Hemlock Growing Next to Other Herbs

I have a major question for you... I have hemlock planted in garden with other herbs. They [the hemlock] have gotten to be HUGE... at least 3 feet tall. All the plants have started to "mix" together. Now my question is, will the hemlock affect the properties of the other plants that are growing near it? The other plants that are growing near it are feverfew, burdock, and stinging nettle... will these be safe to use? Please let me know if I need to do anything or not.

I assume you are referring to poison hemlock (Conium maculatum), not the evergreen tree hemlock (Tsuga spp.).
I am not aware of any evidence that poison hemlock imparts its poisonous qualities on nearby plants. Although I believe the possibility that it does is remote, I cannot rule it out because the roots of some plants are known to exude substances to the soil or to leach compounds from the foliage onto the soil around the plants. But for these substances to present any danger they would have to be stable and not be susceptible to rapid degradation.
The main danger of poison hemlock is harvesting the plant by mistake. There are reports that poison hemlock has been gathered from the wild by mistake because it closely resembles other culinary and medicinal herbs. Poison hemlock belongs to the carrot family – the Apiaceae – which is one of the most important herb families. Some members of the family include parsley, dill, fennel, coriander, and chervil, as well as the medicinal herbs lomatium, dong quai, and osha.
It is important to choose a safe place to grow poison hemlock. The site should be protected from small children and should not be planted with other edible or medicinal plants that could be confused with the poison hemlock. I strongly advise you to remove the other nearby herbs or move the poison hemlock to another location.

Thank you for repsonding so quickly. The flower garden with the hemlock is away from people. Nobody will be near the area and it is secured. It's good to know that the other herbs won't be affected by the hemlock. I am currently waiting word from a friend who is wanting most of the hemlock. They are familar with the uses of it. Thanks again for responding, I know you are a very busy man this time of year.

I didn't say that other herbs won't be affected by poison hemlock; I said that I think it is unlikely that other herbs will be affected but we really don't know because there is no evidence either way – whether it is safe or a danger.
I am glad to hear that the poison hemlock is in a safe and secured place.