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Garden Plot: Bagworms, wood mulch and artichokes

Friday - 7/25/2014, 9:35am  ET

Wood mulch equals worms, says WTOP Garden Editor Mike McGrath. (WTOP/Mike McGrath)

Summer's the wrong time to be trimming trees

Rich in Fairfax Station writes: "I help a neighbor lady who has a large river birch that's very close to her front door. She wants to remove some branches that are beginning to have an impact on her access. They are not small branches. When is a good time to remove them, and how should we seal the cuts to prevent disease from entering the tree?"

You are very wise to ask before cutting, Rich. Now through the beginning of winter is the worst time to remove healthy branches from a tree, especially one as magnificent as a river birch.

Pruning during the growing season always stimulates new growth, and during summer's heat, having to produce that ill-timed new flush of growth greatly stresses a tree. Pruning in the fall is even worse, as it prevents the tree from going into a natural dormancy.

Dead wood can — and should — be removed at any time. But removal of healthy limbs should be done in the middle of winter (the dormant period, when the tree is essentially asleep), or in the spring, when the tree is actively growing again and new growth is forming naturally.

Warning: If you try to remove a 100-pound branch all in one piece, it will swing around, smack you upside the head and break your shoelaces. It will also tear the bark directly below that branch section all the way to the ground.

That's why large branches should be removed in manageable sections, a foot or so at a time. When you are ready to make the final cut closest to the tree, locate the branch collar — which is the round structure where the branch meets the tree. You want to leave that collar on the tree when you remove the last of the branch, so don't cut flush to the trunk.

And nothing should be used to seal the cuts. Nature knows how to do that much better than we do.

"I am shocked, shocked, to find mushrooms on wood mulch!"

Vicki and Danny in Rockville writes: "All of a sudden we are having a huge problem with mushrooms around out shrubs, hostas, lilies and other plantings. The area is hardwood-mulched every year. Yes, we know that you say it's bad, but we've done it for 15 years and this is the first time we have had a mushroom invasion. Is there anything we can apply to eliminate them? The scene out there is horrible!"

So, let's see: You knew it was bad to use wood mulch, you kept using wood mulch anyway, something bad finally happened and now you're surprised?

The truth is that everyone who falls for wood mulch marketing will eventually get hit with a flush of mushrooms and/or other nuisance molds — some of which can cause severe (and expensive!) cosmetic damage to homes and cars.

Some people get hit with such problems the very first year they spread wood mulch, others get away with it for a decade or more. But sooner or later, the chickens — eh, fungal spores — will come home to roost.

For now, you can try spreading coffee grounds, lime or wood ash around the ‘shrooms to stop the spawning. (Don't yank them out. That spreads the spores.)

Coffee grounds supply nitrogen, while lime and wood ash make the mulch more alkaline — both of which help inhibit fungal growth. But don't use both — choose either grounds or wood ash/lime.

And, of course, the long-term answer is to switch to a mulch that isn't attractive to rogue fungus, like compost, pine straw or pine fines.

Wood mulch = worms (But not the good kind)

Dwight in Randallstown writes: "I recently changed my mulch to wood and now bugs have appeared. What are they and what should I do?"

The images Dwight sent show a severe infestation of bagworms on an evergreen. These clever caterpillars (every pest with the word ‘worm' in its common name is actually a caterpillar of some kind) live in small nests ('bags') that look a lot like the pinecones that appear on the plants they attack. So the ‘worms' often escape detection, sometimes while they're eating the evergreen to the ground.

Bagworms, and similar pests like tent caterpillars and fall webworms, often appear in response to stress, like feeding with chemical fertilizers or, ahem, mulching with chipped-up pallets from China spray painted some God-awful color.

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