Q: I want to keep my potted dahlias for next year. Do I have to uproot them by frost, or can I just bring the pot inside instead?

A: I would uproot them. I would not recommend bringing them inside as-is, since it can be difficult to keep the tuber dry enough to discourage rot, but not so dry that it dehydrates and dies.

You can trim off roots and skinny tubers as soon as you dig the clumps out of the ground. You also can trim away the “mother” tuber, which usually has a rougher surface (and may even be shriveled or partially hollow), because it will not regrow.

Once dahlia tubers have been dug out of the ground, you only need to let them cure (air-dry) for a day or two. If you leave them out longer, they may begin to dry out too much and shrivel up. When you first dig out the tubers, the outer skin is very tender and thin — it can be easy to nick with a fingernail. When they are cured, the surface of the tuber is a little bit darker and tougher. Visually, the difference can be somewhat subtle.

There are advantages to rinsing off the tubers. This removes any clumps of soil that might be holding a lot of moisture and microorganisms next to the tubers – potentially leading to rot in storage. Rinsing off the clump also makes it easier to divide the tubers, if you plan to do so.

If you do want to take the opportunity to divide them, you could do that in fall or spring. Most commercial growers divide dahlias in the fall. The tubers are more tender and easier to cut when they are freshly dug, compared to being tougher and harder to cut after winter storage. Plus, dividing the tubers in the fall can make it easier to store them.

The American Dahlia Society has instructions online for dividing tubers and includes various options for winter storage in their article “Digging, Dividing, and Storing Tubers.” They also have a guide demonstrating how to process (rinse and divide) tubers.

Q: A few weeks ago, in bare soil near a public garden pond, I saw a few of what looked like bumble bees coming and going into several ground burrows. I thought they used one communal nest. What type of bee might they have been?

A: I saw this same phenomenon at a park in Washington, D.C., this summer, so I just learned about them myself. With hundreds of native bee species in Maryland, it’s easy to keep finding new-to-you species. These sound like the hibiscus bee (Ptilothrix bombiformis), also known as the hibiscus turret bee or rose-mallow bee. They pollinate our wild hibiscus, a resident of sunny wetland areas, and other members of the mallow family (Malvaceae).

They are indeed solitary bees, but as with other species of solitary bees, they can still form aggregations and be observed in groups, as multiple females choose the same nesting area that suits their needs. Several burrows might be very close to each other, even if the individual bees aren’t helping each other out the way they would in a single social nest (as with bumble bees). This also means that solitary bees are not going to defend a nest like social bees defend a shared home, so they aren’t inclined to sting.

One of the telltale indications of hibiscus bee activity is the pellets of soil they eject from the burrow, which lie scattered around the tunnel entrance. A turret can also be present, though sometimes weather or walking on the path disintegrates them.

This is one example of a native ground-nesting bee that uses areas of bare soil. While it’s a recommended gardening practice to manage erosion and suppress weeds by keeping soil covered with plants or mulch, portions of exposed ground can be important components of a habitat.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Extension” to send questions and photos.