The Saint Joseph flower is native to South America. It was originally planted by farmers in that region as a trap crop for aphids. Today, organic farmers will occasionally plant a perimeter of this flower around their gardens to keep aphids from attacking their vegetables. The flower has brightly colored blooms consisting of five petals and a dark center. For this reason, they are attractive to hummingbirds. The plants can even be crushed and eaten as a crunchy topping for salads.
Place your plants in an area that has plenty of sunlight during the morning and evening hours, but is at least partially shaded during the afternoon. Grow your flowers in containers that may be moved to different locations throughout the day if you do not have a flowerbed that fits this criteria.
Add a support trellis if you have the climbing variety of Tropaeolum majus. Make sure your support is 6 to 8 feet in height and firmly staked into the ground. Clip off any unruly growth with a pair of garden shears to keep the flower growing in an upright position.
Keep the Saint Joseph flowers watered frequently. Water them with a garden hose every other day or so. Pay special attention to the roots of the flower. Mist the blooms lightly with fine spray during the evening hours, especially if you notice them starting to droop or wilt.
Check the plants regularly for signs of aphids. Look for tiny white bugs that are nearly clear. They are similar in size and shape to that of a tick. These will usually be found on the underside of the plant's leaves. Wash the aphids off with a strong spray of the garden hose.
Use an insecticidal soap to wash your flowers if the aphids return. Mix 1 to 2 ounces of soap solution to a gallon of water. Check the soap solution to make sure it is not white or very cloudy. If this is the case, discard the mixture and buy fresh soap. Add the soap solution to a garden sprayer. Spray the plants thoroughly first thing in the morning. Allow the soap to work for around 30 minutes, then rinse off with a garden hose.
Do not fertilize your Saint Joseph flowers. Many commercial fertilizers contain large amounts of nitrogen, which can be deadly to this species. Add organic matter such as yard waste or hay to your flower's soil if it does not seem to be thriving well.
Check the flowerbed frequently for signs of weeds. Pull these out by hand and discard in the trash. Rake the area lightly with a small garden rake to discharge any remaining roots from the soil after pulling the weeds out.
Cover the plants with a blanket or rug whenever the temperatures fall below freezing at night. Bring any flowers that are in containers indoors at sundown. Take off the covers and set container plants outdoors around mid-morning, after air temperatures have reached at least 40 degrees Fahrenheit.