Action plan: Nigel Colborn’s essential jobs for your garden this week 

Time for a boost of flower power 

Now is the time to give containers a midsummer boost. After such challenging weather (gales, heatwaves and crashing thunderstorms), the plants may be a little punch-drunk.

Hasten their recovery with a mid-season pick-me-up.

With fast growers such as pelargoniums (pictured) and lobelias, it may be necessary to shorten lanky stems. Snip some of those back to a lower bud. That encourages further branching and will result in a denser, more robust plant.

Make sure trailing varieties are not smothering upright feature plants. Trim or pull away any surplus growth, making sure each container is well balanced with comfortable plants.

If you used slow-release granules at planting, some containers may begin to run low on nutrients. Overcome that by applying a high potash liquid feed. Tomato fertiliser is perfect for increasing flower production, as well as boosting the crops.

Succulents and cacti outdoors may benefit from feeding, too. Echeverias, sedums, jade plants and other succulents lose colour and vibrancy when undernourished. So give all a diluted liquid feed. When echeveria and other flower stems start to fade, cut those away with care.

A little extra tender-loving care now could help your containers to look fresh and beautiful until late October.

Zap those wicked weeds 

If you have problems with perennial weeds such as bindweed, ground elder or couch grass, take action now. The most effective control is with the systemic herbicide glyphosate, or Roundup. When applied to living foliage, it will reach the roots and the weed will die. Choose a calm, dry day with no rain expected for at least eight hours. But take care not to allow a drop of the herbicide to land on your garden plants.

Take soft cuttings

Many herbaceous plants root readily from cuttings taken in July.

First, add a mixture of sharp sand and potting compost to clean, free-draining pots (7cm or 9cm). Then take cuttings from healthy plants early in the day to reduce wilting. Select the healthiest shoots and remove lower leaves. Cut each stem across a leaf-node and stick several cuttings into each pot. For fastest results, place the pots in a propagator with bottom heat. Or use a coldframe or a windowsill which doesn’t overheat in full sun. Pot up as soon as they are visibly growing.

Reader’s question

Our garden borders a footpath infested with bindweed and ground elder. We try to keep our side weed-free but the weeds creep under the weatherboard fence. Is there any way we can stop that from happening? Sue Johnson, via email.

The roots of both those weeds travel rapidly underground. You can reduce that by installing a rootproof barrier along the bottom of the fence. Made from recycled plastic, a barrier can be 1mm or 2mm thick, 30cm or 60cm deep and comes in rolls of 5m or more. You would need to dig a trench below the fence, set the barrier vertically into the ground and back-fill. That should stop almost all roots from coming through. If one or two manage to get under or over the barrier, they’ll be easy to spot and remove. So you’ll be back in control.

Plant of the week: Lavandula angustifolia ‘Twickel Purple’ 

If you’re looking for a sturdy lavender which grows to a decent size, this is an excellent choice. Deep purple-blue flowers contrast well with the silvery grey-green foliage. As with all good lavenders, the leaves and stems are aromatic and the flowers fragrant. This is no dwarf, growing to 75cm with longish flower stems held well above the foliage. Ideal for lavender hedging, it responds well to clipping. Big varieties such as this also make lovely free-standing shrubs. If there’s a hot, dry spot in your garden, this could be the perfect choice. Butterflies and bees love lavender, too.

Originally from Holland, Twickel Purple was introduced to the UK in 1922.

As with all lavenders, some suppliers may offer plants which are incorrectly named. To be sure of the variety, buy from specialist suppliers such as Downderry Nurseries (downderry-nursery.co.uk).