Ask the Gardener: Propagation, rhubarb, hydrangeas and more

Posted on: May 10, 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.

There are three ways to send in your questions:

  • Email
  • 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.)

Question 1: Shrub propagation

Patti: Can you root spring bushes such as lilac or forsythia by just putting it in water with maybe some fertilizer? If there are any other bushes please let me know as well.

Doug: It’s not quite that easy, but you can propagate shrubs through cuttings and other methods. Each plant is treated differently though. In the case of a lilac or forsythia, it would be easier to simply dig out some divisions. Taking cuttings though can be also done for both, but it takes a little investigation on your part to figure out when to take them and what to use off the plant as a cutting.

Here’s a very basic overview of the process, but again, you need to do a little more research for each plant you want to take the cuttings from.

Newer growth called softwood cuttings are usually easier to root than hardwood cuttings from older growth. Take the cutting from the tips of the plant. Remove a few lower leaves and dip the end that will be planted into a rooting hormone. I use moist vermiculite as the medium for rooting. It’s easy to find at any nursery. Place the cuttings (take a bunch) into the medium, and then cover the container with clear plastic to keep the humidity high. Put the container in a bright location that does not receive full sun. In a couple of weeks, gently pull on a couple of the cuttings. If they resist, they’ve rooted and can be transplanted to a container with a good growing mix.

You could have some fun and practice the basics by trying the technique with something like rosemary that roots easily, then move on to other plants. There’s a certain feeling of accomplishment when making more plants. Here’s a more complete overview of propagation in general.


Question 2: Rhubarb

Liz: My rhubarb is 2 years old. Is this what it’s supposed to look like? Will the stalks eventually turn reddish?

Doug: What’s happening here is that your rhubarb is flowering, called bolting. We usually see this in older plants or when the spring is unusually warm. You need to cut all the flowers off so the plant puts energy into the stems. They are still fine to eat but probably won’t produce as much as last year. Next year, get out there and harvest often and early. Watch for any signs of flower stems and remove them immediately.

Question 3: Hydrangeas

Janet: My hydrangea bushes have been totally decimated by the deer. They ate every remaining leaf and bud. What now? I am tempted to cut the entire plant back to about 3-4 inches and see what happens. It looks as though there is some growth coming at the base of the plant which I will be sure to leave intact. Unfortunately I do not know which type of hydrangea I have. Any suggestions will be much appreciated.

Doug: So your buds are gone, meaning no flowers this year. I’m assuming you are talking about H. macrophylla or another variety that blooms on last year’s wood. At this point all you can do is fertilize with a good organic granular fertilizer and then figure out a way to keep off the deer. They love hydrangeas and will continue to eat the buds. Spraying with Bobbex will work, but it must be applied religiously. I surround mine with deer netting for the winter to keep the four-legged pests from nibbling on them.

If you’re interested in planting a different hydrangea, take a look at Hydrangea arborescens ‘Annabelle.’ It blooms on new wood, so if the deer eat it in the winter, it’s no problem. I love a pink variety called ‘Invincibelle Spirit’ that has pink blooms, is indestructible and a portion of the proceeds goes to breast cancer research.

Question 4: Crown vetch

Connie: My problem is crown vetch which appeared last year growing among my hedges. I tried to pull it out and OUCH! I did not know it has tiny thorns all over: lesson learned! Now this year it began to invade my 70-foot long hillside which is very wild anyway. I spent a couple of hours pulling them out, but I hope they will not return. What can I put on the area that is not poison? I do not use it unless it is a last resort. The hillside is not used except for a natural fence which divides my backyard from the sidewalk below. There are crazy things growing there as well as an ancient apple tree! You wouldn’t believe what’s growing there!

Doug: First off I want to confirm that it’s crown vetch. As long as you’re sure it is, what I would do is just keep using a string trimmer on the area. Hopefully that will work to starve the roots and eventually kill the plant. It’s going to be a battle though as crown vetch is invasive. There are some organic herbicides like Nature’s Avenger and Burn Out that could help you, too.

Question 5: Grubs

Janet: Is there a safe way to get rid of grubs in the garden without hurting the soil or my plants?

Doug: There’s a great organic control for grubs. Beneficial nematodes can be applied to the soil, and they will hunt down the grubs without harming anything else. They are a leap of faith as you can’t see them. They are often applied by using a hose sprayer, but there are other ways to add them to the soil. The ground needs to be 50 degrees or warmer, so we’re getting to the the time that they will work. Many good nurseries have the nematodes, but you can also get them online through this link for Arbico Organics.

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Doug Oster is manager and editor of Everybody Gardens with a passion for gardening and a love of sharing is experiences with other gardeners. You will also find Doug’s gardening contributions in the Tribune-Review each week. He’s an Emmy Award winning producer, television host and writer. Oster is co-host of The Organic Gardeners Radio show every Sunday morning at 7 a.m. on KDKA radio in Pittsburgh. Oster’s Outstanding Documentary Emmy was awarded for Gardens of Pennsylvania, a one hour special he conceived and produced for the PBS affiliate WQED. Doug appears every Thursday morning on KDKA-TV’s Pittsburgh Today live at 9 a.m. “Gardening is fun, he says, enjoy every day spent outside tending vegetables, flowers, shrubs and trees.”