Gupta, AJAI & Gupta, Suphla. (2020).

This article was updated October 2020.



if white ash is 'good', it has nothing to do with flushing. Flushing does not reduce minerals in the buds. Lab tested. There may be other causality behind it, but flushing is just psuedo-science. Curing has nothing to do with color, either. Ash is the same color after it dries and 3 months later. If not, you may want to look into storage practices.

Again, i won't say there is or isn't causality behind white vs black ash. It just isn't these two things in any rational way. Ash is mostly carbon left behind. Smoosh that "white" ash and it'll be black or dark grey, because that's what color carbon is. The color probably has more to do with complete vs. imcomplete combustion.. possibly heat-related? possibly water content? just because it sounds good doesn't mean it is so. both of these hypothesis would have to be tested against a control group and each of suitable size.


I will list some points that not only challenge the absurd impracticality and illogicality of this myth, but point out how the pseudoscience behind it is fundamentally flawed (as is all pseudoscience) and can be countered by what is known about basic plant biology.
1. Robbing plants of essential nutrients at any stage of their life cycle is NOT beneficial for growth. I challenge anyone to provide a single peer reviewed paper from a reputable journal that provides evidence suggesting otherwise.
2. If this was practical, wouldn’t you expect all big agricultural hydroponic growers adopt the same practice?
3. Plants take minerals into their tissues, from their roots via the treachery elements; i.e. xylem. Once these minerals are in the plant, they are there to stay, the plant does not expel them, unless it’s through senescence-driven abscission of leaf petioles. From the treachery elements nutrients are translocated into the phloem - the plant’s ‘blood supply’ - after being integrated into various biomolecules, or are used for various metabolic functions. Where is the logic in thinking the plant ‘uses’ these up in that last week of flushing, in order to avoid smoking them? All the N P K Fe Mg Ca etc. is still there.
4. For arguments sake say we counter the last point by suggesting these minerals in their ‘raw form’ will taste ‘hasher’ or ‘nastier’ in the form of pyrolytic breakdown products (formed when weed is burned) than artifacts of larger biomolecules of which these minerals/macro nutrients are now a part of, for example phosphorylated PO43-. Even if this was the case it still doesn’t correlate with the myth, as the transports steam in the treachery elements is measured in minutes not a week. i.e. a PO43- molecule does not wait around in these vessels for a week before subsequent translocation and modification.
5. If there was any truth to this myth, then plants grown in soil would always taste worse than plants grown in hydro. Why? Because obviously soil is not an inert medium you can flush for a week. And a plant CANNOT distinguish between a PO43- molecule that comes from soil from that of a PO43- molecule that comes from hydro solution (which also debunks another myth, but we’ll leave that one).
6. Are there studies that have conducted double blind trials to investigate if flushed weed tastes any ‘sweeter’ than unflushed weed. Again, need peer reviewed papers. And doesn’t have to be weed, can be strawberries or any other type of fruit.
7. What is the proposed mechanism to support this myth, and how is it consistent with fundamental plant biology.
8. How does starving the plant of food in the last week increase thc production in the trichome? Papers?
9. Given, under certain conditions stressed plants upregulate certain defence compounds, but they will almost certainly produce less inflorescence weight per watt of light. Growth is always retarded under stress - not promoted. Nutrient starvation is a form of stress. Looking for peer reviewed papers that suggest otherwise.
Those of you set in your ways, each to their own and best of luck to you. Those who are willing to change their views in light of new evidence, or lack thereof, be ready for increased yields by feeding those hungry ladies right up until the second you chop.


@NorthernFrostCannabis, They've shown with coco there's a potential you actually upset the balance of elements in the plant by flushing. Flushing may actually do the exact opposite of what is postulated in some ways, which puts a smile on my face. Believe Fe? and something else was higher after flush in a statistically significant way


@NorthernFrostCannabis, it seems the misinformation about flushing will never end.


Excellent article, it is useful to take out, always rinse 20 days before collection, first Ripen 10 days and 10 days of water.


I think it's an article that every cannbis lover should read :ok_hand:

Thank you very much again :clap:


This does not make sense. How do you flush plants grown in soil? You don’t, because there is no such thing.


Great Info