What kind of cucumber is it?

Hi! They are Boston pickling cukes, from seed.

Are all of the plants indoors? Are you self pollinating the blossoms? Most cucumbers require pollinators (bees, etc.) to move the pollen from male to female flowers. If this does not happen then the little female fruit will just whither away like you are seeing. There are pickling cucumber varieties like Vertina that are pathenocarpic which means they do not require pollination to produce fruit. I suggest that you try one of these varieties if you are growing indoors.

I have some indoor and some outdoor and the same thing happens to both

A lot of times the earliest fruit will either get aborted by the plant or won't get pollinated but after a couple weeks they should start to grow. You will need to self pollinate the indoor plants.

Thanks, ill grab a brush and give hand pollinating a shot, stay tuned!

Fertilizer? Sun? Water? Soil? Plants will abort fruit when the plant is stressed. As noted, also when the plants are small. If something is keeping the plants from maturing, that would impact the fruit.

Agree with all of the above. I'd never expect cukes to do at all well indoors. It simply isn't in their nature. A greenhouse with ideal light exposure and temp settings, limited success IF extensive hand pollinating was done. Otherwise no way.

Outdoors - then as Dan asked all sorts of factors come into play. Containers? What size? Soil mix? Nutrients? Pollinators? Water regimen? Pests and/or diseases? etc.

Dave

Thanks all! As you can see the plant is doing alright. Gets lots of sun, is watered regularly but I’m careful not to overwater & no sign of pests or fungus. As for soil I’m using some black magic soil I have left over from other grows in addition to some other organic soil.

Not completely sure what "alright" means. As in, they have stems and leaves? The plant in the window looks pretty spindly, probably from too little sunlight. It's also in a pot that's too small for it. Certainly root-bound. Still no info about nutrients. Potting soil has little to no nutrients.

Ok, so that isn't some tiny gherkin type that you might just be having harvesting problems with. I struggle with gherkins, though I grow other cukes well enough. I don't pickle cukes, though I pickle practically everything else that can be pickled. But someday I will get the right gherkins to grow, and figure out the Milwaukee brine right.

With a Boston.. yep, you got growing problems. others are already addressing that wonderfully. So going to skip that...

I'd skip the windowsill growing of cukes entirely if possible. Dedicate that potential growing space to other pickling goodies like garlic greens, chives, dill, parsley, basil.. rather than a cuke. And instead of a pot between to appliances.. I'd get/make an over shelf setup so the appliances are below, and plant/s growing above.

For nutrients, what would you recommend? I can transfer outside if you really think that’s stunting it. The pot it’s in is pretty big even if it seems small in photos. I do have a 7 gallon planter but that feels overkill...

As to nutrients, just something el basic would be fine. Miracle Gro is a standard. How many hours of direct sun does it get in that window? 5+ is probably needed to do well. Cukes are "full sun" plants. Some would swear by 8 hours. FYI, cukes in minimal sun can be expected to have poor fruit set. A pot that is much smaller than the plant that is in it is a bad sign, especially on those that you want big fruits from.

7 gallon outside would be much better than on the table in the window. It's not overkill. It's giving base mass. It helps keep watering/moisture even, offset top heavy action.

I don't want to be mean but..... seeing those leaves plastered up against the window and climbing into the corners. That plant needs some more pot space, sun, and structured climbing space.

Please to be sure to take the time to harden off this plant while repotting it to the bigger pot and getting it acclimated to the outside.

Just to mention. If you want to have enough to pickle, you will need a number of plants. You can't hold the cukes very long in the fridge and if you are making whole pickles, you will want to pickle within 24 hours of picking them.