The first big planting in the 52ha of historic gardens involved 613 volunteers ranging from two years old to 86 years old, and was planned by head gardener Steve Lannin.
The volunteers planted Narcissus "Actaea" on one mile of four metre wide borders.
"We were amazed at the number of volunteers who turned out to help us and the speed that they planted the bulbs. The first 100,000 bulbs were safely planted in just over two hours and we had to quickly find some reserve stock to keep the many enthusiastic bulb planters busy. People came with serious work in mind and set about the challenge with wonderful enthusiasm, and the large number of younger volunteers was particularly noticeable.
"To see so many tired, grubby yet happy children in the gardens was terrific. The daffodils should flower from mid-April next year and will provide a stunning vista in the high woodland avenues that frame wonderful views to the distant Lakeland fells."
The first phase of the Lowther Castle and Gardens project will be completed by March 2013 and is supported by £8.9m of grant funding from the Department for Business, Innovation and Skills (BIS) and the European Regional Development Fund (ERDF).