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purple stems on cannabis plants

How to handle Purple Stems

Purple Stems on Cannabis Plants: What Causes Them and How Best to Respond

Marijuana growers are sometimes surprised to see the stems of their plants taking on a purplish color in place of the usual woody look. In some cases, the youngest stems and petioles of a plant will look purple from the start. In others, a purplish tint will develop on older stems lower down on a plant that has already become established.

Purple stems and leafstalks are generally nothing to worry about, although they do occasionally signify underlying problems. Quite a few common, popular strains of cannabis (purple haze seed or purple punch seeds) are prone to developing purple or purplish stems at one or more stages of maturity.

Even the stems of a healthy plant will sometimes acquire a purple hue while others of the same strain and crop do not. Although this is unlikely to happen with clones, variations in gene expression among plants from the same batch of seeds, even feminized marijuana seeds, can leave some with purple stems and others without.

When genetic issues are not responsible, purple stems are sometimes symptomatic of nutritional or other problems with marijuana plants. In almost every such case, there will be other sorts of visible evidence that a plant needs some additional attention.

Becoming familiar with the causes of purple stems and how best to respond can only benefit you as a grower. Although purplish stems are normally nothing to be worried about, noticing them early on can sometimes make it easier to save one or more troubled plants.

Anthocyanins: Purplish Pigments Found in Many Plants, Including Cannabis

There are many flowers found in nature and florist’s shops that are characteristically purple, red, or blue. The buds and flowers of cannabis plants are naturally green, thanks to the large amounts of chlorophyll they contain, but can also display colors like purple. Many of the most popular strains of cannabis today, in fact, have been bred to produce dramatically purple buds.

When the purple notes in a plant’s big buds overwhelm the green contributed by chlorophyll, a number of compounds collectively known as “anthocyanins” get the credit. These flavonoids occur in large quantities in fruits like blueberries and blackcurrants that are prized for their antioxidant content.

Purple, blue, and red anthocyanins are found in many other types of plants, high cbd hemp seeds included. Marijuana plants that produce striking purple buds have been bred to favor the production of anthocyanins over other flavonoids.

Purple Cannabis Stems are Most Often Caused by Genetics

Just as even the brownest-looking cannabis stems contain quantities of green chlorophyll, so do they include significant amounts of anthocyanins. In most cases, levels within stems remain low enough that the effects of these purple, red, and blue pigments get lost in the mix.

Some purple strain seeds have been bred to develop purple buds that produce so much anthocyanin that their stems show evidence of the surplus. That can happen at almost any stage of a plant’s life, although genetically-induced purpling is most often seen in young plants and the most recent growths.

Even strains like the blue dream strain that are not known for having purple buds can still be prone to developing purplish stems. It is not necessarily the absolute amount of anthocyanin but the balance with regard to other pigments that makes the difference. As a result, a plant does not necessarily have to produce huge stockpiles of anthocyanin to end up with purple stems at some point.

A Bit of Patience is Usually the Best Response to Purple Stems

While it can be shocking to notice that a healthy-seeming plant is developing purple stems, there is most often nothing at all to be worried about. If a cannabis plant’s purple stems are solely the result of genetic factors, nothing will need to be done about them.

The best thing to do will normally be to wait at least a while to see if any other unusual symptoms arise. If a plant continues to develop normally and on schedule, purple stems can be written off as an expression of its genetics.

While waiting and watching for other symptoms, it can still be helpful to make sure the fundamentals of weed seeds health are in order. Some of the factors that can encourage the development of purple stems in generally healthy marijuana plants are:

  • Anthocyanins break down as temperatures rise, so plants kept at the low end of the appropriate growing range can potentially accumulate more of them than others. On the other hand, a plant’s genetically determined anthocyanin levels should normally be maintained at temperatures that will support steady growth.
  • Plant tissue pH. High pH levels also degrade anthocyanins and so can conceivably contribute to excesses of them within stems. Once again, genetic factors and a healthy plant’s natural ability to maintain targeted balances will normally counteract any pH-induced effect on anthocyanin levels within its stems.
  • Light spectrum and quantity. Finally, increased exposure to short-wavelength light has been shown to encourage anthocyanin accumulation in plants other than cannabis. It is at least conceivable that grow lights that emphasize blue and UV frequencies too much could make the development of purple stems more likely. Simply subjecting cannabis plants to too much light and not allowing them to rest enough could have the same effect.

What to Do When Purple Stems Coincide with Other Unusual Developments

It cannot hurt to check temperature, pH, and lighting while waiting to see if a plant with purple stems displays other signs of trouble. When something other than a genetic disposition turns out to be to blame for purple stems, it will normally be a nutritional deficiency. The nutritional problem most likely to cause purple stems to develop is phosphorus deficiency, which can be identified by:

  • Inhibition of growth. Cannabis plants that lack phosphorus have difficulty developing their root systems and buds. If a lack of phosphorus is the ultimate reason for purple stems, the growth of a plant should be noticeably slowed. Inhibited growth due to phosphorus deficiency will often become noticeable well before stems or leaves show signs of the problem.

Symptoms on older, lower leaves. Phosphorus is mobile within cannabis plants and gets transported to wherever it is needed most at the time. A plant suffering from a phosphorus deficiency will prioritize the youngest leaves higher up when distributing its stockpiles. The older, lower leaves of a phosphorus-deficient plant, even when grown from cheap marijuana seeds, will first show the stress by becoming shinier and darker. Not long after, they will develop brown or purplish spots that multiply and grow over time. Affected leaves will finally thicken and become noticeably drier, at which point necrosis will start to set in.

Phosphorus is so important to cannabis plants that the symptoms of a deficiency should normally be easy to identify, at least for yield-minded growers. Fortunately, phosphorus deficiency that gets caught early on should be fairly easy to resolve, as well. In order, it is normally best to look into issues like:

  • Growing medium pH. If the pH of a plant’s growing medium rises too high, it will have difficulty absorbing enough phosphorus. Flushing the growing medium with a pH-balanced nutrient solution can put an end to the problem. That should also eliminate accumulations of iron and zinc that could be contributing to a phosphorus deficiency.
  • Ambient temperature. The same low environmental temperatures that can encourage an accumulation of purple anthocyanins within stems will reduce a plant’s ability to take in phosphorus. Simply keeping your white widow cannabis plants warmer can help them recover from phosphorus deficiency.
  • Watering problems. Soil saturation due to over-watering is another common reason for plants to develop phosphorus deficiency. Proper watering should prevent this and other problems.
  • Root extent and condition. Plants with overly restricted root systems will have trouble absorbing all the phosphorus they need to thrive. Other root problems can just as well make it difficult for cannabis plants to take up as much phosphorus as they need.
  • Magnesium deficiency. Cannabis plants use the micronutrient magnesium to transport and metabolize phosphorus. Although magnesium is not needed in large quantities, a lack of it can effectively deprive a plant of phosphorus, as well.
  • Supplemental phosphorus. If nothing else seems to help, it can be helpful to add some additional phosphorus to a plant’s growing environment after a deficiency has become apparent. As with other nutrients, going overboard can cause damaging “burning” or lockout.

If a phosphorus deficiency ends up being the reason for the development of purple stems, working through these issues should improve a cannabis plant’s prospects. In the vast majority of cases, purple stems end up requiring no response at all.

As such, it will always be best to wait a bit and see whether any other symptoms appear after the development of purple stems. That time can be used to monitor a plant’s growth and make sure that fundamentals like temperature, light, and pH are in order.

Bottom Line

Although cannabis growers are often concerned or even shocked by the appearance of purple stems, there is normally no need to worry. Becoming familiar with how your favorite strains develop will make it easier to recognize when purple stems indicate a problem that does need to be resolved. Now after all that reading, go and reward yourself with some new purple kush seeds for sale from one of the world’s most equipped cannabis seed banks,!