Why clay coat seeds?

[Scott]

Hi All,

Can anyone explain the reason that seeds would be coated with clay? I realize that it makes the seeds bigger and easier to handle, but what effect does it have on the seed germination, etc.

Thanks a bunch!!

[Dwight Sipler]

The clay coating (pelleting) is primarily to make them bigger and easier to handle. For example, I plant lettuce in 200 trays (200 cells per flat) and I want only 1 plant in each cell. With normal lettuce seed it's a real chore to handle only 1 seed. With the pelleted seed it's a snap.

The process of pelleting seeds sometimes also involves "priming" the seed. I'm not sure whether this is intentional or not, or actually how it is done, but the effect is to pre-germinate the seed. This stresses the seed somewhat, limiting its storage life, but it makes a batch of seed germinate more uniformly. In the case of lettuce, there may be a couple of days difference in the germination time of raw seed, but for the primed seed it's maybe half a day. This helps people who are planting large quantities of seed on a schedule manage the plantings better.