Preparing summer bulbs

Speeding up plant growth: what is it for?

In autumn, frost-tender summer bulbs planted in open ground should be lifted before first frosts, between November and mid-December, then stored cool and dry. Too sensitive to cold, they cannot overwinter in the ground in areas where frosts are severe or in soil that retains too much moisture in winter.

Preparing summer bulbs is a technique that allows:

• bringing forward the period of growth and flowering by providing them with optimum conditions (heat, sunshine and moisture) to get a good start. Once stored frost-free, some bulbs such as Cannas and Hedychium may be prone to dehydration: starting them in a seed tray or pot allows humidity to be controlled;
• in the coldest regions where spring is slow to arrive, this method can be useful, to speed up their cycle or at least not delay flowering;
• storing them in optimal conditions, you will find them intact the following spring, and they will be out of reach of pests often eager for young shoots!

Starting summer bulbs

Which plants can be hastened?

Summer-flowering bulbs colour the garden, borders and containers until autumn. Their cheerful and often very colourful flowering spans from June through to the frosts. From classic varieties to the most exotic and unusual, the selection is vast. While spring bulbs can remain in the ground, most summer bulbs and tubercles must be lifted, cleaned and brought indoors for winter to protect them from frost, as they will not survive severe frosts. From a botanical point of view, summer bulbs are divided into two types, the bulbous and the tuberous; here are the main species that can be lifted:

• bulbous plants: lilies, gladioli, Crinum, freesias, tigridia pavonia
  
  

  Freesias, gladioli, tigridia pavonia ‘Alba’

• plants with tubercles: dahlias, cannas, tuberous begonias, caladium, colocasia, Polianthes tuberosa, Hedychium
  
  

  Dahlias, Cannas, Hedychiums

When and how to proceed?

When?

You can start most summer bulbs by planting them from February–March under frost-free cover.

How to do it?

To achieve this early flowering, start by checking they are perfectly healthy: discard any bulbs that are soft, mouldy or showing spots of mould.

• Place bulbs in pots or a deep tray filled with potting compost
• Simply place bulbs on substrate, taking care to position point upwards
• Cover with sand, without compacting, up to rim of container: top of tubercle should be level with surface of mix (you can also plant in a mix of turf and sand slightly moist)
• Water sparingly at first, just to keep compost slightly moist but not waterlogged, otherwise bulbs will rot.
• Keep them in a bright place, such as a conservatory
• Water at a more regular frequency as they undergo growth: let them grow quietly under cover until temperatures have warmed in the garden, that’s the point!
• To slow their growth and acclimatise them, do not hesitate to place pots outdoors when temperatures are milder.
• Finally, plant them out in ground in spring, after severe frosts late April to mid‑May; wait until the Ice Saints have passed in northern France.