VAL BOURNE offers some useful tips on how best to feed the garden

My garden has hungry soil and my potatoes are not happy. They have suffered cold nights, countless wet and sunless days and I have still to dig my thinly foliaged first earlies. The trouble is I didn't feed my soil and my potatoes are effectively starving. I could have added a thick mulch of well-rotted manure, or grown a green manure crop, like Phacelia tanacetifolia, or added garden compost some months ago.

But one of the best ways to boost a potato crop is to put some chopped comfrey leaves in the bottom of the trench. Comfrey is the plant equivalent of blueberries for humans. The leaves contain 17 per cent nitrogen, whereas horse manure has only 14 per cent. Comfrey leaves also contain silica, nitrogen, magnesium, calcium, potassium and iron, and one or two carefully chosen plants close to a compost heap will pay great dividends and save money spent of liquid plant foods.

However, never ever plant a spreading comfrey. No matter how pretty Hidcote Blue' and Hidcote Pink' sound they are super invasive and have flowers like tobacco-stained teeth. Plant an upright comfrey instead and if you are growing one for leaf content the ultimate is clone is Bocking 14.

Bocking is a village near Colchester and Henry Doubleday (1810-1902) had a smallholding there. Henry was a starch manufacturer who tried to utilise the mucilaginous properties of comfrey roots in order to patent the first glue for postage stamps. Previously, the sticky paste had been used to heal broken bones giving comfrey - or symphytum - the common name of knitbone.

Henry, who never cracked the glue-making, imported several types of Russian comfrey (Symphytum x uplandicum) and gave them numbers. He discovered that comfrey stayed in leaf for ten months of the year and wrote about this in the Gardener's Chronicle and Agricultural Gazette.

Years later the famous organic gardener Lawrence Hills (1911-1991) discovered the articles and visited Bocking where he found Henry's offspring ( nonagenarians Edith and Thomas) in residence - still growing comfrey. Lawrence Hills tested twenty numbered forms and found Bocking 14 the best because the leaves contain twice as much potash as ordinary comfrey (Symphytum officinale). In fact, it is the best source of natural potassium available to gardeners. Potassium increases flowering power and it's the chief ingredient in tomato feeds.

We have several comfrey plants close to our compost heap and the leaves make an excellent accelerator if chopped into the heap. The flowers also please the bees. But by far the best way of releasing comfrey's supercharge is to make comfrey tea for plants. The leaves decompose quickly and the brown fluid is then diluted in 15 or 20 times as much water.

But decomposing comfrey leaves smell worse than stagnant water. The best beloved is immune to such things. He regularly inhales the compost heap with relish. So we have made a visit to Garden Organic at Ryton, near Coventry, to see how to do it properly.

Apparently, my method of shoving lots of leaves in a bucket, with a tight lid to stave off the smell, and then standing well back can be bettered by the system pictured. The rocket launcher on the right is the high-tech Ryton version. The leaves go in the pipe and the liquid accumulates in the bottom before being drained off. On November 5 this year I will be able to launch a large rocket. Unfortunately, the best beloved is too large to send up with it.