Topdressing a container garden means that you put something on top of the soil to cover it. There are several different reasons to topdress your container garden. The primary reason is aesthetic-it often simply looks better if you cover exposed soil in a pot, in fact it can make the difference between a mediocre container design and one that really sings.
The second reason to topdress is that it can act the same way that mulch does--helping to retain moisture in the soil, because there is less soil surface area exposed so that there is less evaporation. The good news is that lots of topdressings can have the advantage of helping to retain moisture as well as look good.
Covering your soil with a topdressing can also help keep your soil in your container when watering, or in a heavy downpour.
Common topdressings include:
- River stones
- Tumbled or crushed glass pieces
- Spanish other moss
- Low growing succulents, likehens and chicks
- When topdressing be sure to keep your topdressing material away from the crown of your plant.
- If you use black stones, or any other black material, it will retain heat and raise the temperature of your soil. This can be a good thing if this is your intention, but if you have a container in full sun in a hot area, it can create too much heat.
- If your soil becomes too wet, you might have to remove the topdressing so the soil can dry out more quickly.
- Don't use more than an inch or two of topdressing and less if your goal is just to hide the soil.
A great article on using crushed glass as a topdressing, by the queen of succulent container gardening, Debra Lee Baldwin...Bling for Pots: Crushed Glass