I see your code, but in game it doesn't seem to work.

<li Class="PatchOperationReplace">
<xpath>/Defs/ThingDef[defName = "Agarilux"]/plant/growDays</xpath>
<value>
<growDays>14.5</growDays>
</value>
</li>

I changed the values in the XML to 1 day, and then reloaded. that seemed to work. So maybe it's just me.

If I recall correctly the grow days is the actual amount of time required to grow. It does not factor in the resting phase so it's probably closer to double. In the future please use the comments or leave a comment to say you made a thread. Steam does not notify workshop creators when a new thread is made and unless I have a reason to check the workshop page it'll miss it.