Not directly underneath. Between will work until things get crowded. Then the Siberian foliage may block sunlight from the daffodils. Or hog the nutrients. Is your daffodil cultivar a vigorous one?

Thanks, iris_gal! The bed hasn't been worked on in 20 years and was totally overgrown, with mats of iris spreading out over the sidewalk. I haven't a clue what cultivar the daffs are, but they've been around (and multiplied) at least 20 years. I was hoping to hide the post-bloom, dying daff foliage in the iris leaves. My main concern was whether the eventual thick mat of iris rhizomes/roots would interfere with the bulbs coming up from underneath. Any advice?

Hi Allium,
Thanks for replying. I hope you have garden-fiend friends who will love some of your excess. And I'm guessing that you weren't in the house at bloom time?

Sib's thick root mass will force a daff bulb underneath to grow out sideways to reach sunlight. I really doubt it would be able to go thru Sib's root mass except at the edges.

There are a couple of clumps of daffs whose aging foliage sticks out like a sore thumb. Ever so loosely I braid it, about a month after bloom when it's beginning to soften, gently arc in half and tie at the base with a long soft leaf. Sort of cute to look at after that. And it can be cut when 1/3 has yellowed.

Thanks, iris_gal! I thought my idea was too good to be true - and it was. The sib transplant is going well, and yes, the entire neighborhood has enjoyed my excess (with a waiting list in case there are any leftovers). Now, on to the daff bulbs! Thanks again.