Mother Nature originally planned for each plant to have a precise flowering period. But you can outsmart nature… at least, to a certain degree. If you know how to do it, you an encourage many annuals and perennials to bloom outside of their normal season. All it takes is a bit of pinching or pruning.
To do so, you have to fool them by blocking their first effort to flower, sometimes even before it takes place. That will push them to either produce more flowers than normale or even to flower a second time! The important thing to know is when and how to go about it … and to know which plants this works on.
Wonderful Vicious Circle
Do you argue with your spouse because one of you wants to bring cut flowers into the house at all costs to make flower arrangements and the other doesn’t want to anyone to touch their beautiful flower beds? Well, you can now smoke a peace pipe, because harvesting flowers as they bloom can sometimes stimulate the plant to produce more flowers later. And that gives you more flowers to pick/admire in the garden. It’s a vicious circle, but in the right kind of vicious circle!
In fact, when you cut off a flower before it starts to fade, very often this stimulates the development of dormant buds located lower on the stem. Two flowers are then formed where nature had originally planned only one! It can almost be said that, in the case of annuals, the more you pick, the more they bloom!
This isn’t quite as true with perennials, but many of them, especially summer bloomers, will flower a second time, albeit sometimes modestly, if part of the first bloom is clipped off early enough in the season.
A Pinch in Time …
“Accidental rebloom through flower arranging” is often fairly successful in stimulating more flowers, but is rarely perfectly effective. When picking flowers at random, the second flowering, too, will happen at random.
However, you can plan the second flowering even before the first one takes place. When planting annuals, for example, remove all the flowers and buds from one plant out of every two: the first set will fill your flower bed with early flowers, but will tire fairly soon, blooming less and less over time. The second series, having wasted no energy with its first flowering, will quickly come to the rescue of the first, often even producing twice as many flowers, and will carry on for a longer time, as, while it wasn’t in bloom, it was building a stronger root system!
The same can be done with many perennials: Shasta daisies, delphiniums (larkspurs), loosestrifes, etc. As soon as a flower stem begins to form, remove it on every second plant.
The first will therefore bloom on the normal date, but the second will bloom about a month after the first. In the latter case, the flowers will usually appear on slightly shorter stems and will often be smaller, but also more numerous. Essentially, you’ll be doubling your plant’s bloom period. Not bad in return for such a minor intervention!
The most generous of these “prunable perennials” is undoubtedly the chrysanthemum (Chrysanthemum × morifolium). Pinch it back once and that will often double the number of flowers. But pinch it back a second time, as new stems start to appear, can triple the effect. That’s how nurseries produce those huge cushion mums with hundreds of flowers. In fact, the more you pinch the tip of a chrysanthemum’s stems, the more flowers it produces. Stop by mid-August though, or you risk delaying its flowering so much that it will only begin in November!
And here’s a new prunable perennial! The New York series of Oriental poppy (Papaver orientale), including such cultivars as ‘Brooklyn’, ‘Central Park’, ‘Harlem’ and ‘Manhattan’, all have the capacity to bloom again in the fall if you cut them back after their first bloom in spring. Try them and you’ll see!
Gardeners will certainly be seeing more and more reblooming perennials as hybridizers explore the hidden genetic potential of the plants they work on.
Pinch for Stronger Stems
There is another reason you may want to try pruning flower stems of perennials before they bloom. If you do it at the beginning of summer, well before blooming, it will stimulate more floriferous growth. Great! However, these flowers will also be on shorter, sturdier stems, less likely to flop in case of strong winds or heavy rain. For plants like asters (Symphyotrichum, Eurybia, Doellingeria, etc. ), delphiniums or larkspurs (Delphinium spp.), chrysanthemums (Chrysanthemum × morifolium and C. zawadskii latilobum ‘Clara Curtis’) and autumn sedums (Hylotelephium spp.), this can make the difference between a floppy plant with its blooms covered in mud and an upright plant with immaculate flowers.
But pruning to strengthen the stem doesn’t always work!
In case of peonies (Paeonia lactiflora), for example, even if you remove the first flower buds from a floppy peony (and there are many of these monstrosities still on the market), that doesn’t solidify its stem one iota and when the secondary buds bloom in place of those that you removed, they still flop… unless you offer them sturdy staking. Read Just Ditch Those Floppy Peonies to learn more about these plants that should be banned from any laidback gardener’s repertory.
Never Too Late?
If you hadn’t thought about pruning your annuals earlier in the season, there’s a good chance that they’ll start to look a bit down in the dump by the end of July. Busier making seeds than flowers, many annuals are no longer looking their best as August rolls in.
However, you can “wake up weakening annuals” very quickly… with your string trimmer! Just run it quickly over the top of your fading annuals and clip off their seed capsules. Without seeds to feed, your annuals will quickly switch back into bloom mode. Or at least, most of them will.
In the case of lowest growing annuals, like sweet alyssum and groundcover varieties of petunias, you can even have a go at them with your lawn mower! Set it to its greatest height and run it right over your plants. That will only cut off the top of the plant, where it’s producing seeds, leaving the roots and most of the branches and leaves intact. In just a few weeks (because the annuals are very fast growing), your plants will be in bloom again, and often more strongly than the first time!
Which Plants Should You Prune?
Obviously, not all plants react to this treatment. Don’t waste your time pruning apple trees or tall shrubs like common lilacs (Syringa vulgaris) after they bloom expecting to stimulate a second flowering. Most trees and bigger shrubs simply won’t bloom again. Rather, it’s something we see more in annuals and perennials (a fairly large number of species are likely to rebloom) as well as roses, long known for their reblooming habits. But also, more and more, you’ll be seeing dwarf shrubs, such as Bloomerang lilacs and Double Play Doozie spireas, that rebloom faithfully if you deadhead them.
Some other plants seem destined to remain single-flowering, though. Bulbous plants are, by their nature, inclined to bloom only once. Many are so ephemeral — they rise out of the ground, bloom and begin to go dormant so quickly, in less than 10 weeks — that they don’t have enough time to bloom twice. Very early flowering perennials also don’t seem to offer much hope of repeat flowering. But the plants mentioned above, yes: you can certainly get two bloomings just by doing a quick pruning.
Try this technique at home and you’ll discover how effective it can be. There’ll most likely be a few failures, but soon you’ll discover that your garden can be even more floriferous in August than it was in its heyday at the end of June if you just clip back at least some of your plants at the right time!
Great writeup and good news for oriental poppy lovers! How far should they be cut back in the spring? A third? Halfway? Thanks!
I’ve been so curious about this technique but have hesitated. However, your clear instructions, additional information and examples make me want to try it. But before I go prune the asters, I’m off to read about ditching my floppy peonies! Thank you.
This is great advice and a lot of things we already do successfully. But, there is a lot of additional ideas/advice that could only be learned by experience. I appreciate your sharing this niche info.