Lavender is one of the undemanding plants. Except for plenty of sun, they are rather modest. This also applies to fertilization. The rule here is: less is more!

Whether in a pot on the terrace or in a bed, with regular care and the right treatment, you can enjoy your lavender for a long time.
Fertilize lavender moderately
The most important thing when planting and caring for lavender is the soil. It should be lean and not too damp, otherwise root rot and mold would form due to the waterlogging. Lavender comes from the Mediterranean and therefore likes it rather dry.
Great care must also be taken when fertilizing. It is sufficient if you add some compost, manure or potash-containing fertilizer (available from Amazon) when planting. Lavender doesn't need more. If the soil is too nutritious due to the fertilizer, the shoots will wood faster and it will become more sensitive to frost.