A plant that is hardy to USDA zone 4 is one that can survive temperatures from -25 degrees F to -30 degrees F. Zone 4 includes most of the State of Montana, parts of Colorado, Idaho, Wyoming and the northeast corner of Utah. The most suitable hibiscus to grow in zone 4 is the hardy hibiscus, and some varieties that do especially well in the area include Fireball, Copper King and Disco Belle, which has a very tropical look. Start your seeds indoors in early spring, then transfer outdoors after the frost.
Scarify the hardy hibiscus seed by rolling it gently between two pieces of sandpaper. You can also use baby nail clippers to slightly nick the seed coat. Don't cut too deep; just until you can see the white endosperm. Scarifying, which is the process of breaking the outer coat of the seed, will help it to break dormancy by allowing moisture and air to get to the embryo.
Mix together the compost and perlite in a small container. Pour the mixture into a 4-inch planting pot that contains potting soil and water it well. Allow the pot to sit, draining, for at least one hour. You want the soil to be wet, but not soggy, when you plant the seed. This is so it will sit well in the soil and not float around.
Plant the hardy hibiscus seed one inch into the soil with your fingers and cover it with soil. Place the pot in a plastic bag, and secure the top of the bag with a twist tie or a rubber band. This will create a mini-greenhouse effect and keep the soil moist and the humidity high, which aids in germination.
Place the bagged pot in a well-lit area. Check the soil daily to make sure it is moist, but not soggy. Too much water will cause the seed to rot. If the soil feels dry, use a plant misting bottle filled with water to slightly moisten it. If you notice a white, powdery fungus on the surface of the soil, open the bag for an hour or two every day to allow air to circulate.
Remove the pot from the bag when the seed sprouts. Germination can take anywhere from three weeks to six weeks. When the danger of frost has passed, it is time to transplant the seedling. Until then, the seedling will be fine in the germinating pot. Just make sure it gets enough bright, indirect sunlight.
Choose an area of the garden that gets sunshine all day when you are ready to plant the seedling outdoors. The hardy hibiscus requires at least five full hours of direct sunlight a day. Using a gardening trowel, dig a hole in the soil the same depth and width as the pot in which the seedling is growing.
Tip the seedling carefully out of the pot and place it in the hole. Fill the hole with soil, making sure to pack the soil down with your hands as you fill in order to remove any air pockets. When the hole is full, tap the soil around the base of the seedling to make sure it's in good contact with the soil.
Water the seedling with the fine mist setting on your hose so you don't disturb too much of the soil.
Poke your finger into the soil, and when the top one inch of soil feels dry, you will know it is time to water again.