Thanks for reaching out about planting celery seeds. You asked about soaking seeds before planting. You can but it is not necessary.

Celery is propagated by seed and is best started indoors with temperatures at 70F to 75F, about 10-12 weeks before planting outdoors.

Note: It can take 14-21 days to germinate so plan accordingly.

Seeds should be planted and covered lightly with soil and pressed into the soil at bit so they stay put. Water with a mist so they don’t move around too much and roots can set.

Celery seeds will need light to germinate.

Keep the soil moist but not soaked.

Once the plants start growing they can be moved to a cooler location, 69F-70F. Thin them out to allow space for each plant to grow without being crowded.

Transplant outdoors 6-8” apart 2 weeks before the typical last frost for your area.

Thanks for reaching out to us for recommendations.

For more information please check the website links.

http://www.gardening.cornell.edu/homegardening/scene810e.html