The island’s first purpose as a military prison introduced the construction of the Sally port and this is where all visitors first walk by today on their way up to the cell house. Before entering the Sally port, they are greeted with the island’s first garden and home to some survivor plants thought to be planted in the 1920s. Among this bed are two historic Cordyline that are very old and are showing signs of decline. The Cordyline australis planted in the Sally port gardens is an old variety and have been very hard to find in the nursery trade. The Cultural Landscape report suggests that these be replaced, but not until we have the same plant with the same genetic makeup of the replacements.
In efforts to replace these declining historic Cordyline, we have tried several propagation methods to ensure they remain as part of the gardens for years to come. All of the methods were done in mid-March and we recently have had some promising results. Below are detailed descriptions of the propagation techniques trialed.
Methods of Propagation
We first tried just a cutting of one of the canes and potted it up in a pot of our compost. We removed some of the foliage and trimmed some of the fronds back to reduce that amount of energy going into the foliage and instead put it into the formation of roots. At first, it seemed as though this method might work, but after about a month, the fronds were almost all dead. The cane itself had become soft and the inside had become rotten. I think this method would work using a thinner cane or a smaller one with less foliage.
For this method, we took three pieces of cane, about 6 inches long each and laid them horizontally, half way deep, in a tray of sphagnum peat moss mixed with our compost. I had thought this method would work best, and we actually did have roots start to form alongside the canes, but I think they ended up getting over watered and the canes started to rot. Unfortunately, all three were unsuccessful. I think if we were to try this method again, we would use a different media composition and not allow the soil to get too wet.
The air layering method turned out to be the most successful of the three that we tried. This method is actually done on the mother plant itself. We started by soaking sphagnum peat moss for a few hours. This is crucial to keep the stem moisturized to allow roots to form. On one of the canes, we cut an inch wide ring through the cambium layer and removed the bark around the cane. Next, we took the soaked peat moss and wrapped it around the cut tightly and then wrapped it with plastic wrap and tied string around it to hold it in place. We did this twice more on separate canes. We recently cut the three successful air layered canes from the mother plant because roots had formed and they were ready to be potted up. We first soaked them before potting them to allow the peat moss to rehydrate. We put the new plants in five gallon containers and they are happily living in our greenhouse until they reach a more mature state with more developed roots to replace the ones at the Sally port.
The air layering method can be used for other woody shrubs and works well for some trees. This method does take a while to see some roots form, but once they do and it is cut from the mother plant, you already have a bigger plant than you would if you propagated it by seed or a cutting.
To replace the survivors, it is important that they are replanted with the same species of the current Cordyline. By propagating them by the methods we tried, it ensures that the replacements have the same genetic makeup of the current plants. We are very excited to have successful clones to replace the current failing Cordyline.