Tropical hibiscus

Question: Third yr plant. Early spring I repotted and trimmed roots. Leaves turning yellow in the past week. Watering daily. Why? Thanks!

responder: Answered by theHome and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 26, 2024, 9:52 AM EDT
response: Underwatering, overwatering and stress in general can cause leaf yellowing and drop in Hibiscus. They are generally forgiving plants once things are corrected. (The yellow leaves will fall.) While we can't tell the pot size in your photo, we think that the pot looks undersized for the plant and would suggest that you re-pot to a larger size, but don't trim roots. They take well to a pruning back in spring and naturally flush with new leaves into a bushier plant. Next spring do just that and not the roots. If there is no time-release fertilizer such as Osmocote in the soil mix, give it a dose of fertilizer.  We assume that you have a good drainage hole in that pot so that the water flows out freely each time you water. Add a saucer to catch excess and allow the pot to soak up extra for a bit- maybe 20 minutes, and dump any extra that is left so roots don't sit in water.  Depending on how much sun the plant is getting you may not always need to water every day. Stick your finger a few inches into the soil to see if it feels dry, or if it is cool and moist. Water when the first inch is dry.   Christine

responder: The Question Asker Replied June 26, 2024, 10:39 AM EDT
response: Ok so my pot is 15 in circumference and 12 deep. What ipsize would you recommend? When I pruned the roots I did put Biotone in the compost. I went ahead and dosed w Osmocoate today! Thanks!Sent from my iPhone On Jun 26, 2024, at 9:53 AM, Ask Extension <<personal data hidden>> wrote:   ﻿

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 26, 2024, 3:31 PM EDT
response: It's hard to recommend a pot size without knowing the overall plant size; the photo might be making it look much larger than it is, since to us, the pot does not look that large. Generally, a 15-inch diameter container is probably fine for most sizes of tropical Hibiscus.  Bio-tone isn't necessary since its primary marketed use is to provide beneficial microbes to the soil (which tend to colonize potting mixes by themselves, and aren't necessary for tropical plant root health). Its mild nutrient levels of 4-3-3 aren't harmful, but probably insufficient for most container-grown plants, since the nitrogen component will leach out somewhat quickly and continually as the pot is watered often to keep it hydrated in hot weather. Osmocote or any other time-release pelleted fertilizer should suffice since it tends to have higher nutrient levels. Sometimes Hibiscus benefits from an occasional boost in iron, manganese, or magnesium if the younger foliage becomes yellowed, which some fertilizer formulations (Bio-tone included, for two of those three) do not have in their nutrient mix.  It will potentially take a couple weeks, more or less, for the Osmocote to start being absorbed by the roots, which is fine. It won't reverse yellowing on any lower or older leaves that have begun to change color, but that's okay (no fertilizer will), and they will still shed once they have turned yellow. If the yellowing abates and new growth looks good, though, then the plant is recovering. Since its roots were pruned earlier, the plant might also just need time to regrow more roots in order to make use of all the added nutrients.  Miri

responder: The Question Asker Replied June 26, 2024, 4:30 PM EDT
response: Thanks again!Sent from my iPhone On Jun 26, 2024, at 3:31 PM, Ask Extension <<personal data hidden>> wrote:   ﻿

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 26, 2024, 5:00 PM EDT
response: You're welcome!