Get Growing: Snip, pinch and chop: Pruning for summer flowers

As gardeners we are so proud to see growth that we’ve helped encourage. For example, houseplant parents may post about a new leaf on their Philodendron ‘Birkin,’ while other gardeners might flaunt pix of newly sprouted seedlings. That’s why what I’m going to suggest now is difficult. There are times when you’ll want to pinch, snap, and remove vegetative growth and even flowers or fruit.

It's one of those delayed gratification things, like that famous marshmallow impulse-control experiment where kids are promised two marshmallows if they wait, while they can have one right now. 

Here are some examples where a pinch or a whack now will boost your plant’s health or production later in the season.

Chop while watching Chelsea

First up, and the reason for writing this article now, is the famous “Chelsea Chop,” named for England’s flower show held in late May. This period through early June happens to be the perfect time in temperate climates to steel yourself and “shwack,” as a friend of mine used to say, the spring growth of many summer/fall-flowering perennials from 1/3 to 1/2 in size. I like this term because its playful sound shows you this isn’t scary.

Why would you put your young plants through this? Because it will encourage bushy, lusty growth with stout stalks, and side shoots with more flowers. Often sudden warmth in late spring causes erratic and lanky growth. The Chelsea Chop averts this issue on plants that can take it. The caveat: the flowers will be slightly smaller and emerge a little later than if the plants were left on their own. 

You can’t do this to just any plant, but some that respond well to shwacking include:

Achillea

Aster

Campanula

Echinacea

Helenium

Helianthus

Lavender (take care not to cut into oldest wood)

Monarda

Nepeta

Penstemon

Phlox

Rudbeckia

Sedum/Hylotelephium

Solidago (goldenrod)

Veronicastrum

You can hedge your bets, owning the pun, by creatively pruning portions of a plant or a grouping to stagger blooms over a longer period. Prune to just above a healthy leaf in each case

The Royal Horticultural Society offers a video on how to do it: https://www.rhs.org.uk/Videos/Advice/chelsea-chop.

At planting 

This may be the toughest one of all. When you are buying plants at the nursery in flower, it may be helpful to snip off those flowers before planting so the plant sends energy to promoting roots instead of supporting the flowers. The idea is that it helps get the plant established in its new home faster. I’d guess this is more useful for shrubs and large perennials than for annuals.

I generally try to buy them before they are in flower unless I am buying a plant from a seed strain (meaning a multicolor seed collection) in which case I want to see which flower I are getting, because color is very important to me.

Another exception would be tomatoes — while I avoid buying tomato plants with flowers on them, if a rare variety mysteriously found its way into my car I probably wouldn’t cut them. Here in Seattle, if a plant has managed to pump out a tomato flower in spring it deserves a medal, not a chop. Also you may mess with later fruiting depending on the variety.

A little pinch

Dahlias are another plant that benefits from getting snipped early in life. 

When the plants reach eight to 12 inches high, you can pinch the central growing stem down to foster basal growth and side shoots, which equals more flowers.

According to Floret Flowers, based in the Skagit Valley, “After plants reach 8- to 12- inch (20 to 30 cm) tall, give them a hard pinch by snipping out 3- to 4- inch (7 to 10 cm) of the growing center to encourage low basal branching, which increases flower production and overall stem length.” Stem length means more dramatic bouquets.

When you prune the top of many plants’ central leaders, from roses to rubber trees, it encourages them to send out more side shoots. (And vice versa: snipping side shoots will cause the central vertical to skyrocket.) Not all plants can survive their central leader being pruned, but dahlias are fine with it.

Here is a video from Swan Island Dahlias in Oregon https://www.youtube.com/watch?v=qMQpKELBN2U.

The potential downside, especially in a cool Seattle spring, is that it may delay the flowering until you are chewing your fingernails to nubs. The upside is more flowers with better stems for cutting, and more color in your late fall garden.

While blooming

Deadheading performs a similar function to pinching by telling the plant to send energy into new flowers to reproduce its seed. Repeat-blooming plants, also called “cut-and-come-again” varieties like zinnias and dahlias send up more and more flowers each time you snip one, so the more bouquets you cut, the more you’ll have to give!

If you are going for size, you can selectively prune flowers to create larger ones. This is a popular technique when raising exhibition flowers or fruit, like apples or pumpkins. Removing all but two or three flowers in a cluster of apple blossoms will grow more robust fruit.

After blooming

You can create a renewed or second flush of bloom in many plants by doing a Chelsea chop whenever they get lanky. In my experience, annual pansies and petunias as well as perennial wallflowers (Erysimum), achillea, calendula and perennial salvias can be perked up for a second round of flowers. 

So be brave and grab those snippers.