In my other life, answering garden problems, one of the most difficult problems to address, when explaining why plants have died, is watering. If the compost is dry, plants will wilt but the hard thing to explain is why plants that are in wet compost can wilt. It is often because, with sodden compost, the roots are deprived of air and they rot. And if the roots rot the plants can’t get any moisture and they wilt.

Which brings me to cell trays, which have been the theme of several problems I have had to answer lately.

In the old days, when phones were securely confined to glass glazed boxes and phone numbers were stored in a flip-up directory or in your head, we grew bedding plants in trays. We often used home-made wooden trays and pricked out the seedlings 6 x 8 in the trays. Dad was a keen gardener and we sold bedding plants at the gate and we would cut strips of plants, usually a dozen or so, and then pull the plants apart to plant. We are obsessed with root disturbance these days but the plants always recovered and grew – if the slugs didn’t nobble them the first night. Then commercial growers moved onto ‘strips’ with ten or a dozen plants per strip and with four or five strips making a tray. At first these were expanded polystyrene – hateful stuff. The broken trays could be used for drainage in large pots but it was an awful job to get rid of the stuff. Then thin plastic trays took over. These were the days when most bedding was grown from seed and was relatively inexpensive.

But plant breeders started introducing ‘improved’ plants that were sterile and grown from cuttings or micropropped. They sold for a premium price and now no one buys trays of bedding. Even things as easy as cosmos are now sold in one or two litre pots (madness in my eyes but people want instant).

But back to our cell trays. I confess that I like them because the plants can be planted without damage to the roots. But while it was easy to water all the plants evenly when they were in a tray – because the water could flow and move from one plant to another, in cell trays things are different.

The problems begin when you grow different plants in one tray or if some plants grow more quickly than others. Because it is almost impossible to water one cell without watering some others, problems start to appear. If a few plants start to grow well, because they are bigger than the rest, they will dry out more quickly. So you water the lot – you have to. But the smaller plants, and there may be a few runts, will already be wet and when you water they get saturated. As a result their roots start to suffer. When it comes to having to water the bigger plants again they will still be wet and they get another soaking. Apart from the fact that the wet compost will probably get infested with fungus gnats (those annoying little black flies that bother you in the lounge), the little plants will eventually die.

The key with cell trays is to keep everything in each tray as consistent as possible – but it is not always that easy. I sow in rows of cells. I try to sow things that germinate at the same rate and by sowing some seeds in each cell, if there is a problem with damping off there is a good chance that the disease will not spread to all the cells.