Grow a patchouli plant by planting it in well-drained soil under full sun, watering it regularly, keeping the soil moist and carefully pruning the plant to encourage growth. Plant the patchouli in a pot when in an areas with winters that fall below 10 degrees Fahrenheit, or transfer the patchouli to a pot every winter.
Plant patchouli in an area that receives plenty of full or partial sunlight. Water the plant regularly once the top 1/2 inch of soil dries out, but avoid overwatering as this can cause rot. Hot weather and potted patchouli require more water. Add 4 inches of leaf, straw or compost mulch to the soil around the roots to retain moisture, inhibit weed growth and add nutrients to the soil.
Give the plant a diluted, general-purpose, water-soluble fertilizer once a month during the growing season or once every six weeks during the growing season for outdoor plants. Stop feeding the plant in the fall and winter so that the plant can go into dormancy. Pull out any weeds regularly. If hoeing the weeds, don't damage the patchouli roots.
As the plant grows, snip 1/2 to 1 inch off the ends of stems down to the nearest leaf node to encourage the plant to grow bushier.