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Hardy Annuals: Part 2

Hardy Annuals: Part 2

In this second part, Graham Rice discusses cultural matters and recommends familiar and unusual varieties.

In the first part of this examination of hardy annuals, I looked at the practicalities of preparing the soil, sowing, thinning and support. In this final part I will be concentrating on the remaining practical matters, looking at summer and autumn sowing and selecting some plants to grow. I'll pick out both the best of the old favourites and some of the more unusual hardy annuals which may be unrecognised but which are well worth growing.


By sowing the seed in rows it becomes easy to distinguish the weed seedlings from the cherished seedlings of your annuals. If the rows are far enough apart a hoe will deal with the young weeds otherwise hand weeding will be required until the seedlings are big enough to smother.

Weeds growing in the rows with the seedlings can be removed in the same way as unwanted seedlings are removed when thinning out, carefully protecting the seedlings you want to retain and re-firming any that are disturbed.

Pests and diseases

Fortunately the number of pests and diseases that attack hardy annuals is fairly limited but there are a few which can cause problems, and one or two can be very troublesome.

  • Aphids - Aphids come in a huge range of colours and can build up quickly in warm conditions. Spraying with a suitable insecticide, will kill them within half an hour but will not harm any beneficial insects.
  • Birds - Small birds can cause a problem by dust-bathing in the fine soil shortly after the seed is sown. The netting suggested in the first part of this article will certainly do the trick otherwise use black cotton. But beware of cotton thread with a nylon core which is very strong and could injure birds if they become entangled.
  • Botrytis - This can affect the tightly packed petals of some double flowers in which case the damaged flowers should be removed at once and the plants sprayed with a Suitable fungicide.
  • Capsids - Small, uneven, yellow-edged holes appear in the shoot tips of a wide variety of plants. The tips can be pinched out or you can spray with a suitable insecticide.
  • Caterpillars - Occasionally troublesome, picking them off often gives adequate control. Otherwise plants can be sprayed with an insecticide.
  • Cats - Unfortunately being a cat lover won't stop them digging holes in your seed beds. The netting or string described for birds should keep them off.
  • Leaf miner - Small whitish tunnels appear in the leaf surfaces of members of the daisy family. Pick them off when first they're seen or spray with an insecticide.
  • Mildew - Powdery mildew is the one problem that is almost certain to cause problems if you grow Larkspur, Cornflower, Calendula and Verbena especially in a hot, dry season. It can be devastating but some varieties are more resistant than others. In bad years they all suffer.
  • Rust - A problem with Antirrhinums and sometimes with Lavatera. Spraying with a suitable fungicide helps, otherwise it’s the bonfire that’s the only answer.
  • Slugs - Can devastate young seedlings so its wise to take precautions. Clearing nearby weeds and rough vegetation will remove their daytime hiding places. Traps using stale beer or milk work well, there are liquid preparations to water on the soil and there are pellets. Choose the blue pellets, but make sure they contain an additive to stop pets and wildlife eating them, and use them sparingly.

Dead heading

If there's one thing that keeps hardy annuals flowering well it's regular dead heading. If the dead flowers are removed as they fade more and more flowers will appear.

Some quick flowering plants like Phacelia and the modern mimulus hybrids can be rejuvenated when they fade by cutting back the plants to within 3 inches (7.5cm) of ground level. But it's essential that this be accompanied by regular watering until they start to grow away again. It also pays to put some liquid feed in the first soaking they get after cutting them back. If they dry out after getting cut back you will be guaranteed bare soil where otherwise you'd have another flush of flowers.

Watering and feeding

If plants are sown reasonably early in the spring so that they can establish a deep root before the driest weather they will probably only need watering in very dry spells. However, even when the soil is only moderately dry watering can help to extend the flowering period.

Two things are important about watering. The first is that the plants must be adequately supported otherwise the irrigation spray will simply beat the plants down and your border will be ruined. The other important thing is that you follow the usual rule and give them a really good soak. Simply dribbling on a little bit will do more harm than good.

Watering may also be needed if you transplant any seedlings when you thin them out. But once they are growing away they can often be left to take their chance except in very hot areas.

Feeding is not an important feature of the care of hardy annuals as long as the soil is at least reasonably well prepared in the first place. Apart from raking in a general fertiliser before sowing they should be happy without further feeding.

Plants growing in containers may need liquid feeding as the soil becomes full of roots especially if there is a great many plants packed in.

Summer and autumn sowing

Some hardy annuals grow reasonably quickly and can be sown rather later than the spring season which is normally recommended. They will then give you a display which is just approaching its best at a time when spring sown plants may be past their peak.

In the UK this means sowing in the second half of July and the timing can be crucial. So it pays to experiment a little with the timing if you're not sure. Plants which have been found suitable for this approach include Californian poppy (Eschscholtzia californica), dwarf cornflowers (Centaurea cyaneus), clarkia (Clarkia elegans), dwarf larkspur (Delphinium ajacis), dimorphotheca (Dimorphotheca aurantiaca), godetia (Godetia grandiflora), candytuft (Iberis amara), linaria (Linaria maroccana) and baby blue eyes (Nemophila menziesii). Again some experimentation would probably reveal plenty of other suitable plants and of course quick growing annuals which are usually started off indoors in warmth earlier in the year, like African and French marigolds, will respond well to this treatment.

There are some annuals, especially those which originate as cornfield weeds, which germinate in the autumn and overwinter as young plants before flowering early the following summer. These are known as winter annuals. Cornflower is a prime example. This tendency can be enhanced in the garden by sowing in late summer and early autumn.

The plants which overwinter tend to flower before their spring sown counterparts and also to produce larger plants which obviously produce more flowers. Any of the tougher annuals can be tried in this way but I would especially suggest pheasant's eye (Adonis aestivalis), corn cockle (Agrostemma githago), cornflower (Centaurea cyaneus), godetia, sweet pea (Lathyrus odoratus), fried egg plant (Limnanthes douglasii), love-in-a-mist (Nigella damascena) and baby blue eyes (Nemophila menziesii).

Some annuals will suffer in especially cold or damp winters and two precautions can be taken to minimise losses. Firstly, choose a sunny and warm spot in which to sow annuals for over-wintering and secondly, improve the soil drainage by forking in grit, especially on clay soils.

One thing worth remembering about sowing in summer and early autumn is that the soil may be very dry at sowing time. Rather than soak the whole area to be sown, the best plan is to draw the drills a little deeper than you normally would and then to dribble some water into the drills from the spout of the watering can. The seeds will then have some damp soil in which to germinate and the dampness will penetrate some way beneath the drill so providing a water reserve.

Tried and tested varieties

  • Calendula officinalis (English Marigold) - From tall cut flowers, Indian Prince, to dwarf edgers, Fiesta Gitana, mainly in hot shades of orange and yellow.
  • Centaurea cyaneus (Cornflower) - Tall and waving or short and squat, the colours vary from deep purple through rich and pale blues to lilac, pink and white. Polka Dot is a good medium sized variety in mixed colours.
  • Chrysanthemum carinatum - Very showy plants for the back of the border in a huge range of colours and bicolours. Court Jesters is probably the best.
  • Clarkia elegans - In single colours or mixtures of double flowers this is easy to raise in all soils.
  • Delphinium ajacis - Again, a variety of sizes, the double hyacinth flowered types, tall or short, are the most popular.
  • Godetia grandiflora - Large open, upward facing cups in various reds and pinks plus white.
  • Iberis (Candytuft)