Containers dry out faster than anything else in a garden and have no soil life to speak of. Hemp turns up in pots for both reasons — as a mulch on top, and as structure inside a peat-free mix.
2–3 cm on the surface of a pot cuts evaporation noticeably and stops the compost capping into a crust that sheds water off the side instead of into it.
The easiest win hereUp to about a fifth by volume adds air and structure to a peat-free compost, which is the thing peat-free mixes most often lack once they have been watered a few times.
Up to 20% by volumePressed hemp mats hold water evenly and let roots through, so seedlings can be planted mat and all. Convenient rather than transformative, and they compost afterwards.
Microgreens and modulesRough proportions by volume. Peat-free composts vary enormously bag to bag, so treat this as a starting point and adjust to what yours is like.
The base. Buy a decent one; the cheap bags are usually under-composted green waste and no amount of amendment fixes that.
Air and structure. This is what stops a peat-free mix slumping into a dense block after a month of watering.
Drainage and weight. Pots that blow over are pots that dry out, and grit fixes both.
Biology and slow nutrition. Container compost is close to sterile and stays that way unless something living goes in.
Whatever the mix, a container runs out of nutrition in about six weeks. That is true of every potting compost sold and is not a hemp question.
Not on its own — it holds almost no nutrition and dries unevenly. It is an amendment and a mulch, not a growing medium.
More than in a border, because there is less soil to buffer it and roots occupy the whole volume. Keep it to about a fifth of the mix and feed from week six and it is a non-issue.
Two to four seasons outdoors before they start to go. They air-prune roots well, which produces a better root ball than a plastic pot, and they compost at the end.