Below zero temperatures usually don't bring flowering lemon and lime trees, but Dakota College at Bottineau has the advantage of a greenhouse.
Horticulture instructor Diann Beckman said two bare seedless lime trees and one Meyer lemon tree are heavy with fruit this winter.
"That litle (lemon) tree is only about 2 feet tall and it had 26 lemons on it," said Beckman.
Dakota College at Bottineau’s greenhouse has flowering lemon and lime trees.
Students and visitors to the greenhouse can pick the fruit off the tree.
"There's a lot of lemonade and lime water," said Beckman.
One of the lime trees is 6 feet tall and another is only a couple of feet tall. The greenhouse is also full of other fruit trees exotic by North Dakota standards, including a banana tree.
"When the bananas are ripe, we eat bananas until we're sick of them," said Beckman.
There's also an orange tree in the greenhouse.
Beckman said the secret to a successful harvest is making sure that the fruit tree gets lots of bright light. She put the trees outside last summer and let them soak up the sun. They flowered heavily, a good indication of a bountiful fruit harvest.
In the winter the trees should face a sunny south window for between 8 and 12 hours.
Beckman said indoor citrus trees are easy to grow. They require a well-drained soil mix containing hardwood shavings, sand and peat moss, which should be kept moist. Garden soil doesn't work well. The tree should be fertilized each month during the active growing period.
Fruit trees that can be grown indoors include dwarf lime trees, orange trees, lemon trees, grapefruit, tangerines, calamondin oranges, clementines, dwarf pomegranates, banana plants, pineapple plants, olive and fig trees.
"People should give them a try because they're fun and they're really easy to grow," said Beckman.