Grafting with Hylocereus undatus
General Growth Parameters
Light intensity tolerance: Accepts full sun if acclimated slowly.
Daylight Hours: 11-16
Shade tolerance: Tolerates partial shade, benefits from at least a few hours of direct sun. Stems will become very thin and stretch profusely when in low light.
Water tolerance: Tolerates massive amounts of rain if not cold.
Drought tolerance: Can take some drought, but will begin to noticeably dehydrate within a few weeks of no water.
Growth speed: This is a very fast growing cactus, and is very good at growing grafted scions fast. This is one of the fastest growers for grafting purposes.
Hylocereus undatus, and other Hylcoereus species, are not often grafted onto other species usually because in the cactus industry the reason for grafting is for increased speed. Seen as Hylocereus grows fast on its own, it is not usually ever grafted among cactus enthusiasts.
In the fruit production industry, the story is much different. As with most fruit species, individual plants, clones, are grafted by the thousands onto root stocks because they have shown desired characteristics such as fruit size, shape, flavor, ability to ship well etc. Although dragon fruit is relatively new on the commercial market, it is now starting to get bred more and more and grafting to propagate specific fruit types is becoming more of a reality. Because Hylocereus is normally used as a root stock with amazing success, and the simple fact that same species grafting is pretty much always easier, it can be used as the rootstock for individual valuable fruit producing plants as well.
As already discussed in our grafting sections (seen in our Cactus Cultivation section), the process of grafting Hylocereus onto other stocks (preferably other Hylocereus) is straight forward. Some things to keep in mind with Hylocereus as a grafted scion in contrast to other cactus is the fact that older growth is woody and poor choice of grafting selection. New growth, and preferably the apical meristem (tip) should be grafted. Because new growth in Hylocereus is very soft and fragile, it is easy to break the tip when grafting, so extra care should be taken when taping down. In fact, this kind of situation is one of the *very few* times I would actually recommend using super glue to adhere the scion to the stock instead of tape, as with tape you are probably going to break about 50%+ of the tips of the scions when using fresh new growth tips.
When using superglue for cactus grafting, the basic principles remain the same. You must align the vascular rings of both stock and scion and make al the same cuts in all the same places. We still prefer flat grafts for Hylcoereus. The only real difference is that instead of using tape to push down on the scions top and allow to heal, you remove this upper pressure and glue the joins together. To do this, after both scion and stock are already cut (you can view this process here: Grafting Cacti) you use your fingers to gently press the scion down onto the root stock. When doing so, use a small piece of tissue to wipe away plant juices that squeeze out from the join where you intend to apply glue. When ready, apply a drop of glue where the 2 cuts join. I would suggest doing 2 drops per rib, 1 per side, most dragon fruit stems have 3 ribs, so a total of 6 drops. Adjust this number if you find the scions are drying out between the join and separating, which often happens in drier areas.
With all that said most fruit producing farms don°¶t bother with grafting Hylocereus as cuttings are very easy and grow very well on their own roots. Although we have not personally witnessed this example, it could still be beneficial if a given exceptional fruit producing clone does not perform well on its own roots, but as of yet we see little reason for grafting Hylocereus as a scion for any reason other than experimentation.
Hylocereus undatus (and a few other Hylcoereus species which can all be treated the same when it comes to grafting technique) is a mainstay in the cactus industry. Cactus plants are a notoriously slow growing family, though not all slow many are so slow people do not wish to wait a decade to have a 5cm plant. The benefits of grafting cacti are obvious and well covered in other pages. Hylocereus has many advantages as a root stock over other species because it is very fast growing, very water tolerant and grows its scions incredibly fast. From cheapo "moon cactus" mass produced in Korea and exported worldwide to $30,000 Astrophytum hybrids produced by some Japanese cactus guru, Hylcoereus is used by everyone because it is just simply a good root stock.
Weaknesses of Hylocereus as a rootstock
* Not cold tolerant, should be kept above 3C to live and about 10-15C to grow fast.
* Not super strong, it will not support large heavy scions unless they rest on something.
* Tricky for beginners to get used to grafting with often due to vascular bundles becoming woody fast.
Grafting onto Hylocereus rootstocks
We have discussed grafting on top Hylocereus in some detail already, you may view that page at: How to properly graft to Hylocereus
Here are some pointers to make grafting to Hylcoereus easier
* When rooting new cuttings for future use, use fresh new growth that is pale green and soft/flexible, not hard stiff old growth. Old growth quickly becomes woody in the vascular bundle and very difficult to graft to. This is the biggest issue, I believe, people have with using Hylocereus as a rootstock.
* If time allows, clip out all the areoles of the cutting when you go to root it. If you do this, also snip the very tip few mms, this stops the stem from sending out any offsets, stops it from growing upwards and the tip also does not become woody for many months when this is done.
* If you do clip areoles/tip, make sure you root in a drier area to avoid rot. Hylcoereus is prone to rot when not rooted and is more sensitive than normal.
* Keep rootstocks a little on the short side with bigger scions, as they cannot hold up a lot of weight in the scion. 10-30cm is the range we always use, though in experimentation (With a small species, Lophophora williamsii) we did use stocks that were about 100-150cm, though leaning is a problem.
The biggest flaw when people go to graft to Hylocereus is they graft to stocks that have already become woody. The inner vascular bundle in a Hylcoereus stem becomes woody relatively fast simply because it has a vine growth habit. They climb up surfaces, often using aerial roots for attachment, and this requires some strength of the stem. Woody vascular bundles, comprising of woody (meaning dead) cells, are not good at healing/bonding with other cells via graft. This is why when rafting cactus we want soft new growth that has not gone woody yet.
To prevent vascular bundles from going woody we can do 1 of 2 things. First, root them fast and graft them fast before they get a chance to get woody. This is good if you have many things to graft and are good at this skill. But when doing this you are often left with a very thin cortex and thus grafting is less successful. The second way, and one that I much prefer but involves considerably more effort and time is to prepare the stocks well and get them ready to graft.
To prepare a Hylolcereus grafting stock "properly" you must make cuttings from new growth. New growth is easy to differentiate as it will be lighter green, flexible and far more rubbery feeling, in contrast to older growth which is darker, hard and smooth to the touch (thick waxy layer). These thick old stems have gone woody inside and are thus terrible for grafting. Take this new growth cutting and with finger nails, knife, scissors etc. cut out each areole. The process is easy and relatively fast with new growth and when i set out to do a big batch of Hylcoereus I simply grow my pinky and thumb nails longer for a few weeks so I can just use my fingers, which is far faster than messing with any kind of tool. Whatever method you use, the idea is to clip out the areoles into the flesh a little, but without removing too much cactus flesh.
With all the areoles removed, it is time to remove the very tip, the apical meristem. Why would we do this? With all the areoles removed, the stem cannot send out new stems as we have removed all possible "exit" points, like a node on leafy plants (in fact in all plants we just say axillary bud). So there is just one place left for the plant to grow, and that°¶s from the apical meristem, or the tip. We don't want this to happen because as it grows and ages, it becomes woodier, and thus worse for grafting. So we clip this little tip, only a few mm is sufficient. We now have a Hylocereus stem that is completely unable to offset and grow (technically they still can find ways, but itís not common). We now set this to root.
Once rooted, continue to water for a month or so, this will make the Hylcoereus stock very fat and plump, in some cases actually becoming round and the 3 ribs are not defined. This is ideal for grafting and in act makes grafting far easier because now the cortex more resembles that of a fat columnar species of cactus rather than a thin ribbed Hylocereus. At this time, graft as you normally would onto any columnar type species of cactus.