Ask Mr. Smarty Plants

Well, see, when you put that mulch down to control weeds, you are also controlling seeds that you want to sprout. The function in that respect is to cut off light from the seedlings, thus keeping them from developing. Certainly, the perennials will be able to spread by clumping, or growing from the roots. You would then get more plants by dividing the clumps every couple of years.

If you want to grow plants from seeds, you really have two choices. One is to plant seeds in flats, then transplant to four-inch pots and then put them in the ground when they have a good root system. The other is to forget about the mulch.

If you decide to go with planting seeds in flats, go to this Arizona Cooperative Extension site, which gives you excellent information on all the steps to take.

Mulch is very attractive and a good mulch will decompose and help the soil. But, weeds do still manage to come up, and the mulch will need to be replaced from time to time, as it either decomposes or washes off in hard rains. In your climate, you may need the mulch to protect the roots of your perennials over the winter. So, it's your choice.