Ask the Gardener: Mystery bugs, rhododendrons, ornamental grasses and more

Gardening editor Doug Oster gets asked a lot of questions. A lot. And he doesn’t mind offering gardening advice. But rather than just limiting those answers to the person who asked, we thought it might be a good idea to share that wealth of knowledge with everybody.

There are three ways to send in your questions:

• Email askdoug@535mediallc.com

• Submit your question on our “Your Garden” section of our site

• Send us a message on Facebook.

(The questions may be lightly edited for grammar/clarity/etc.)

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Green stink bugs

Rando: Any idea what kind of bugs these are?

Doug: My expert confirms those are nymphs of green stink bugs. I’m not sure they are the problem with that tomato, but they are a pest for the plant. I would handpick what I could get to by knocking them into a jar of soapy water.

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Rob: I have 3 red rhododendrons I bought two years ago. (I bought eight and only three are barely surviving.) They didn’t bloom this year, and they were blooming when I planted them. What can I fertilize them with before winter? I am hoping they survive and bloom next year.

Doug: First off, rhododendrons are best grown as understory plants, as they like a partially shady spot. They can grow in full sun when established, but it’s hard to get them started in those conditions. The best fertilizer for the rhododendrons is called Hollytone. You could add a light application this time of the year to help the plant, but you don’t want to force new growth this late in the season. Hope that helps.

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Bud: Are grasses still available at nurseries this time of year, and is it best to wait till spring for buying and planting?

Doug: This is a great time to find ornamental grasses at the nursery. You might even get a deal. Getting them planted now will allow them to get established, plus you get the bonus of seeing the plumes over the winter. Next spring trim them back and they will sprout again.

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Carol: My mom asked me to send these two photos of plants she has been unable to identify. They are both growing against the foundation of her house. She is concerned the first is a tree that could damage the foundation if allowed to remain in that spot. It has a white flower with a burgundy center.

Doug: That’s a plant called Datura or moonflower. It’s a pretty cool annual, which will be gone after a frost so no worries about the foundation. The flowers are fragrant at the end of the day. One thing to note is that the seeds are poisonous. They will be in a thorny seed pod.

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Jeannie: After Tithonia have bloomed, are there seeds in the center? Can they be kept and planted next year?

Doug: Yes, the flower head will produce seeds, and they can be saved to replant next season. The trick to saving seeds is getting to them right before the plant discards them. Keep an eye on the seed head. When it’s dry and looking downward, the seeds will be ready to be distributed. Store them in a paper envelope, and then put it in a an airtight jar, like one used for canning. It should be stored in a cool, dry place.