I am not a current resident of Toronto but was born and raised there.I hope I can still ask for your help. I have a grapefruit tree as a houseplant that grew from seed 40 years ago. It puts out a few new branches every spring and sometimes during summer. This year 2024 it started putting out new growth on every branch throughout the tree. I has never produced so much new growth all at once before. You can imagine how excited i was. But then after a few days all growth stopped. It like it is in suspended animation. this happened the end of Feb 2024. This tree has lived in bright light but not direct sunlight for most of its life, and just this past Dec. 2023 i move my tree to a south facing window where it gets full sun for a few hours a day. I live in Edmonton, Alberta. I’ve enclosed a couple of photos to show what stage that the new branches and leaves stopped growing. Is there anything that i should do from here? Thank you for your help.
Thank you for contacting the Toronto Master Gardeners. Congratulations for having this houseplant for over 40 years.
It appears you have been successful in growing and maintaining your grapefruit tree so far and the only change has been changing its location to a south-facing window with direct sunlight.
A few thing to consider:
Perhaps by moving your plant to a sunnier spot, it was tricked into regrowth earlier than normal.
Is your plant drying out due the new spot being near a vent or from too much sunlight? As daylight increases, you may need to increase the watering frequency. Water well and keep evenly moist. Good air flow is also important.
Another thing to consider is whether your plant needs re-potting. If your plant has lots of roots, you may need to re-pot it into a slightly larger pot using a good well-drained all purpose potting mix. As citrus plants generally prefer acidic conditions, adding a mixture of one-third perlite or vermiculite, and one-third peat or other organic matter to the potting mix will help keep the ph down. Starting in April you can begin to fertilize your plant with a fertilizer designed for acid-loving plants.
The leaves in the picture you sent look quite healthy so it is unlikely that your plant is being infested by a common citrus plant pest such as scale, whitefly or spider-mite. Keeping the leaves clean by occasional washing and checking the undersides and tops of leaves for pests will prevent any infestation.
The following resource from the University of Minnesota provides a good guide on growing citrus plants indoors:
https://extension.umn.edu/houseplants/growing-citrus-indoors
Another resource that you might find helpful is the Gardening Know How “Guide to Growing Citrus Trees Indoors” which is attached:
https://www.gardeningknowhow.com/edible/fruits/citrus/growing-citrus-trees-indoors.htm