Perennials: to chop or not?

(Originally posted: October 15, 2019)

Well it seems as though the gardening season is progressing at an alarming rate- is it really October??? We are now on to fall gardening tasks, and one of the main tasks is cutting perennials back (not to be confused with pruning trees and shrubs which I addressed in my previous post, Temper your Enthusiasm). At this time of year, I am often asked: “what should I cut back”? I am going to try to answer this question as concisely as possible in this post (no promises).

Before getting into the nitty gritty, however, I should first start with the other question that I am often asked which is “when should I cut back my perennials?”. In general, I wait until things are well on their way to dying back on their own. Right now, plants are gathering up some last rays of sunshine (as are we!) and beefing up their energy reserves in their root systems to help them survive the winter and have the ability to flush out new growth in the spring. Letting perennials go through this natural process allows the plants to properly prepare for winter. Usually when the leaves have turned colour (which is a sign that the plant is no longer photosynthesizing or making energy) is when I start whacking things back; this is usually (but not always) shortly before or shortly after the first frost.

What to Cut Back

Now… the all important question, what should we be cutting back? Using these 6 questions about your perennials can help point your secateurs in the right direction:

1) IS IT EVERGREEN?

Let’s face it. We don’t always grow perennials for their floral display. Take Heuchera (coral bells) for example, many cultivars of this perennial are not winning any awards for blooms- A+ for effort, but no awards. So what does this plant have going for it? Foliage! Not only do Heuchera come in all sorts of gorgeous foliage colours, the leaves of coral bells persist year-round. They are evergreen (or ever-purple, or ever-chartreuse or ever-pink…). Other examples of perennials in the evergreen category include various species of Helleborus (Lenten rose or Christmas rose), Bergenia, and Yucca. Additionally, there are also some perennials, such as Leucanthemum superbum (shasta daisy) whose flower stems die down while their basal foliage remains evergreen. So as the saying goes ‘if you’ve got it, flaunt it’ and these plants have got it…foliage in the winter, that is! Leave these perennials standing tall! Sure they may look a little ratty come spring (depending on the kind of winter we are served and the growing conditions that the plants are subjected to) but the fact of the matter is that they have the potential to look nice, even during the winter months. In areas with unreliable snow cover (ahem… southern Ontario) this can be a really nice addition to the garden.

Examples of evergreen/semi-evergreen perennials (clockwise from top left): pigsqueak (Bergenia spp.)., lenten rose (Helleborus sp.), the basal foliage of shasta daisies (Leucanthemum spp.) and coral bells (Heuchera spp.),

2) DOES IT RETAIN IT’S STRUCTURE?

Some perennials, such as many ornamental grasses will retain their structure well into the winter months. These perennials will not only add structure to the garden but some gorgeous texture too (see ‘ornamental features’ below)! Other perennials such as Hosta spp. will essentially turn to mush come the first hard frost, while Polygonatum spp. (Solomon’s seal) will drop it’s leaves and loose it’s graceful form in the process. In any case, I am going to make the assumption that no one finds an indistinguishable mess of mushy leaves to be attractive. If your plants seem to crumble as soon as the cold weather hits, cut them back! It will be one less clean-up job to do in the spring and your winter garden will thank you for improving her aesthetics!

The hosta- a beautiful addition to the shady garden… absolutely useless in a winter garden.

3) IS IT WOODY?

Some perennials develop woody stems such as Perovskia atriplicifolia (Russian sage) or Lavandula (lavender). These are guaranteed to retain some structure in the winter and pruning for these two perennials is best left to the spring anyway. Leave them up and enjoy having some added structure to your garden!

4) DOES IT HAVE ORNAMENTAL FEATURES?

Beautiful texture? Ornamental seed pods? Pretty dried flowers? These are all features that look oh so beautiful when touched by a frost or coated in a light dusting of snow. Remember- winter is a beautiful season, if a plant has something that can help capture this beauty, then let it be!

Ornamental grasses and perennials such as bugbane (Cimicifuga spp.), Sedum spp.) and Joe Pye weed (Eupatorium spp.) have seedheads that capture a dusting of snow beautifully. * Remember, if you have a plant that tends to seed itself prolifically, you may want to chop the flowers before they go to seed. *

5) DOES IT HAVE WILDLIFE VALUE?

Many perennials produce seeds valued by wildlife (especially birds); some of the more common ones include species of: Echinacea (coneflower), Rudbeckia (black-eyed Susan/gloriosa daisy), Sedum (stonecrop), Eupatorium (Joe Pye weed and boneset), Helenium (sneezeweed) and Heliopsis (false sunflower). Leave these perennials standing over the fall and winter months and you can feel good about providing a food source for our feathered friends.

Some perennials with wildlife value. Clockwise from top left: black-eyed Susan (Rudbeckia hirta), stonecrop (Sedum spp.), sneezeweed (Helenium autumnale) and coneflowers (Echinacea spp.)

6) IS IT DISEASED?

Did you notice anything funny on the leaves of any of your perennials this year? Perhaps a white fuzzy coating or little rusty pustules or unusual blotches? If you suspect that a perennial in your garden was diseased, it is best to cut it down (or even dig it out). Often diseases will overwinter in the garden on diseased plant material; this can become a source of infection for the next season. Cut anything suspicious down and DO NOT compost it. If it is a re-occuring problem, it may indicate that the plant is not growing in its optimum conditions (stressed plants are more prone to diseases) or it is a problem that the perennial is particularly susceptible to. If you have plants that seem to be hit by disease year after year, it may be time to think of some more robust replacements (an excellent task for the winter!).

Even though this Phlox would retain some structure over the winter, it is diseased and should be cut down (and the clippings removed from the garden).

OK OK, so that may not have been overly concise but I hope it helped! Remember- if you are not sure what to do with a certain perennial, you can always leave it alone to see how it fares the winter months. It can often be surprising what plants look attractive in the winter. So don’t be too hasty in chopping down all your perennials- right now you are the designer of your winter garden!

Temper your Enthusiasm

(Originally posted September 15, 2019)

The crisp nights and cooler days have arrived- a sure sign that fall is around the corner. Fall is generally a time of yard work and many people become very enthusiastic to tackle outdoor chores- even people with no interest in their yard whatsoever throughout the rest of the year tend to catch the ‘gardening bug’ during the autumn months. Often this enthusiasm is directed at whacking back various trees and shrubs in their yard. While there is certainly lots to do before the snow flies, pruning is the one task that we want to minimize at this time of year. (Sorry Edward Scissorhands wannabes!)

Let’s start with the effect that pruning has on a tree or shrub… it promotes new growth. New growth is tender and needs time to toughen up to the environmental conditions around it. At this time of year, our frosty mornings are just around the corner. If we prune now, new growth that emerges will not have the time to properly harden off before the cold weather hits, which can ultimately lead to death of the new plant tissue… therefore you will get dieback. On deciduous trees and shrubs (ones that lose their leaves for the winter), this dieback would be apparent in the spring; on evergreens it could become obvious during the fall and winter months. Dead new growth is not the nicest thing to look at on a plant that is supposed to stay green for the winter!

Furthermore, plants are using this time to start shutting themselves down for the winter. They are gathering sugars and carbohydrates from their leaves and storing them in their stems, trunks and root systems; valuable energy to help the plant survive the winter and flush out new growth in the spring. Removing the leaves before they fall doesn’t allow the plant to relocate these sugars to their ‘winter storage facilities’ and therefore the plant is robbed of it’s energy sources for the months ahead. Additionally, the stimulation of new growth through pruning counters what the plant is trying to do. Instead of putting energy towards properly ‘shutting down’ it is putting energy towards new growth; this can weaken the plant going into the winter.

While it is true that plants can rebound from a late season prune, it is not an ideal time for this gardening task.

So… if you feel the call of the pruning saw, hedge shear or lopper- ignore it! Opt to warm up some apple cider, mosey through the garden, and start your ‘to do list’ for next year. Those shrubs and trees that you are just dying to hack back now will still be there in the spring and they can be first on your ‘hit list’ for a dormant season prune come a mild day in March***! Not to mention, with all that energy [properly] saved-up for a spring flush, the plant will be able to quickly rebound from your ‘haircut’.

Can you hear that?

That is the sound of your shrubs and trees breathing a huge sigh of relief.

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***While any plant can be pruned in the dormant season, it is important to note that if you prune anything that flowers early in the growing season, you would most likely be removing flower buds. For these plants it means that a hard prune = no flowers for the upcoming growing season. While some people may gasp in horror at the thought of this, sometimes it is a necessary evil in order to renovate an overgrown shrub. More on pruning and timing of pruning in future posts… I promise!

Remember these early season beauties? A prune at this point in the year (or any time leading up to their flowering period) would remove their flower buds. Believe it or not, plants such as these are already prepared for their 2020 show!

Clockwise from top left: lilac (Syringa sp.), serviceberry (Amelanchier sp.) magnolia (Magnolia sp.), Dogwood (Cornus sp.)

Deadheading Technique #3: Pruning to a Lateral Bud

(Originally posted: August 17, 2019)

Well hello there… it’s been a while! No, I have not given up on this blog or had writer’s block, I have simply been relatively unplugged for the last couple of weeks, save for the GROW Instagram account. Despite the time away, believe it or not, not much has changed in the gardening world. In reality, the tasks I am completing today are essentially the same as those that I was completing two and three weeks ago… deadheading, deadheading and more deadheading!

So, with that said, I think it is time to address the last main deadheading technique that gardeners use, and that is deadheading to a lateral bud/flower.

This technique is really easy, once you know what you are looking for. So let’s start with the basics… what on earth is a lateral bud or flower?!

Let’s have a look at this Echinacea below… if you follow the main stem from the ground up, you will notice that the stem terminates in a flower. It should be no surprise that this is called the terminal flower (which originated from a terminal bud).

Now follow the stem back down until you notice a branch of sorts. This is a secondary growing point that originated from a lateral bud (a bud that sends growth sideways); in the photo below, that sideways growth is well on it’s way to becoming a lateral flower.

As this Echinacea flower stalk enters it’s blooming period, the flowering will begin at the terminal flower bud and work downward. As flowers wane, the spent flowers can then be deadheaded to the bud that is next in line. For the Echinacea, the cut would be here…

Not all lateral buds are as obvious as those on the Echinacea. Have a look at the Monarda (beebalm) in the photos below… if you follow down the stem from the top flower you come across two buds nestled into the stem.

Pruning to the lateral buds involves cutting the stem of the spent blossom just above those buds…

Deadheading of Monarda (bee balm) to lateral buds- this can extend the bloom period of this perennial.

Even trickier are plants such as Platycodon (balloonflower). The buds for new flowers are actually right next to the old blooms. In this case it is just the spent bloom that gets removed, while being careful not to snip any buds in the process! The photo below shows the flower buds of balloonflower. The largest one will bloom first, get snipped off at the yellow ‘cut’ line and the smaller bud is next in line.

In general, a lateral flower bud is not always a guaranteed bloom. This deadheading technique encourages these lateral buds to flower and therefore this technique helps to extend the bloom period of many perennials.

What is the mechanism at play here? Think of it this way… a plant’s main purpose is not to put on a pretty floral display for us, it is to reproduce. If a plant flowers and is allowed to set seed, it can consider it’s mission complete- no need to send out more blooms! The plant’s resources get allocated towards seed production, instead of additional flower production.

I like to think of deadheading to a lateral bud as a way of freeing-up that lateral bud to bloom.

One Final Step

Once the blooming period is complete, some perennials (ones that have a clump of foliage at the base of the plant- known as basal foliage) will get one final snip. For these plants, the spent flower stalks are cut down to the basal foliage. This often tidies the look of the plant. With that said, I tend to leave flower stems standing on plants that provide food (in the form of seeds) for wildlife; plants such as Echinacea (coneflower) and Monarda (beebalm) are only a couple in this category. Additionally, I will leave plants standing if they have attractive seedheads. Yes, I will admit, I am thinking about winter here, but it is important to keep in mind that winter is, in fact, a season and seedheads are a really great way to have interest in your garden during the months of frost and snow!

So…there you have it! Deadheading to a lateral flower or bud. Now it’s time to get out in the garden and inspect your perennials… take a good look at how they grow. If you get close enough, they will speak to you and tell you how to prune!