dear green thumbs I live in soutern ontairo I have a grapefruit and lemon tree both 6 foot tall with branches all the way up should I trim them off . Nice looking trees but no flowers yet.
You can prune to shape your citrus. You say " branches all the way up should I trim them off?" Why would you want to trim them off all the way up? Maybe I'm not quite getting what it is you want to achieve. If a serious pruning is what you seek, remember citrus bark can sunburn. Most trees are allowed to carry low branches for this reason.
More information is needed. Are these trees grafted? If they are grown from seed, the thread grapefruit | UBC Botanical Garden Forums may be helpful; the juvenility period for a lemon is 2-3 years - much shorter than that of a grapefruit. If they are grafted, they may need to be exposed to a period of lower temperatures to promote flower buds. As for pruning, if a patio tree is what you want then the lower branches will of course have to be removed. Since you are in Ontario I assume the trees will be grown as indoor/outdoor trees which means they'll need pruning for size control. Having said that pruning should be kept to a minimum as it will slow the development of a citrus tree.
If you want your trees to fruit you must not prune them. All citrus will ONLY begain to flower and fruit when the trees becomes mature. A citrus tree (lemons, limes, oranges, grapefruits, kumquats, and ect.) become mature ONLY when they have produced (grown) the required number of nodes. A node is every place a leaf is connected to a branch. In the beginning after a citrus seed germinates, it will produce a small branch and its first attached leaf, that is the first node. Soon the branch grows longer and produces a second leaf, that is node number two. After a year or so the branch has grown approximately 18 inches long and has produced perhaps 24 leaves or 24 places on the branch where a leaf is attached, thus the branch now has 24 nodes. As the years go by the tree gets more and longer branches with more and more leaves attached to them and thus more and more nodes. Finally the tree reaches the required number of nodes and it begains to bloom and produce fruit. I don't know, of course, what that number is, maybe 15,000 - who knows. Another way to say it is when the tree has grown the required amount of nodes (attached leaves) it is now a mature tree. If you take a cutting from the top of a mature tree that has reached the required amount of nodes, thus is now producing fruit, and graft it onto a small rootstock, the cutting "remembers" where it came from off the mother tree ("remembers" its node count) and will produce blooms and fruit on the new grafted tree in a year or two. All it will require is to get a little height. That is why grafted trees fruit in just a year or two, and why seedlings take 4 to 15 years depending on the variety of citrus. So if you prune your citrus trees you are constantly reducing the number of nodes (leaves), and therefore you are keeping the tree from ever reaching the required number of nodes to become a mature tree, thus the tree cannot flower and fruit. Pruning greatly delays a citrus from ever producing fruit. Also when someone says it takes 4 to 15 years for a seedling citrus tree to produce fruit they are talking about a tree growing outside. A tree that spends half of its life indoors where the growth slows down or stops for 6 months of the year can take MUCH longer to begain fruiting. There is a seedling grapefruit tree for sale on e-bay at the present time that is 15 years old and so far has never fruited. Hope this helps you, take care - Millet
