This, he tells Grower, is the first time in years he has been able to devote more than a hurried few weekend hours to tend to the woodland at his home in Penzance, Cornwall.
"In the past few days I've been clearing fields that until now I could not get into for fallen trees," he says. "It's been so frustrating that I have not been able to get out there for so long because I really enjoy being outdoors."
But it's little wonder that Hayman has not had much time to spare. His expertise is in high demand. His 40-year career as a horticultural adviser - with ADAS and as an independent consultant - has made him an international authority on protected salad crops.
But turning 65 has made Hayman realise that he wants some time to "get back to basics", which is why he stepped down as secretary of the Tomato Working Party (TWP).
A large part of this role, which he held for more than 25 years, is collating technical and financial data as the party's dozen tomato-grower members meet up every month to swap notes. This information is then studied and used to develop methods of improving the quality of British tomatoes and the cost-efficiency of their production.
The party has been running for some 50 years now and, while the British tomato industry has seen some significant changes in that time, it has operated in the same way. Its members have always shared data - on tomato yields and average fruit size, for example - and they continue to do so despite the competitive nature of today's fresh produce industry.
Hayman says: "Some companies often find it difficult to accept that we share data. But British tomato growers only represent about 20 per cent of the tomatoes we eat in this country, so it makes sense to help each other out. We are not competing against each other, we are competing against imports.
"By being prepared to share data, growers have examples of how people investing in new technologies are doing. It gives them confidence to see what their colleagues have done." For example, TWP data helped find ways of doubling production rates from around 10 kilos a hectare in 1975 to around 22 kilos a hectare in 1995.
"In the 1990s yields had plateaued. At the beginning of the year fruit was small and in the summer it was too large but plant vigour was poor. But our data helped us realise that if growers manipulated their plant populations they could increase yields - starting off with low plant populations to get an earlier good fruit but then increasing them in the summer to get a good yield with smaller fruit.
"Much more CO2 also became available, so the combination of more plants and more CO2 really gave tremendous increases in yields and good fruit quality all through the year."
Such was the strength of the working party that the British Tomato Growers' Association (BTGA) was born out of it. "We thought people who were not members should have a voice so we set up a national association," says Hayman.
"What I have been able to do is take the TWP commercial data and use it to talk to the Horticultural Development Company about its research priorities for our sector. We also use it for the BTGA promotional campaigns, such as how efficient we have become at reducing our water use."
But Hayman is now ready to pass the baton onto someone else. In this case, he jokes, it is someone far younger than him - Young Grower of the Year winner Paul Simmonds of Cornerways Nursery.
"It's never a bad idea to have a fresh start - and there's a lot more research still to do to improve returns. The low price of tomatoes has put pressure on the industry. When yields went up in the 1990s that was how growers kept ahead of the game. But since yields have levelled out and fuel and labour costs have gone up, the price of tomatoes has become a lot more of a problem."
Fortunately the ongoing difficulties faced by growers did not stop Hayman's TWP colleagues from throwing him a great leaving do, with dinner for Hayman and 37 of his colleagues at Buckland Manor Hotel in the Cotswolds.
There, speeches paying testament to his enormous contribution to the TWP were given and Hayman was presented with the Stapley Cup for his "sterling work". He was also given several gifts, including a hand-crafted glass bowl commissioned by his colleagues at Wight Salads.
Hayman told Grower: "It was a fantastic event. I was humbled. I've loved working for the TWP. Growers are the salt of the earth." He continues to be an independent horticultural consultant and provide technical and administrative support for the BTGA.
1961-62: Horticultural worker/trainee, Harrisons Seeds, Leicester
1962-65: University of Nottingham, School of Agriculture, Sutton Bonington
1965-88: ADAS, covering most sectors including vegetables, nursery stock and soft fruit
1988-93: Director, John Hall Nurseries, Chichester
1993 to date: Self-employed agronomist and horticultural consultant.