Lavender never looks good at this time of year but thirty minutes in the glasshouse with a tray of a dozen can make them look better. The simple act of potting on allows a larger root run for the plants and you can improve drainage. We potted on with a fifty-fifty mix of general purpose compost and sharp grit. I potted on the lavenders to six inch pots and pinched out the leaders, some of these carried flowers and these didn't go to waste. A modest bunch adorns our kitchen table and though they are not large flowerheads the scent is still a lovely reminder of summer in the depths of winter.
Potting on is easy for the novice gardener. When the lavender pots you have your plants in start to show stress, discolouration of foliage or stunted growth, it may be a time to feed or pot on. You can tell when you need to pot on by lifting the pot up, if roots are escaping the drainage holes, it is time to give your plants a bigger home. You don't have to go mad and give them a large pot. A large pot could kill a new plant as they struggle to fill the compost and can sulk, the die. I always recommend a pot two finger widths wider than the original pot. This allows you to get your fingers and thumbs down the side to get fresh compost around the roots. Loosen the plant from the old pot after watering the tray of plants first, then tease the plant out of the old pot. In the new pot, place some of the fifty-fifty mix and then place your lavender plant sans pot into the new pot. You want the root ball to be below the new level of the compost. Taking some of the same compost mix fill the gaps around the edges of the pot. Tap the pot on the side to shake down loose soil and keep doing this until all the gaps are filled. Then give it a final tap to level the surface of the soil and place on the staging clearly labelled. No roots should be showing when you have finished.