By JOE LAMP'L, Scripps Howard News Service

No doubt you've heard of at least one of the following: red imported fire ant, Japanese beetle or the emerald ash borer. They are exotic, invasive insects that are causing great harm in the United States yet rarely get noticed in their native land. Non-native, invasive pests are a popular topic of discussion in the fight to protect ecosystems and biodiversity.

There's a great debate going on these days about whether to have a lawn or not. In fact, a growing number of people across America are replacing their sod with low-maintenance ground covers, ornamental grasses, perennials or some combination of the above.

Recently I was in Baltimore to install another community garden for Fiskars, under its Project Orange Thumb initiative. The company selects sites in neighborhoods where poverty rates are high and urban blight is all too apparent, believing that community gardens can be the catalyst and inspiration for great change.

Throughout the year, one of the most common questions I get relates to the best time to plant or transplant trees and shrubs. My quick answer is that as long as the ground isn't frozen, you can plant any time, although you decrease your chances of success substantially if you don't do it in autumn; no matter where you live, fall is the very best time.

At some point, you've driven by or visited a house that just grabbed your attention the moment you saw it. I'm not talking about the look of the house per se. I'm referring to the overall good feeling you experienced as you took in the view. What you were enjoying was "curb appeal."

Thank goodness for community gardens. If it were not for them, some of us wouldn't have a garden at all. Yet, ironically, I know a few people who have plenty of space in their own home gardens but choose to spend more time cultivating a small plot of earth blocks or even miles away.

Every year about midsummer, I start getting a lot of questions from people wanting to know what those white or gray powdery spots are on their plants. They often cover most if not the entire leaf surface, plant stems, flowers and even fruit. Some of the most hospitable plants for this fungal disease known as powdery mildew include zinnias, phlox and hydrangeas.

Raise your hand or nod quietly if the following scenario applies to you: "My tomatoes are big and green on the vine, but they just don't seem to be getting ripe. They just sit there! What's happened?"

The one thing I like most about gardening is its challenges. It can put the best horticulturists and other experts on a level playing field with even the newbies sometimes. Reflecting on years of challenges, Thomas Jefferson, a passionate gardener, said, "But though an old man, I am but a young gardener."

I'm often asked: From where or whom did I acquire my love of gardening?