The yellowing of dragon fruit plants may be their natural response to reduce the amount of sunlight they're getting.
Let's see some ideas why the branches are turning yellow–and some possible solutions:
It May Be Too Sunny
Although dragon fruit is a type of cactus, too much sun can actually cause it to turn yellow. Dragon fruits like semi-tropical climate, meaning, not too much sun & not too much cold.
Some folks say this is sunburn. You may see this more often in the summer when the outside temperature may be over 100F (38C). The yellowing plants are experiencing some summer stress.
You could also have a quick squeeze of the dragon fruit branch to see:
If it feels firm, then there may still be some water inside it. If it is dry like this one, then the plants may be thirsty or losing quite a lot of moisture:
To protect the plants from too much heat, people cover them with sun cloth or a piece of burlap. Some others use plant guard or sunscreen for the plants.
It's made with plant oils & organic paint powder to help coat the trees from extreme heat. Shade cloth blocks out 75% of sunlight, which might affect fruit production & sweetness.
If your dragon fruit branches are soft (crispy), this may be a sign your plants are thirsty. This can be a result of the high temperature. In this case, if possible, move your plants into somewhere cooler. Give it a little bit of water to recover.
If yellowing happens too frequently, consider choosing some tolerant variety like Tricia. This one naturally produces a white powdery film to protect itself from extreme heat waves & extremely cold weather. The only downside is their thorns:
Alternatively, you can plant some big trees (e.g. red wood trees) around your garden to filter out some sun & give a nice cool shade for the dragon fruits. Red wood also keeps some mites & ants away.
As a note, yellowing happens more with younger plants. As your plants age, they will develop more resistance & can tolerate more heat. Thus, less yellowing.
If It's Been Sunny for Some Months and Then Rains...
If the weather has been sunny for 1-2 months (the dragon fruit plants are yellowing) and then it suddenly rains, some branches may slowly turn green again while others may experience some rotting.
If the branches have started to rot, here is how:
How to Treat the Rot
Opportunistic fungi in the high humidity rain may take the chance to eat up the branches, creating some dark mushy spots on the branch:
Quite yucky, I know. But if the rot has incorporated the whole branch, then the solution here is to let it go and snip it off, before the infection spreads further. The rotted branches will be gathered and thrown away afterwards.
However, if the rot is quite small, then you can use a rod to scrape off the mushy part to stop the spreading. After a few days, that part will turn dry.
After snipping and scraping, you don't really need to spray any chemicals. The plants can self-heal on its own. However, if you want the healing to be faster, you could use protective fungicide 2 times, spaced out 7 days apart.
When the plants are quite weak and yellowing, it's advisable to reduce the amount of fertilizer, especially the nitrogen. A lot of nitrogen now could make things worse and slow down the time to recovery.
And about 20 days after the rain and our snipping-scraping, these sun-stressed (for 2 months) branches were starting to green up again happily:
Another aspect for the yellowing could be:
The Roots & The Soil
Check the roots of your dragon fruit plants. See if there are any black, mushy stuff in there:
In the picture above, the string roots have just sprouted but have already turned black. A weakened root system means a weaker water & nutrient transport system. Your plants then may not be getting enough to nourish their branches.
Make sure also not to overwater the trees. Overwatering may cause little particles in the green branches to go burst, turning it into yellow. But the excess water also invites other guests to the party (like bad bacteria) which may cause more troubles.
Using too much chemical fertilizer may also weaken the roots natural defense ability & in some cases harden the soil. To save the plants, you can:
- Use well-draining soil
- Don't pour too much fertilizer near the base (better to spread it out)
- Don't overwater the plants
Dragon fruit plants survive well in environments that get 50-100mm rainfall/month. The higher water mark can be around 66-166mm/month.
Grafting a dragon fruit variety on another strong rootstock may also help with the yellowing (chlorosis). In some cases, it can also keep the bad guys away while still nourishing your plants.
If you'd like to explore more, check out this how-to guide on grafting dragon fruits:
>> Link Blog post: How to graft dragon fruits
But may be, the yellowing is one of nature's things:
A Natural Variegated Yellow Dragon Fruit
Some varieties naturally have a bi-color yellow-green on their branches. The Worth Variegated Dragon fruit is one example of this unique color variation. It may start as green first, but then as it grows the branches turn more yellow with red lining on the edges of the branch.
Richard, the guy behind Grafting Dragon Fruits, shares this cool new specie in this video. In this case, you may get yourself a great specie and the yellowing is only its natural phenomenon. So nothing to worry about here. The flowers of this variety will be all yellow and the fruits sometimes have both yellow-and-green skin. Very interesting.
>> Link YouTube:New variegated yellow dragon fruit
Some people say this yellowing is also a genetic mutation:
For this mutated yellow variety, the price per cutting is about 10-30 times more expensive than the white, red or purple varieties.
Lastly, we can:
Observe & Let The Plants Recover
Keep observing the plants to see if they improve. Some growers also use Epsom salt (MgSO4). Because the yellowing may also be a lack of magnesium or iron.
Sometimes, too much nitrogen in the soil may also lock out the the calcium intake for the plant. Chelated iron or magnesium then may add back the nutrients for the dragon fruit plants to grow green and healthy again.
>> Link YouTube:What to do when your dragon fruit plant is turning yellow
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