By Sunny Datko
At some point in the growth of your plants, you will have to consider moving your young, developing plants on to the next stage: a bigger pot, cube, or basket. This is called transplanting. Transplanting is often considered the second most stressful event of a plant’s life, cloning being the first; however, there are many things we can do to minimize or even eliminate this stress.
Before you remove the plant from its existing pot, prepare the new medium and be sure the environment is forgiving. If transplanting to an inert medium (e.g. soilless mixes, coconut coir, rockwool, or hydroton) it’s important to pre-load the medium with some nutrition. For cuttings this should be a fairly weak nutrient solution. Adding B1 vitamins and mycorrhizal fungi may also help ease transplant shock. A good tip is to try adding some seaweed extract, which contains natural hormones and plant growth regulators that help stimulate root growth and reduce transplant shock.
For optimal results it’s important to transplant at just the right time. For clones this is when they have been fully hardened off and preferably have plenty of air-pruned roots showing from the cube or pellet. For more mature plants this is when the roots have fully filled the pot or cube but haven’t become root bound.
When transplanting, follow these simple steps
1. Prepare the new medium for use – Add any desired amendments and/or beneficial microorganisms. Wet the medium with the same level of plant food that you used to grow the plant until this point (you may wish to add a drop or two of B1 vitamins to the solution). Make sure the soil is completely saturated with your water-fertilizer solution, leaving no pockets of dry soil but not dripping wet either. The idea is to help moisten and settle the medium, lowering the risk of transplant shock.
2. Fill the growing containers about halfway to two-thirds full with pre-moistened growing medium. Leave a slight bowl shape at the bottom for the new plant.
3. Gently remove the plant from its previous container. Place your hand over the top of the container, keeping the stem between the thumb and fingers. Turn the container over and carefully ease it off the plant. If the grow media is hardened or stuck, you can use a butter knife to help loosen it.
4. Carefully loosen the root ball with a finger or a fork, but be careful not to cause any root damage. Tease out the roots and unwind circling roots. If you find any dead or damaged roots, use pruning shears to trim them off.
5. Center the plant in the new, larger container, making sure it’s upright and that all the roots are pointing down. Plant it at a depth of half an inch from the top of the pot, and no deeper than the top of the root ball. If you plant it too deep, it will rot, and too high, it will dry out. Gently push soil or soilless media around it. Make sure the top of the soil or soilless media is intact and isn’t cracking apart in lines, exposing the roots.
6. Water the plant lightly with a fertilizer solution until the water runs out of the bottom of the pot. Allow the pot to drain completely before placing it in its permanent location. Make sure the soil is saturated, but not soggy. This will help settle the media and give it good contact with the roots.
7. After transplanting, your plants will need time to adjust and re-establish their root systems. They must get sufficient water, but not yet the full amount of light. Keep the light schedule the same as it was in the previous phase for one week (example: if moving from vegetative to bloom phase, keep HID lights on an 18 or 24 hour light schedule for the first week before adjusting to 12/12. Also raise lights at least 4-5 feet above the plant for 1000-watt bulbs and 3-4 feet for 600-watt bulbs). After one week, the plants can go under the full light of the HID lamps.
Additional Transplanting Tips
If using loose growing media, place it gently into a pre-dug hole and gently backfill the hole and consolidate the media around the plant. Be careful not to compact the media (especially if using soil) when you back-fill the hole, but make sure you haven’t left any large air pockets. Then lightly water again to really settle the media around the newly transplanted specimen.
Some fast-growing plants, like the tomatoes, can go from a small pot into a quite large pot and they’ll do just fine. They grow a large root system, and the roots grow pretty fast, so they do well in larger containers. Other plants, such as some of the edible herbs, might need to be treated a little more carefully. If you move them to too large of a pot too soon, the soil can stay too wet and the roots will rot. This can kill the plant. Potting up in stages can help reduce this risk and produce a healthier plant with a denser root mass. “Potting up” is simply the process of planting seedlings in a larger container so that their roots have more room to grow.
As a rough guide for many fast-growing vegetables, freshly rooted cuttings and seedlings will thrive if they are transplanted from a 2” to a 1 gallon sized pot and later into a 3 or 5-gallon pot. A good rule of thumb for high-energy crops is to transplant the plant into a container that is double the size of the current one, or larger. Be careful not to overwater new transplants, as this can impair root development.
With a hydroponic medium like rockwool the same basic principles apply. Soak the cube or slab beforehand with distilled water or for better efficiency, use Europonic Rockwool Conditioner. Maintain a temperature of 68°F (20°C) for 24 hours, and then drain off the excess nutrient solution. The plant should be placed on a slab or into a larger cube or container when many roots are beginning to poke out the bottom of the existing cube. You can pull the plastic wrapper aside and check to see if there are plenty of roots showing. Again, you don’t want them to be circling the cube.
To use rockwool slabs, start by cutting an X in the plastic on top that is the same size as the cube your plant is rooted in. Next, lift the plastic tabs you created from making the X and place your cube between the tabs on top of the slab. Lastly, cut a few slits in the bottom so excess nutrient solution has a place to drain. Don’t try cutting up your rockwool slab to make mini-cubes; it’ll just fall apart. Instead, if you need small rockwool cubes, buy them.