dont recall.. and cant see.. where you are ...

whats the sun back there ... soil.. etc ...

about the only thing i can think that will grow 12 feet in one season.. would be sunflower ... in full sun ... with proper watering ...

otherwise.. you are dealing with tree time.. aka shrub time.. and as you note.. nothing is going to grow to that size in one season ...

perhaps if you gave us a pic.. we might be able to come up with some alternatives ...

also ..dont limit yourself with one solution ... perhaps the sunflower would work.. for immediate impact.. and you plant some long term projects behind ... one giving the other to grow.. in tree time ...

ken

ps: one other thought.. is that too many peeps want a solution down at the property line ... and we suggest.. you think outside that box ... and look toward planting closer to the deck/ house.. and creating a sight block in a different manner ... e.g. if you can get into full sun.. in the middle of the lawn ... you can accomplish your goal faster .. again.. i am struggling.. because i dont see the whole concept ....

What is the height you need?

I'm not sure I can suggest anything that will grow to full size in less than a single season from planting. Even large growing ornamental grasses take a couple of seasons before they reach full size.

A very temporary measure while you wait for whatever you select to establish and mature to size would be to install some sort of trellis in that position and plant annual vines. I was watching a recent segment of Gardener's World where they were trialing various annual vines and they had constructed these tall, teepee like structures from tree saplings or trimmed branches to support the vines. The supports themselves were about 8' tall but in some cases, the vines exceeded that. They were trialing purple hyacinth bean, morning glories, blackeyed susan vine (Thunbergia alata) and cup and saucer vine. All had fully covered the supports and were in full bloom by midsummer (i am guessing they used more than a single vine per structure, as they were very dense and full and I doubt a single vine would accomplish that).

And annuals are fast going...they only last a season. (tongue in cheek)

Location more specific than USA is important, say nearest large city because what grows in Maine won’t necessarily grow in CA or NC or OK or ND.

Annual vines might work as suggested, but a temporary fence such as rolled bamboo matting attached to posts will give you instant screening while forsythia or other plants grow.

Eastern PA, yes plenty of sun. Looking for 4 feet maybe more over time. I could throw a few arbs in there with grass plants in between. I do not recall how big the grass plan gets it's first year. The Arbs though tend to grow way to high for our liking. We have on grass plant that hides a small fence that hides our propane tank (LOL)...if I had a few of those suckers it would probably work well..but I do not recall how many years it took to get that big. Of course the grass it offers little in the winter....we usually cut it back late fall...Can they be cut back in Spring? I will try to get some pics tonight.

As to soil, not sure. I originally planted a few forsithia a few years back. Of the 3, 1.5 survived. Again, I'll try to get a pic tonight. To be fair, they were end of season 'save me' forsythia from lowes.

If you already have forsythia, you can start more by rooting branches. Then you will have a whole matching hedge.

Ha! I got some tips on tat here years ago...never could get anything to take root!

And for most of us, it's fight the forsythia (or eliminate it) because it's trying to take over the world by rooting everywhere.

Just cut pieces of Forsythia, stick them in the ground and leave them to it. That's all the tips you need.

That's what I did. I ended up with a bunch of sticks in the ground. I'll take a picture tonight, perhaps its not forsythia.....

How fast do those grass plants get the first year? I have another shrub or plant...I'll take pic...note sure what it is..It looses its leaves and I cut it back every few years...it seems to grow fast...I'll get a pic of that as well...

I just googled sunflowers...never new they got that big and could offer privacy. Are the annuals? Where do you get them? What size pot (?) should I start with? How close do you plant them? How big will they get? Do they spread? They look promising!

what about some of the taller panicums like cloud nine or miscanthus, malepartus? i don't grow these, but i've read that they can get pretty tall. ask folks on the ornamental grass forum. i'm sure somewhere there can give you some great advice.

some photos..the neighbors are always out and my daughter feels weird. The one forsythia is doing great. Is the other worth keeping? The original ones (LEFT)

are just stating to bloom..I assume these are all forsythia. The last photo is a close up the one's to left that are just starting to flower...

Yes, that's forsythia

No, ornamental grasses do not grow to full size their first summer after planting.

And unless you plant them very close together, sunflowers will provide minimal privacy. And yes, the tall types are annuals and are typically grown from seed.

red twig? it was suggested earlier at Lowes.

Right now your little forsythia are competing with the grass, and if you use something like weed-n-feed or anything with a lawn weed killer they are getting a dose of herbicide that isn’t helping either. Remove grass in at least a 3’-4’ strip across the whole gap and mulch it. Keep lawn herbicides away from the area.

Nothing shrubby is likely to fill that gap in one season other than a fence or doing something like Peter did. But Peter’s will be too large for what you want within a few years, and may well be too large within less than 10 years for what he wants, looming over the patio.

I would buy and plant another couple of the largest, healthiest full-sized forsythia, or even buy more and stagger them in two alternating rows as Peter did. Create a proper bed without grass within 2’ or 3’ of the plants so that the forsythia isn’t having to compete with the grass, mulch, and make sure you water your new plants when the soil is still just a bit moist. The goal is not soggy, but also not allowed to dry out. This will give them the best possible growing conditions. Then plant a couple of large pots with tripods of pole beans to fill in gaps or some of the branching types of sunflowers or something else quick and place them where they won’t shade the forsythia. Or as I said above, get rolled fencing of some type.

if you plant red twigged dogwood, IMO it will look a bit weird to have one or two random plants amidst the large blocks you already have, and IME won’t grow any faster than forsythia. Your current little forsythia will grow better given better conditions and would have filled in better had they been in better shape to begin with, so the fact that they haven’t grown better is more a function of their conditions than forsythia’s ability to create a good screen quickly. Plants operate on their own time, not ours, and the best you can do is to get good quality plants and give them optimal growing conditions. That will give you the quickest permanent living screen.

I can try again with the forsythia. like I had said, I planted them in the fall (saved from lowes) 2 seasons ago. At the time there was mulch around them. By last season 3 were dead (I had a couple to the left of the original ones too. I probably should removed the one that has the single long branch and put two new ones in. I wish there were an ARB that only gets 6 feet tall. In my old home I planted over 50 - 3' emerald greens arbs along two sides of the home. By the time we moved I was almost going to need a chainsaw to keep them at an 8 foot height. The new owner gave up I guess...they must be 20 feet tall now and look crappy. But they looked great when I was able to keep them around 6 foot tall.

Don’t remove any that are growing now, and don’t just mulch right around the plant. Remove all the grass across the whole are you want a screen. Plant your new plants staggered in two rows like Peter did, but a bit farther than 3’ apart. I honestly don’t think there are many plants that will fill in faster than forsythia. Yours were in tough shape to begin with, and so no wonder that they didn’t grow well.

Any arborvitae that only gets to 6’ tall will take its own sweet time getting there. It won’t roar up to 6’ and come to a screeching halt.

Well I think there is only room for 2...one on each side of the little sad looking thing...the with one long branch. Can I transplant the sad one somewhere else. I do not want to stager..then I'll have the two sticking out in front of the main set that has always been there.

I second gardengal’s advice to grow annuals as a temporary measure until your hedge fills in. :)

purple hyacinth bean bean is a nice one, grows fast and looks great.

I saw some wonderful, full, on the large size(5'?) Hollies at a greenhouse near me. They were in pots, but so nice. Didn't check the price. Quite a few had Sold tags on them already. And no, I don't know which kind of holly they were for sure.

ETA: over on the Trees forum - just saw that there is a picture I believe to be on the hollies I speak of. Under "Unusual Holly...."

Well, how wide were they? Of course I'd need to know what they would cost. I might have to just plant two more forsythia. At least one...maybe a hollie or something on the end.

I didn't pay attention to particulars in regards to the hollies, as I didn't anticipate anyone asking. Just happened to remember them when I read this post. You could Google or ask on the Trees forum.