It seems that you are able to buy most veg plants as seedlings.Are parsnips not available like this?Do I have to grow them from seed?
Parsnips are a root vegetable and should be direct sown into the garden.
https://www.gardeningknowhow.com/edible/vegetables/parsnips/how-to-grow-parsnips.htm
Tops are already sprouting with little or no root
This may not be the best idea quite yet! I would wait to see how many tap roots form, as there may only be one. Splitting this will likely kill it, if this is the case.
If there is more than one taproot, then it might be possible without harming the plant. It will all come down to how many taproots form.
This article will help you with the care of parsnips: https://www.gardeningknowhow.com/edible/vegetables/parsnips/how-to-grow-parsnips.htm
We thought that if we shrink-wrapped parsnips and refrigerated them they would last all winter. This was about a month ago. We discovered all bags of them have bloated upend bags are about to pop. Will these still be safe to eat?
They should be just fine. They were attempting to still "breathe" as most things will if not flash frozen or cooked first. This is ethylene gas and small amounts of oxygen. As long as they do not smell spoiled then cooking them will be safe.
We recently moved into a new house and after using an app we identified we have a wild parsnip plant in our garden. Since learning that this plant is highly toxic we are keen to remove it from our garden but are unsure how best to go about this. The plant currently stands at around 5 and a half feet
Since you only have one, you can pull it or cut off the stem (be sure to wear gloves, long sleeves, pants) as outlined below. Glyphosate non-selective herbicides as well as other chemical treatments are also effective.
https://portage.extension.wisc.edu/files/2018/04/Wild-Parsnip-Management-A3924-15.pdf
I use vegetable tops to regrow young leaves for fresh salads - beets, celery, carrots - and am trying parsnips but I have read that they can contain a toxin caused by sunlight. Since mine are grown indoors w/o sunlight will they be safe for consumption?
No. Phytotoxicity doesn't refer to the toxin being synthesized from the sunlight. It will refer to the action of the toxin, which is activated in your body with sun contact. Your skin will become very sensitive to sunlight.
Do not consume the leaves.
Here are some articles that will help you to grow and harvest parsnips:
https://www.gardeningknowhow.com/edible/vegetables/parsnips/how-to-grow-parsnips.htm
https://www.gardeningknowhow.com/edible/vegetables/parsnips/how-to-harvest-parsnips.htm
w a couple of inches and are only about 1/2 inch in diameter.. The bed has good soil and is watered but not over watered. What is happening? Seeds are planted in early spring and harvested the following spring. During the summer the plants make healthy tops, but I haven't checked on roots until spring harvest. My concern is why plants at either end of the bed grow well, but those just 1ft from the end are grow only 2 to 3 inches, perfectly formed but only 2 to 3 inches.
This sounds like there could be too much Nitrogen in the soil, or not enough Phosphorus and Potassium. Testing the soil will confirm. These articles will help:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
Here are some articles to help you with Parsnip care:
Luxurious leaves and not much stem
Are you in an area where it gets cold? Parsnips like cold weather. Here are growing conditions needed for parsnips:
https://www.gardeningknowhow.com/edible/vegetables/parsnips/how-to-grow-parsnips.htm