Marigolds are very hardy plants, able to survive even in partial shade with moderate rainfall. While marigold seeds do not require extensive day-to-day care, you must pay close attention to soil quality during planting.
Marigolds will grow in soil with partial sand. If the soil is more than half sand, however, the seed may not establish a solid root structure. Ideally, marigolds should be planted in peat or loam.
Sand does not retain moisture as well as loam or peat. If your soil is sandy, your marigolds will require watering more frequently. Marigolds can handle arid conditions, but keeping the soil slightly moist to the touch promotes better growth.
A soil pH between 6.0 and 6.2 is recommended. After the seeds germinate and take root, a pH of 5.8 to 6.2 is acceptable. Soil pH testers are available at many garden stores. Hydrated lime mixed into your sandy soil to raises pH and sulfur pellets to lower it.