Growing Piper methysticum
Growing Kava Kava
Natural Growing Conditions
Piper methysticum is a slow-growing, vine-like perennial shrub from the Pepper family. Native to the Pacific/Polynesian Islands (eg. Fiji, Samoa, Tonga, Papua New Guinea), it grows best between 300 and 500 metres above sea level. It can reach a height of 7 metres (23 feet), although I height of 3 metres is far more common.
Methods of Propagation
Piper methysticum is not grown from seed as its flowering parts are usually sterile. The most common means of propagation is division of the root-mass, or removal of offsets from the root-ball of the plant. To perform a division, remove the plant from its container, remove excess soil and split the root-ball up in appropriate looking places. Removing offsets is a little simpler as obvious looking offsets need only be pulled off the edge of the root-ball.
Piper methysticum may also be propagated via greenwood nodal stem cuttings in Summer. Remove cuttings with a sterile blade from this year's growth (if firm or greenwood) and pot up in a rich but open potting mixture (a 50/50 mix of organic compost and vermiculite or coconut coir would be ideal). The cuttings will need to be placed somewhere warm (20°C - 25°C or 68°F - 77°F) and humid; ideally in a heated propagator.
Piper methysticum requires a very rich soil mixture as it soon depletes poor soils of their nutrients. Large amounts of humus and well-rotted horse manure are ideal. Alternatively, a good quality organic compost can be used. The addition of small amounts of chicken, pigeon, goat or other animal fertiliser will not harm the plant. The soil mixture should also be quite open (containing a lot of air space, not compacted), particularly of root mass production is required.
Potting and Repotting
For maximum root growth, a large container is required. However, a small plant should not be placed directly in a huge pot; several repottings over a period of years would be more suitable (as it is with most other plants). These plants should be repotted annually for the first few years and less often thereafter. A good soil mixture would be a 50/50 mix of rich organic matter and grit (or coir).
General Growing Requirements
As Piper methysticum is a tropical shrub it requires tropical conditions to grow in. In the temperate zones it should be kept in the greenhouse or conservatory throughout the winter months at least. For optimal growth it should be grown under glass/plastic all year round (like it's tropical Pepper relatives). In tropical and sub-tropical regions, it can be grown outdoors all year round.
If you are growing this Kava Kava in the greenhouse/conservatory, regular pruning (just above a leaf node) will help keep the plant compact and bushy and stop it outgrowing its surroundings.
Although Piper methysticum likes a lot of humidity and regular, deep watering, it should never be left standing in water, or watered so frequently the soil becomes sodden. Too much water will damage the fine root hairs and retard growth.
As with most other plants, a good method of discovering your plant's water requirements is to only water once the plant begins to wilt. You can use this timespan as a guide to the plants water needs; watering just a little before you expect the plant to begin wilting.