To Prune or not to Prune? That is the Question of Summer

We’re smack dab in the season of very bad pruning decisions! Mike McGrath, host of You Bet Your Garden, will answer questions about a hornbeam, a magnolia and some very unhappy fruit trees. Plus: Mike speaks with author Ken Druse about why shade is important in the age of climate change and your fabulous phone calls!

Photo: Pat Sullivan via AP Images

Question of the Week:

“When is the best time to trim a Magnolia tree? I have one whose branches are drooping down to the ground and the tree’s profile is uneven. Can it be trimmed without hurting it?”

— Marcus in Clarksville, Tennessee

Learn more about pruning trees in summer »

Highlights from show:

Loosestrife Finds a Way

Margee from Collegeville, PA heard a call a few weeks ago about propagating Purple Loosestrife and she had a few comments about this invasive plant. First of all, the sale of purple loosestrife is actually illegal in many states, as it has a tendency to push out native plants and generally disrupt the local ecosystem, however in some states it is still legal to sell a “noninvasive” or sterile variety of loosestrife. Unfortunately, as Margee notes, “sterile” only means that these cultivars aren’t capable of self-pollinating or even pollinating with other loosestrife plants of that same cultivar. Meaning that while these plants do produce seed, if that seed was pollinated with pollen from that same plant, or one of its many brothers and sisters, that seed won’t be viable. It’s not capable of eating its own tail, so to speak. However, when crossed with other varieties of loosestrife, or really with any other genetically compatible plant, they can, and very often will, produce viable seed, and they become just as invasive as its relatives. Mike notes that she is not the first person to call us about the loosestrife problem, only the nicest to do so. Mike had thought that the original call was interesting because he had never heard of a noninvasive cultivar of this plant and gave his advice assuming theoretically that the variety was indeed noninvasive. But Margee notes that she thought he’d handled it well with his warnings, as Mike had taken the same stance as Jeff Goldblum in Jurassic Park. “Life will not be contained. Life breaks free. It expands to new territories. It crashes through barriers, painfully and maybe even dangerously. Life finds a way.”

Raised Beds

Bill from Clinton, NJ has been a flatland gardener for quite some time, and in light of his weed problems this year, he’s decided to build raised beds. He wants to know what sort of stuff he should fill them with. Now, in terms of construction, Mike gives the following advice:

1. Till the soil one last time. This will bring weed seeds to the surface, but there are ways of taking care of that.
2. Construct areas no wider than four feet, but as long as you want. Mike recommends 4×8 foot beds, as they use standard sizes of lumber, and they’re easy to walk around.
3. Make sure you have two-foot walking lanes between the beds.

Now, when Mike first built his raised beds, he discovered that with all of the soil he pulled out of the lanes and with all of the hoeing he had done, he had more than enough soil to fill the beds. His soil also didn’t need much lightening at first, but it’s never a bad idea to add perlite to lighten. “You will never regret that you added a lot, especially when we get really rainy times.” If times are dry, you should be watering your raised beds. Now that your soil is ready, the weeds will begin to emerge. Now, about two weeks after building the beds, get a really sharp hoe and gently slice off any plants that grow up out of the beds at the soil line. “That’s about 95% of all the weeds that’ll emerge in these raised beds.” And since you don’t step in the beds, you don’t ever need to plow them ever again. “You’ll just add an inch or two of fresh compost, every year, maybe mixed with more perlite.”

Featured Interview: Ken Druse

Mike speaks with Kyla Kruse, Communications Director for the Energy Education Council and she gives us some great tips on what kind of tree to select and how far to put it from power lines. When you are selecting a tree to plant she stresses thinking about how tall it will be in 10 years or 20 years and imagining what objects it might impact near by. Also don’t forget to check whats in the ground before you dig.

Zucchinis and Cucumbers

Sean from NW Pennsylvania has grey leaves on his zucchinis and cukes. Now, the cucumbers are growing on the ground, so Mike recommends that he give them some kind of structure to support them. If these plants are growing on wet ground, they’ll stay wet and get moldy. He recommends getting a tomato cage, or some kind of fence, or even just putting in a trellis. Anytime a plant is called a vine, that means it should get some sort of support, which mimics its natural state. The zucchini, on the other hand, are bush style, and they’re growing close together. Mike says that he spread them apart a bit. “I know this seems counterintuitive, but you’ll get more fruit and better fruit from four plants in a raised bed that have a lot of room in between them than eight or nine plants all jammed close together.” And this is for the same reason as the cucumbers. There needs to be a lot of air flow between the plants so that they can dry off, keeping them from rotting. He further recommends going in and pulling off any grey leaves before taking a closer look at those zucchini plants, determining which ones to keep and which ones to lose. “The more air you get around the plants, especially underneath the leaves, the better you’re gonna do in a wet season.”

Rhubarb Plants

Lillian from State College, PA has a couple fifty-year-old rhubarb plants that are growing quite well, with very thick stalks, but they are growing some tiny spindly stalks. She’s wondering if she has to transplant them. Now Mike doesn’t personally grow rhubarb, but he says that it’s an interesting and unique plant. For instance, there are dozens of fruits that we eat as vegetables, but rhubarb is the only vegetable we eat as a fruit. Mike could tell right away what was wrong the minute she told him how old it was. Every five years, the root system will become so internally crowded that production just drops off. What you need to do is, in the spring, or even in the fall, dig up the entire root, cut it up into pieces, then replant those pieces. “With a smaller plant, we would divide it maybe by pulling it apart with garden forks. This may need a chainsaw.” After all, this is a fifty-year-old plant. These sections should be planted in loose ground, up high. And then, in the spring, it won’t hurt to feed them with compost or worm castings, or even well-composted horse manure. After all, rhubarb is a nitrogen-loving plant. Just make sure that the manure no longer smells, and has no heat, as fresh manure is too weedy. “You’re gonna have tons of rhubarb. People are gonna be coming by to take it off your hands to make delicious rhubarb pie.”

Disappearing Cucumbers

John from Germantown, PA has a large raised bed garden, and in that garden is growing all sorts of things, including cucumbers. One day he went out and say five little cucumbers growing out there, but the next day, he saw they were gone. A few days pass, and this keeps happening until one evening, he sees a big fat field mouse running off with his cukes. Mike recommends that John go out and get a material called hardware cloth. It’s much like window screening, but made of thicker more durable material. Cut it to fit over your garden, sink it into the ground around the outside, then bend the tops out as a baffle, making a structure not unlike a barbed wire fence. This keeps them from scaling that tiny little fence. Mike also recommends a new style of mouse trap called “Rat Zapper.” Mice go in, and they don’t come out alive. “One or both of those is gonna be your answer.”