Extreme Heat

[jpiper82]

The weather in Texas (Dallas) is unbearable, night time lows in the high 80's and low 90's. Daytime highs 102 to 105 with heat indexes running around 110.

With that said all my Hibiscus are severly stressed! Flower production is scant and the blooms are 25% of normal.  All I can do is make sure they are hydrated, I water 3-4 times aday depending on the individual needs of the plants.  Yellowing of the leafs have increased substantially.  Not to much bud drop, but some.

Because of the huge amounts of water required, I have reduced the amount of fertilizer I use, only giving them some every third watering. I still use chelated iron and SuperNova once a week.

The only positive note is that Heaven Scent, has proved to be a superior plant, and has kept its great bush. Flower production has reduced, and the flowers are smaller but still good.

If I can get the plants to the middle of September, possibly this fall things will improve.

John

[Doll]

I feel your pain. Temperatures in Houston aren't as high but with our famous humidity the heat index is running the same. High Voltage and Simple Pleasures are holding up the best for me. All of my 4 inch plants had to be moved to a shady location. They couldn't even take an hour of sun in this heat.

[Charlie]

Hard to relate to that kind of heat here in southern CA where we are just now trying to get to 80 but not making it. Much of the country has had extreme weather this summer but for us that has meant cold and overcast.

My worst experience with hot weather happened one spring when my supplier was late in getting the shade paint we rely on to shade and cool the greenhouse in summer. During the 2 week wait the temperatures inside the greenhouse hit 115-120F during mid-day. The change in the hibiscus was dramatic, much as you all have described despite being flooded with water twice a day. Most quit blooming and the others made blooms that were 1/4 the normal size. One did OK - Fantasy Charm. Bloom size went down from 10 inches to about 7 inches but that seemed great compared to the others. Not sure why but it might have to do with the small buds that it makes before the flower opens.

The August, 2010 HVH Newsletter contains more tips and tricks for helping hibiscus get through very hot weather. Anyone with experiences to share or tips to pass on is invited to reply to this thread and share with us your story.

Charlie

[Darkhorse]

Where I live it can get pretty hot, so I've learned a few tricks to keep my plants happy when I'm gone all day.  There are a few days of the week when I'm gone to work for about 14 hours, so watering them throughout the day is out of the question.  

First, on really hot days I water my plants (with fertilizer) in the morning, and place saucers under them.  I fill the saucers with plain water so the plants can "drink" from them throughout the day as the soil dries out.  I remove the saucers at night and replace them the next morning if necessary.

Second, I've heard that soil retains water better if it isn't flooded all at once.  For each watering I water my plants twice.  I give the whole group half their water, letting it soak in as I'm watering the other plants.  By the time I start at the beginning again with the second half of the watering, the soil is wet and should retain more water than if I just dumped it all in at once.

Finally, on days I'm home I spray the pots and around the plants with the hose.  It's not humid in the central valley at all, and this gives them a little bit of temporary humidity to enjoy.  

[Doll]

I have mine planted in the ground. I think the problem with the heat is the soil temperature when the sun is beating down on it. I have found if I use a soaker hose to keep the soil temperature down the plants do much better. Before they were wilting even though the soil was wet.
It helps that I am home during the day since I work at night.

[Charlie]

A couple of good suggestions there. I should consult you guys before I write the newsletter articles! I do agree that root zone temperature is one of the big issues. Whether it is water in a saucer or from a soaker hose the roots will stay cooler with water passing through them. Interestingly, the same is true in the opposite condition - when it's really cold most water from the faucet is warmer than the surrounding cold air and can prevent hibiscus from freezing.

Charlie

[Doll]

I have been trying to find out if any of the trace elements help plants endure the heat better. Apparently calcium is very important when it comes to heat tolerance. I am going to experiment a little with adding calcium to the soil on a few of my hibiscus and see if I can notice any difference.

[Charlie]

Did the extra calcium make a noticeable difference? Things have cooled down a lot in TX I think. Hopefully John Piper will be back with some better news from the Dallas area.

Charlie

[Doll]

No it didn't. Yes it has cooled down. Now it is almost too cool.

[davidwood]

Had a buzy Easter, fitted a sunblind, hopefully this will give some cv's a break from the miday sun.

[Charlie]

Good move, David. You've done remarkably well dealing with the hot sun and temperatures in Vietnam.

Charlie

[davidwood]

Good move, David. You've done remarkably well dealing with the hot sun and temperatures in Vietnam.

Charlie

Thanks Charlie, it is a constant battle with the sun, providing shade as needed is a challenge, some cv's are easy, Hot Pepper High Voltage Acapulco Gold, and some like Pink Delicious will never handle it. But some, and Dark of Night being a good example really adapt, at 2 years old  it now sits in full sun all day with no ill affects and is actually improving, nice shape bush as well.

[Charlie]

You are in an excellent position to give us feedback about extremes of heat and sun - really good information, David! Beautiful bush of Dark of Night, too, whodathunkit?

Charlie

[jpiper82]

Well we are about to do it again! my shipment of 4" plants are on the UPS truck and will be here friday.  The temps are running in the mid to high 90's, along with same temps in route from CA to Dallas, TX. The best I can do will be to unpack them and keep them in the garage @ 82-89 deg.
It seems every time I buy CV's the temp goes to 100 deg's!  This time we are 30 days ahead of schedule.  I have a new bag of HVH potting soil that I am going to blend with water/SuperNova/HVH fert, then bring inside overnight to cool down to 74deg before repotting sometime next week.
Thats the latest from Texas
John Piper

[Charlie]

Good luck, JPiper! 

I have a feeling your wife has nixed the idea of growing any hibiscus in the house. I can understand that but it is a great place to grow them in any house that has windows that let plenty of indirect light in along with some direct to stimulate blooms. Arizona is a hard place to grow hibiscus, as you can imagine, but I always remember the couple who lived in Santa Fe and had great results with their plants. I finally wrote to ask them their secret and they responded that they grew them in a large entryway under a sky light and it worked great. As David W in Vietnam has discovered, you have to get innovative to grow them anywhere it is too hot or too cold but it can be done and brings a lot of pleasure when it works out.

Charlie