Is Deadheading a Waste of Time?

 

Rosa - Rose @DBG 19sept05 LAH 136

“Deadhead” can mean a number of things: a fan of the Grateful Dead, to complete a trip without paying passengers or freight, or an airline crewmember hitching a free ride on a plane so they can get to their assigned flight. If you’re a gardener, then deadheading means pinching off faded flowers.

According to Gardeningknowhow.com,

Deadheading is an important task to keep up with in the garden throughout the growing season. … As flowers shed their petals and begin to form seed heads, energy is focused into the development of the seeds, rather than the flowers. Regular deadheading, however, channels the energy into the flowers, resulting in healthier plants and continual blooms.

This is what I’ve always been taught. Then I came across a post by Bec Wolfe-Thomas, on the Garden Professors Facebook blog, that disagrees:

The myth is that you need to deadhead spent blooms to get the plant to re-bloom. The theory people apply is that the plant will put all its energy into seed development and won’t bloom anymore because it no longer needs to for reproduction. This is false, plants are either genetically predisposed to re-bloom or they are not. To what degree they re-bloom also relates back to their genetics. It is a trait that plants are bred for.

Monarda didyma_Bee Balm_DBG_LAH_1205

She included a number of photos, of roses, fuchsias, and petunias, with both flowers and seedpods (or rose hips) on them at the same time (such as in my photo at the top of this page). Even in cases where we deadhead and are rewarded by another wave of bloom, her assertion is that the new flowers were genetically programed to happen, and deadheading was just a coincidence. For example, catmint (below) will often re-bloom whether or not you deadhead it, while bee balm (Monarda, right) won’t.

I found myself confused. Should I rush out and deadhead all the plants in my garden, as I’ve always been taught? It’s a lot of work, but it might be worth it if I get more flowers that way. Or is she right, it won’t force the plants into re-blooming, and I shouldn’t worry about it?

Nepeta_Catmint_DBG_LAH_0973

I decided that, for now, I’ll only pick off dead blooms that are unsightly. Brown flowers just don’t look very nice. Removing them refocuses our attention on the fresh blooms, and makes the garden look fresh and healthy.

Violas - Johnny Jump-ups @DBG 2008jun26LAH 446-2Probably the best reason to deadhead is for aesthetic purposes, but another very good reason is to eliminate next year’s volunteers. For example, I pull my bolted cilantro the moment I see those seeds turning brown. Yes, I could save them as coriander, but I still have plenty from past years’ crops, and I don’t want cilantro all over my yard come spring. Cilantro, parsley, rose campion (Silene coronaria), and Johnny-jump-ups (left) are just a few of the plants that reseed with enthusiasm.

On the other hand, if you want to save the seeds—whether for sowing next year, winter interest, or as food for wildlife—then leave them be. You may be able to have the best of both worlds, as some plants are structured so that you can remove the dead petals but not the developing seedpod.

Annuals are the Exception
Basil @DBG 19sept05 LAH 277Does deadheading encourage annuals to keep blooming? The whole point of blooming is to produce viable seeds; if the gardener pinches off the dying flowers, the plant will try again. Therefore, picking annual flowers before they go to seed will often encourage more flowers, as I discovered with these basil plants.[i]) Note that many annuals, such as petunias, have been bred to keep blooming whether or not they’re deadheaded.

Don’t Prune Now
Note that deadheading only applies to dead tissue. Often, gardeners include the live tips of the branches in their pinching. This is technically pruning, and pruning definitely stimulates the plants into new growth. Early in the growing season, this is how you get bushier plants, and (for those that set buds on new growth) more flowers. You can keep petunias, for instance, from getting leggy, while promoting branching.

Petunias_DBG_LAH_3259

Pruning this late in the season is a bad idea. We don’t want our perennials and shrubs putting out new growth now. Rather, they should be hunkering down, storing resources for next spring, and in some cases, sending “antifreeze” to exposed stems and branches. Tender new growth is more apt to be damaged by cold weather, and often, our winters arrive without warning—with highs in the 70s one day, and lows in the teens the next.

As you might imagine, Bec’s post generated an extensive discussion. Were there any studies supporting her claims? Apparently, no one could find anything in the published literature. That’s likely because 1) deadheading isn’t practical on a commercial basis—and it’s commercial agriculture that funds most research, 2) journals don’t usually publish negative results , so if there was research, we won’t hear about it, and 3) you can’t prove a negative; the burden of proof is on those who say deadheading causes reblooming.

This is a terrific opportunity for a science-minded home gardener. Consider running your own experiment. Include plenty of subjects, say a large planting of ornamental salvia, and deadhead only half. Then wait and see if and how much they rebloom. Is there a difference? Finally, share your results. I’d love to hear what happens!


[i] As long as I pinch the tips of the leafy stems, basil plants respond by branching. This year, I was out of town and didn’t get a chance to tend the plants until after they had started flowering. Hoping for a bigger harvest, I carefully stripped off the fresh flowers, but all the plants did was produce more flowers, not more leaves. Similarly, removing the flower stalk from a bolted lettuce plant doesn’t encourage more leaves, or make them less bitter. Apparently, once an annual thinks it’s time to blossom, nothing will reset its biological clock.

The Myth of Weed-free Landscaping

Today I’m revisiting a topic I first talked about back in 2013. I normally don’t do this, as I assume you can go back and reread whatever you’d like, using the options at in the sidebar at right. However, this is an issue that I think needs a lot more attention. I’m so frustrated, I could scream.

What is this horrific landscaping practice that makes me cringe? Landscape fabric.

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Does Your Garden Need Dawn?

LAH_7580Once again, the blogosphere is full of recipes for weed killer, lawn restorer, insecticides, etc., all containing dish detergent. Most of them call specifically for Dawn, although I recently encountered someone promoting Joy instead. The most popular herbicide recipe includes vinegar and dish detergent. Some add Epsom salts. Others add plain table salt. It’s a supposedly “organic” or “natural” alternative to a purchased product.

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Garden Advice: Blossom End Rot

blossom end rot - public domainYou’ve put in the effort and grown your own juicy tomatoes. But when you finally go to pick them, you realize that the end opposite the stem is sunken and oozing. Yuck—it’s disgusting. Who wants to eat a tomato that’s rotting on the vine?

What you have is a tomato with blossom end rot (BER). It’s just what the name suggests—the blossom end of the tomato (where the flower fell off long ago) is decomposing, ruining the fruit. (Yes, we all know that tomatoes are fruit.) The question isn’t identifying the problem, it’s solving it. How can we keep our tomatoes (and peppers, watermelon, cucumbers, and squash) from succumbing?

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A Garden Retrospective

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How did your garden grow this past year? Did everything flourish? Did you make mistakes? What do you intend to keep on doing, and what will you change for the future? Occurring as it does in the coldest part of the year, New Year’s is an excellent time to review last year’s garden and then apply the knowledge gained to this coming growing season.

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Garden Advice: Don’t Waste Your Vinegar

Death to Weeds @TacomaWA 14oct07 LAH 037Every so often I come across an article that explains something so much better than I ever could. This is one of those times.

Tsu Dho Nimh writes a blog called Lazy Gardening SMACKDOWN. Back in 2013, he tackled the viral advice about making your own herbicide out of vinegar, detergent, and some other ingredients. I’ve been meaning to cover this topic, because this homemade “herbicide” doesn’t work. But then I saw Nimh’s article, and realized that he did a much more thorough job of explaining it all.

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