Paul James answers the following questions from viewers:
Q: I found this strange white stuff growing all through my bark mulch, with tentacles stretching several feet. What is it, and will it kill my plants?
A: What you discovered growing in your mulch is a fungus called mycorrhizae, and the white tentacles are known as mycelium. The good news is that this is great stuff. This fungus forms a symbiotic relationship with plant roots, which means both the fungus and the plants derive some benefit from each other. Don't try to get rid of it--just be glad it's there.
Q: Can I safely stick a new plant in an established bed without harming the root systems of the existing plants?
A: Of course you can. The technique you describe is called pocket planting, and it's a great way to fill bare spots--with annuals or perennials--in a bed that's full of plants. To avoid disturbing the root systems of neighboring plants, buy small plants in four-inch pots. They don't require a very big planting hole, and they don't cost much either.
Q: How do I keep cats out of houseplants?
A: My solution is to take a piece of galvanized screen or hardware cloth and cut it to fit the inside of the pot. Then make a straight cut to the center of the screen, and create a hole large enough to accommodate the trunk of the plant. Carefully fit the screen around the trunk, push it gently into the soil, and cover it with a light layer of potting mix or mulch. When your cat comes to do its duty, it'll naturally begin to scratch first. When it encounters a hidden screen, it'll head elsewhere, ideally to that ingenious device known as a litter box.
Q: I've heard you call some plants invasive. Is that a good thing or bad thing?
A: It's neither. Invasive is a term used to describe plants that spread quickly, either by reseeding or by sending out runners above or below the ground. It's generally thought of as a negative trait, but in some cases an invasive plant is just what you want. Suppose you want to cover a steep slope to halt erosion or need a groundcover to fill an area quickly. An invasive plant is what you need.
Some of the most popular plants can be considered invasive, including mints of all kinds, various ivies, strawberries and turf grasses such as Bermuda. Some invasive plants, such as golden bamboo and weeds, can create serious problems.
Q: How do you transform a solid hedge of shrubs into a more treelike form?
A: By pruning. The technique doesn't work for all shrubs, however, and once you've gone to the tree look, it may be hard, if not impossible to return to the shrub form. For example, take a row of privet. It is a rugged shrub that stands up to radical pruning. At the end of the row, the privet has been allowed to grow naturally, although it's been sheared to maintain a certain height. It's filled out nicely, and as a result creates a sort of living fence. At the other end of the row, the lower branches have been removed to expose the inner branches, which gives the privet a treelike form. It's simply a matter of taste; however, if you go from this to that and decide later that you want to go back, you might be out of luck. Think carefully before committing to altering the natural growth habit of any shrub.
Q: Is it okay to remove the lower limbs of trees, even if they're healthy?
A: Yes. This process is known as limbing up, and people do it all the time; however, limbing up can destroy the look of certain trees. I recently limbed up a stand of white pines because much of the lower wood was dead and I wanted a little more light to hit the ground below. I think the trees look better as a result. But I've seen people limb up big Southern magnolias, and I think it destroys their look. In the case of pin oaks, whose branches often hang to the ground, you can limb them up all you want, but sooner or later the lower branches will begin to droop again.
