HTA president Boyd Douglas-Davies said ornamental nursery staff had been sent back home by police in Scotland, reported to be at Pentland Plants, and garden centre staff on the way to work in England had also been stopped and questioned.
He said plants need to be maintained and watered, especially in the sunny, dry and windy weather we're having, and were essential to prevent losses.
One grower said: "I had heard this today, but if staff are essential (growers for example) and they have a letter from their employers stating this, then it’s okay. We had already given our employees letters 10 days ago, we also grow a high proportion of young plants for edible growers. I believe one of the issues was staff car sharing that were from different residences."
The HTA, NFU and RHS are calling for a £250m scrappage scheme for growers, and garden centres, who are set to lose millions of pounds worth of plants after garden centre sales in the UK were shut down last Monday.
Douglas-Davies has had hundreds of emails of support to BDD@britishgardencentres.com. He is also seeking reports to be emailed to him of growers being stopped by the police to build the case for the scrappage scheme.
Growers and garden centres have furloughed or laid off much of their workforce as orders were cancelled after the Goverment's lockdown on retail caused garden centres and DIYs to close this week. They are left with glasshouses and plant areas full with plants they cannot sell but have to look after in case the restrictions lift.
The Government has said people must work from home if they can but if not they should try and stay 2m away frim colleagues at work.
Stricken Dutch growers have been seeking Government cash too: VGB's Matthijs Mesken said: "This week has been filled again with crisis talks -w ork to get an emergency fund for the horticultural sector. Without an emergency fund, and that becomes clearer by the day, many companies are not going to make it."
Meanwhile, police in Cumbria said officers in the Lake District will be stopping motorists to ask if their travel is essential. And officers in North Yorkshire said they too were setting up vehicle checkpoints.
The government has said people should "stay local" and not travel unnecessarily for exercise.
It follows confusion over whether people could drive somewhere to go walking, running, or cycling.
#The Government has announced a temporary suspension of "wrongful trading laws", which stop company directors from being prosecuted for keeping a business going when it's insolvent or hasn't got a reasonable prospect of survival.
#The Government has allowed cars', vans' or motorcycles' MOT expiry date to be extended by six months if it’s due on or after 30 March 2020.