I have purchased new planters with a water reservoir system(Mayne brand). YouTube has suggestions for filling the cavity with a first layer of chunky pine bark mulch, then potting soil, lastly more pine bark mulch. My Lantanas will be living in these year round, being overwintered at a garden center. My concern is, will the pine bark mulch have a negative effect on the lantanas? I believe this medium is suggested to help with the uptake of water from the reservoir. Is there a better medium to use instead of the pine bark mulch ?
Thank you for posing your question to Toronto Master Gardeners.
The genus Lantana, commonly known as lantana, includes more than 150 species in the verbena family. Lantana prefers a well-drained, loamy, slightly acidic to neutral soil.
The pine bark nuggets in the YouTube video are quite large, so would allow for drainage, as well as allowing the roots to reach the water in the reservoir. Smaller nuggets will provide better water retention.
Larger nuggets will be slower to decompose and thus will last longer at the bottom of the planter than other types of organic mulch.
Pine bark is slightly acidic, which may or may not be an advantage, depending on the pH of the potting soil.
Pine bark is a natural product compared to inorganic fillers such as broken up Styrofoam or lava rocks. Depending on the amount of filler needed, weight may be a consideration.
As for covering the potting soil in a planter, the size of the mulch is mostly a matter of taste.
When using a water reservoir it is important to water in the conventional manner until the roots reach the reservoir and to decrease watering during the winter months.
Hopefully this will help you decide on a suitable product.