August gardening guide: what to do in your garden this August
August is officially the last month of summer, and the garden and vegetable plots are still at their best. And weather permitting, enjoying the garden as an entertaining space is one of the joys of late British summer.
Many summer perennials will finish flowering by the end of this month, and late summer shrubs like Buddleja and Abelia and the richly coloured autumn daisies such as Echinacea, Rudbeckia and Helenium will begin taking centre stage.
There is time to sow quick growing salad crops such as Lettuce, Rocket and radish. Deadheading flowers is essential to prolong flowering well into September as the late flowers come to their peak.
August gardening guide: Planting
Plant up autumn-flowering plants
Plant up autumn-flowering cyclamen to replace any faded summer bedding plants. Also, mark out any gaps in your border that are prime locations for spring-flowering bulbs that can be planted over the next couple of months.
Sow seeds of perennials that need a frost to germinate and leave them outside in a cold frame. This is also an ideal time to take cuttings from pelargoniums to raise plants for free for next year.
Make new strawberry plants
Strawberries are all over now, and so you can use the runners to make extra or new plants for next year. Let the runners develop and peg down into a pot adjacent to the plant so that the runner can be cut away from the main plant in a few weeks when they have properly rooted.
Just place a pot of compost near the plant, peg the runner into the pot, water it properly, and leave it for a few weeks until it is well-rooted. Cut off excess runners to conserve the plant’s energy. Strawberry plants need replacing about every 4 years as the yield gets less, so this is an easy way to obtain extra plants.
Sow the last rows of lettuce and rocket
There is still enough summer left to sow the last rows of lettuce and rocket, which prefer cooler conditions and will be less prone to bolting (running to seed prematurely because growing conditions are too hot and dry). Any late crops sown during August will need cloche protection later when the weather becomes cooler.
August gardening guide: Care and maintenance
Late August is the time, after flowering, to trim spent flowers from lavender and clip the plant into a neat shape. This will help to keep the plant in good shape for next year. Do not trim Lavender stoechas (French lavender), which flowers continuously, just deadhead throughout the summer.
Cut back tired looking foliage on perennials
It is not too late to cut back perennials that are looking tired, such as hardy geraniums, Nepeta (Cat Mint) and Alchemilla (Lady’s Mantle). Cut back to tidy shape, and when doing so, you may notice at the base and centre of the plant there is already new growth spurting. After cutting back, the plant may, or may not, flower again depending on the weather, but it will grow new foliage that will look fresh.
Ongoing tomato care
There is plenty to do with ongoing tomato care that is important as the plants start to fruit. Tomatoes produce masses of leaves, and these need to be thinned out to encourage fruit production.
The tomatoes have set several trusses of flowers by this stage, and the top growing point needs to be pinched out to stop the plant from growing any taller. The goal is to stop the planting growing and producing yet more leaves and divert its energy into fruiting.
Even after pinching out the growing points, the plant will keep producing new top growth because, if allowed, tomatoes will grow vigorously. You will need to keep on pinching out all top growth.
If you are going on holiday, you still need to look after the garden, especially plants in containers.
August gardening guide: Harvesting
Many of the crops are ready to harvest during August and September, and it is a priority job to keep harvesting. Picking the vegetables in a similar way to deadheading flowers encourages continued fruiting and so a better yield. After all the hard work of growing the crop, to miss the moment when the beans, courgettes and salads are at their peak. The vegetables quickly go over if not picked regularly, every day or so.
It is possible to get a second crop of broad beans, especially if the summer is good. In late July/early August, when the broad beans plant has finished, cut down the stem close to the ground about 15cm near a growing point and give it a feed. In a good year, it will regrow and produce a second smaller but perfectly acceptable lighter crop of fresh broad beans in late summer/early autumn.
Depending on the aspect and geography of your veg plot, Onions, Garlic and Shallots should be ready to harvest by the end of the month/early September. As soon as the top growth goes brown, bend over the top growth, which is said to aid ripening, and then pick a dry spell to ease the bulbs out of the earth carefully before resting them on the soil to dry out before bringing in for storage. Onions need to be stored in the light.
Garlic is similar. Wait till the top growth turns brown, usually in late August/Sept. Store in a dry and light spot in the warmth rather than a cold area.
With our variable weather, it can be hard to find a dry spell, and so if the weather is wet, you will need to find another way to dry the onions. The onions must be bone dry before they are put into storage. If damp, they will rot and quickly become unusable.
One way to dry off the onions is to bring them indoors, into a conservatory, greenhouse or under glass and dry off in the warm atmosphere. The greenhouse is ideal, and you can dry them on the slatted shelves.
August gardening guide: Wildlife and pests
Keep bird baths topped up with fresh water. Leave seed heads on some of your plants as extra food for birds and small mammals. Also leave some windfall fruit on the ground as a tasty treat for wildlife.
August gardening guide: Other garden tasks for August
- Spot treat weeds in your lawn, filling in any holes with gritty compost to encourage regrowth.
- Keep ponds and water features topped up. And don’t forget to clean out your water butts if they are empty, removing sludge and algae.
- Sweep your patio areas regularly and treat any small weeds as they germinate.
- Hoe weeds from gravel areas and treat with a residual weed killer to prevent more weed seeds from germinating.
- If August is warm, damp down the greenhouse to control temperatures. After watering the greenhouse plants, finish off by watering the floor, which provides cooling by evaporation. Damping down is best done in the morning to keep the greenhouse cool for the high daytime temperatures.