I've heard of some strange gardening practices over the years, but some of the tips offered in a medieval gardening book which is said to have inspired Henry VIII's lost Great Garden at Whitehall Palace take the biscuit.

The Ruralia Commoda, written in 1304, due to go on display at an exhibition at Buckingham Palace in March, claims that a squash will bear fruit after nine days if planted in the ashes of human bones and watered with oil, and that cucumbers shake at the sound of thunder.

It also mentions that lettuce loves goat manure and that combining the seeds of lettuce, radishes, nasturtium and colewort will result in a particularly tasty crop of greens.

The book, which will be displayed alongside some of the earliest and rarest surviving records of gardens and plants from the Royal Collection, entered Henry VIII's library after the death of its owner, the King's chaplain Richard Rawson, in 1543 and explains the importance of a king's garden to the Tudors.

But just how much truth is there in its horticultural growing tips?

Guy Barter, head of the RHS advisory service, says: "They didn't have squashes as we know them in those days."

Perhaps the Latin text has been lost in translation.

"It would have been a marrow. Squashes come from North America, which hadn't been discovered at that time. If you watered oil on the ground it would have no fertiliser effect. It might inhibit loss of moisture by evaporation but it wouldn't control pests.

"They would have used vegetable oil as they didn't have synthetic oil in those days and it would have been broken down in the soil. But if an old-fashioned gardener wanted to give it a go, it wouldn't do any harm. Just don't use engine oil!"

The manual also suggests that lettuce loves goat manure; and Barter agrees.

"Gardeners throughout history have gathered sheep manure which is an excellent quality and balanced feed, not too high in nitrogen like bird manure and probably better than cow manure. The problem is, goats are pretty thin on the ground nowadays. If you can get hold of a goat, I'm sure there's potential there."

Burnt human bones were obviously valued for their horticultural properties in Henry VIII's day - and they would have added nutrients to the soil, Barter agrees.

"Mixtures of blood, fish and bones are widely sold today. Bones are a very good fertiliser. Before they had good machinery to grind up bones into bonemeal, they would have been burned and the ashes would have been rich in phosphorous and in lime. Whether human bones are better than any other bones, I wouldn't like to say."

While it's not the case today, in Tudor times many soils were deficient in phosphorous. The growing of root vegetables and legumes was often inhibited by lack of phosphorous, which is needed for the healthy production of roots and good root systems.

"Plants don't use much phosphorous but there's desperately little of it in virgin soil, so it was lacking until the invention of the fertiliser industry in the mid-19th century," says Barter.

He is, however, flummoxed by the claim that cucumbers shake with fear at the sound of thunder.

"I've never seen a cucumber shake with fear," he laughs. "They would have been grown in cold frames covered with glass or wax. But even so, I can't imagine why a cucumber would shake with fear. There's a lot of thunder at RHS Garden Wisley and a lot of cucumbers and they've always remained rather stoic."

However, the 14th century manual was ahead of its time in some respects, declaring that combining the seeds of lettuce, radishes, nasturtium and colewort will result in a particularly tasty crop of greens.

"Isn't that amazing? They predicted the invention of bagged mixed salads by hundreds of years. What a brilliant idea! It's come full circle. We used to grow everything separately and now gardeners have come back to sow these mixed salad packs and grow their own versions of the supermarket ones.

"Those plants would all grow happily in the same soil together. Radishes are a little bit hairy, but there are versions of radish that haven't got hairy leaves so perhaps the Tudors grew those. But they would all combine well together."

:: Painting Paradise: The Art of the Garden is at The Queen's Gallery, Buckingham Palace from March 20 to October 11.

BEST OF THE BUNCH - Fern

The Victorians loved ferns and in recent years we have rediscovered them, thanks to their year-round interest, tolerance to shade and perfect backdrop that they provide to bulbs such as snowdrops in winter, or placed next to astilbes beside a pond or foxgloves in a woodland setting. Most ferns like partial-to-deep shade and the soil requirements vary greatly from those that need damp soil to others which can tolerate dry sites. Try the evergreen Asplenium (spleenwort) if you want one which tolerates dryness, or Blechnum spicant, a native species, which is easy to grow in moist, acid conditions like a shady shrub border or woodland.

GOOD ENOUGH TO EAT - Forcing strawberries

Get a head start to summer by planting strawberries under glass now to encourage early fruits. Plants need exposing to a period of really cold weather to set plenty of flowers, so don't bring them in too soon. You can lift and plant them into a pot filled with compost and soil, then bring them into the greenhouse or cold frame, or alternatively cover any plants which are in the ground with a cloche, to encourage an earlier crop. Make sure that the plants which are under cover can be accessed by pollinating insects. Throw open the doors of your greenhouse and remove cloches when the weather is mild and sunny, closing everything up again at night. In the greenhouse, once the strawberries start to flower, take a soft paintbrush and just run it over each flower once a day. This way you will ensure good pollination. You won't need to do that with the plants you grow outdoors.

WHAT TO DO THIS WEEK

:: Cut back hedges before birds start to nest in them.

:: Prune large-flowered (Group 3) clematis.

:: In mild areas, start to prune roses, removing dead, diseased and dying stems.

:: Trim back winter-flowering jasmine when it has finished flowering.

:: Top-dress or repot pot-grown camellias when they pass out of flower.

:: Check supports on wall-trained fruit trees or bushes before the new season's growth starts in earnest.

:: Test the soil in your garden to see if the pH needs adjusting or if it is deficient in any major nutrients.

:: Put cloches in position to warm the soil for early sowings of vegetables next month.

:: Sow under glass slow-maturing bedding plants such as African marigolds, petunias, lobelia and antirrhinums.

:: Prune autumn-fruiting raspberry canes.