Mammillaria marcosii isn’t famous for being easy to cultivate, but in good conditions with excellent ventilation, it grows without difficulty. It is especially sensitive to over-watering. So careful watering and an open mineral potting soil are a must. Avoid the use of peat or other humus sources in the potting mixture.
Don’t add limestone to the potting mix, which must be moderately acidic. Can be sensitive to frost. Requires maximum sun exposure to reach its full potential. and in order to achieve success in flowering.
A winter rest that allows the plant to shrivel will encourage flowering and long term survival. Be careful to encourage slow growth.