This Old House recently published an article about splitting overgrown perennials. They suggest doing so every three to six years--however, I have a large bed of daylilies, and it's hard for me to imagine how they'd be considered "overgrown."

Is this a necessity for the plant, or is it just a cosmetic issue? And if cosmetic, I assume this only applies to small plantings, not an entire bed? It would be helpful to see an example of what people consider "overgrown" to look like vs. a more desirable appearance.

2 Answers 2


The harm potential for overgrown perennials is largely cosmetic, but in a severe enough case it is possible for it to become a health issue. When perennial plants with shared root systems, such as Astilbe, Hostas etc. become very large the center of the plant may begin to wilt, decline or even die out completely. The easiest fix for the problem is to divide the plant as described in the link in your question or as described in this question.

The reason your day-lilies don't seem to have a problem is partly due to differences in root structure (day-lilies have individual tubers, rather than a shared root system) and partly due to the fact that day-lilies are very hardy plants that can and will grow nearly anywhere.


Day lilies are perennial, yes but they are not A perennial. The group of plants called Perennials are grouping plants that share the same root structure. That's like Mums and montauk daisies.

Daylilies are actually in the bulb group. Each Daylily is its own independent bulb.

Now, bulbs also can benefit from being split by giving them more room to divide and grow nice big healthy bulbs, but Daylilies in my experience don't need this treatment. They are very prolific and will spread with decent swiftness on their own and may even become a pesky weed if you let them get out of control.

Something interesting about Daylilies is that the bulbs are edible and a viable and sustainable food source. If you have enough of them you can supplement your food root supplies with the bulbs. The bulb itself is interesting, looking kinda like a snail shell in so far as its pattern of growth. It tastes like a nutty flavored onion.

Another interesting edible, which has a lot of flavor variety between strains is the dahlia which is similar to a sweet potatoe but with varying flavor.

  • I didn't know daylilies are edible. I have lots, and will have to try that this year. @GardenerJ is right about the root structure, though. They're called roots or tubers. They don't have the same characteristics as other bulbs, and aren't classified that way. See here, here and here for details. Commented Mar 25, 2016 at 22:34
  • That's very interesting reading. Although they may be classically called tubers and Inwill acquiesce here, I have dug up enough that I am comfortable continuing to call them bulbs. The leaves grow right out of them bulbs like, but out the side rather that out the top and they develop a snail she'll like pattern, maybe they are officially tubers, but they don't appear tuber like to me.
    – Escoce
    Commented Mar 25, 2016 at 22:46

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