Description:
Industrial Hemp Seeds seem to be growing at a slower rate compared to other crops. Initially thought that hemp was not growing at all over time or with using bonemeal and watering can to assist with growing. However, after a very long while, hemp do eventually grow, although still took very long to reach fully grown. When fully grown, the top bit was broken leaving the bottom as per the usual, however, it was still very slow to regrow its top (tested AFKing for about 15mins).

Is this intended or clearly a bug?

Using:
Immersive Engineering 0.12 - 86
Forge 1.12.2 - 14.23.5.2772

Since nobody more official has responded, perhaps I can help. I notice in your image that you're growing the industrial hemp in a cave. I've seen in a few other closed issues that industrial hemp grows much better when it can see the sky. If building your farm open to the sky is impractical for you for some reason, maybe you could look into building a Garden Cloche.

@MauveCloud nailed it down, let it grow under open air or glass if i remember correct

I find it strange that industrial hemp actually checks if it's below open sky or glass and that all factors into its random growth tick.

a lot of mods do this kind of stuff and it is quite an task to manage the environment to match optimal operation of sth. but beyond 1.7.10 most mods did skip those checks and some are relicts ... but i miss em ... a game should be at least a little bit difficult

Thanks! I'll give it a try. Garden Cloche was eventually gonna overtake it but early on vanilla style farming is the only option available. However, I find it strange that industrial hemp actually checks if it's below open sky or glass and that all factors into its random growth tick.

However, I find it strange that industrial hemp actually checks if it's below open sky or glass and that all factors into its random growth tick.

That's actually a pretty simple check compared to what some mods do. I think IndustrialCraft 2 crops might hold the record for the most factors influencing growth speed.

Well, it is „industrial“ scaled ;)

Yeah what everyone above said basically. Hemp wants to see the sky to grow at a reasonable rate. Cloches are always an option for underground setups however.