Garden soils fall into one of three categories: clay, sand or loam. There are variations within these three categories. For instance, a sandy loam is a soil that contains organic matter but has a slightly gritty texture. This kind of soil drains well, but may need amendment to retain needed nutrients. Clay soils also need to be amended with organic matter to prevent compaction. Loam is the perfect garden soil. Its texture allows water to drain but also retains enough to keep plant's satisfied between waterings. Moonflowers thrive in loam soils. To test your soil, take a handful and clench it in your fist. If, when you open your fist, the soil is crumbly and lightly held together then you have loam soil. Soil that sticks into a ball is clay and soil that retains no shape is sand. Both clay and sand should be amended with compost before moonflower seeds are sown.
Moonflowers grow in pots as well as in garden plots. When choosing, or making your own, potting soil mix be certain to limit the amount of water retentive peat moss. Coarse builder's sand, vermiculite or perlite aid in drainage. A good seeding mix contains equal parts soil, peat and sand. Moonflowers do not transplant well so it is recommended that seeds are started in situ. Seeds, when nicked or rubbed against sandpaper prior to planting, will sprout and grow to maturity in a mix suited for seed starting.
Moonflower fails to thrive when planted in areas with standing water, compacted soil or other drainage issues. Seeds rot in the ground before they have a chance to sprout and mature. Mature plants develop root rot, wilt and die. Assess growing conditions before planting and amend soil as needed.
Soil temperature is just as important as soil texture and irrigation. Moonflowers cannot grow in cold soil. These heat-loving tropical plants germinate only when temperatures are above 65 degrees Fahrenheit.