Winter protection for the Dwarf Redblush Grapefruit - Knowledgebase Question

Chehalis, WA
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Question by allrede
October 3, 2005
I'm very new at gardening, so I need all the help I can get. I was told that the Redblush Grapefruit does well in our Hardiness Zone 8 if protected during winter. This plant already had one fruit on it when purchased last spring, and it was delicious. The summer temperatures were good this year, but I'm afraid I might have over-watered. Fragrant and pretty blossoms did appear, and many starts of fruit are there, but they haven't developed in size for over six weeks.
Now I'm worried about the temperatures dropping to the upper 30's this week at nights, and winter's not here yet. I've put the plant in an 8x5 mini-greenhouse placed on my back deck (facing southwest), and protected from the wind (plant is still in original container). I now have a moister meter, also.
Is there some website I can get really good step-by-step instructions on how to preserve and protect this plant in this zone with our varying winter temperatures?
Thank you
Lu Allred

Answer from NGA
October 3, 2005
The first step is to transplant your tree into a new container. Containers come in a wide range of materials these days, so it is often hard to choose the right one. I tend to go for those made of terra cotta. The look is classic and if it's a well-made pot, it will last for years. Whatever type of material you choose, it is important that water can drain out of the container. Citrus trees must have good drainage; so select a container that has plenty of holes in the bottom.

The size of the container you choose depends on the size of the plant. If you purchase your dwarf citrus tree in a nursery pot, go up one container size. Bare root plants should be planted in a container large enough that the root system can be comfortably spread out, but not so large that the tree is swamped by soil.

Every 2 or 3 years as the plant grows, it should be repotted so it doesn't become root bound. As you increase pot size, consider using a more light weight material than terra cotta or purchasing a plant stand on casters so that you can easily move your tree around.

As I stated before, citrus trees appreciate good drainage so it is important to get the soil mix right. I have often seen recommendations to mix equal parts soil, sand and peat moss but I find that a good, light commercial potting soil or a soil designed for cactus works just fine.

Citrus trees require a long day of full sunshine and good air circulation to thrive. Position your plant outdoors so that it receives plenty of light and protection from strong winds. They can remain outside as long as temperatures stay above 40 degrees F. If your mini-greenhouse maintains a temperature above 40 degrees, your tree should winter over outdoors without problem. If not, you should plan to take it indoors.

If you plan to overwinter your tree indoors, place it in a shady spot for about two weeks prior to making the move. This will allow it to acclimate to the temperature change and prevent leaf drop. Once inside the citrus tree will do best if placed near a bright, southern or western facing window and away from heating vents.

Water your containerized citrus tree as you would any other houseplant. The soil should be consistently moist, but not soggy. In general, you should deep soak the plants every 5 to 7 days and fertilize them once a month. Use a water soluble, acidic fertilizer that is high in nitrogen.

It is important to prune back any growth that emerges from below the graft. This is sucker growth, which will not bear fruit. The graft is identifiable as a knobby area on the trunk.

To maintain a nice shape, prune the limbs any time of the year if the plants are overwintering indoors. If you live in a mild area of the country and leave your citrus trees outside for winter, it is best to save any pruning until the danger of freezing temperatures has passed. Pruning encourages new growth, which is susceptible to cold weather and even some of the warmest regions of the country can experience a surprise drop in temperature.

Citrus fruits require 6 to 12 months to mature, depending on the type and cultivar. Lemons and limes usually take about 6 to 9 months to go from bloom to edible fruit, while oranges generally take a year. It is hard to determine ripeness just by looking at the fruit, so your safest bet is to taste one. Look for fruits that have deep color and feel heavy. Harvest from the lowest branches first and work your way up.

Just like growing other types of produce, I believe that you will find nothing beats the taste of fresh citrus that you have nurtured from flower to fruit. It is a fabulous way to bring the garden indoors.

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