layering in bulbs with other plants
Jane McGary (Thu, 21 May 2015 10:35:46 PDT)

Kathleen asked about ground covers that will coexist with bulbs but not
provide a haven for weeds and slugs.

I can't answer for the slug problem, but my larger rock garden has some
mats of thyme (Thymus spp.) through which bulbs of various kinds emerge
and flower successfully, and in which weeds rarely germinate. Thyme
would not, however, outcompete weeds that spread underground. I also
have a patch of Fuchsia procumbens (which might be a thug in Kathleen's
coastal site) hosting a colony of the modest-sized lily Lilium davidii.
Other bulbs here are growing in a lawn, which is getting its first mow
of the year today, now that the bulb foliage is sufficiently senescent.
It is a weedy lawn because of the need to let the bulbs grow, but at
least it's flat and green. Other bulbs are coexisting with prostrate,
semishrubby penstemons, Scutellaria spp., and a small but all too
vigorous Epimedium. You can also put spring-flowering bulbs near hostas
and Pulsatilla vulgaris forms, which later fill in the space with their
large leaves.

All these combinations except the thyme assume that the bulbs are
tolerant of some summer moisture. For those that are not, I'll be
installing a raised, rock supported bed this summer to host dryland
bulbs and small xeric perennials such as Arenaria and Draba. I already
have such a combination on a tufa rock garden.

Some growers succeed with the combination of spring bulbs and summer
annuals, though I haven't tried this much. If you want the annuals to
reseed, you will be faced with weeding out the cress and Epilobium among
the tiny annual seedlings, while avoiding the growing bulbs, which would
be a real pain.

Jane McGary
Portland, Oregon, USA