The Ruby Red grapefruit (or Citrus paradisi “ruby red”) is a citrus tree that is known for producing a yellow fruit with a seedless, red flesh interior. Also referred to as a “redblush tree”, the Ruby Red is a fast growing tree that can get to a mature height of 15-20 feet tall (if left unpruned) and a width of 8-10 feet. The tree is a tropical citrus and will thrive well if planted outdoors in zones 8-11 but can be potted and brought indoors for zones 4-11 during the colder seasons. The best time to plant a new Ruby Red is after the threat of frosts have passed and before hot summer heat sets in.
Choosing a location: Location is very important when deciding where to plant your new grapefruit tree. These trees must have a full sun location with well draining soil. Avoid planting within 25 feet from buildings, driveways and sidewalks for adequate space to grow. Amending your soil before planting is recommended and a drainage test should be done on the soil. Dig a 1 foot by 1 foot hole, fill it with water and wait one hour. If the hole has drained all the water, then the location is good. If there is water retained, then amend in some sand and perlite.
Planting directions (in ground): Try to find a spot on the southernmost area of your home for optimum sun exposure and optimal cold weather protection.
1) Make your hole twice the size of the root ball and just as deep to accommodate the root system.
2) Keeping your tree straight, begin to back fill the hole (be sure the bud union is just above the soil surface). When you have the hole half way filled, firmly press down on the soil to rid it of any air bubbles and then add water to settle the soil.
3) Back fill until the hole is level with the surrounding soil or slightly mounded. Citrus hates to be in any standing water.
4) Apply a 3-4 inch layer of organic mulch such as leaves, pine needles, hay or compost and spread to the edge of the canopy. Keep the mulch 2-3 inches back from the trunk to discourage rot, disease and insects. Water slowly and thoroughly.
*TIP* For Hot, dry areas where sunburn can be an issue, cover the trunk of the tree. You can use an equal mixture of non-enamel, flat, latex paint (interior) mixed with water or just wrap the tree.
Planting directions (potted): Avoid using any type of porous containers as soil moisture is more difficult to monitor. Try and find a nice smooth edged pot like plastic which is also more lightweight and easier to move in or outdoors during cold/hot seasons.
1) Your pot should have multiple drainage holes for water to pass through easily. Drainage is essential!
2) Your potting soil should be a good quality mix that is lightweight and has inorganic materials such as vermiculite and perlite which will assist with drainage and aeration. Avoid any potting soil with chemical wetting agents.
3) When you go to pot the tree look for the grafting union. This is where the fruit tree was grafted to the root stock slightly above the root ball. This needs to remain above the soil line. Tamp down on the soil slightly to avoid air pockets.
Watering: Be sure to water your tree regularly for its first year once every 5-7 days and more frequently during the hot season and periods of extended drought. Water deeply right at the base of the tree so the root ball stays moist. After the first year the tree’s roots will become a bit more established and you can reduce to watering once every 7-14 days. Water further out from the trunk at this point to ensure all of the roots are receiving an ample amount of moisture.
Root rot is always the biggest concern with potted citrus trees so you will have to monitor the soil moisture closely at first to get an idea for how often watering will be needed. A good way to indicate when you need to water is by using your index finger. Stick it into the pot and feel around for moisture, if there is still some present in the soil, hold off on watering. If it feels like it is drying out on the top couple inches, water just enough until you see it escaping the drainage holes and stop. The aerated potting mix should assist with the drainage.
Pruning: As with most citrus trees, suckers can form near the base of the tree and rob the primary trunk of nutrients if left unchecked. Remove these growths as they appear by pinching them off of the tree or use a sterilized pair of cutters to remove them. You can easily sterilize your tool(s) by wiping them with a household rubbing alcohol. Prune off any dead or damaged branches in the early spring after the threat of frosts has passed. DO NOT prune your tree more than absolutely necessary to avoid the spread of “gummosis.” This can be a major health threatening issue that comes from excessive pruning of the grapefruit tree. The potted Ruby Red will not require any pruning, it should develop its natural shape on its own.
Fertilizing: During the spring and summer months, feed your Ruby Red with a tablespoon of ammonium sulfate once a month during the first full growing season. The following year use a ½ cup of the sulfate once every 4-6 weeks beginning in February and ending in August. The third year use 1 ½ cups of the sulfate in the same time frame (Feb-Aug). Water thoroughly after each feeding.
Container grown Ruby Red grapefruit trees will require a well balanced fertilizer formula specialized for growing citrus. This formula already contains all of the micronutrients that the tree will need. Feed the trees regularly, but be sure to follow the directions on the fertilizer’s packaging to ensure you don’t overdo it. The typical time frame for container grown citrus is to start in February, and provide fertilizer once every 4-6 weeks until September.