To Cut or Not to Cut?

Lee ArmilleiField Notes

So your landscape is filling in, and it looks simply gorgeous, but for how long will it last? Often the key to maintaining a healthy, vigorous garden is actually to cut it back. Pruning and dead-heading allow you to promote the kind of growth you want to see and manipulate the plants for their best features. To get started, let’s distinguish between some general pruning terms:
 

Prune: Selective cuts made using a sharp tool to select locations on a woody tree or shrub.

Pruning is done to remove dead wood; alter the shape or size of the plant; allow more air flow through the plant; or to encourage a specific branching habit.

Cuts are typically made above a node on a branch or stem, which encourages more branching. Some branches are removed at the branch collar to remove the branch or stem entirely.

Dead-head: Remove spent (wilted) flowers from annuals, perennials, and occasionally shrubs.

This is done to prevent the production of seeds after flowers. Plants require a lot of energy to produce seed and will pull that energy away from other desirable traits, such as more flowers. To prolong the flowering display of your favorite plants, pinch or prune the flowers off of the plant.

In some plants, such as herbs, the desirable trait is the foliage. In those cases it makes sense to pinch flowers off as soon as they begin to develop so that energy goes into foliage (flavor) production.

Dead-heading is most often done to perennials and annuals and only requires a pinch between fingers to remove the flower. Removing flowers from woody plants may require pruners.

Cut-back: To “cut a plant back” means to take the whole plant down to just a few inches. If it’s a shrub, it’s usually cut down to ~12-18” depending on the shrub. Perennials and grasses are usually back to only a few inches above the ground.

The cut-back method is best done in late winter. The plant is still dormant then, but is getting ready to flush out new growth. This way you’re left with bare, boring space for the minimal amount of time.

Shearing: Shearing is a method of cutting all of a plant to one plane, regardless of where the branches “should” be cut. Often, you’ll see boxwoods, cherry laurels, or privet sheared into shapes like spheres, boxes, or other shapes.

Shearing provides a neat-and-tidy look immediately after a skilled horticulturalist makes the cuts, but unfortunately the whole plant doesn’t grow at the same rate after that cut, so those same shrubs are often left looking raggedy after just a couple of weeks unless the plants are sheared again.

 

Basic pruning principles

Whether you’re pruning, cutting back or dead-heading, the best place on the plant to do it, is almost always above a leaf or leaf-set. You will typically encourage additional branching from that point, which is usually a good thing, but keep in mind you may not want branching there.

If you’re not sure of the best time to prune a plant, immediately after flowering is usually a safe bet. Many do very well with a late-winter or early-spring pruning, however, you can ruin the floral display of quite a few species if their “old-wood” is cut or their buds are removed. If you had minimal Hydrangea blooms over the last few years, nature pruned that “old-wood” for you the last two very cold winters.
 

Common plants to cut back in the summer and why

  • Pruning HydrangeasHydrangeas: Specifically Big-leaf Hydrangeas (Hydrangea macrophylla) require old-wood to flower. So while it may be tempting to remove those “straws” left on your hydrangeas each winter, those are actually necessary for flowers to be produced. Now and over the next few weeks is a great time to prune hydrangeas; the plant will still have enough time to produce new stems, which will harden into next year’s old-wood.

Cut off select blooms back to a leaf-set. How heavily you want to prune determines how far back to make the cut. The best part is, you can bring those cut blooms inside to display in a vase!

  • Lavender: Lavender is often pruned in the early spring to remove any dead branches that did not survive winter weather. However, your lavender plants should be doing well right now (if they’re in proper growing conditions) and you may want to shape them into more attractive mounds.

Summer Pruning Lavender

Cuts should follow the flower down and be made into the green, fleshy tissue, not the wood at the base. Prune to the shape desired and then use the cut lavender stems rather than composting them. Stems can be tied together and dried indoors and then used for decoration or to make lavender sachets.

  • Deutzia: This non-native shrub is commonly found in the landscape, but improper pruning can result in a lost floral display over the summer. To maintain a more attractive habit for Deutzia and still have flowers every year, the shrub should be pruned immediately after flowering, which is right about now!

Depending on how many shrubs you have, you can either hand-prune each one by gathering a handful of stems and using pruners to prune sections at a time, or you can pull out the hedge-trimmers and get a whole lot done fast! The sooner you can do this after flowering, the longer stems have to re-grow and provide the old-wood needed for a floral display next year.

  • Cut back RudbeckiaRudbeckia: This native perennial can go gangbusters in the garden! However, depending on the species or cultivar of your Black-eyed Susan, you may get the whole display in just a few weeks. Extend your bloom time of Black-eyed Susans by pruning approximately 1/3 of the mass back earlier in the season; the second third back around now; and don’t prune the final third. This will result in the pruned sections blooming later than the unpruned sections with an overall longer bloom time. You can also try this with other perennials such as coreopsis or daisies.
  • Mums: Mums or Chrysanthemums are typically treated like annuals in this area. Growers shape and prune them to bloom anytime from September through Thanksgiving and that’s when most of us buy and plant them. However, mums are hardy in the Greater Philadelphia area and will come back year after year. Cutting them back now can reward you with fuller plants, more flowers, and a later bloom time.

July fourth is the date to remember for cutting back mums, so if you haven’t cut them back yet, get out there this weekend! You only want to cut your mums back by approximately 1/3- if you remove too much, you can stress the plant. Cut the top one third off of the plant, each stem back to a leaf-set, and prepare to double your blooms! Just like the suggestion for the Rudbeckia, try just cutting back some of the stems, and you may end up with blooms for a much longer season.

  • Pruning BasilBasil: One of my favorite herbs, not just for flavor, but also for its prolific growth habit, is basil. It is an annual, so it won’t come back year after year, but with intentional pruning practices, you may end up with a bush of Basil that could last you for years in your culinary efforts.

Most people know they are supposed to dead-head their basil plants. The reason for this is that a lot of energy goes into flower and seed production- energy that takes away from producing the desirable leaves of the plant. Soon after you plant your basil, start pinching the stems back, immediately above a leaf set. At each pinch point, two new stems will grow, creating a bushier habit. I pinch my basil back even if I’m not ready to use it, and the pinched stems last for a week or more in a bud vase on the kitchen counter- rarely a week goes by where I don’t use my pinched basil!

 

Remember, this is your garden, so have fun with it! Try different pruning techniques each year to see what works best for your property. Using the tips above, or any combination of them, you can shape or prolong the bloom period of many of the plants throughout your property. If you’ve tried something new and cool, share it with us on Facebook!