Annual flowers might need to be repotted several times during the growth period to keep growing. This of course depends on what size of pot it's in right now and if / what you're fertilizing it with. But, here are some tips on how to know when it's time:
It’s wobbly, pale and has stopped growing
Roots have started to grow out of the drainage holes in the bottom
It’s nose-heavy and easily falls down
Water runs straight through the pot when watering it - without really making the soil wet
THREE OPTIONS TO CONSIDER WHEN REPOTTING
USE A BIGGER POT Good for plants that grow a lot and where the current pot has started to inhibit its growth.
SAME POT, NEW SOIL For plants that you don’t want to get any bigger.
CHANGE THE TOP LAYER OF THE SOIL For big plants that are too hard to repot. Remove the top layer of the old soil and add a new fresh one.
THE POT SIZE IS IMPORTANT
When picking out a new pot, think about using one that’s only slightly bigger than the last one. About 1”-2” larger is a good rule of thumb. If you pick a pot that's too large, there's a risk that the new compost won’t be able to dry up quickly enough between waterings, which might cause your plant to suffocate in the wet compost.
THIS IS HOW YOU REPOT YOUR PLANT
Water the plant Water your plant to loosen up the soil from the pot.
Remove the pot Gently take hold of the plant and start to loosen the pot, avoiding pulling on the trunk or branches. If it’s hard to get the pot to come off, try to cut the soil loose from the edges of the pot with a small knife. You can also gently tap on the outside of the pot with a tool or on the bench.
Prune the roots Do a root control and remove anything that looks dead, moldy or rotten. If both the soil and the roots look healthy, avoid touching the root ball, as it causes stress to the plant. If there are thick roots that are coiled up, loosen these with your fingers or cut them off.
If you’re using the same pot again, shake the soil off from the plant and cut away about 25% of the roots. This will help the plant stay fresh and small enough to continue living in the same pot.
Clean the pot Make sure the new pot is clean from old soil. Wash it with soap, rinse well and pat dry. If you use a dirty container when repotting your plant, there’s a risk that microorganisms are alive in the old soil, which can infect your plant.
Pour soil in the bottom of the pot Add soil to the bottom of the pot. Make sure that you put down the right amount - the root ball should be placed a few inches under the edge of the pot - if you place it too high your pot will overflow when watering.
Put down the plant Place the plant on the soil and check that it’s centered before you start adding more soil.
Add soil Add soil around the plant: gently tap it with your fingers to make it firm and check that your plant is not planted deeper than it was before.
Water Water the plant until water starts to exit through the drainage holes. If your plant was watered close to the repotting you might skip this step and just stick to the schedule instead.
More soil? Sometimes you need to add more soil after watering the plant. Make sure that your plant has enough soil around its roots before you are done.
Repotting is stressful for plants. It takes about one month before your plant is fully recovered and can start to enjoy the new and improved environment.
During this period make sure to:
Place the plant in a bright, but sheltered place.
Water it but stick to the schedule if possible. Follow the instructions in Planta to get it right.