Bulbs (here, hyacinths) easily push up through mulch. Photo: nittygrittydirtman.com
Question: I want to plant many bulbs in my flower bed this fall. It’s covered with mulch and I’m afraid the mulch will prevent the bulbs from growing. Can you plant bulbs in a mulched bed without them being smothered? If so, how do you do it?
Answer: Mulch and bulbs actually go very well together.
Imagine: bulbs are planted fairly deep in the soil, yet their leaves easily manage to pierce the soil, often dense and heavy. Do you think a mulch, usually light and fairly fluffy, would stop such determined plants? Bulbs will easily grow through 4 inches (10 cm) or even more of mulch as if it weren’t there.
Bulbs do this in the wild too, pushing their way up into the light, first through the soil, then the plant litter that covers the ground.
Perennials do just the same thing, by the way. They die to the ground in winter, then push their way up through any mulch present in the spring.
So, proceed as follows:
Temporarily move the mulch from the spots where you want to plant bulbs. Plant them at the recommended depth (about three times the height of the bulb), add a little mycorrhizal inoculant, cover them with soil, replace the mulch, and water well. It couldn’t be simpler!
The purpose of a mulch is not to smother established weeds: they too will pass right through the mulch. What the mulch does is to prevent the germination of weed seeds. (And will also prevent bulbs and perennials from self-sowing, by the way.) That’s why you always have to thoroughly weed a flower bed before applying mulch: if any perennial weeds remain in the soil, they’ll just grow right up through the mulch.
So think of it this way: mulch is not a weed smotherer, it’s an anti-germinator. And it won’t harm your bulbs!