Selbourne farmer Annette Reed of Tasmanian Natural Garlic and Tomatoes said a large amount of fruit appeared on their vines early in the season but was now taking longer to ripen, resulting in a late season.

She said they were doing everything they could to ripen the fruit.

"We should be in full swing, we should be shipping out hundreds of kilos of tomatoes by now. I did a pick this morning and I was scratching around to get two kilos for an order," Mrs Reed said.

"We need warmer temperatures. We need sun. Even when we had what would of been those hotter days, the smoke haze has shut out the sun and cooled the temperatures," she said.

"After last season we are better prepared than we ever have been for heat waves, with shading and sprinkler systems set up throughout our tunnels, but we've just taken the tunnels away."

Mrs Reed said the tomatoes would still eventually ripen, and when they do it will be a busy time for their small business.

"When it does come we will have a lot of fruit all at once, so for a while it will be frantic," she said.

"We value add a lot of our excess, we do sauces and sell seconds, but it will be a challenge."

On the North West, Turners Beach farmer Marcus Brandsema said his tomatoes were less impacted due to a heating system used on the farm.

"[The smoke haze] impacted a bit but there were a few bright days in between to lessen the impact," he said.

"Any day that is dull is a lost opportunity ... when it is dull we have to run the greenhouses cooler, and so it starts to slow up production, and when it is bright we run the greenhouses warmer.

Mrs Reed said their garlic cultivars had also been impacted, by the dry conditions of the season.

"The garlic has suffered...we have a period where we have the tomatoes coming and the garlic ready to come out, and during that crossover it was nice if we could rely on a bit of rain," she said.

"We can't rely on that anymore now."