Here are their responses. Herbert answered all the questions and Benn answered most with some contributions from the Labour team. The Liberal Democrats, however, failed to respond by the deadline. For comparison, we included some key points from their rural manifesto.
Q: Applied R&D is the lifeblood of production horticulture in the UK and numerous reports have highlighted the crisis it is facing. What proposals do you have to ensure the development of a sustainable R&D base for horticulture?
Conservatives: "Strengthening the focus on R&D is crucial to help the industry raise production in harmony with the environment. The Conservatives will look to prioritise R&D in the departmental budget and develop a long-term strategic research agenda across the whole food chain that reflects the importance we attach to raising production sustainably.
"We must uphold our world-class science base, share expertise with international partners and work to ensure that blue sky research is effectively translated into real practical value at the farm level."
Labour: "When I launched Food 2030 I set out how R&D and its application are crucial to meeting future food challenges. So last October we announced a new partnership to fund research with the Technology Strategy Board (TSB) and the Biotechnology & Biological Sciences Research Council - that's £50 million of extra Government investment in research over the next five years.
"The TSB's Sustainable Agriculture & Food Innovation Platform will bring together business, academia and Government to understand better the issues of how to produce more with less - and how to solve them."
Q: There is huge concern about the forthcoming loss of Warwick HRI Wellesbourne and our last remaining horticultural scientists. Will you intervene to prevent this loss, and if so, how?
Conservatives: "I share this concern - we should be strengthening our capacity for horticultural research, not diminishing it. Conservatives have backed the call for the secretary of state personally to intervene to ask the University of Warwick to consider the impact of this decision on the UK's agri-food science base."
Labour: "It's important the right decisions are taken to protect the huge national asset of our horticultural scientists. My department has invested heavily in Wellesbourne, as has the Biotechnology and Biological Sciences Research Council.
"I wrote to (vice-chancellor) Professor Nigel Thrift to express my concern in December and he offered to meet with me to discuss the situation. I would hope this meeting could take place as soon as possible after the election."
Q: What is your "vision" for the supermarkets ombudsman and will it extend to ornamental plant suppliers and major DIY outlets?
Conservatives: "The Conservatives will introduce an independent supermarket ombudsman to enforce the Grocery Supply Code of Practice. We will ensure that the focus of the ombudsman is the protection of those smaller businesses that lack the market strength to stand up to retailers who are acting unfairly.
"I am happy to consider the case for extending the ombudsman's ambit to cover plant suppliers and DIY outlets when the new unit is established."
Labour: "Food producers need a fair market and the security to plan ahead. That's one of the reasons why we gave the go-ahead for a supermarket ombudsman.
"We're consulting on how this will be implemented. We want to achieve a system that strikes the right balance between farmers and food producers getting a fair deal and supermarkets doing everything that they can to give consumers high-quality British food at an affordable price.
Q: Would you stick to the peat elimination target of 2020 and how will you help horticultural companies make the transition to alternative growing media?
Conservatives: "Damage to peatland is releasing carbon dioxide at an enormous rate and this is something that we must tackle, so the 2020 target is important and we will keep it.
"Protecting peatlands from development and degradation will remain vital, but Conservatives want to change the way conservation is managed in the UK, moving away from hundreds of top-down targets towards policies that provide positive incentives.
"We see scope for using conservation credits - where market incentives are used to open up new revenue streams - to help us protect and enhance important habitats, like peatlands.
Labour: "I am absolutely committed to meeting this target. We've been working with the horticultural trade, DIY chains and garden centres to give information to gardeners on peat-free products and lower-peat alternatives at point of sale.
"We have alternatives and more are being developed - by raising awareness we can reduce demand. I am very optimistic that we will meet this target within the next ten years and ideally even sooner."
Q: Will you introduce specific targets to increase our canopy cover? If so, how will this be implemented?
Conservatives: "We need to do more to increase forestation and raise overall woodland cover. However, trees are valuable in all settings, not just woodland, and so in addition to ongoing woodland creation, we will launch a national tree planting campaign, planting more than one million new trees to green our towns and cities in the next parliament.
"Starting in 2013, as part of our radical reformed planning system, we will offer funding to enable local communities to plant up to 700,000 trees per year - one for every child born - where and how they choose."
Labour: "Reforestation is important to this country for so many reasons and that's why our Low Carbon Transition Plan committed to increasing it by 10,000ha every year over 15 years.
"The Read Report told us that by increasing the area of land covered by forest by just four per cent we can reduce expected levels of carbon emissions by 10 percent by 2050.
"Working with communities and businesses, we want to provide new incentives for UK forestation so it can play its part in controlling our climate and protecting our valuable ecosystems for the future."
Q: Will you introduce minimum targets for the percentage of each new development spent on soft landscaping?
Conservatives: "We are opposed to Whitehall targets - we have pledged to scrap Labour's density targets, which have resulted in 'garden grabbing'. We will give councils stronger powers to protect gardens and to respond to public pressure to safeguard green belt and develop new urban green spaces.
"We will create a new generation of local parks by introducing neighbourhood budgets from development planning gains and giving communities greater control over the planning system. Communities can create new parks on derelict land through re-zoning and use this direct source of funding for playground equipment and park maintenance."
Labour: "Each site should be taken on its own merits and it is for the local planning authority to agree the level of soft landscaping with the developers as part of the planning process. With our new eco-towns, however, we are committed to ensuring that 40 per cent of the total is allocated to green space."
Q: How will you ensure that local authorities make use of their new powers under the Community Infrastructure Levy (CIL) to lever in funding from developers for green infrastructure?
Conservatives: "Our radical planning reforms will see a simplification of the current complex section 106 and CIL into a unified tariff. This would give local residents a stronger say in how such funds should be spent. Local residents could then choose to use such funds to improve or add to green spaces."
Labour: "The CIL is available to local authorities to support the development of new infrastructure projects and these can include new parks and green infrastructure. The CIL can also be used across authorities.
"Local authorities will be able to look across their full range of funding streams and decide how best to deliver their infrastructure priorities, including how to utilise the CIL. This flexibility to mix funding sources at a local level will enable local authorities to be more efficient in delivering the outcomes that local communities want."
Q: Across departments, the implementation of policies that affect horticulture has often been left to non-governmental bodies. What cuts will be made?
Conservatives: "We will reduce the size of Whitehall and quangos by a third. Any quangos that do not perform a technical function or a function that requires political impartiality, or those that act independently to establish facts, will be abolished. Policy-making functions will be brought back into the department where there can be direct ministerial oversight."
Q: Would you be prepared to divert funds from the Department of Health for the provision of green space in local communities?
Conservatives: "We will provide public health funding to local communities that will be accountable for and paid according to how successful they are in improving their residents' health. They will be free to spend this money on the things that they think will be most effective. That could include green spaces, but that would be something for communities to decide."
Q: What are your plans for the Change4Life campaign and the marketing of fresh fruit and vegetables for public health?
Conservatives: "We support this campaign and efforts to encourage people to eat more fruit and vegetables. However, ultimately it is individuals and especially the parents of children who must take responsibility for their own diets and the food that they buy."
Q: Would you be prepared to revise the Sunday trading laws to allow garden centres to trade on Easter Sunday?
Conservatives: "We have no plans to change Sunday trading laws."
Q: Would you relax planning laws for new build/extending garden centres in rural areas to boost the rural economy?
Conservatives: "Our new planning system would favour sustainable development provided the application is in keeping with the guidelines in a local plan, drawn up with the input of local people. Because of the challenge of food security, we would not routinely permit development on grade 1 and 2 agricultural land."
Labour: "Such planning decisions are for local authorities to take within the existing guidance, but with an understanding of the real role to be played by such centres in supporting local jobs and economic growth."
Q: Skills funding for horticulture is already under threat. This will be exacerbated by the failure to include horticulture in the priority areas identified by the UK Commission for Employment and Skills for future funds. Will you make horticulture a priority?
Conservatives: "We will continue to support industry-led initiatives to ensure that horticulture has a workforce that is capable of delivering increased production and tackling environmental challenges.
"Conservatives are committed to reforming skills and apprenticeship training, providing assistance to small businesses that may have difficulty meeting the cost of hiring and training apprentices and we will remove bureaucracy and unnecessary inspection from further education colleges."
Q: What would you do about the EU's crippling pesticide policy?
Conservatives: "While farmers and growers should be encouraged to reduce pesticide use, rules must be based on science and supported by proper risk assessment. This is just one regulation we would want to look at again to ensure a better balance between the EU and the realities of agriculture.
"Regulations derived from such directives will be the subject of our joint industry-led review of environmental regulations that we will set up within three months of taking office."
Labour: "These regulations run the risk of hitting agricultural production very hard without any benefit to human health. We're effectively being asked to agree to something when no-one actually knows what the impact will be.
"We've lobbied hard in Europe and have managed to secure some improvements to the original proposals. But as things stand, we have made it very clear we do not and cannot support them."
Q: What are your plans for the Agricultural Wages Board?
Conservatives: "Under a new Conservative Government, the board will be abolished, reducing costs to the taxpayer."
Liberal Democrat Rural manifesto highlights
The Liberal Democrats failed to respond in time. However, their rural manifesto, launched last week, states:
"We will stop supermarkets bullying farmers, ensuring both farmers and shoppers get a fair price for food. We'll do this by creating a legal Supermarket Code and a powerful independent regulator of Britain's food market.
"We will help consumers to choose foods with the least environmental impact through clearer labelling and work with the EU to make sure country-of-origin labels identify the source of the products, not where they are packaged.
"We will introduce a minimum level for the Single Farm Payment and concentrate future reductions on the highest claims so that big landowners get less and the money goes to working farmers who need it, not people who farm one field as a hobby.
"We will use the money freed by reform of Single Farm Payments to provide extra support for hill farmers, cheap loans to help farmers invest in environmentally friendly bio-gas digesters and a farming apprenticeship scheme. Organic and reduced-input foodstuffs should be encouraged.
"We will make national parks democratically accountable, allowing a proportion of park boards to be elected, and will create a new designation similar to site of special scientific interest status to protect green areas of particular importance or value to the community. We will aim to double the UK's woodland cover by 2050."