When should we plant summer bulbs?

Summer-flowering bulbs, which are they?

Under the heading bulb or bulbous, we find plants that have a nutrient storage organ which remains underground, in the form of a bulb, but also of a corm, a tuber or a rhizome. Summer bulbs will flower from June to September. Some even bloom a little later, such as dahlias, because their flowering starts later, often in August, and some toward the end of summer like Abyssinian gladioli (Acidanthera or Gladiolus callianthus). The most popular summer-blooming bulbous plants in our gardens are the Gladioli, the Cannas, the Dahlias, the Lilies, and the Freesias. We also find some rarer plants such as the tuberous tuberous (Polianthes tuberosa) and Lycoris (or spider lily). We generally place in this category some rhizomatous perennials or tuberous-rooted perennials for convenience, such as Agapanthus, Alstroemerias or Daylilies.

Here, by bulb type, are the most ornamental species for summer:

• Bulbs : Gladioli, Galtonias, Ismene, Eucomis, Bletilla
• Corms : Gladioli, Freesias, Ixia, Sparaxis, Crocosmia, Tigridias, Abyssinian Gladiolus (Gladiolus callianthus), Babiana and Watsonia
• Tubers : Dahlias, Tulbaghia, Liatris (herbaceous perennial with a tuberous-rootstock), Begonias (tuberous), Alstroemerias, some Arisaema, etc.
• Rhizomes : Agapanthus, Gingers (Hedychium, Curcuma…), Cannas, etc.

Gladioli, Cannas, Sparaxis, Lilies and Dahlias: a burst of colour, a wave of exoticism in the garden!

When to plant them?

All summer-blooming bulbs should be planted in spring, between March and May. It’s really the same principle as for spring bulbs, which, in contrast, are planted in autumn in advance (they must endure the winter cold to grow). So don’t be misled by the term “summer bulb”: these plants must be planted several months before flowering. They will take a few weeks to come into bloom during the summer months, often over a long period, unlike spring bulbs which flower in a more ephemeral fashion.

Planting dates are always shown on the packs you buy and receive. Differences between summer bulbs are mainly due to their hardiness. Because these plants, many of which originate from exotic, tropical or southern regions, can be frost-tender, which means that we don’t plant at the same time a Hedychium or a Canna as we would a truly hardy Lily such as the Lilium regale or the Lilium candicum. The hardiest bulbs, such as some lilies and lily hybrids, should even be planted in autumn (between October and November) because they require a period of cold, but you can catch up if you plant them in February–March.

The frost-tender bulbs (Canna, Dahlia, Abyssinian Gladiolus, coloured Arums, Tulbaghia, etc.) are planted, however, in late April or early May to protect them as much as possible from the last frosts, for a flowering from July to September, or even October. Obviously this depends on your region; these bulbs can be planted a little earlier in the south than in the north of the country.

Finally, late-season flowering bulbs, blooming in September, such as Nerines or Crinums and the Amaryllis Belladonna, can, for their part, be planted a little later, up to late May or June.

If you plan a cut-flower garden for your summer arrangements, try, where possible, to space out the planting to obtain flowers for a longer period!

And what if I plant my summer bulbs too late?
This is a common question for the forgetful or busy gardeners, wanting to know if it’s too late to plant this or that bulb. As with spring bulbs, you can plant them late; however, this will affect the duration of flowering, which will be delayed and consequently shorter in the first year.

Summer bulbs can, conversely, be forced and thus bloom earlier in the season. To speed up their flowering, you would start as early as February when you have a greenhouse or a frost-free, well-lit room. Read Virginie’s article on this topic: Preparing summer bulbs and Alexandra’s tutorial How to force Dahlias to flower earlier?

Hedychium gardenarium

Tips for planting summer bulbs

Upon receipt of an order or your purchase at a garden centre or plant fair, don’t delay! Plant your bulbs in loose, well-drained soil (if necessary, mix in a little sand at the bottom of the planting hole). The depth of the hole is generally considered to be roughly three times the size of the bulb, but this does not apply to Cannas, Dahlias, or Begonias, for example, which have a rootstock or a tuberous root.

Mark the location of your bulbs so you can spot them if you plan sowings or some perennial plantings in spring to fill the gaps, while awaiting flowering and the emergence of the foliage.

Agapanthus

A selection of summer bulbs for different uses.

That will depend, of course, on your tastes in the matter, but as often, on the hardiness displayed by certain bulbs. Here we provide some of the most charming summer-flowering bulbs, from the most common to the rarest, for a summer garden bursting with colour:

– Summer bulbs suitable for pots : Agapanthus, Liatris, tuberous begonias, Tulbaghias, Sparaxis, Freesia, Ixias, Ismène, Watsonias, Curcumas…

→ Read also: Growing summer bulbs in pots and The best bulbs to plant in pots

– Summer bulbs for a sunny border : Cannas, Crocosmias, Dahlias, Lilies, Agapanthus, Liatris, Agapanthus, Gladioli, Tulbaghias, Galtonias, Abyssinian gladiolus, Freesia, Ismene, Watsonias…

– Bulbs for partial shade : Begonias, Arums, Lilies and Eucomis, Crocosmias, Tigridias, Ixias, Ismène, Hedychium. Arisaema and Bletilla will thrive better in shade.

– For your cut flower arrangements : Summer is a wonderful time to love creating your own bouquets thanks to the abundance of blooms that fill the garden. The pleasure of making your own floral arrangements is second to none, and if you enjoy growing flowers for cutting, you can rely on these blooms that perform well in a vase: Lilies, Gladioli, Dahlias, Freesia, Arums, Sparaxis…

→ Read also: 6 summer bulbs for creating cut flower arrangements, Plant bulbs to make your own home bouquets and Dahlias: the best for making bouquets