What’s in­side a bulb

The anatomy of the un­der­ground stor­age sys­tem

Gardeners' World - - Bulb Special -

Most true bulbs, such as onions and daf­fodils (see left) com­prise a basal plate at the base where the roots grow from. Then there are lay­ers of scales, which are the leaves in their em­bry­onic state and both store en­ergy and pro­tect the in­ner work­ings of the bulb, namely the stem and flower. There is a thin outer skin, called a tu­nic, which helps stop bulbs dry­ing out, and the shoot, com­pris­ing the de­vel­op­ing flower and leaf buds. When plant­ing bulbs, it is im­por­tant to get the base plate point­ing down­wards, so the roots can grow down and the shoot can grow up­wards to­wards the light. Lily bulbs don’t have a tu­nic, so the scales are ex­posed. These scales can be snapped off, put in a bag with damp, gritty com­post, some­where warm, and new bul­blets will de­velop. A tu­ber just has a stor­age root and a plant bud. Dahlias are an ex­am­ple. Dahlia tu­bers can be di­vided in spring af­ter they’ve sprouted – en­sure each sec­tion has both shoot and stor­age root. A corm is a swollen stem that has been mod­i­fied into a stor­age or­gan. It has a basal plate, tu­nic and grow­ing point. Clumps of cro­cos­mia corms like these can be dug up in spring and the in­di­vid­ual corms re­planted to de­velop into new plants.

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