Kumquat tree: was dying, got it to stop dropping leaves, but how to stimulate growth?

Question

Kumquat Hi!

Thank you for taking the time to answer our questions!

Please find the attached images.

I have a Kumquat tree, and the label said "Fortunella".

I bought it from a flower shop this summer, and it was flourishing and bearing a lot of fruit. My apartment does not have much direct sunlight, so I placed it in the windowsill in it's original pot, only covered with a bag and basket to keep moisture inside. I also watered it too often and the bag collected water like a drip-basin, resulting in my tree almost dying. To make matters worse, it was attacked by spidermites which I brought into my apartment on another plant I purchased. However, by reading an article on this site, I saw my errors, and dried the poor thing for about a month after flushing salts and removing the bag, and at the current state it has stabilized and stopped dropping leaves (only I fear there are too few left). The spidermites also disappeared after some spraying and cleaning and after I removed about 2 cm of top soil from the pot. All the branches affected dried out and became brown, so I cut them off.

Now that I have tried to explain how things got to the state seen in the attached images, here are my questions:

First of all, is there any hope for my poor tree?

Can you please explain to me the basics of pruning?
 -Shall I cut the dead branch where it is brown (often 0,5 cm from the joint), or right at the joint where the bark is still green?
 -Is there any specific way to cut a branch resulting in new growth from the cut (as you can see, my tree only has "active" branches on one side)? My main goal now is to nurse the tree back to health, and try to stimulate even branch and leaf growth again.

How to I decide how the tree grows?

I've also considered buying a growing lamp, since I live in Scandinavia, and winter is coming. What kind of lamp should I get?

Can I even dream of fruit next year?

How often exactly should I fertilize, water, etc. as all guides I read say something like "occasionally", which to me means nothing since I have no garden experience on which to conclude on.

Again, thank you for taking the time to answer questions like this!

Best regards,

Alex

Answer
Hi Alex, let me help the best I can.  

I have a Kumquat tree, and the label said "Fortunella".  Fortunella is a root stock your kumquat tree may be on if it was't killed prior to your buying it.  If there is thorns on your tree it is gone, if not you saved it.  Toward the bottom is where the root stock is attached to the kumquat, nothing should grow out of the bottom part or it will take over and kill the tree.

I bought it from a flower shop this summer, and it was flourishing and bearing a lot of fruit. My apartment does not have much direct sunlight, so I placed it in the windowsill in it's original pot, only covered with a bag and basket to keep moisture inside. I also watered it too often and the bag collected water like a drip-basin, resulting in my tree almost dying. To make matters worse, it was attacked by spidermites which I brought into my apartment on another plant I purchased. However, by reading an article on this site, I saw my errors, and dried the poor thing for about a month after flushing salts and removing the bag, and at the current state it has stabilized and stopped dropping leaves (only I fear there are too few left). The spidermites also disappeared after some spraying and cleaning and after I removed about 2 cm of top soil from the pot. All the branches affected dried out and became brown, so I cut them off.

Now that I have tried to explain how things got to the state seen in the attached images, here are my questions:

First of all, is there any hope for my poor tree?  IT LOOKS LIKE YOU HAVE DONE A GOOD JOB BRINGING IT BACK TO HEALTH

Can you please explain to me the basics of pruning?
-Shall I cut the dead branch where it is brown (often 0,5 cm from the joint), or right at the joint where the bark is still green?  CUT BACK A LITTLE INTO THE GREEN ON A ANGLE SO WATER DOES NOT COLLECT ON IT.
-Is there any specific way to cut a branch resulting in new growth from the cut (as you can see, my tree only has "active" branches on one side)? My main goal now is to nurse the tree back to health, and try to stimulate even branch and leaf growth again.   ONCE IT IS HAPPY IT SHOULD START SENDING OUT BRANCHES ON ITS OWN.  A CITRUS DOES NOT NEED TO BE PRUNED ONLY IF IT IS CROOKED AND YOU WANT IT TO LOOK NICER AND OF COURSE THE DEAD BRANCHES ALWAYS REMOVE.

How to I decide how the tree grows?  I HAVE HAD CUSTOMERS GROW A TREE AND BRING ME A FRUIT WHEN THEY RETURNED FOR A VISIT TO FLORIDA.  THEY GREW IT IN THE BASEMENT, ETC.  BUT HAVE USED GROWING LAMPS TO HELP THEM.  OR YOU COULD PUT IT OUTSIDE WHEN IT IS NOT FREEZING AND BRING IT IN WHEN IT IS.  BE CAREFUL TO SLOWLY GET IT USED TO THE SUN OR IT COULD BURN ITS LEAVES.

I've also considered buying a growing lamp, since I live in Scandinavia, and winter is coming. What kind of lamp should I get?  AS I LIVE IN FLORIDA I DO NOT HAVE TO WORRY ABOUT SUCH THINGS SO THAT IS SOMETHING YOU WILL HAVE TO CHECK OUT ON YOUR OWN.
 
Can I even dream of fruit next year?  IT IS POSSIBLE, BEING IN A POT IT THINKS IT IS OLDER THAN IT REALLY IS WHERE IN THE GROUND IT WOULD TAKE MANY YEARS FROM THAT SIZE.

How often exactly should I fertilize, water, etc. as all guides I read say something like "occasionally", which to me means nothing since I have no garden experience on which to conclude on.   USE A SLOW RELEASE FERTILIZER SO YOU DO NOT BURN YOUR PLANTS.  GO BY THE MANUFACTURERS INSTRUCTIONS.  IF IT IS IN THE SAME POT AND THE ROOTS ARE FULL IN THE POT, AND AGAIN I AM GOING BY FLORIDA WEATHER AND HEAT.  I WOULD WATER ONCE A DAY, AND LET IT DRAIN, NEVER LET IT STAND IN WATER LONGER THAN 15 MINUTES   IF NEWLY PLANTED REMEMBER IS DRIES FROM THE OUTSIDE IN SO THE CENTER MAY BE WET AND THE OUTSIDE DRY SO WATER THE OUTSIDE WHEN DRY AND ONCE IN A WHILE THE WHOLE PLANT.  HOPE THIS HELPS.  HAPPY GARDENING.  KATHY