What to plant and sow in August

What to plant and sow in August

John, Passionate gardener, Cambridge

Guide written by:

John, Passionate gardener, Cambridge

83 guides

August may mean holidays for most, but there's no rest for the home gardener! Whether you have a vegetable patch or ornamental garden there's still plenty of sowing, planting, transplanting and plant dividing to do if you want to enjoy flowers and vegetables through the autumn, winter and even next spring!  

Important features

  • Planting and sowing in an ornamental garden
  • Planting and sowing in a vegetable patch
  • Transplanting
  • Maintenance
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Biennial and perennial flower care

Towards the end of August is the best time to transplant any biennial plants that were sown in the spring such as daisies, pansies, wallflowers, and sweet Williams. The same goes for any perennial flowers that were sown over the course of the summer such as baskets of gold, geraniums, Japanese primrose and scabious.

Use your secateurs to trim back your lavender to keep it neat and compact. You can keep anything you cut, dry it out and use it to freshen up laundry! Cut back hollyhock once it has finished flowering to lower the risk of it getting hit by the rust it is so prone to developing.

Take cuttings from begonias, hydrangeas, lavender, rosemary, roses and honeysuckle by taking some of this year's growth. Gardeners who have mastered the art of layering might also want to divide winter jasmine, passion flowers and perennial carnations.

If you want early blossoms next year, now is the best time to sow snapdragons and marigolds. Don't forget to collect seeds from your annuals (cosmos, poppies, carnations, and so on) to sow next year.

Planting autumn-flowering bulbs

Now is the time to plant bulbs that will bloom in the autumn (meadow saffron or autumn crocus, for example) and next spring (e.g. cyclamen, scilla or ornamental garlic). Another interesting bulb to plant in August is the Madonna lily which will put out large, beautifully fragranced white flowers come the spring.

If you have clay-heavy soil, place a shovelful of coarse sand at the bottom of your hole to ensure proper drainage. This should help to prevent excess moisture which is a common cause of bulb rot. Divide any variety of irises you may have before the end of the month by separating them at the roots using a hand fork

Towards the end of the summer is the ideal time to divide peonies. Dividing plants not only helps to breathe fresh life into existing plants, it also allows you to fill a new area of the garden.
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Planting autumn vegetables

August is the time to plant vegetables that will be harvested throughout the autumn. Cold-hardy leek varieties (such as Bluegreen winter) can be planted directly in the ground. Be sure to earth them up two or three times as they grow to ensure the stem stays white. You can also plant a variety of veggies from the cabbage family (cabbages, cauliflower, broccoli, brussels sprouts and so on) and celery. Celery and cabbages grow well together so it's a good idea to alternate rows.

Sowing vegetables in August

The following crops can be sown at any point in August:

  • cabbage varieties such as Sweetheart; to transplant in the autumn or spring;
  • rocket;
  • turnips ;
  • swedes (rutabaga);
  • lamb's lettuce; which is traditionally sown in late summer. 

Seeds that need to be sown in the first half of the month include:

  • Chinese cabbages such as napa and pak choi; can be sown before mid-August for an autumn harvest;
  • winter radishes (black and purple varieties); 

Seeds that need to be sown in the last half of the month include:

  • winter lettuces; 'Winter Wonder', 'Winter Brown', etc. and cut-and-come-again lettuces;
  • spinach which is unlikely to go to seed at this time of year;
  • white onions; can be transplanted in October for a spring harvest.

Sowing green manure seeds

Fill any empty spots in the vegetable patch using green manure crops such as phacelia, fenugreek, broad beans or white mustard seeds to prevent nutrient loss and maintain soil fertility. These crops can simply be buried come spring.

If you live in a cold region or have clay-heavy soil, opt for frost-resistant, slow-growing green manure seeds like rye.

Maintaining your garden  

Continue working the surface of your soil to remove any unwanted weeds, aerate the soil and limit water evaporation. Keep the hoe moving and you can cut down on watering!

Place boards or tiles beneath crops such as melons, squashes and any other vegetables that may come into contact with the soil and be exposed to moisture.

Be sure to remove suckers from the base of your tomato plants.
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Floor tiles

Some herbs can still be sown in August including:

  • chervil
  • parsley
  • angelica.

Now is also the perfect time to take cuttings from woody herbs such as thyme, sage, rosemary, bay leaves, and lavender, and to divide plants that need it such as tarragon and rosemary.

Cut back any non-remontant raspberry plants. Prune the ends of your grape vines to allow more light to reach your grapes. Be sure to follow up with a copper sulphate treatment. A Bordeaux mixture can also be sprayed or sprinkled on plants to prevent powdery mildew. However, be sure to spread out treatments as sulphur can make your soil too acidic.

Water any fruit trees planted in the winter or spring , especially in periods with little rainfall. Continue to espalier-train your trees if you're growing against a wall or trellis. Don't hesitate to provide extra support any fruit-heavy branches (on plum trees, for example).

Keep a close eye on any house plants that have been spending the summer outdoors. It's important to keep on top of watering, feeding and treating them. Don't be afraid to water plants generously if the soil has dried out. Repot any plants that have become root bound but avoid doing so when the weather is too warm.

The exception to all the rules is amaryllis which should be left entirely alone at this time of year; this means no more water until the autumn.

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House plants

Continue to mow and water your lawn twice a week. If there is a heat wave, spread grass clippings on the lawn and let it grow a bit longer than usual. Don't forget that lawnmowers also require regular maintenance!

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Sprinkler heads
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Guide written by:

John, Passionate gardener, Cambridge, 83 guides

John, Passionate gardener, Cambridge

When I was young, I was already working in the family garden. Perhaps that is where my interest in plants and gardening came from. So, it was logical for me to study both plant biology and agronomy.   At the request of various publishers I have, over twenty-five years, written many books on the subject of plants and mushrooms (a subject that is close to my heart).They were mostly identification guides at first, but shortly after they were about gardening, thus renewing the first passion of my childhood.   I have also regularly collaborated with several magazines specializing in the field of gardening or more generally in nature. There is no gardener without a garden, I have cultivated mine in a small corner of Cambridge for the last thirty years and this is where I put into practice the methods of cultivation that will I advise you in as well.

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