Sowing Summer Annuals

Author: JM   Date Posted:29 September 2018 

Sowing Summer Annuals main image Sowing Summer Annuals image

Whether you are growing summer annuals to cut for the house, a special occasion or just to enjoy their vibrant colours in you garden here are a few tips and tricks to help make your endeavour that much more successful.

Sow later rather than earlier

Many of the annuals we grow over summer hail from tropical and sub-tropical regions and should be treated in the same manner as tomatoes. Just like the tomato, most summer annuals dislike a large diurnal range so  it is advisable to wait until night temperatures increase significantly before sowing seed.

In our experience  there is little to be gained from starting seeds too early - even under cover.  The temperature of the soil needs to be just right before plants will bound away and leaving plants to become rootbound in seed-trays is not a good idea. Seed sown a little later when soil temperatures are to their liking will grow away without check and soon catch up with any seedlings that were sown and planted  prematurely.

( A good indicator of when to sow is when pumpkin or tomato seedlings start  popping up on the compost heap. )


Sow in trays or directly into the garden.

New varieties of annuals can be expensive  so sowing them in trays allows just the right number to be raised for the area involved -  the remaining seed can be stored until next season. It is often suggested that Zinnias resent disturbance and whilst they are resentful of being left in their cells awaiting planting out, if sown late and planted out  as soon as they are large enough they get away without any check to their growth.

 In our experience the reliability  of sowing seeds in cells outweighs the extra effort. To have to start all over again just  because the birds got into the seed bed or a hot spell came through just at the wrong time is no easier than sowing in trays.

The secret of sowing seeds in trays in to match the fineness of the seed-raising mix with the fineness of the rose on the hose or watering can and if  you have  reserved a  small area  for raising seed which has permanent irrigation make sure the spray jets are of the mist type -  the less disturbance of your seed-raising mix  the better and if you are heavy handed with the hose try using grit or well-washed course sand to cover your seeds.


Soil preparation

While waiting for seedlings to reach transplant size  ready the beds with plenty of additional humus.

A good dose of lime will raise the Ph of the garden bed and make a wider range of nutrients available for the young plants. Digging will depend on the level of soil preparation in previous seasons , if it is a new bed then deep digging  with thorough humus incorporation is advisable. In subsequent years the preparation becomes easier with only a light forking being required in combination with a topdressing of compost.



If your bed has been  well prepared with plenty of well rotted compost and some blood and bone then your seedlings will not need much  more for the season other than maybe a liquid feed with Seaweed or Fish Emulsion once a fortnight.  The thing they most appreciate is an even soil moisture. Just at the time when you tip out the first buds changing the liquid feed to one which is  high in potassium ( think Tomato food) will increase flower quantity and quality.



If you make a bed which your annuals are going to appreciate it goes without saying that the weeds will be appreciative as well , so keep the swoe going ( a n old knife will suffice)  until  the young plants are closing in together by which time the worst of the interlopers will have been dealt with.


Tipping Out

Nipping out the leading shoot of young plants when they are  about thirty centimetres tall makes for longer  secondary stems and more flowers when the  plants start to flower and is well worth the little extra trouble. This process also makes for a sturdier plant that is less likely to 'rock' in the wind or during summer squalls.



Depending on the type of annuals and the variety  being grown as well as  the prevailing conditions staking  can be necessary. If a little thought is given to this  over the winter twiggy branches  from pruned deciduous shrubs and trees can be saved for the purpose . When plunged into the ground they create a cage-like network  through which annuals can grow and can be pruned down to below the foliage and flowers for discreet support. Both annuals and twigs become one unit which is much more stable than any number of  bamboo canes.


Pests and Diseases

In general summer annuals  are remarkably pest free but depending on the season the lush new foliage can be marred by whitefly and aphids - a bit of pest oil will take care of both. In the case of humid climates, mildew maybe a problem on things like zinnias if detected early a small outbreak can be treated with quick spray of diluted milk - make sure the entire plant is covered.

Summer annuals are susceptible to snail and slug attack so be prepared with either coffee grounds, copper rings, lime or snail-bait.



Many annuals , particularly those from the daisy  benefit form dead-heading, so don't be timid about picking flowers for the house hand make old flowers are removed to prevent the plants energies from being directed towards seed development.


Storing unused seed

If you have any seed left over reseal the packet and  pop into an air-tight container in the fridge until next season. 

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