For citrus to grow well, the golden rule is NO grass below them.

In fact, they like the grass removed right out past the dripline. The dripline is the area directly below the outer branches. Citrus tree roots feed close to the ground surface and usually below the dripline, so grass will deprive them of their food.
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Most citrus are durable plants able to survive temperatures close to freezing.
However, at low temperatures plants go very dormant and can be slow to wake up. A better bet is to aim for a minimum of 50 ̊F in a cool, bright room indoors. Our lime lived out the winter parked at the end of a dining table, sharing a humid microclimate with other plants. Fed roughly once a month with a citrus winter feed, the lime was a cheering sight all winter with glossy leaves and a succession of scented, cream-white flowers (inset). But now all citrus need a little attention to keep them flowering and fruiting.
Citrus trees are heavy feeders, requiring lots of rich organic composted matter to produce a tree ladened with juicy fruit.

After removing the grass, spread organic fertilizer onto the soil, keeping it away from the trunk. Fully organic fertilizer promotes strong and robust growth. Use a citrus fertilizer at a rate of 1 – 2 lbs. for every year of age. Fertilizer should be applied around drip line of tree. Do not put up next to the trunk. Slow release fertilizers work well and can be used less frequently; follow the instructions of the manufacturer.
Citrus flourish when well mulched.

Spread a layer of mulch on top of the fertilizer. Be sure to spread this out past the dripline and leave a gap around the trunk.
Don’t forget to give your citrus a good deep watering.

This will help promote strong growth, ultimately producing crops of sweet and luscious fruit. Newly planted trees should be watered regularly for the first three months, if rains are inadequate. The soil should dry down between waterings. For trees in containers, watering will need to be more frequent since the tree isn’t planted in the ground. Let soil dry between watering. If the tree stands in water, it will get root disease.
Citrus trees require full sun year round.

It is best to plant your tree such that it will get as much available sunlight as possible. If you live in a northern climate where you must move your tree indoors, try to place in a sunny location. Morning sun is the most beneficial for your tree. The south side of your house will usually provide the most sunlight.
Finally, don't forget to stop and smell the blossom!

Although citrus don't always follow a strict fruiting season, they usually flower at some point between February and May, so do find time to enjoy the fragrant blossom when it's out.