It's been well documented about the population decline and near extinction of the beautiful monarch butterfly. It is essential that existing habitat be protected and new habitat created. Fortunately, here in the SF Bay Area, our suburban and rural environment is relatively compatible with these treasured insects. It's not that difficult, but it does require some basic elements. Space is needed for the rather large milkweed plants to grow. I would say a minimum of 30 square feet would suffice for the milkweed plants. Also you need to have other plants to attract butterflies and insects in general. I use Mexican Sunflowers (ie Torch) to attract butterflies, bees, and hummingbirds. Milkweed and Mexican Sunflower plants need direct preferably afternoon sunlight to grow big and strong. Don't expect to use a shaded area near a tall fence or building UNLESS it faces south. Once the milkweed plants are established, they will live very nicely without irrigation for several years. The milkweed plants will die back to the ground in the winter, leaving stems will help locate where they are to avoid disturbing them. Mexican sunflowers will die back and need reseeding in the spring.
The biggest problem I have encountered with growing milkweed plants is with the aphids they attract. These are not ordinary aphids my friends, these are oleander aphids. These bright yellow invaders look like aliens from space. I had tried all kinds of things to control the yellow oleander aphids. Some things worked temporarily, or they hurt the milkweed plant itself. Isopropyl alcohol is an example. Too week on the concentration and the bugs are able to survive, and too strong will kill the branches where the bugs are camped out.
So the thing that has worked the best for me is a simple soap and water mixture. This tip was given to me by a friend who specified using Dr. Bronner's castile soap in a 1 to 3 part ratio with water. So that's three parts water to 1 part liquid soap. Spray the effected parts of the plant, taking care to give the aphids a nice coating. It works great! In a day or two, the aphids will have started turning black, meaning they died. But the milkweed plant is completely unaffected.
It is important to check your milkweed plants for aphids daily. Being proactive will confine the infestation to small colonies which are managable. I take little ties or ribbons to mark the infected branches. That makes them easier to find when following up later to spray or inspect again.
A brand new store has just opened in New York City that sells Husbands. When women go to choose a husband, they have to follow the instructions at the entrance: You may visit this store ONLY ONCE! There are 6 floors and the value of the products increase as you ascend the flights. You may choose any item from a particular floor, or may choose to go up to the next floor, but you CANNOT go back down except to exit the building! 
