''It's just about impact,'' said Tim Baber, of PoHo Flowers in Potts Point, who will be stocking more Colombian roses this year.

''Most guys almost always opt for the Colombians because the bud is about 3-4 centimetres across and the local is about 2.5.

''When you multiply across a dozen stems it makes a big difference''.

''They're [local growers] going to lose out,'' said Mr Baber.

An overcast La Nina summer has made flowers bloom more slowly and produce smaller buds. Wet and humid weather also exposes maturing flowers to mould and rot.

''Half our crop isn't going to flower in time for Valentine's Day,'' said Gabriella Zaia, of T&G Growers in Horsley Park.

''We've had constant rain. We're spraying for fungicide and pesticide. It's been a really tough time.''

The poor weather has given Colombian exporters a greater foothold in the local flower market over the past year despite their higher price. At PoHo Colombian roses sell for $160 a dozen compared with $120 for local varieties

Colombian roses grow fat in the high altitude of the Andean mountains. The greater exposure to sunlight allows them to bloom over four months, compared with an Australian average of three.

Cos Demasi, of Demasi Flowers in Cecil Parks, reckons he's lost about 20 per cent of this year's crop to the weather.

''Imports have had a big impact,'' Mr Demasi said. ''They're driving the Australian product down and it's very hard to compete''.

The forecast does not hold much cheer for farmers. According to the Weather Channel, Sydney has received three fewer hours of daily sunshine than usual this February. The overcast weather is expected to continue this week. After a weekend of severe storms, the Bureau of Meteorology is forecasting a top of 27 and thunderstorms today, with showers continuing through most of the week.