Q: I think that I am growing a different kind of petunia this year. The stems are trailing across the ground, and I want to trim them back. How do I know where to cut? I am afraid that I will prune at the wrong place and cut off the spots where the petunias are trying to grow new flowers.
A: Not to worry. With petunias you can't make a mistake. First decide how much smaller you want each plant to be. Then, working on one stem at a time, hold the stem with one hand and cut it off at what seems like the right place. Prune your way around the plant until all the stems are shortened. If any stems still seem too long, cut off another piece. If any are too short, don't fret. Within two weeks they will have grown a few inches.
It is true that there are several kinds of petunias. Some have fewer big flowers. Some have many smaller ones. There are also first cousins of petunias, native to Australia, which bloom with hundreds of miniature flowers. Some petunia varieties lengthen their stems quickly and are thus especially good in hanging baskets. All petunias make flowers in the same way. As each stem grows longer, new flower buds develop at the tip. Throughout the summer the green center of the plant expands; the fringe of flowers moves farther and farther out. Whether a petunia is planted in the ground or in a container, it is by this time a straggly looking creature. It needs pruning if it is to look good until fall.
It is true that every pruning cut on a stem removes the tip where new flowers would have grown. The magic of petunias, though, is that those cuts allow the plant to make new tips. Just inboard of the pruning cuts, at the base of leaves, are spots where new branches will start. Some petunias branch more easily than others; a really skilled variety may already be starting new tips before the old ones are removed. But every kind of petunia will make new flowers at new tips. There is no easier plant to prune.
The branches removed will make good cut flowers, lasting in a vase for several days. Tips can even be rooted in potting soil to make new plants for the late garden or for indoor winter flowers.
Q: We are calling this the Year of the Basil. Why is this year's crop so much bigger than usual?
A: Your basil is a good example of gardening being a mixture of art and science. If every gardener planted exactly the same things at exactly the same time in exactly the same place, results would still vary wildly from season to season. Gardens are not laboratories. There are a huge number of variables in the gardening equation, most of them beyond the gardener's control.
Weather certainly can make or break a garden crop, but it is not a simple issue. Careful experiments were carried out in England a few years ago, to determine whether weather really mattered to garden plants. The answer was unequivocally yes, but the biggest weather effects showed up not in a day or so, not in a week or so, but three months later. If you can remember what the weather was like in the middle of May, you may understand better the success of your basil.
Q: When is the right time to cut off some of the leaves on huge tomato plants?
A: There is no right time unless you are trying to grow tasteless tomatoes. The sugars in a tomato mix with the natural acids to produce the complex tomato flavor. Since the leaves manufacture 80 percent of those sugars, to cut off leaves is to cut back on the flavor of the tomatoes to come.
Master gardener Molly Hackett, whose motto is “Never trust a gardener with clean fingernails,” welcomes your questions. Send them to 1384 Meridian Road, Victor, MT 59875; call 961-4614; or email email@example.com. Please include a garden-related subject line in emails.