If you’re just about to plant a seed, seedling, or plant that needs repotting into a new pot with a fresh batch of potting mix, you might be wondering if you should pre-moisten the soil before planting. Is it going to make it easier to work with? Is it going to somehow upset your plant? Is it going to ruin the soil structure?
Here’s the short answer:
Potting mix should be watered thoroughly before planting so that it’s easier to work with. To ensure the mix is completely moistened, add water until the water begins draining from the drainage holes. After pre-moistening, wait 1-2 hours to allow the soil to fully drain.
Let me explain why pre-moistening your soil before planting is good practice and what else you can do to prepare for planting or transplanting.
Why You Should Pre-Moisten Your Potting Mix Before Planting
The main idea behind pre-watering your potting mix before planting is to make the soil easier to work with. You can think about it like trying to build a sand castle using dry sand vs moist sand vs sopping wet sand.
Completely dry soil is a little bit more difficult to work with because it tends to crumble and fall apart. This can make things difficult if you are trying to dig a hole in the shape of your pot-free plant. Dry soil will crumble and fill the hole, much like digging a hole in dry sand.
On the other extreme, you don’t want to plant in sopping wet soil that you’ve just watered thoroughly a few seconds ago. In this case, the soil will probably be muddy and messy to work with.
Working with muddy soil can also disrupt the soil structure if you work with it. It might lead to compaction, where the little air pockets within the soil get filled in or squeezed out.
This can cause the soil to become hydrophobic once it dries out since there will no longer be any openings for additional water to enter the soil. It’s a lot like what you see with dried tire tracks on a once-muddy trail.
If this happens, you could probably break up the hardened soil to artificially create more air pockets.
The best soil to work with is moist, but not sopping wet soil. Like moist sand, moist soil keeps its shape pretty well. This makes it much easier to dig a hole very close to the shape of your pot-free plant.
To get the soil moisture just right, you should wait about 1-2 hours after pre-moistening so that all the excess water will drain from the soil.
How to Prepare Your Plant for Planting
Ideally, you should transplant a moistened plant into moistened soil. Pre-moistening your plant will ensure that it is as healthy as it can be prior to the shock of replanting.
Your plant will have to expend a lot of energy trying to adapt to its new environment. Having a plant that is hydrated will help it transport nutrients throughout its structure to support new growth and development. It’s a lot like going into a workout well-hydrated.
Just like pre-moistening your potting mix before planting, your plant should not be dried out and not just-watered.
When your plant is dried out, the roots can be brittle and easily damaged. The leaves and stems might also be easier to damage if the plant is starting to wilt.
On the other hand, when your plant is just-watered, it might not have had enough time to absorb the water. It also might be messy to work with if the soil is muddy.
For best results, you should wait at least 2-4 hours to allow the soil to fully drain and to allow the plant time to take in the moisture. If you’re repotting your plant and it has a root ball, it’s worthwhile to soak the ball in a bucket of water so that it’s fully saturated.
After you’re done planting/replanting, you should also water your plants again to allow the new soil to fill in any gaps around your plant roots. But don’t press down on the potting mix because you want to avoid compacting the soil.
Should You Soak Your Terracotta Pot Before Planting?
In case you’re planting your plant in a new terracotta pot, you might have heard it’s worthwhile to soak the pot before using it to house your new plant. The idea is that a dry terracotta pot will suck the moisture out of the soil.
It turns out, soaking your terracotta pot before planting is actually not necessary. Any moisture the pot might absorb through soaking will probably evaporate within a day and won’t do much to slow the moisture loss in the soil.
The terracotta pot will only suck water out of the soil when the soil is overwatered. It acts more like a buffer that helps stop you from overwatering your plants.
Instead of spending time soaking your terracotta pot, it would be more effective to commit to watering your plant regularly.
Can You Mix Old Soil With New Soil?
Mixing old soil with new soil is a great way to make use of your old potting soil.
Don’t get me wrong, there is something to be said about old soil losing its quality over time. In fact, I wrote another blog post about that if you want to read more about how long potting soil retains its nutrients.
But the reason why it can be fine to mix your old and new soil is that the nutrients from the new soil should restore and rebalance the overall mix.
This is assuming that the old to new mix ratio is 1:1 or has a majority of new mix. The heavier the ratio skews towards old or new means that the overall mix will skew more towards old or new soil quality.
I would also recommend taking some time to sterilize the old soil. This will prevent any remaining pests or disease from transferring into your new mix.
If you want to learn more about that, you can check out another post I wrote about how to make pest-free potting mix.
Hope this helps!