On days like the one pictured above where I was imprisoned in the greenhouse by torrential rain it's hard to imagine that anything ever needs watering at the allotment. Of course, this isn't true and it only takes a day or two of sunshine for plants to need a drink. I have to say that on the whole I take a tough love approach on our plot and only water when absolutely necessary in the the belief that most plants do better if they're allowed to find water for themselves. And if your soil is high in organic matter and you mulch whenever you can you'll be amazed how much moisture the soil will retain even in the hottest weather.
Despite this there are some things that definitely need an extra drink from time to time. For example, all the plants in the greenhouse need watering at least once a day. Twice on a really hot day. In addition to this all seedlings need to be well watered when they're planted out until they're well established. Don't be tempted to leave them to fend for themselves too early as any weakness at that stage in their development will leave them more vulnerable to attack from slugs and other pests. You may also find that if the weather is particularly dry potato, onion and garlic plants won't reach their full potential so it's worth giving them a good drink if this situation arises. If you do need to water any crop outdoors you're always better to give them a really good soaking once or twice a week rather than a cursory dribble of water everyday.
One thing that can cause some degree of controversy on our plot is what time to water. I'm of the argument that on the whole you're better to water in the morning so that the water warms up as the morning sun warms the plant. I also always try to use harvested rainwater as it will have warmed up where it has been stored and be much kinder to the plants. My partner in gardening crime however is of the opinion that watering in the evening is the better bet as the plants will have the chance to absorb more of the water before it is evaporated by the strong morning sun. What we both agree on is not to water at the warmest part of the day and to always water the roots, trying to avoid wetting the leaves if possible.
So there you go... My simple, or not so simple, guide to the practice and politics of allotment watering! To water or not to water? Morning, evening or not at all? I guess that is the question...