Melocactus ernestii grows with light yellowish green to dark green, almost spherical to short cylindrical bodies that reach heights of 9 to 45 centimeters and a diameter of 7 to 35 centimeters. There are 9 to 13 more or less rounded ribs or ridges with a slightly sharp edge, each with a row of spines usually about long. The spines are banded red and yellow or reddish or brownish in color. The 3 to 8 central spines, the lowest of which are curved or straight, the spines can occasionally be as much as in length, exceeded only by
Ferocactus emoryi subspecies
rectispinus. The 7 to 13 straight or outwardly curved radial spines reach lengths of 4 to 15 centimeters. The cephalium is the red, columnar, formed from more or less pink-red bristles, which is rarely covered with white wool at the top, is up to 18 centimeters high and reaches a diameter of up to 8 centimeters composed of hundreds of small, tightly packed flowers and grows a little longer each year. The light to dark magenta pink flowers are 1.95 to 2.9 inches long and have a diameter of 9 to 18 millimeters. The fruits, which are deep pink to red at the top, are 1.4 to 4.5 centimeters long. ==Distribution==