Thanks for your question David!
It’s very common for succulent arrangements to come with pebbles on them like you’ve described. I usually refer to this as a top dressing. Many times, a glue is painted on the top dressing to help the arrangement stay in place while it’s in shipment.
Sometimes these are actually water soluble and will wear off over time. But other times… they aren’t.
You don’t need to break up the pebbles if you feel confident you can get water to the roots of the succulent. Otherwise, I would try to loosen up the pebbles and allow some areas for water to flow down to the roots better.
Another point of concern for succulents that seem to be glued into place this way is they won’t have as much room to grow or spread out, and they can’t push up through the glue-down top dressing.
I talk more about how close to plant succulents in episode 13, and mention that if you don’t mind the arrangement staying about the same size for a while, keeping things tight like this is just fine. If you do want those succulents to get larger and spread out, breaking up the glue barrier on the top dressing will help.
Another problem with a glued down top dressing is lack of air flow. The layer of glue makes it much more difficult for your soil to dry out because it limits the air flow around your succulent’s soil. It’s kind of like having a lid on a container you put in the fridge. Nothing gets in, and nothing gets out.
If you start to water your arrangement with this glued-on top dressing and it doesn’t seem to wash away after a few waterings, it’s time to break it up and possibly take it off. The biggest reason for doing this is to improve air circulation to allow the soil to dry out more quickly.
As I mention in episode 4, succulents do not like to sit in wet soil for very long. So, if the glue on the top dressing is preventing air flow, it can cause your soil to stay wet for too long causing your succulents to rot.
I want to point out that having a top dressing on your succulent arrangement is not a bad thing. It’s mostly a problem if it’s glued in place and preventing water penetration. I use top dressings on nearly all of my arrangements, and they’re really awesome!
Let’s go over a few reasons why you might want to include a top dressing when you’re making your next arrangement.
First, it helps keep the soil in place while you’re watering. This is especially true if you’re not using the Bonsai Jack gritty mix that I mention in Episode 4.
Second, it can help enhance the colors in your succulents, or compliment them. Often, I’ll use a top dressing that includes subtle tones of the different succulents in my arrangement, helping pull all the elements together.
Third, it helps your arrangement look more professional and finished. All of the succulent designers that I’ve worked with use some sort of top dressing to complete their arrangemnet. The most common finishing elemetns include various colors of rock and moss. There are a lot of different things you can use, so you’re sure to find one that worsk fodr your arrangement.
Top dressings aren’t just for container arrangements either! My friend and succulent designer Laura Eubanks uses quite a few different types of rock for the various succulent landscape designs she creates. Covering up the soil beneath your succulents really improves the overall aesthetic of your design, and helps the succulent stand out and get noticed.