I don't know it ever produce seeds. Mine produced lots of runners.

Horsetails have reproductive organs like some ferns, strobili that hold hundreds of spores. An appendege attached to the spores aids dispersal by the wind. Removal of the strobili before maturity would eliminate dispesal of the plants in your garden.
One common species, Equisetum arvense also spreads by deep rhizomes and can become a nuisance. Once established, it is nearly impossible to eradicate, because of the deeply buried rhizomes.
If you want to grow one of them, Equisetum hyemale would probably be the best choice. I think it has a more attractive habit and is easier to control. I grew it at one time, but became concerned about it spreading and removed it.
Rb

Here is a link that might be useful: Horsetail