Few flowers encapsulate the spirit of summer better than sunflowers. However, if you want them to bloom faster, BBC presenter and gardening expert Monty Don recommends that they should be “hardened off” first.
Typically, the best time of year to plant sunflowers is between mid-April and mid-May. This allows the last of the winter frost to melt off and ensures warmer temperatures needed for the sun-seeking plants to thrive. Ideally, they should be placed somewhere where they have equal access to shelter and light.
However, it’s not generally advisable to stick the flowers straight into the soil after picking them up from a garden centre. Exposing them to harsh conditions too soon can send them into shock.
This is because in a garden centre, they will have become adjusted to warmer, more humid temperatures. Unfortunately, this rarely matches the reality of British weather.
Sunflowers placed outdoors straight away can suffer from leaf burn and structural damage from strong winds. This is particularly true if their leaves don’t harden quickly to protect themselves.
Therefore, ‘hardening off’ refers to a process by which flowers are kept in a sheltered location for a few weeks. During this time, they are gradually exposed to outdoor elements.
After a short period, the leaf structure of the plants should have hardened and become more waxy. Ultimately allowing them to better withstand the unpredictable weather.
Monty Don writes in his blog: “By the middle of May tender annuals like Sunflowers, Zinnias, Cosmos or Tobacco plants can be planted out into all but the coldest gardens, especially if you have hardened them off for at least a week.”
He explains that ‘hardening off’ is important for faster plant growth. He continues: “if you buy any of these annuals from a garden centre over the coming weeks, do not plant them out immediately but put them in a sheltered place for a week to acclimatise to your garden, as they will probably have been kept sheltered for best retail display.”
A great place to harden off flowers is to place them in a greenhouse. The warmer temperature and sheltered conditions will allow them to adjust while avoiding any lasting damage.
However, if you don’t have access to a greenhouse, another viable option is to place them by a hedge. Likewise you can place them by a different garden structure that offers protection from the elements.
You can also cover the flowers in a fleece during the harsher parts of the day. This prevents the leaves from becoming burned or the structure of the plant suffering damage.
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