Thrips thwarting hibiscus from opening its buds
Q: I bought this hibiscus in late May. It had beautiful pink blooms, and continued blooming for a couple of weeks. Now it has completely stopped blooming. It gets a lot of buds (in fact the plant is loaded with buds) like it’s going to bloom, but never does. I gave it some MiracleGro fertilizer to see if that would help. That made the leaves get real pretty, but still the buds won’t open up. Any suggestions or comments would be helpful. — T.K., Albuquerque
A: When I read your letter, my first thought on the blooms not opening was thrips.
Thrips are a wee tiny bug that live deep in a bud, and as they eat or rasp away at the base of the bloom petals, they cause so much dysfunction that the blooms can’t open properly. I don’t know how all of a sudden they show up, but since they are so very tiny, perhaps they are wind-blown or hitch a ride upon some unsuspecting pollinator and jump off when they arrive at a plant that offers lots of flower buds. I just don’t know.
Anyway, you can test for the presence of thrips and that’s a fairly easy project. You’ll need a bright white piece of paper, a flashlight, a pair of scissors and a fresh bud from your hibiscus. In a spot where there is no wind, perhaps the kitchen counter or on a patio table, lay down the paper and then snip the bud open.
Next, thump the bud pieces on the paper several times. Using your flashlight, investigate any specks of what looks like sand granules that are on the paper. Hold the flashlight close to the “sand” so it warms up a bit from the light. If the sand starts to move around, and if it is thrips it will, then you know that’s most of the reason your hibiscus buds aren’t opening. If you own a magnifying glass or a loupe, that can help you look at the “sand” even easier.
So if you do discover thrips, you can then treat them. First thing you’re going to want to do is snip off any and all buds the hibiscus is wearing. I mean all of them, from the smallest undeveloped bud through the older ones. All of them have to go since that’s where the thrips infestation is living.
Next, you’ll spray the plant with a ready-to-use pesticide that contains either insecticidal soap or pyrethrin. First, give the plant a good watering. Then spray the plant thoroughly, top to bottom, inside and out, and even spray the top of the soil in the pot with the insecticide of choice. Please be sure to do this very first thing in the morning before the heat of the day or late afternoon, especially if the plant lives in a spot with a lot of sun. I would treat every five-toseven days, at least three times, to hopefully eradicate the thrips.
Be sure to throw away the snipped off buds too. Don’t allow them to sit on the ground near the pot, and certainly gather any that fall back into the pot as you do the snipping. I won’t recommend composting the snipped buds either. Be as tidy as you possibly can.
The plant should set a new and continuing series of flowers, and as long as you are committed to applying a maintenance spraying when you first see very young buds, you could get lots of flowers opening. Keep the potted plant well-watered as the picture does look like it is being kept on the dry side. Also, the color of the pot seems dark. If it’s sitting where it’s getting cooked by a lot of sun daily, consider replanting into a lighter-colored pot or relocating it until this wicked heat abates. Dark pots can act like ovens, cooking plant roots. Granted the plant may be surviving but as a defense mechanism it aborts any bloom it might set.
Also, the plant I believe you have is a tropical hibiscus. Know that it is not winter hardy here and will need to be brought in before the first frost this coming autumn.
You can win the war against thrips and with your description of what’s happening to the hibiscus, I think that’s what’s going on.
Hope this helps and keep on Diggin’ In!