Ruby Red Grapefruits
'Ruby Red' was discovered on a 'Pink Marsh' tree in 1929 in McAllen, TX, and was patented in 1934. The fruit is of excellent quality, seedless ( 0 to 6 seeds), red-fleshed, oblate and thin skinned. The fruit usually has a red blush on an otherwise yellow peel.
The major grapefruit varieties in Texas are Rio Red, Ruby Red, and Henderson/Ray. All were discovered in Texas and all are red-fleshed, seedless and have varying degrees of redness in the peel.
'Henderson' and 'Ray' are usually lumped together in the industry as they are nearly indistinguishable. Both were discovered in the Valley in the early 1970's.The fruit of these two varieties is similar to 'Ruby Red' except that the peel is more attractive than 'Ruby Red' and the flesh is even redder. It retains some semblance of redness far longer than is the case with 'Ruby Red'.
Texas markets its 'Ruby Red' and 'Henderson'/'Ray' under the name Ruby-Sweet. Some 'Henderson' fruit are marketed as 'Flame' to distinguish it from 'Ruby Red' and to capitalize on Florida's 'Flame' grapefruit which is a nucellar 'Hendersoní.
Mature Tree Care
Watering of your grapefruit tree should be slow and thorough; probably every week or two would suffice in any but the very sandy soils. Nutrition should continue at about 1 cup of ammonium sulfate per year of tree age annually with split applications in February, May and September. .You'll need to adjust the rate for other fertilizers based upon the relative nitrogen content.
No pruning should be necessary, as the grapefruit tree will develop its natural shape without pruning. While mulching is not recommended for citrus trees, if you must mulch, keep the mulch at least one foot away from the tree trunk.