It's quite possible it was a pollination issue. If the female flower isn't pollinated properly it will abort. The easiest way to do this is to pollinate the flower manually using a male flower. You can peel back to petals of the male flower and use it like a q-tip.

The second reason might be nutrients. Depending on the soil, plants may limit their production. Poor soils tend to stress the plants. It sounds like this isn't the problem for you though.

The final reason I can think of is sunlight. Pumpkins and squash are full sun plants and if it's in a shady area it might be struggling to generate enough energy.

Usually I plant 2 seeds of each type to allow the plants to cross pollinate. Your plant looks generally healthy and it might just be overcrowded. Pumpkins tend to be greedy feeders and such. I would say more should appear so be patient. It's starting to get a little later in the season though so early august flowerings are usually the point where I don't expect the fruit to ripen fully before the first frost. I wouldn't be too discouraged though, it looks like you're making good progress in your attempts and we all stumble at first. My sugar pie pumpkins only had one (relatively well developed) fruit on 3 different vines until the past week when 2 more female flowers pollinated.

Oh, if you're not picky about which type of pumpkins/winter squash and are ok with smaller ones to carve and cook, there are bush type varieties that use less space. A butternut hybrid that comes to mind is butterbush. These types can be useful in small gardens. to maximize space and yield :-)

Thank you so much for your response. Still only the one pumpkin, from what I can see.. but the plant is still seemingly healthy, and so is the one pumpkin. I have a question regarding pollination: You said that I could hand pollinate with a q-tip to encourage more pumpkins. Once a tiny pumpkin appears, does the flower still need to be pollinated, or is it successful in pollination once the tiny pumpkin appears? I seem to have a ton of bees in the male flowers.. but not sure if all bees move the pollen around? Since my veggie garden is like 2' away from my wildflower garden, the bees and butterflies are always swarming the area, and seem to hide out inside the pumpkin flowers for extended periods of time.

As far as nutrients go, maybe I didn't add enough fertilizer or compost. I did add a bag or two of compost in April, and added a decent amount of fertilizer and some other soil amendment, but I just kind of sprinkled those in.. I don't know that I used enough.. since it was my first time! Everything in the veggie garden bed got huge and yielded good amount of produce, except the cucumbers. As I think I said in first post, my cucumber plant only grew one big healthy cucumber and the rest shriveled up when they were still small. The plant is still alive, but isn't growing cukes at all now. So the pumpkin plant seems to be doing the same thing. Everything else did great, though.. tons of kale, lettuce, broccoli, cauliflower, green beans, peas, tomatoes, etc. I still have Brussels Sprouts growing, too.. haven't harvested any yet, but they look like they're almost to the point of being ready to pick. Do you know if they normally reach maturity so late in the season? I thought they'd be ready around the same time as the broccoli.

I'm not sure if I get full sunlight. I do get several hours worth, but could be partial. Hard to tell. Does the sun need to beam onto the pumpkins themselves or just the foliage and flowers? The pumpkin itself is pretty shaded by its leaves and things surrounding. My kale is getting tough and not so edible anymore. I have 6 big kale plants right near the pumpkin plant.. maybe I could pull them out and perhaps that'd let the pumpkin breathe a bit more..

Thanks again! Appreciate your time and help..

The leaves are what need the sun. They generate the food to feed the rest of the plant including the pumpkins. If you watch the flower development there will be a baby pumpkin at the base of the female flower the whole time it develops. The female flower opens for a few hours one day and needs to be pollinated during that period. It sounds like you have plenty of bees so that probably isn't a problem. You can tell a fruit failed to pollinate because after the flower opens the little baby pumpkin will turn yellow, shrivel and fall off the vine after a few days.

If the plant is not generating female flowers it may just be a fertilizer issue. Use a phosphorous rich fertilizer to promote flowering and fruit growth.

The Kale won't necessarily harm the plant but crowding and dense leaf cover will promote fungal problems in a lot of cases by creating moist and shady conditions.

The pumpkin or squash plant is very smart as to the growing environment. My kabocha has an early squash near the base. It is already mature size and has been there for a month or so. The vine is very robust. But the plant refused to bear another squash. I do not think I have pollination issue since we have a lot of bees and ants working. There are many male flowers every day. But the baby female flowers came out with a yellow base. So the female flowers were bad to start with. Just about two weeks ago, finally it grew another squash. Then another plant grew the 2nd squash shortly after.

So sometimes we over-think. There may not be anything wrong. As long we provide all the plants need, the plants should bear whatever the plants should bear...

Your Jarrahdale squash plant is actually quite smallish, despite being 6' long. A healthy plant given what it needs will grow 30' in every direction with so many vines you can't count them as they carpet everything in their path. A plant like that will grow many fruits. Your plant's growth is limited by crowding, limited root space and maybe limited sunlight. It will naturally not produce much. Still, one sizable squash is so much better than none.