How to keep plants a cut above the rest

Now is the time in the gardening season that the violas and pansies are looking a bit ragged and stretched. So to continue on the theme from last week, let’s get down to disbudding and deadheading these flowers and other varieties of plants, vegetables and fruits.

Flower varieties

Your violas and pansies will bloom all summer as long as they are growing in a spot where they are protected from afternoon sun and the spent flowers are pinched off religiously. Better yet, give them a hard pruning, removing about half their growth, and they may rebound with surprising vigor.

Note, there is a downside here to deadheading some plants. I depend on my violas to self-seed between the cracks in the pavers on my walkways and patios. If I continue to disbud them, they won’t drop seed and the number of returning plants will thin out.

Other annuals, such as cosmos, salvia, snapdragons, zinnias and non-hybrid marigolds and petunias, as well as geraniums—especially the hanging types—will also perform at their best if they are deadheaded regularly and not permitted to set seed.

Remember though, F1 petunia hybrids are often sterile and it’s not necessary to deadhead. Conversely, if the plants are not hybrids and are allowed to drop seed, you can find your patio, garden beds or peastone driveway covered with petunia seedlings the following year. This can be a very interesting effect, but it can also drive the anal-retentive type of gardener to become suicidal.

Perennials like lupines, foxgloves and delphiniums may (may being the key word) also rebloom if deadheaded. In the case of delphiniums, they may even try to rebloom again in early fall. But it’s my experience that delphs that are encouraged to flower late in the season are the ones most apt to overwinter poorly.

Digitalis, more commonly referred to as foxglove, allowed to fall to the ground and not get covered by soil or garden debris can result in these plants self-seeding. But lupines will germinate only if the seed is buried below the soil.

The practice of cutting back is probably best demonstrated with catmint (botanical name nepeta). This perennial will bloom prolifically through the spring and early summer. The taller varieties do tend to get leggy and will eventually topple over or cascade into a stringy tangle of fragrant but untidy foliage if not disbudded.

Get out the shears or scissors when this happens and cut the plants back to 6 to 10 inches above the ground. Several weeks later, the plants will fill in again and rebloom, though this bloom will not be as heavy as earlier in the season. If left unpruned, this perennial will also self-seed and show up next year in the lawn and garden. Gaura and aegopodium can be handled the same way.

The most common example of plants that benefit from disbudding are perennial chrysanthemums (genus dendranthema). From the time they first set buds until the Fourth of July, the buds can be pinched or rolled off. This encourages bushiness and masses of flowers instead of leggy plants with few flowers.

Keep in mind that commercial nurseries accomplish this with chemicals that stall the formation of the buds, and many of the newer varieties claim not to need deadheading. But in the home garden, disbudding is preferred.

Deadheading will delay flowering for perennial chrysanthemums. So, if you have been in the habit of seeing a particular mum bloom in the end of September, and you disbud it this year, don’t be surprised if it blooms later.

Mums are also very sensitive to day length and some of mine grow in partial shade. I disbud them to keep them tight. And while the shade makes them want to bloom earlier, the deadheading makes them bloom later. Warning, disbudding of mums too late will simply result in no flowers at all.

Those who grow mums and tuberous dahlias for show and competition will disbud the stems so only one bud is allowed to develop. The result is a single flower that is much larger.

And then there are the roses. Since there are just over a zillion books on rose care, I’ll be brief.

Most roses, save for the rugosas, benefit from deadheading as it encourages the formation of new flowers. And when the deadheading incorporates light pruning, it also encourages several buds to develop at the same point.

For those who grow show roses, when two to five buds appear at the same spot, all but one is removed and the remaining bud then develops into a large specimen flower as opposed to several smaller and less significant flowers. This practice is also common for specimens and stems that may be cut for indoor vase use or exhibitions.

Once a rose has bloomed, the flower should be removed. Again, the rugosa roses are the exception where most want the colorful hips to develop for late summer and fall color.

It’s critical to use the proper pruning tool (the best is a cross-cut hand pruner such as a Felco). Next you need to know where to prune and how much. Cuts always should be made at a 45-degree angle and about ¼ inch above a leaf set.

At this point in the season you need to look at the cane the faded flower is on and go down the cane until you can find a leaf set that has at least five leaves on it. Make your cut just above this leaf set. This information is basic and somewhat oversimplified, but it will get you started until you can read up a bit more.

One thing to remember is that roses should not be pruned after late August.

Vegetables and fruits

If disbudding works so well, why not use it on vegetables and fruits? To some degree we can and the principle is the same. If you remove one or more of several flowers, the fruit or vegetable that develops as a result will be larger. Sometimes. However, know that disbudding a cherry tomato plant will not cause the remaining buds to develop into Beefsteak-type tomatoes. Disbudding doesn’t change genetics, it allows the remaining to grow to a full potential.

Having said that, I know gardeners who will remove some of the flowers on zucchinis and cucumbers so that fewer and better fruits will develop. This is also a common practice among those who try to grow competition-size pumpkins.

Fruit trees are often thinned either manually or chemically so that fewer, but higher quality, fruits develop.

And among herb growers, cutting back the early growth of a number of herbs results in bushier, more productive plants with more foliage. While this is more akin to pruning, it’s usually just considered cutting back.

It’s a bit late for some of the plants we’ve discussed, but take a walk around the garden to see what you can work on now and make a mental note of what needs to be done earlier next year.

No matter what you do, don’t remove next year’s buds that are now forming on shrubs. And of course, keep growing.

Andrew Messinger has been a professional horticulturist for more than 30 years. He divides his time between Southampton, Westchester and the Catskills. E-mail him at: Andrew@hamptongardener.com. The Hampton Gardener is a registered trademark.