Cruel to be Kind

Perennials to Cut Back Now in Early July

When I worked at the Great Big Greenhouse in the early ‘80s, the owner assigned me to a enthusiastic horticultural expert to get a quick tutorial on plant care. She was a bouncy always smiling character, and incredibly enthusiastic about anything having to do with plants.

The first thing she taught me was how to mix soils. We dragged unsellable ripped bags of vermiculite, perlite, sand and potting soil off the shelves in the nursery, and dumped each as needed onto a huge gray plastic platter. She showed me how to blend soils for different plant types. Succulents got lots of sand, ferns got perlite and peat moss and so on. I fell in love with the whole tactile experience of potting perennials. I felt initiated into the world of Nature, and was proud of the black soil under my fingernails.

For lesson 2, I followed her out to the perennial area. “ Today we’ll review cutting back perennials!” My jaw dropped as I looked at hundreds of leafy plants in one gallon pots. “We have to prune these now so we can get a second bloom and sell them later in the season.” she said.

“You have to be tough and sometimes heartless to be a good gardener. We are going to move down the rows and whack these back.“ The hit song by Nick Lowe entitled “Cruel to Be Kind” drifted into my musical mind.

When to Prune

After a hot spell like we have had these past few weeks, it’s tough to know whether and when to cut back plants that have stopped blooming. I am not talking about just dead heading individual flowers after they bloom. The technique of “dead heading” I’m reviewing is to cut the whole plant back as much as one-third to one-half.

Perennials splay and fall flat when they get too tall or long. I prefer a tight full look with thick flowers, so I cut back now for a second and possible third flush of color. If this was late September, I would not prune this heavily. There is less time for the growing season in autumn, and you will have nubby looking plants for months. July is still early in our long hot summers which in Richmond usually includes September.

My splayed sedum is pictured below. It wasn’t even that tall, but was full and dropped flat.

How to Prune

Nepeta (Catmint)

This lovely purple/blue perennial is used a lot now by homeowners and in commercial properties. It is a gorgeous reliable bloomer, but must be cut back to retain its beauty after it’s profuse blooms fade. If you don’t prune these their leaves get mushy and gray. You have an ‘ugly factor’ for months, instead of repeat blooms.

To cut back nepeta I gather the whole plant in my hand and make a ponytail much like you would do for someone’s head of hair. As you hold the plant stems, cut about 8” up from the center stems and let what is left fall into place. You can use pruners to do this, but for older plants the foliage might be so full that manual or power hedge clippers are easier and faster.

Woman cutting back Nepeta – Catmint in Autumn using Jakoti shears

It might take 2 people to do the deed. One person to hold and one to cut. Be ready for a lot of plant clean up.

Bee balm is another perennial to cut back about 1/3 for a second bloom. If you leave an cut big stand of dead flowers you might get a re bloom, but flowers will come off of bent stems that are lying on the ground. I have only ever gotten 2 blooms cycles out of a season for this plant but I always cut it back after it blooms.

In the photo below you can see how all the blooms are finished. This is when you cut the plant back about one third.

Asters should be cut in half now so you get flowers in the fall. The whole selling point of asters is their fall blooms. If you don’t cut them back now while they are still just leaves, they will bloom too soon. You won’t have a punch of color in late September.

Russian sage

I cut back this wonderful Native Russian sage last week instead of waiting til it’s flowers faded. It was stunning in full bloom. The fragrance as I brushed against it was sage blended with mint and lavender. I had planted it, however, right next to a heavily trafficked walkway. As a magnet for bees I risked being stung every time I brushed by.

My dogs were snapping at bees as they passed the sage flowers. That alone was a motivator to reduce the plant’s size. We can’t have our labs eating bees!

Pruning before the lawn mower strikes.

Hopefully you don’t have to the cut the plant halfway, but I prune anything that falls into the path of a lawn mower like these Annabelle hydrangeas. I feel kind of bad doing it, but if you don’t tip prune any plant in a mower’s path, human or robot driven, in a weeks time it will be shredded. Nothing is worse than seeing ripped blooms scattered across a newly cut lawn and a blunt cut stem waving in the breeze.

This photo of Annabelles hydrangeas shows flowers tip pruned back off the lawn.

If you decide to venture out in the garden to “do the deed” the morning time is best. The sap isn’t fully flowing in the stems early in the day. It will not be such a shock on the plant itself.

Christie lives in Manakin Sabot , Virginia where she manages a 3 acre garden. Her blogs are written from her 35 years as a personal and professional gardener.