What to do in the garden in August

The last true month of summer and the garden and veg plot are still at their best. There is time to sow quick growing salad crops  such as Lettuce, Rocket and radish. Dead heading flowers is essential to prolong flowering well into September as the later flowers come to their peak.

If you are going on holiday, you still need to look after the garden, especially those plants in containers. 

10 Best tips for looking after the garden while you are away holiday tips  and ideas. 

Summer prune Wisteria

Lovely Wisteria blooms

In order to ensure that Wisteria flowers reliably year after year pruning is essential in summer (August) and winter ( Feb) Video  tips on how to summer prune Wisteria.

Unless Wisteria is pruned twice a year, it will grow very large and outgrow its allotted space, and over time it will cease to flower. Looking at the Wisteria now in August there is always a huge amount of growth put on over the summer, and it is time to get it in check, cut off the long whippy growth and all the laterals at the base. This will also ensure the Wisteria does not grow into stonework crevices, drainpipes or anywhere else where it might cause damage. 

August is a good time to prune Shrubs which have flowered earlier in the season to shape the shrub, encourage growth and blooms for next year and if they are getting too large for the allotted space. Early August is the last chance to prune Weigela, PhiladelphusChoisya, and Wisteria.  Late July/August is the best time to give Wisteria it's essential second prune. I often delay until later in August to enjoy the second flush of flowers, which although less that the spring flowering is still a welcome sight. To ensure that Wisteria flowers it must be pruned correctly and for more about pruning and  how to grow Wisteria . 

If you are interested in growing Wisteria on the YouTube Sunday Gardener channel there are videos on winter and summer pruning Wisteria, how to  make Wisteria flower and a short video showing Wisteria in full bloom.

When pruning mature shrubs the cuttings can make good plant stakes, and for free. How to make your own attractive wooden plant stakes.

Black spot on Roses

As the summer goes on the Roses become more prone to black spot. Black spot will make the leaves turn yellow and spots appear, some leaves will fall to the ground. It is best to pick up the diseased leaves and destroy (not in compost bin) and spray.

I do not like to use sprays in the garden, without doubt regular spraying of the roses with a good spray such as 'Roseclear' really does work and the Roses are healthier as a result. The current product Roseclear controls the key diseases on roses such as rose blackspot, powdery mildew and rust. It also protects plants from further infestations of aphids and diseases. With the earlier versions of this product it was necessary to  every week or two it is now recommended spraying interval is 3 - 4 weeks between applications. I don't have shares in the manufacture of Roseclear, although it sounds as if I do, but it does the job.

Lavender 'Hidcote' on a  path

Late August is the time, after flowering, to trim spent flowers from Lavender  and clip the plant into neat shape. This will help to keep the plant in a good shape for the next year. The Lavender, as in the image left, has been trimmed each year into a nice round shape and planting by a path is ideal as Lavender release scent on contact, brushing past will produce the lovely Lavender perfume. This variety 'Hidcote' is one of the hardiest of the various Lavender varieties, which can be helpful, as Lavender detest cold wet winters. If you like the faded stems on Lavender, you can delay trimming it back until early spring.

Do not trim Lavender stoechas (French lavender) which flowers continuously, just dead head throughout the summer ideas with Lavender

To ensure your summer display continues to bloom for as long as possible,  dead head as much as you have time to do. Once a plant has flowered and set seed, it will slow down and stop flowering unless prevented by regular dead heading.

Cut back tired looking foliage on Perennials

Even now it is not too late to cut back some Perennials which are looking faded, such as hardy geraniums, Nepeta (Cat Mint) Alchemilla (Lady's Mantle.) Cut back to tidy shape and when doing this 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 which will look fresh.

I have cut back Alchemilla almost to the ground in early July and by August the new growth has replaced the old, tired, and browning foliage. I will not flower again, but the foliage looks much better and fresher.

 Some plants, such as Delphinium may have very tired foliage and cutting them down maybe the only option as the foliage becomes an eyesore.

This is also an ideal time to take cuttings from Pelargoniums and raise plants for free for next year. Easier than most plants to raise from cuttings check out the blog for a guide on how to take cuttings.

August in the Veg plot

Harvesting crops

Broad beans producing a second crop

Many of the crops are ready to harvest during August and September, and it is a priority job to keep harvesting. Picking the veg, in a similar way to dead heading 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 veg quickly go over if not picked regularly, every day or so. 

If August is warm, damping down the greenhouse helps to control temperatures. After watering the greenhouse plants, finish off by watering the floor, which provides cooling by evaporation, and is best done in the morning to keep the greenhouse cool for the high daytime temperatures.

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 bean plant has finished, cut down the stem close to the ground about 15 cms near a growing point and give it a feed. On a good year it will re grow and produce a second, lighter smaller crop, but perfectly acceptable producing fresh broad beans in late summer/early autumn. Looking at the image left you can evidence of both old and new growth ( the leaves are a paler colour,) on the broad bean plants, the new growth being produced after the bean has been cut down to aid a second crop;  more advice on growing broad beans.

Drying and Storing Onions Garlic and Shallots

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 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.

If there is a decent dry spell, onions and shallots once harvested can be left on the ground to dry.  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. It is very important that before the onions are put into storage that they are bone dry, if damp, they will rot and quickly become unusable .

onions and shallots

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.

For both onions and garlic, once dried, their winter storage requirements are the same; a dry light place and either in net letting air circulate or they can be platted and hung in dry shed/garage/conservatory where they look nice provided you don't mind the onion smell.

Onions and Garlic will store for 12 months in a suitably light dry environment, not the kitchen. An easy way  is to lay onions and garlic out on the greenhouse slates to dry, check out growing onions for more information.

Tomato Care

There is plenty to do with ongoing tomato care which 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 growing any taller. The goal is to stop the planting growing and producing yet more leaves and to divert its energy into fruiting.

  Even after pinching out the growing points because tomatoes grow vigorously if allowed, the plant will keep producing new top growth and you will need to keep on pinching out all top growth. The plant will keep growing, keep pinching out and removing leaves so all energy goes to the fruit.

This is the most important time for regular watering and feeding to ensure a good crop of sweet tasting tomatoes. Without the right amount of water and feeding, there will be tomatoes, but of poor quality. More about growing tomatoes

There is still enough summer left to sow last rows of lettuces, rocket and crops such as Pak Choi  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 it becomes cooler. 

 Maincrop potatoes can be harvested once they have flowered and should be ready to harvest in August/Sept.  You can leave them in the ground for a while after the top growth has died back. Potatoes already harvested/still being picked are usually the earlies and salad potatoes which will keep fine in the fridge. Maincrops are harvested later  and it is essential that they are stored somewhere dry and dark. It is most important when they are put into storage that the potatoes are 100% dry and light is excluded. Hessian sacks are good for storing Potatoes.

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 when properly rooted in a few weeks the runner can be cut away from the main plant. Strawberry plants need replacing about every 4 years as the yield gets less, so this is an easy way to get extra plants; more about growing strawberries.

Last updated 31.07.2020