Ask The Gardener: Changing rose colors, tomatoes, caterpillars and more

Posted on: May 31, 2019 | Written By: Doug Oster | Comments

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.

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

Question 1: Changing rose colors

Michele: We have had the Yellow Regular Rose Bush for five years and always had beautiful roses as you can see in the one picture of my 92-year-old mom by them. As you look at the other picture, that’s where the mystery lies and thought maybe you could answer what the heck happened? There are now what looks like red knockout roses along with my normal yellow rose growing. If you could please explain what happened or what we did wrong, we would greatly appreciate it.

Doug: Here’s what I think happened. Your yellow rose is a grafted variety. That means a tough rootstock was used and the pretty yellow rose variety was grafted on top of the rootstock. The rootstock has sprouted, and those are the rather unspectacular red flowers. Take a look at the bottom of the plant and see if you can see where the two plants were joined. Sometimes when the graft union gets buried, the rootstock will sprout from below or sometimes just send up suckers. See what’s happening underneath and let me know, we’ll go from there.

Question 2: Tomato 101

Mary Beth: I made a spur-of-the-moment decision and purchased a small ‘Red Deuce’ tomato plant. It’s about a foot tall and has drawn comparisons to Charlie Brown’s tree. Questions about making my plant a success in the backyard (where we have a dog that “waters” everything, wildlife and a mix of sun/shade:

Can I plant it in a container rather than the ground? (If so, how big should the container be?)

Should I stake it or place a metal cage around it?

Should it be in full sun?

Do I need to worry about anything eating it?

Doug: ‘Red Deuce’ is a great, early variety that’s known for high productivity and great taste.

If you’re going to go with a container, it should be able to hold 10 gallons. The trick about growing tomatoes in pots is to make sure they never dry out. If they do, the tomatoes could get blossom end rot. When the plant can’t uptake calcium (that’s usually in the soil), they will form a black spot at the bottom of the fruit. I like something called an Earth Box or another type of self-watering container for tomatoes. They have a reservoir at the bottom and as long as that’s full the soil can’t dry out.

The plant will need support regardless of growing in a container or out in the garden. A cage is easier than staking, but both work well.

If it was me, I’d find a spot in the garden, fill the planting hole with compost then plant the tomato. Water it in and then mulch with something like straw. Surround the plant with a big cage, mine are five feet tall and the tomato will outgrow that.

Feed your plant Tomatotone or another organic fertilizer like Grow once a month.

Full sun is best, but tomatoes can grow with as little as six hours of sun.

Deer will eat tomato foliage, so the cage also keeps them off the plant.


Question 3: Caterpillar and bees

Daniel: I took a picture of this caterpillar on my rose; should I be worried? Also I have 4-6 large bees outside my shed every day, how do I tell if they are safe or harmful, as my aunt thought they’re carpenter bees?

Doug: Yes, that caterpillar could be a problem. There are very small caterpillars called sawfly larvae that will defoliate roses. I would hand pick what you can see, and if you start noticing some chewing damage that you can’t keep up with, Captain Jack’s Dead Bug Brew is an organic solution. (You can get that here.)

Carpenter bees look a lot like bumblebees. Take a look at the shed and see if they are making holes in the wood, that will answer your question.


Question 4: Rhododendron issues

Debbie: I was happy earlier this year to see the many buds on my rhododendron and fed it Hollytone in mid-April. But I only had a few flowers and for some reason, the majority of the buds did not open up. They also seem to have a powdery mildew on them. What could have caused this and how do I prevent it next year? I already deadheaded them.

Doug: It’s hard to know specifically why some buds did not open. I would continue fertilizing with Hollytone, with one more application in late summer. Put about half of what you did in the spring.

Powdery mildew can be a problem for rhododendrons. Apply an organic fungicide like Serenade (available here) every few weeks until we get into hot dry weather.

Question 5: Dogwoods

Greg: I’m a little concerned about one of my new dogwoods. I think I know that the leaves are generally curly, but there are some spots that are particularly curly. And they feel drier. Not crispy yet but not as fresh feeling. We’ve been watering them. Not enough? Too much? Some other issue? Any ideas?

Doug: Sounds like leaf scorch to me and if that’s the case, nothing to worry about. Young trees often look this way as their root system has not developed, which can take three to five years. I would recommend to water it once a week when rain is scarce and add a good layer of mulch. Never let the mulch touch the trunk of the tree — it should look like a doughnut, not a volcano.

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