Cutting Back your Plants in June
There are many perennials that we grow in our CT gardens that benefit from cutting back in June. We used to call this "pinching" but in reality we are cutting a fair amount off of each plant- pinching has always meant nipping out the tip of the new growth.
Why do we do this?
The first and most important reason is to cause plants to branch at a lower height and NOT NEED STAKING later in the summer or fall. This is such a time saver!
When you cut back a plant, you set back its bloom time by about 2-3 weeks. Take this into consideration when you are planning succession of bloom in your gardens.
Avoiding staking plants is only ONE benefit of cutting back many of your perennials in June. Cutting back in stages will also prolong the bloom time (double or triple it) and will often hide the unsightly part of the plant after blooming.
This is one of the most exciting advanced maintenance techniques a gardener can learn.
The concept is to create a layered effect. The back ½ of the plant is left alone to grow to its normal height and bloom at its normal time. The front half of the plant is cut back by 1/3-1/2 in May or June, at the latest early July. The exact time of cutting back depends upon how quickly the plant grows and what time during the summer or fall a plant blooms. Early bloomers such as Shasta daisies (Leucanthemum), bee balm (Monarda), and yarrow (Achillea) are cut back in Southern Connecticut in May as the growth is elongating but before the buds are setting. Late bloomers such as asters and mums can have the front half of the plant cut back as late as early July. The result is that the back of the plant blooms first at its normal time. The front (pinched or cut back) half of the plant then begins to bloom 2-3 weeks later. As the back half is finished, it can be deadheaded, it will be hidden by the blooming front half. This doubles the bloom time and serves to detract the eye from the dying flowers and declining foliage of the back half of the plant.
Shown above is Eupatorium 'Little Joe'. The left picture shows the plant after cutting back. The picture on the right shows the result in late August. Note the big flowers on taller stalks in the back and the smaller flowers on shorter stalks still to bloom in the front. This is a good example of layering and doubling the bloom time.
- This technique can be applied to a plant in three stages as well, which will triple your bloom time. Just be sure to finish all of your cutting back by the 4th of July.
- You can also take a large drift of one variety of perennials and cut back various sections at two week intervals, then manipulating and spreading out the bloom time for many more weeks wherever you desire.
- If you discover that you have created jarring color combinations, this technique can be used to delay blooming of one of the two plants and thus prevent clashing colors!
- This can be done with MANY perennials. Some of my favorites to use this technique on in June up until the 4th of July are: asters, mums, perennial sunflowers (Helianthus), ironweed (Vernonia), turtlehead (Chelone), Rudbeckia 'Herbstonne', Rudbeckia 'Henry Eilers', Eupatoriums (Joe Pye weed, boneset, and more).
This is Rudbeckia 'Herbstonne'. It has been pinched. The open flowers on tall stems are blooming in early August. The second layer will bloom in September on shorter stems.
Another great benefit of this June perennial pruning is to hide the "ugly legs" of many perennials. What does this mean? Some perennials, by the time they bloom, have “ugly legs”, i.e. they loose the lower leaves or the lower leaves become unsightly. Therefore, when you view them the flowers are pretty but the foliage detracts. By cutting the front of a plant in stages, you can create a stepped or layered effect to the front foliage of the plant, hiding the ugly legs. Try cutting the very front to 6”, the next level to 8-12”, the next level 15-20”, etc.
There are two additional ways to use these cutting back techniques to your advantage:
a. Vacation cutting back – If you know that a plant will bloom when you will be away on vacation, you can manipulate its bloom time by cutting the entire plant back. An example is perennial hibiscus, which normally blooms in August. If you cut this plant back by 1/3 – ½ in early July, you will create a shorter, branched plant that will not begin flowering until two to three weeks later than its normal bloom time. i.e. the very end of August or the beginning of September. Thus, when you return from vacation after Labor Day, your plant will just be starting its peak bloom time.
b. Cutting back to achieve peak bloom for a party, wedding or garden tour. Use the same concept described above to time blooming of perennials for special events. For example, if you are planning a September wedding in your garden, you can purposely cut back your late July and August bloomers hard in late June or early July. Then, these will bloom in tandem with your regular September bloomers.
These techniques were gleaned from studying the book The Well Tended Perennial Garden by Tracy Disabato-Aust. If you grow perennials, you must study this book. At Natureworks, we consider it our "bible".