Of all the plants in your garden, container-grown plants are among the most vulnerable. Restricted to the soil that is contained by their pots, their roots cannot branch out in search of more water or nutrients than is in their immediate vicinity. This means that the soil can easily end up dry and depleted unless you feed and water your containers well. The good news, however, is that if you give your container-grown plants just a little bit of TLC now, most summer annuals will keep flowering right through to autumn.
Watering tips for containers
Due to the large surface area of containers versus garden borders, the soil in containers heats up far more quickly than the soil elsewhere in your garden. This makes the compost in containers far more prone to water loss through evaporation, which can be an especially big problem when the weather is as hot as it has been in the UK this year. Again, smaller containers with even larger surface areas dry out even more quickly than their larger counterparts.
To keep pot plants looking their best right through to the first frosts, then, watering is all important. In summer, containers need to be watered at least once a day—and you should increase this to twice a day when the weather is really scorching. This is especially true for hanging baskets, which often have an even greater surface area than other pots as well as contending with the wind whipping past them and increasing the evaporation rate of water from their compost.
The time of day at which you water is an extremely important factor in ensuring that your plants remain properly hydrated. Water in the midday heat and your pots will rapidly lose moisture, making it difficult for plants to take up enough before the compost dries out. To avoid this problem, water early in the morning or late in the evening when conditions are cooler and soil will remain moist for longer. This will also help to protect foliage from damage due to water spray concentrating the sun’s rays onto leaves and resulting in sun scorch.
The most effective method for ensuring that all the compost in your pots is properly moistened is to water until the water level rises above the surface of the soil, leave it to soak through, and then return a few minutes later for another round. Using a hosepipe like the YOYO extendable hose to water your containers is the most hassle-free way to ensure they get the water that they need. Its lightness and anti-kink technology makes it easily manoeuvrable around collections of pots and hanging baskets no matter how much you wind in and out while watering your containers. It’s advisable also to feed plants once a week with a well-balanced liquid fertiliser, but always do this after watering them thoroughly first—otherwise you can burn plant roots.
Of course, in very hot weather UK reservoirs can become depleted, in which case a great tip is to use grey water—that is, water that’s been used for another purpose—to keep plants hydrated. For instance, instead of letting bath or washing up water drain away down the plughole, scoop it out and use it to give your plants a drink. Cooled boiled water that you’d normally tip away out of your kettle is also a great option for watering ericaceous plants like blueberries and Rhododendrons, since it is more acidic than normal tap water.
Planting drought-resistant containers
If you’ve lost some of your container-grown plants due to the unprecedented heat of our June and July this year, then I’d encourage you to get back on the horse and plant up some fresh summer annuals. If you visit your local garden centre, you’ll find that so many of their summer bedding plants will now be reduced to make way for next season’s stock—but if you look after them properly, many of these will continue to flower right through until the first frost. Chrysanthemums, Pansies and Violas all fall into this category and make for fantastic late season colour.
Since it looks like we’re in for a sweltering August as well, here are some tips for making your newly planted containers less prone to the effects of drought for the rest of the season. First, gets your hands on some hydration crystals at your local garden centre and add them to the soil as you plant out your containers. These crystals create little reservoirs of water within the soil that gets released as the compost around the crystals dries out, slowing the loss of water from your containers somewhat.
Second, if you have the inclination to replace your containers themselves, opting for wooden or clay containers which are better insulated against the heat will be better than choosing metal or plastic containers which absorb and retain heat more readily. So too, choosing larger containers with a smaller surface area will help to prevent soil from drying out too quickly.
Finally, another top tip is to cover the top of the soil with a mulch, as this helps to stop water evaporating as readily off the surface. Choose bark chippings for a natural feel or add some colour with tinted glass beads, the choice is yours and your plants will thank you for it. For more top watering tips, see my blog How to Water Your Garden This Summer.