Some ground covers I enjoy crowd out weeds during some seasons of the year but disappear during others. An unusual one for being edible is Corn Salad, which in the milder PNW grows all winter and self-sows reliably so can carpet the ground and get large enough to pick leaves for salad-
Here is some that forms a tiny green river in a crevice between some rocks-
Another plant that is very adapted to the wet/dry seasons here is Anemone nemorosa. I started with just a few of the little stick-like rhizomes and have spread them over large areas of my yard, where they multiply rapidly over a year or two to fill in densely in the early spring and become covered with flowers. They result in an enchanting spring look to the beds, then with hotter weather become ephemeral until the next year.
Here they are combined with a hardy geranium that is understated during the winter but will start growing and take over the ground cover function when the Anemone is dormant in the summer and fall.
Another surprising winter ground cover discovery is Meadowfoam, Limnanthes douglasii, Poached Eggs. This was my second year to grow it so it is growing from having self-sown. I was surprised to see it coming up last fall, and even more surprised when it made it through the winter in a dense patch. On a large scale this could be very effective in crowding out the many weeds that start growing in the fall and taking over big sections of the garden, making me have to do a lot of weeding. Perhaps with every successive season of bloom and seed formation, more seed will be formed resulting in more plants and better coverage the next year. The California hills can be covered with Meadowfoam in bloom. I also found a good source of more California native annuals in an Annie's Annuals catalog, I want to try some of them.
I had been on the look-out for just such a list of other low-growing biennials or hardy annuals that can be fall-sown to grown densely over the winter and bloom the next spring. One I am growing now under lights is Gilia capitata, with blue pompom flowers, another west coast native adapted to dry summers. I will plant it out to self-sow for hopefully more plants next year. I also plan to do some fall sowing of some of the annuals.
Forget-Me-Nots also grow with the fall rains and during the winter and carpet the ground extensively, and are lovely for a while when blooming, but end up usually mildewed and needing to be pulled out of everywhere, unlike the low-growing Meadowfoam, and the Corn Salad, that fade gently away.
Columbines can also self-sow and increase in a area, and can become nice clumps during the winter, only to create a blooming wonderland in spring. The only downside is cutting off the dried up bloom stalks later.
Most deciduous ground covers grow during the summer and are dormant in winter, like this Bishop's Weed that is coming up with delightful chartreuse edges. It is supposed to be invasive but has not gone beyond this little patch. I enjoy the variegated leaves and the flowers.
Another very useful but invasive plant is Phalaris, variegated ribbon grass. I would not want it in a bed where it could overrun other plants, but it is very useful along an unmowable driveway edge where weeds used to take over, as over time it shades and crowds them out. Even if the old dead grass is not removed, it will grow up through it and the old grass will eventually disappear.
Another plant that is dormant in winter but makes a nice ground cover in summer and fall is Lady's Mantle, which self-sows well. I have spread it extensively on a former steep grassy bank which was hard to control and it filled in well and is covered for a long time in airy chartreuse blooms that also look nice for a long time as a filler in a vase, as does Phalaris. For summer photos of it in bloom click here.
I hope your spring garden plans are progressing. What plants have been good temporary ground covers for you?