As for essential oils that have long shelf lives usually, they are the thicker ones, such as Cedarwood, Sandalwood, Patchouli, Vetiver and a few others. Exception to this thick oil quality will be the essential oil of Rose Otto.
The season for them is generally a short one. Begins in early July and last for 2 to 3 weeks. Black raspberries tend to ripen before most red raspberries varieties expect for the early ripening summer ones.
You can apply a single application of fertilizer in the winter to your raspberries, whether you are using organic or inorganic fertilizer. Organic fertilizers are best for use in the early winter, but wait until the late winter or early spring to use inorganic fertilizers.