Many people are turning to peat pots and peat pellets as natural alternatives to plastic pots and trays for starting seeds and propagating seedlings. They are designed to reduce root shock during transplant because the seedlings can be buried together with the biodegradable pots directly in the ground.
But do peat pots and peat pellets actually inhibit root growth?
Peat pots can leave seedlings root bound especially for those with tender roots that cannot push through the tough walls of the pots. They generally take a year to decompose and get moldy easily, posing a high risk of root rot. Also, they can wick water out of the soil and dry up the root ball.
In this article, we have compiled 7 reasons why peat pots can restrict the growth of your plants.
Peat pots are natural, biodegradable planters made of sphagnum peat moss and shredded wood pulp compressed into the shape of individual round plant pots and seed trays.
They are also known by the name of a major peat pot manufacturer, “Jiffy pots”. There are also “peat pot” manufacturers that use paper pulp instead of peat moss.
Peat pots are used for transplanting seedlings, especially those with fragile roots like cabbage and eggplants. They are designed for lowering the risk of root injury and transplant shock, as the pots can be planted directly into the garden soil or raised beds, where they will eventually lose form and become part of the soil.
Compostable Jiffy pots for starting seeds and seedlings
2. Why peat pots restrict root growth
2.1 They take a long time to decompose
Peat pots generally take a year to break down. Some gardeners have even reported digging up sections of peat pots nearly two years after being buried in the ground.
How fast peat pots decompose depends on the size and thickness of the pots. The thicker the pots are, the longer they take to decompose.
The amount of moisture in the soil where the pots are buried also affects how fast they break down. Peat pots decompose faster in moist soils because there are more organisms in moist soils to break down the pots.
In fact, the reason why peat moss has been a popular soil amendment substance is that it does not break down easily. According to a study, peat moss can last several years in soil, keeping the soil aerated and holding onto water and nutrients. (Perry, n.d.)
2.2 Peat pots have tough walls and no drainage holes
Many peat pots or seed trays do not have drainage holes at the bottom or the sides. Even for those with drainage holes, they are small.
Also, peat pots have thick walls that only plants with strong deep roots like cucumbers, squash, and zucchini can push through the thick pots.
The only way to mitigate this problem can be cutting out the bottom and cutting slits on the sides before burying the pot in the ground. But this would be a lot of work for many pots and may also damage the whole pot if not careful.
2.3 Higher risk of root rot
A study has shown that peat can retain as much as 20 times its weight in water (Sjörs, 1980).
The soil in peat pots often holds too much moisture constantly which is not conducive to root development and may result in root rot.
2.4 Peat pots get moldy easily
White or bluish mold appears on the bottom and sides of a peat pot when there is too much moisture in the peat.
The mold can harbor fungi and cause allergies, especially when starting seeds indoors. Also, their appearance indicates that it is too wet and may cause root rot for the plant. So you would need to cut down on watering and let the pot dry out for a bit between watering.
Move the pot to a more ventilated location so that they can dry faster. If there are many pots, spread them out so that air circulates better.
2.5 Peat pots can wick moisture out of the roots
Although peat can absorb much water, it also draws water from the surrounding when it is dry.
This happens when peat pots are not entirely buried in the soil with the top edges exposed.
If they dry out, they will wick moisture away from the soil and dry out the root ball.
2.6 Different moisture inside and outside of pot
Since peat is highly water retentive, the growing mix inside peat pots holds more moisture than the garden soil where it is buried in. The roots of the seedlings thus tend to just stay within the peat pot for an extended period rather than growing out into the gardening soil. Therefore, peat pots in fact slow down root growth.
2.7 Peat pots require much upkeep
It is hard to water seedlings in peat pot without providing too much or too little water to the seedlings.
First, you have to water not only the soil but the pot also because peat draws water from its surroundings when it is dry.
Second, you need to keep the pots constantly moist, but not waterlogged.
When the peat pot becomes dry, it will turn light yellowish-brown like when you first got it. That’s a sign that you should water it again. When peat is wet, it turns dark brown.
You can water the seedlings in peat pots by bottom watering. Put some water in a shallow tray, and place the peat pot inside. The pots and soil will soak up the water from the tray.
3. What are peat pellets?
Peat pellets are also made of peat compressed in small discs.
When it is watered, the peat which is held together by a tall netting expands to its full size (usually about 1.5 inches) in about 20 to 30 minutes.
Similar to peat pots, peat pellets are used for germinating seeds and are also designed for transplanting directly into the ground to avoid root shock.
Peat pellets do not need to be watered regularly, and some can last up to a week without water. And this is because of the excellent water retention ability of peat.
You only need to water the pellet when it turns from dark brown to light brown, indicating that it’s drying out.
4. Do peat pellets restrict root growth?
The problem with peat pellets is with the netting that roots cannot penetrate through and remains root bound in the pellets. The netting is also not biodegradable in the soil.
You can definitely reuse the pot when the seed you planted didn’t germinate. As long as the seed didn’t sprout because of infection, you can dig out the old seed and put in a new one.
Another instance when you can reuse the pots is when the roots haven’t grown enough to reach the sides of the pot. In this case, you can remove the plant and reuse the pot for another seed.
Peat pots do restrict root growth because peat holds onto too much moisture or it dries out too fast. Keeping it constantly moist would require much work.
If you have peat pots and don’t want to waste them, you can tear off the bottom of the pot before putting it in the ground. Also, ensure that the pot is completely buried in the soil, as exposed sections can act as a wick, removing moisture from the soil and the roots. Finally, you can break them up and put them in the compost.
Sjörs, H. (1980). Peat on Earth: Multiple Use or Conservation? Ambio, 9 (6), 303–308.
Buckner, D. (2021, July 20). A Guide For Planting in Peat Pots And How to Use Them. Planteli.Com | Grow Your Own Food At Home.
Perry, L. (n.d.). Peat moss or compost? University of Vermont.