The National Trust is to begin opening gardens and parkland properties in England and Northern Ireland for people who have booked tickets in advance.
The Royal Horticultural Society (RHS) is also reopening its four gardens around England with a pre-booked tickets system as rules around lockdown begin to ease.
The moves come after the UK Government amended regulations to confirm that people in England could visit gardens and land maintained for public use, while, in Northern Ireland, the Executive permitted the reopening of outdoor spaces.
The National Trust warned that all properties and car parks in Wales remain closed in line with Welsh Government rules.
The phased reopening will begin with around 29 gardens and park properties opening from June 3, with only visitors who have booked in advance allowed entry to limit numbers and keep the public safe, the Trust said.
More sites will open over the coming weeks for properties where social distancing can be observed, and with only around a third of the normal number of visitors permitted.
All National Trust houses and shops remain closed, along with holiday cottages and campsites, and, while coastal and countryside car parks are mostly open, some busier ones may need to be closed or pre-booked, the charity said.
Booking for parks and gardens opens on Friday morning on property web pages via the National Trust website, and will be free for Trust members, while other visitors will pay an admission fee.
The charity, which said sites will be displaying information on how to stay safe and socially distanced, is also urging people to limit how many visits they book, stay local if they can, and avoid busy hot-spots.
Director-general Hilary McGrady said: “We want to provide safe, local, welcoming spaces for people, and, wherever possible, we will open our gardens and parks, and coast and countryside car parks.
“The fresh air, bird song, big skies and open spaces people have missed will be there, but things will be very different, particularly at first.
“We want to thank people for their patience and support while we gradually begin reopening and welcoming our visitors.”
The Royal Horticultural Society is also opening its gardens from June 1 as part of the easing of lockdown, with strictly limited numbers of pre-booked tickets available each day for members and visitors at the four properties.
Safety measures will be brought in, including limiting numbers allowed in the garden centres at any one time and floor markings to help customers queue safely, separate entry and exit points where possible, hand sanitiser points, and card transactions only.
RHS director-general Sue Biggs said: “We are delighted that the Government has said it is safe to reopen our RHS gardens because it is proven that spending time outside in green open spaces surrounded by plants has an immensely positive effect on our health.
“We look forward to welcoming our members and visitors safely back from June 1 and to bringing the joy of plants, flowers, trees and nature back into people’s lives, which for so many will be a much-needed tonic.”
She added that it is “imperative” that a timed slot ticket is booked in advance on the RHS website for every visitor, warning that those without tickets would be turned away.