Fragrant, colorful and delicious, citrus trees are a joy to grow if you give them a little attention.
Here are plant and care recommendations.
By Sue Price
One of Marcela Ot’alora G.’s favorite memories is drinking lime water made with the fresh limes that grew so readily in her native Colombia. But when Marcela exchanged the Andes for the Rockies, she thought perhaps she could never grow a lime again.
She isn’t alone in that belief. Many local gardeners think they can’t grow citrus in our climate. While a year-round citrus grove isn’t feasible, local home gardeners are experiencing sweet success in growing their own lemons, limes and oranges, both in and out of their homes.
A Boulder resident for the past 12 years, Marcela says her love of citrus trees starts with the blossoms’ wonderful fragrances. “I have a little lime tree that gives me tasty limes all year-round. When it flowers, the aroma is like French perfume,” she says.
Four years ago, Marcela bought a small lime plant from a local grocery store. “I just really wanted some fresh fruit, so I thought I’d try it,” she says. She potted her tree in the fall and then didn’t pay much attention to it. By December, it was covered in blooms and emitting an “amazing fragrance.” By March, about 10 limes sprang from the limbs. Her tree continues with this pattern twice a year, but citrus can actually bud all year.
To keep her tree small and portable, Marcela carefully clipped the roots—a practice she learned in her native Colombia—before potting it into a 12-inch pot. She has since repotted it into a 14-inch container and prunes back the branches by at least a third twice a year.
She keeps it inside in winter, and takes it outdoors in summer. “I do it slowly,” Marcela explains. “I take it out in the day, then bring it in at night for the first few weeks.” In fall, she lets the tree stay outside in the daytime, but always brings it in at night..
Nick Snakenberg, curator of the tropical collection at Denver Botanic Gardens, agrees that cautious treatment is needed when growing citrus out of its natural element. “You can definitely grow citrus here,” he says, “but you can’t grow them out in the yard. You need to grow them in a container, similar to a ficus tree.”
Snakenberg suggests buying dwarf varieties—trees that naturally stay smaller. “The bigger the pot, the bigger the tree is going to grow. You should err on the side of under potting a tree, because logistically it gets harder to move it inside and outside with the seasons,” he says. When the tree is inside, place it near a south-facing window. The tree will likely drop a lot of leaves, but don’t be alarmed. Just keep it alive until you can place it outside again.
Citrus trees flourish in full sun, but you have to let them gradually adjust to the outdoors. “At the Gardens, we have them in a greenhouse,” Snakenberg says. “These trees will take as much light as you can possibly give them.”
When transitioning to the outdoors, put the tree in a partially shaded area for at least a week, he advises. “They can’t handle full sun right away. Plants can get sunburned, too, and leaves that get sunburned will die.” Protect the tree from the day’s strongest sun by placing it in a sheltered area where it can also avoid the full brunt of dry summer winds.
Because Colorado’s variable weather can trick plants into thinking warm temps are here to stay, it’s best to wait until mid-May to transfer the tree outside. Snakenberg says citrus trees can handle a light freeze, but if a hard frost is predicted, put a protective sheet over the tree or bring it indoors for the night.
Bring the tree back inside by mid- to late September. .
Watering a citrus tree is not an exact science. “People always want some exact formula for watering,” Snakenberg says, . “but the best I can say is, ‘Water when it needs it.” Citrus trees originate from hot, dry climates, so they should never be soggy. Water throroughly, then let the plant dry out between watering’s, he says.
A tree will need more water while outside than during the winter. When it’s inside during the dry winter season, occasionally mist the tree to boost humidity.
Snakenberg prefers clay containers because they help the plant dry out faster. But as long as the container has drainage holes any pot will do, he says. To aid drainage, blend three parts potting soil with one part gravel.
Citrus trees also benefit from fertilizing. Any general fertilizer is sufficient, Snakenberg says, as long as it includes micro nutrients such as iron and magnesium, and additional phosphorus.
“Phosphorus is considered a macronutrient—a nutrient that a plant needs in larger amounts than other nutrients,” he explains. “Phosphorus is a necessary nutrient for citrus trees, and is especially helpful in promoting strong root growth and flower production.”
In hot weather, a layer of mulch on top of the pot will keep the roots from overheating, and also slow evaporation from the soil, “reducing the frequency of watering’s,” he says.
Pests are the biggest threat to citrus trees. “Citrus trees are susceptible to every kind there is,” Snakenberg says, adding that the trees are more vulnerable to pests indoors. Pests are less problematic when the tree is kept separate from other plants and garden areas.
One of the most prevalent is hard-armored scale. These soft pests with a heavy shell glue themselves onto vulnerable limbs and leaves. The best way to remove them is to scrape them off by hand or with a cotton ball.
Snakenberg recommends spraying the tree with horticultural oil to suffocate pests, rather than using pesticides, which can end up in the fruit. Aphids and mealybugs also attack citrus, but are easy to remove with rubbing alcohol or a small amount of mild dish soap. A high-pressure hose can “blast” aphids off the tree in the yard..
Of course, the best reward for growing your own citrus tree is enjoying the freshest fruit possible.
“The taste is just incredible,” Marcela says. “When I cut one open, I am instantly transported to my home country of Colombia. If I close my eyes I am there in the Andes drinking lime water. It’s amazing.”
Snakenberg agrees: “You’re not going to have a huge, constant supply of lemons, limes or oranges, but knowing you grew them makes them taste better.”
Here are the best citrus trees to grow in this area, according to Nick Snakenberg, curator of the tropical collection at Denver Botanic Gardens. Remember to look for the drawf varieties.
Improved Meyer–This tree is perfect for patio growing, and it’s lessthrony and more disease-resistant than most. The fruit is sweeter and less acidic than the average lemon, making it ideal for cooking and baking.
Eureka–With this dwarf variety, you can make lemonade out of lemons anytime. Pick this plant for year-round production.
Bearss Seedless–No need to get pricked when you pick! This variety has mercifully fewer thorns than others, and the fruit is juicy and seedless.
Mexican Lime–This is a true Key lime variety. It can get a little thorny, but the wonderfully tart flavor made so famous by Key lime pies makes up for it. It’s also easy to grow and pleasantly low maintenance.
Washington Navel–This hardy seedless variety is very popular for its exceptional taste and easily peeled fruit. It’s considered the best for patio growing, even though it has a tendency to grow too large for easy mobility. Pruning can keep that in check.