I have nothing as far as advice, I am hoping someone will be able to give you the secret so you can try again.

I Am growing sunflowers for the 2nd time, the 1st time I got nothing! But they were seeds a friend gave me from her plant up north and I did not give them enough morning light... She said morning light was more important that late day light.

This time I bought seeds from Lowes/ Walmart and have then center of yard no shade... So far they are growing!

But iam in Tampa so not the same as South Florida

These are the best quality zooms I could get. They were cell phone pics.

i am in Broward county to. That sunflower is big,not as massive as i am trying to grow,but it is a heck of a lot bigger than i mange to EVER get. Very cute daughter....just a bag of topsoil mixed into our 'sand' here in Broward? So you plants in spring. I see only 2 got 'very tall' or the others caught up later. I would be glad to get a big patch of that size. But I am really trying to get a MASSIVE trunk/stem, with a platter sized flower. Maybe it is like vegetables in south Fla. I have to plant in the winter here...to hot for anything in the summer here....even sunflowers!

I would imagine they would have gotten bigger if I actually took care of them lol. Also, I should have planted earlier. It's scorching hot and dry in June. Just wanted you to see it can be done. I probably won't do it again. Ripping those massive roots out was a chore! There are 2 out of frame leaning to the side and 2 shorter ones in the middle.

Hi Poohbearlvr

The only reason that you were not successful was probably the right timing, and I think you came to the same conclusion, it is very important here in any part of Florida. Most sunflowers seeds from any type of packets did very well for me when planted. I don't plant them too often because they need a big space for the roots, they can also get a lot of bugs which is not too good for my veggie garden. I am sure if you try it again you will be successful, when planting it is always a good idea to amend the soil.

Silvia

Might you have nematodes? I've grown sunflowers taller than my house. I know nematodes can stunt plant growth....

Yes, you can grow them, but they require consistent watering and often tend to wilt in the intense sun.

boy...from what i recall my sunflowers didnt have BIG root systems. THATS why they toppled over all the time and never got huge. Up north I even recall the roots being in a big ball almost and always had to stake my Russian Mammoths. But they ran deep...alas in south Fla. nothing goes to deep.and thats why trees topple over in minor wind storms here Hmmm.....maybe nematodes are stopping my success at huge stands of sunflowers. Never though of that. The small bushy sunflowers grow pretty easily, the new varieties, maybe they are resistant to the root bugs.

Sunflowers will grow anywhere there is sun to shine down on them. However, every climate, and most importantly the ground that can support them is the #1 factor!!! I live in Pa and know the that my #1 concern is how those roots can grow in the soil beneath! For starters, I would dig down about 2 feet in a one foot diameter. Fill the hole with some potting mix in(preferably miracle grow garden soil). And plant a seeding you have already sprouted on your windowsill. Mix the sand around it and give it a good base. These plants also need water, but don't spoil it every single day! If you really want a mammoth, you'll be able to tell when it needs it just by looking at the leaves. I know how hot is gets down there, so make sure it's just Mother Nature feeding it water or you in the morning. Also if you want a real giant, and it is growing as that,...,,, you may want to think about staking it when it starts growing where the wind can take it for a ride!

I grew an heirloom variety in 2013. They were about 6 too 8 feet tall. I grew the in the fall, in a heavily amended raised bed, facing North. I am also in West Broward.

I had success growing them here last year by starting them out in pots then onece they were about 7 inches tall, I transplanted them into myvveggie garden and tied them very looselyvto a wire fence so they wouldnt get tipped over if it was windy. Worked out really good.

I'm thinking rich soil is the answer. At the community garden I used to be in here in Gainesville, there were sunflowers and Tithonia that grew 8 feet tall at least. That soil was so rich with organic matter from all the additions over the years, it didn't even need fertilizer. If you can get some horse or cow manure, mix that in. Seems to do the trick.

Tithiona does good here. I think mine was only around 6 1/2 ft though. Attracts a lot of pollinators.

Last weeks pic, 8 feet tall, hubby said he remeasured the other day and it was about 8'5". and the face has yet to open so it might just keep growing. The others are about 6-7 feet. Planted April 1st.

FWIW, I had a Mammoth sunflower that grew taller than our house. Never get to have the seeds tho, worms & birds get 'em first...

This is my second year I brought in topsoil but the seeds at Home Depot last year I have 12’6” this year they’re up to 7 foot I live in Fort Lauderdale right after new River and Las Olas I put in a drip irrigation system for them with an online fertile wish me not good just lucky I did this for our mom will try and post photo Tomorrow

Hi, I’m in Palm Beach Gardens (Zone 10B) There are three varietals in this bed, the two taller ones are Mammoths. The one on the right is 10ft. This is my first try at Mammoths but, I’ll share what I did and what I think worked well.

Planting Time: Direct sow in February, thin out slow growers to prevent crowding. Two seeds every 30”.

Soil Prep: Dug a 2ft deep trench, 1ft wide. I have sand as well so I amended the soil with a compost/top soil mix from HD and granulated fertilizer for shrubs. Next go around I‘m going to add bone meal earlier, probably around thinning.

Watering: Water in the morning daily until they get about 1ft tall, then I typically water every other day if there’s no rain. Important to make sure soil dries a bit between waterings and very important to give them a slow deep soak to encourage good root growth. These just survived a severe storm with 40mph+ gusts and hail. I think the care to the root system helped them.

Feeding: Liquid fish fertilizer heavy nitrogen every 14 days. Added an inch of manure on the surface when they got about 2ft tall and dug out a 3” deep moat, 1ft radius around the stalks. This really helped to direct the fert and water to the roots. Added bone meal to the surface around the stocks in mid April, I’m going to do this earlier next time. Although it seemed to really help with producing new buds on the Autumn Sun varietal.

I applied neem oil at night a couple times early on, soak the leaves on top and bottom as well as spray the soil surface. Also I had to apply copper fungicide early on to fight leaf rot. Got a little lazy and the Jerusalem Golds suffered.

These get great morning light, slight shade in midday from a palm. The shed in the background blocks a significant portion of direct afternoon light and there’s a row of Autumn Suns on that side as well. I think they’d be taller with more light but, that’s a guess. I also, didn’t apply liquid fertilizer as regular as I could/should have. I think they could’ve benefited from a couple more feedings. Next go around, I’ll experiment with the feedings. I hope this helps.

I don’t know how to send a picture on this but right now I have four or five sunflowers that are over 8 feet tall I live in Central Florida they’re surpassed the roof of my house already

Are use just regular sunflower seeds that came from another sunflower in fact I didn’t even plant them the bird scrap them out and they are they are and they’re just regular old sunflower seeds from like previous sunflower plants that I’ve had

I am as lazy as HU is ambitious...so have been unsuccessful especially with sunflowers and morning glories. After a recent rain I found sunflower seedlings popping up - but probably from the birdseed I sprinkle.