How to Have No-Flop Perennials

Stakes are a hassle and unsightly and detract from the natural form and shape of our plants, but the good news is that they can usually be avoided.

Use minimal fertilizer, or none at all

Don’t overfeed — or better yet, don’t feed at all. That’ll just make them taller and more likely to flop. I only feed perennials that seem to be underperforming in the blooming department, and only once. (After that, I figure the problem is not enough sun, so I move it.)

Give them enough sun

Give them enough sun. Plants tell us they’re not getting enough sun by growing tall and leaning toward the sun in desperation. Of course, we can’t always give them the perfect site, so read on.

Water deeply

We should all be doing this anyway, for many reasons, but here I’ll just repeat that deep watering encourages deep roots, and deep roots are better at holding up the aboveground part of the plant. Here’s more on this extremely important topic.

Prune!

This my favorite because it’s so easy and produces such a great result. Late-blooming perennials are notorious for flopping, but all it takes to prevent that is hacking them back by one-half sometime before July 4 (a last-chance cut-off point that’s easy to remember). When plants are a foot tall, cut them back by half. Really late-bloomers like asters and mums benefit from a second pruning of this type — as long as it’s before the cut-off date. The photo above shows asters in the foreground just after their haircut. Purple coneflowers are behind them, already in bloom.

The result is shorter and bushier plants that will bloom a little later, and won’t flop! Brilliant, huh? The gardening world has Tracy diSabato-Aust to thank for spreading the word about the benefits of pruning perennials, so I’ll thank her, too. Her best-selling book is listed below and is highly recommended.

Good candidates include:

• Asters.
• Mums
• Tall sedums, like ‘Autumn Joy’
• Purple coneflower (though no later than early June)
• Rudbeckia
• Boltonia
• Lespedeza. Though usually listed as a shrub, this nonwoody plant is really a large perennial (it dies back to the ground in winter) and because mine gets less than full sun, I hack it back by half at least once for a better size and no flopping.

Oh, and another excellent time to hack back by one-half is when you’re moving perennials that have already achieved some height, even if your’e moving it to a nice sunny area. Those newly disturbed roots simply can’t hold up tall stems, and reducing their height gives the poor plant a fighting chance to survive being moved at a time of the year when it really should be left undisturbed (but hey, I sometimes do it myself).