This year my family harvested another bumper crop from the apple tree in our front yard. These are good apples, surprising to many people who don't expect such fine fruit to grow in Manitoba. They are big, rosy, crispy, sweet and tart – great for pies and crisps and, of course, great for eating straight from the tree.

We enjoy this tree and its produce. After all, we planted it more than a decade ago, nurtured it through its infancy and watched it grow to fruitful maturity. The day after we picked apples this year, I was walking to work with these things on my mind when it struck me that the tree provides a useful metaphor for the trajectory of Christian discipleship. It takes time, endures hardship, enjoys fruitfulness and demands long-term commitment. Let me explain.

Patience. It was just a sparse twig with two leaves on top when we stuck it in the soil, smothered its roots with sheep manure and soaked it with water. In the winter it scarcely poked its point above the snow. In the summer it had to be protected from wayward frisbees and the grasping hands of playing children. In the first year it produced only a few leaves and looked like a lonely umbrella abandoned on the lawn.

But it had life and began to thicken and grow. Although it still seemed fragile and small, each year it sprouted new branches and more leaves. About year five it developed nice blossoms and shortly thereafter the beginnings of a crop. The first year it produced fruit we picked two apples; the following year six – enough to make a pie.

Pestilence. It didn't take long for the pests to arrive. The wasps were particularly nasty one year, searching for soft spots and taking up residence inside apples. Hail can damage quite a bit of the crop and the wind always shakes more than a few loose long before their time. Birds are also fond of the fruit, pecking and choosing their way through the tree, lacking the manners to eat a complete apple.

But humans present a greater problem. A fruitful tree on an unprotected front lawn is a magnet for neighbourhood kids and passersby of all ages, whose zeal for fruit is greater than their respect for property. Leaves sometimes litter the lawn after they help themselves to apples that aren't even ripe.

Which sometimes makes us feel like the bad apple – grumpy Jonahs jealously claiming an abundance not our own. We capture kids and subject them to stern warnings, but always offer to give them apples. "Just ask," we say. "Don't throw rocks and sticks into the branches." And slowly we've learned that conflict with kids can lead to contact with their parents and more places to give apples; and that kids who cause problems one year can become guardians the next. Yes, the fruit can be sweet.

Plenty. Harvest is fun. We pull out the ladder and the laundry baskets and start picking and throwing, catching and eating. It's a family affair, often with extras around to help out. We pick the tree clean, making much of the biggest ones and separating those with bruises. And then the boys do the counting – 664 this year. And that doesn't count the ones already in our stomachs or freezer, or those lost to theft or already given away. More than 800 fine apples each year from a small tree that was a twig. Amazing.

Perseverance. But this too I learned the hard way. A successful harvest does not finish the work. In fact, it creates a lot more. Dealing with bounty is a whole new calling. Attend to it or it will spoil. There is coring, peeling, slicing and freezing. There are pies to make and gift bundles to prepare and deliver. And the tree itself will soon need pruning. And...

So what does this teach me about Christian discipleship? That the pathway to fruitful maturity takes time and attention; that struggle is the arena to develop true strength; that growth is exponential and joy is part of the journey; and that good results are not the end of the story. In fact, they create more opportunities for growth, more work, more need for patience, more struggle and, if we are faithful, an even greater harvest of righteousness.