Thought citrus growing was just for folks down south? Meet David Tessier, a dentist in Kingston, Ont., who grows an astonishing 50 varieties of citrus in his suburban house and city office. As far as he knows, that's a Canadian record.

Tessier's trees are small versions of the ones in southern groves, but you can still eat the fruit. What first intrigued him as a teen some 20 years ago was the sight of small trees bearing miniature oranges in a supermarket around Mother's Day. They were calamondins and, like all citrus, they have edible, colourful fruit and glossy evergreen leaves. As if those attributes weren't enough, they also have scented blossoms. Tessier says, “One of the biggest attractions for me is the fragrance of the flowers. It's almost intoxicating.”

One of his first purchases was a ‘Ponderosa' lemon, whose two-kilogram (five-pound) fruit is the Goliath to the calamondin's David. Over the years Tessier added plants and reference books to his collection whenever he could and even toured research groves in Florida where, he says, “they had most of the known citrus varieties – more than 250.”

Most of these varieties are difficult to obtain in Canada without resorting to importation. Calamondins and the similar looking kumquats are easier to find, showing up from time to time in supermarkets or nurseries. Fortunately these two plants, along with lemons and mandarin oranges, are among the easiest citrus to grow indoors. “The kumquat is my own personal favourite,” says Tessier, “because it's just loaded with fruit like a Christmas tree with baubles on it.” He cautions that grapefruit, limes and regular oranges are difficult and adds that it's seldom wise to plant the seeds you find in fruit – that is, if you hope for more than just a leafy, thorny houseplant. Citrus are so variable that you could plant an orange seed and end up with a grapefruit, and they are also very slow to mature from seed. “I planted a grapefruit seed 25 years ago and still haven't had any fruit,” says Tessier. Better to purchase a fruiting plant or root a cutting taken from a plant you like.

Indoors and out
Citrus can stay indoors year round. A south or southeast window is best, says Tessier. But the plants will thrive outdoors after spring frosts have ended – none can tolerate more than a touch of frost – provided they are hardened off properly in preparation for the outdoor move.

To gradually acquaint them with outdoor conditions, set them in the shade and only for an hour the first day. Increase the length of time they spend outside and gradually expose them to the sun for two weeks. Then, if you like, leave the plants outdoors all day and night in a place that is in full or partial sun and sheltered from strong winds. Too rapid a change from inside to outdoors can lead to sunburn and defoliation. If frost threatens, cover plants with old sheets or move them inside for the night.

Hooked on citrus
Tessier, who is married and has two children, is forced to use every suitable niche both inside and out for his ever-growing collection. In summer his small backyard is so full of citrus plants of all types and sizes that his eight-year-old daughter, Charlotte, told him, “Daddy, if you keep this up we won't be able to play in our yard.”

In the house his plants press up against every window. “We don't need blinds,” Tessier laughs. “We can't see through the windows in winter because the citrus leaves are in the way. My wife, Nadine, says we need a bigger house and I agree. Maybe then I could grow 20 grapefruit instead of only six.”