How to Grow Annuals and Biennials Successfully

Annuals and Biennials

Hardy Annuals

The term ‘hardy annual’ is used to describe any annual flower which can be raised from seed sown in the open ground in spring and needs no protection whatsoever during its cycle of growth. Quite a few (the hardiest of the hardy annuals) can be sown in the open ground in August or September to come into flower in late spring or early summer, but one takes a gamble with the weather when sowing at this time and one must be prepared for losses if the winter is severe. Calendulas, larkspurs, nigella, godetias and sweet peas are some of the annuals often grown in this way.


The time to sow in spring depends very much on the locality and the weather prevailing (late and early seasons occur as frequently as ‘normal’ seasons in Britain). In some areas it is possible to sow in the latter part of March while in colder areas it may be advisable to wait until late April or early May. A fine day must be chosen for carrying out this task. Gardeners have their own ideas about how best to sow annuals. With small seeds I like to sow with my finger and thumb, holding the seeds in the palm of my left hand and just lightly sprinkling them over the ground with my right. I find that this allows me to sow thinly and reasonably accurately.

Afterwards, I rake the seeds into the surface soil. Sowing broadcast, though, has its disadvantages, for weeding can be very difficult. A better way if the ground is known to be weedy is to sow in prepared drills which can be cleaned and thinned much more easily. If this method is used the depth of the drills will have to be adjusted to the size of the seed being sown, the smallest only having just a light covering of soil and the largest as much as 1-1/2 to 2 inches.

Make the first thinning as soon as the seedlings can be conveniently handled. It should then, after a further two to three weeks, be possible to make the final thinning.

Half-Hardy Annuals

These are annuals which cannot be planted out in the garden until all danger of frost has passed. If one has a heated greenhouse or frame in which a day temperature of about 13°C (55°F) can be maintained, raising these plants is quite straightforward. If such facilities are not available an alternative is to make spring sowings in the open ground and cover these with cloches until the danger of frost has passed. Also, many half-hardy annuals may be  sown in the open in early May but they will be much later coming into flower.

There is no point in starting seed sowing under glass too early in the year or the plants may be ready too soon for planting out, which cannot be safely done until late May or early June when they have been hardened off. This being so, I consider late February to be about right for sowing seeds of antirrhinums, lobelias, salvias, ageratums, Begonia semperflorens, nicotianas, petunias and verbenas, and late March for stocks, asters, French and African marigolds, nemesias, alyssum and cosmeas which germinate and grow more rapidly.

When the time comes for setting out the plants in the border (after hardening off), remove them from the boxes with care so that the delicate roots are not damaged. Plant them firmly with the aid of a trowel and water them in afterwards.

biennials Biennials

A great deal of what I have had to say about increasing annuals also applies to biennials. Any experienced gardener will stress the importance of early sowing for biennials. This is done outdoors in a prepared seed bed during late spring or early summer, with the seedlings being transplanted into a nursery bed in July and into their flowering quarters by the autumn – or the following spring if they are not ready for the move soon enough for establishment before the onset of winter.

Perennial Plants

So far as I am concerned, it would be unthinkable to have a garden which did not include some perennial plants, including both herbaceous perennials and half-hardy perennials like the invaluable pelargoniums (geraniums), marguerites, dahlias and chrysanthemums.

These, with the exception of the geranium, are grown in a conventional herbaceous border.  After all, they have so much to offer between April and November and their wide diversity of form and colour make them perfect flowers for the gardener with a taste for experimenting. When you have planted trees and shrubs you have planted them in the sense that, if it becomes obvious later that they are in the wrong place, moving them to a new position is an operation fraught with some hazard.

Herbaceous plants, on the other hand, mostly need to be lifted and divided once every three or four years, and a general re-shuffle to ensure new plant associations present no problems, to provide new interest and the result can give the garden a distinctive new look.

14. September 2010 by Dave Pinkney
Categories: Annuals, Biennials | Tags: , , | Comments Off on How to Grow Annuals and Biennials Successfully


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