e-mail Jane Owen with your gardening questions: jane.owen1@timesonline.co.uk

Are marigolds really edible and if so is it just the flower or the whole plant? I ask because I would like to grow them with my three year old who loves anything he can eat. Elspeth Hamilton, Tooting

The reason that they are sometimes called Pot Marigolds is that in the past they were used as vegetables. The pot refers to a cooking pot rather than a flower pot. I am told the leaves aren’t about to set the culinary world on fire but at least they are edible. The flowers, or at least the petals, don’t have much flavour but they look pretty sprinkled on salads which is how I use them. Are you going to plant nasturtiums too? The whole plant is edible as you probably know and they have a peppery flavour which can intrigue children

I would like to plant some plum trees for eating. Please suggest some good eating varieties which do not need advanced gardening knowledge. Can I plant now? Moira Sharp, East Grinstead

Victoria is rightly popular – a delicious fruit, self fertile and a good cropper. ‘Czar’, another old variety, is also self fertile with a sweet fruit and a good crop. Finally the Early Transparent Gauge, which is self fertile and delicious has been winning awards from the Royal Horticultural Society since the nineteenth century. Early Transparent Gauge is what I call a proper green gauge unlike some of the insipid green plums sold in shops. The flavour is unbeatable. Brogdale, which houses the National Collection of Fruit, is a good source of fruit trees. Any container-grown plant can in theory be planted now although many people feel that fruit trees still do better planted in autumn. However I once planted a small orchard with bare-rooted plums and apples in May (a nurseryman was chucking them out) which is against all the rules. I kept them very well watered and they all did well. Plums need, moist, free-draining, neutral soil and do best with a thick mulch of farmyard manure in spring. When planting dig a hole at least three times bigger than the root and mix in a decent amount of rotted manure with a handful of blood and bone fertilizer. The trees need to be kept well staked and watered and the fruit needs to be thinned, particularly on young trees, to prevent the brittle branches snapping.

I found some frogspawn and a frog in a dip under a pot when I lifted it. Is this possible and what should I do? I do not know where the frog has come from but it has been here since we arrived five years ago even though we don’t have a pond. Kylie Bennett, Chelmsford

There was probably a pool in that area at one time and the pot must have left such a damp hollow that the frog was convinced she’d found the original pool. Scoop the spawn into a bucket/dish/pool of rainwater with some aerating weed and see what happens. If tadpoles emerge remember to add a plank or rock so they can get out of the pool.

I need a dark red dahlia for a border with dark leaves but DON’T want Bishop of Llandaff which is what my father always grew. I’d like something much darker and neat. Bel Brown, Wells

How about ‘Miss Campbell’? The leaves are paler than The Bishop and the pom pom head makes a neat ball of deep red.

Two years ago my mother gave me some asparagus crowns but they don’t seem to do much. Out of 20 plants we got about ten small spears. Sue Palmer, Windsor

It may have been a little early in the plants lives to have been cutting. When asparagus is settling in it sometimes needs about three years to build up strength. On the other hand, some varieties are a lot of hard work for relatively little reward. Without wanting to offend your mother would it be possible to replant using ‘Gijnlim’ which all male and therefore produces no seed which means that all its strength goes into producing lots of juicy asparagus spears? Plenty of people supply this including Mr Fothergills

Friends are coming from Canada to spend next week with us. Any garden recommendations please? We are not garden visitors at all and so any suggestions would be welcome plus a guide book given we don’t know anything about gardens. Laurie Havercroft, Cirencester

You’re in a prime position to visit some of the loveliest gardens in the country. The National Trust’s Hidcote is an Arts and Crafts garden which is looking fantastic and it’s in some beautiful Cotswold countryside. At the end of Hidcote’s drive you’ll find Kiftsgate, an outstanding private garden with and Arts and Crafts theme plus a dramatic contemporary garden at one end. The arboretum must be somewhere you know and, although some of the blossom was knocked back by frost, there’s still plenty to see. Prior Park in Bath (National Trust) is an outstanding eighteenth century landscape; Owlpen Manor is a magical Tudor place tucked into a secret valley of the Cotswolds and, if you’re feeling rich, you could have lunch in Barnsley House’s beautiful garden where Liz Hurley recently got married. There are many more stunning gardens in the area and I commend two books: the National Gardens Scheme Yellow Book and the Good Gardens Guide 2007 both of which are available in book shops and larger garden centres

Is there a trick to growing echiums? I sowed one last year and planted it outside in a fertile, sunny border but it has not returned. Chris Wood, Southampton

They probably got a bit damp this winter. Down there in Southampton you have good growing conditions for this wonderfully outrageous plant but, if the roots were waterlogged even for a short time, they would have died – they need very well drained soil.

I read about your debate at the Oxford Union last Sunday and would have liked o have been there. Is it possible to get a transcript? In particular I would like to have now what James Alexander Sinclair made of it. Sam Raj, London

He mostly talked about frilly thongs and the importance of understanding horticulture although, being James, he put it rather more poetically than that. You can read his thoughts about it on his blog. Incidentally, the debate was part of the Oxford Literary Festival at Christ Church, not the Oxford Union.

e-mail Jane Owen with your gardening questions: jane.owen1@timesonline.co.uk

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