What do purple and red cannabis stems mean?

Often your cannabis plants will have green stems and branches at harvest. But sometimes you will see striking red and purple colours appear and may have wondered why. Cannabis can often show pigmentation and rich colours in the leaves and buds. But the stem can also show colours and pigmentation. This can be a result of environmental factors and/or the result of the cannabis genetics. But in some cases, coloured stems can also indicate potential problems.

Purple and red cannabis stems

Many cannabis growers love seeing a flash of colour on their plants as harvest approaches. Buds with delicate hues of red, orange, purple etc often have greater bag appeal and can catch admiring glances. But cannabis plants can also produce pigmentation on branches and stems too. This can be beautiful to see, wonderful candy-coloured stems/branches add great visual appeal and increase the cultivation pleasure for any grower.

If your cannabis plant is otherwise healthy, these colours are usually nothing to worry about. Just enjoy them. You can see red and purple coloured stems on plants grown from autoflower seeds, feminised seeds or regular cannabis seeds. But occasionally extra colours appearing on your stems/branches may signify potential problems.

Light intensity

When exposed to light, the normally green cannabis stem can develop colours thanks to the natural pigments present in cannabis. Normally these colours/pigments are expressed in the leaves and flowers. But the stem and branches can also develop pigmentation when exposed to light. This can mean pretty pastel shades of red, pink, purple or lilac can develop. Observant growers will have also noticed that the stems produce plenty of terpenes too, try rubbing the stem and then smelling the scent on your fingers.

If you have recently de-foliated your cannabis plant, you may expose the stem/branches to more light which can cause the colouration. Growers that have used cannabis plant training techniques e.g. LST may also notice the onset of stem pigmentation.

Temperature

Many cannabis plants will exhibit a beautiful display of autumnal/fall colours in response to reduced temperatures as harvest draws near. Typically, these colours are most clearly noticeable on the leaves and cannabis buds. But cool temperatures also allow pigmentation to become visible in the stem and branches too.

Some growers even deliberately decrease grow room temperatures during late bloom to induce pigmentation in the hope that it will increase bag-appeal and potential harvest value. Piling ice around the stem in late bloom is one such approach. Experienced growers will note that temperature reduction also comes with certain risks - reduce temperatures too much and you also reduce plant growth/metabolism.

Plant stress

If your cannabis plant is otherwise healthy and growing well, coloured stems and coloured branches is something to admire and enjoy rather than something to worry about. But occasionally plant stress can produce pigmentation, in these cases it’s important to identify the problem. In seedlings, the fungi Fusarium can cause brown stems which may quickly collapse as the plant dies and ‘damps off’. In mature plants, Botrytis (bud rot/mold fungi) can also create dark colours on your plant - these are indications of a serious disease which needs urgent attention.

Nutrient deficiencies

Nutrient deficiencies can produce a range of issues. These can include yellowing (or brown/dark colours) on leaves and stem. Phosphorus deficiency is one such issue, creating brown leaves with occasional red/purple pigmentation of the stem. However, to the experienced grower, it is usually clear when a plant is showing nutrient deficiency.

Usually, with some experience, the grower can spot the difference between a healthy plant showing natural colours on the stems/branches vs an unhealthy plant which may be showing growth issues and other problems.

pH levels

Cannabis generally prefers a slightly acidic pH regime. Soil/compost growers tend not to worry too much about pH, but often get the best results with pH levels at around 6.5. Hydroponic growers may even prefer to use pH levels nearer 5.6 - 5.8. If your pH drifts too far away from this range growth rates may be affected, plant colour can also be affected as pH drifts away from normal.

The experienced grower tends to use pH meters to check the acidity/alkalinity levels on their prepared nutrient feeds. Note that pH meters will eventually start to fail and produce erroneous readings, which could have disastrous implications if you never check or calibrate your pH meter. Therefore, regular re-calibration of your pH (and E.C.) meter is essential.

When are red stems normal for cannabis plants?

If you have your grow room under good control, then any red or purple cannabis stems are likely to be results of the genetics and/or environmental conditions rather than anything more serious. The experienced grower is usually easily able to spot the difference between a healthy plant with natural pigmentation and an unhealthy plant that is struggling with other issues.

If you enjoy seeing extra colour in your grow room, you are not alone! Many growers love the added grower-appeal that comes from a flash of extra colour in the grow room. If that sounds like you, then perhaps you would be interested to grow some cannabis seeds which are particularly prone to red and purple pigmentation.

The Blue family of cannabis seeds (related genetically to Blueberry) are well known for their rich colour display. Auto Blackberry Kush, Blueberry, Auto Blueberry and Blue Auto Mazar are all recommended to such growers. So too are some outdoor cannabis seeds such as Purple #1, Shaman, Frisian Dew and other members of the Dutch Outdoor cannabis seed collection.

Grow your own colourful cannabis!

If you adore the added appeal of purple and red stems when growing cannabis you are in good company! Many growers enjoy the extra colours and as a result Dutch Passion have carefully curated all their best-coloured cannabis genetics into the Purple Weed Seed collection. These are perfect cannabis seeds to browse if you want to see some added colour, bag-appeal, and quality in your next harvest!