By Alex Lyneel @theEnglishGardener
With Spring officially starting on 21st March, the next few weeks will be crucial in preparing your garden for what comes next and transitioning smoothly from spring bulbs to perennials and summer annuals. In early summer, some countries like the UK experience a “June gap” which means less forage available for pollinators. To avoid this, the key is to work two seasons ahead by sowing early summer flowers now, whilst also preparing for late summer.
1. Sow hardy annuals under cover now to plant out in Spring
As we approach the Spring equinox, light levels and temperature increase again which improves growing conditions. As a result, the overwintered seedlings sown last Autumn will resume growth, and new seeds sown in early Spring will be able to germinate. However, if sown too early or left on a heating mat too long, the seedlings will grow leggy in their search for light. To avoid this, let’s look at the two variables to keep in mind when sowing, which are warmth and light.
For seeds that do not require any light to germinate such as Sweet Peas, an increase in temperature will trigger germination. However, without sufficient light the seedlings will quickly grow tall and lanky rather than short and stocky. This is where the second seed growing variable comes in: light is essential to grow healthy seedlings in optimal conditions. To avoid growing leggy seedlings, as soon as germination has occurred, slow their growth by transposing them off the heating mat into an unheated greenhouse or a cold frame where they can continue growing at a slower place with better light.
If you are unsure whether to sow your seedlings indoors or outdoors at this time of year: up until April in the northern hemisphere, you will obtain a better germination rate by initially growing them indoors on a sunny windowsill or a heat mat. From April onwards depending on local temperatures, they should be able to germinate either under cover in an unheated greenhouse or when sown directly where they are to grow. The back of your seed packets will also give you further growing advice: some seeds such as those of Cobaea Scandens will require light to germinate and need to be surface-sown, whereas others such as Phlox or Sweet Peas can be pushed in the soil.
Finally, when to plant out your seedlings will depend on when the last frosts are expected in your area: hardy annuals can withstand light frosts (with fleece for prolonged frost or snow periods), however other annuals are best planted out in the garden after the last frosts.
Here are some examples of what you can sow before Spring for early summer display.
What to sow in late Winter/early Spring for early Summer blooms:
- Hardy annuals: Poppies, Ammi majus and visnaga (‘Queen Ann’s Lace’), Antirrhinum (‘Snapdragon’), Centaurea cyanus (‘Cornflower’), Sweet Peas, Calendula (‘English Marigold’), Nigella (‘Love-in-a-mist’)
- Early summer annuals: Phlox, Borage
2. Use half-hardy annuals and Dahlias for your late summer garden
Now that your early summer blooms are taken care of, how should we plan for late summer blooms?
As daylight and temperatures have increased considerably by Spring, the range of flowers available to grow expands to include half-hardy annuals: these are more sensitive to cold, however will bloom until the first autumn frosts. You can sow these either under cover before the last frosts, or directly where they are to grow once the last frosts are over (this is usually around April or early May in the northern hemisphere).
As my garden isn’t large, I like to keep full control over how I edit the planting along the year: hence my preference is to grow half-hardy annuals from seed under cover year long, and to sow them 12 weeks ahead of the required flowering time. Once they are large enough, transfer the seedlings to individual pots and harden them off outside until ready to be planted out.
Dahlias are also an essential part of late summer planting schemes: they are tender annuals and will flower non-stop from July until end of October in temperate climates. Their tubers need to be awoken from their winter slumber in early Spring by potting them up individually and watering them to rehydrate the tubers, before transplanting them into the garden after the last frosts. There are hundreds of varieties to choose from between decorative, pompom, cactus or collarette types which can be used either to make a statement in the garden or as cut flowers.
To recap, here are some examples of what you can sow in Spring for late summer flowering.
What to sow in Spring for mid to late Summer blooms:
- Half-hardy annuals: Strawflowers, Zinnias, Nasturtiums, Tithonia rotundifolia (‘Mexican sunflower’), Cosmos, Sunflowers, Nicotiana alata, Thunbergia alata (climber), Amaranthus
- Tender annuals: Dahlias (sold as tubers)
3. Transitioning from Spring to Summer
The last aspect to look at for year-round gardening lushness is how to transition successfully between seasons. To do so, consider your garden as a canvas: some elements of the canvas will be permanent features (such as evergreen perennials), some others will be seasonal (spring bulbs and annuals). The seasonal parts should be used to add colour and lushness to an already established perennial structure which is what you’ll see in winter. Some perennials such as Alchemilla Mollis (‘Lady’s Mantle’) or Sisyrinchium striatum will have an evergreen presence during winter months then flower from May until the autumn in temperate climates.
When planting spring bulbs in the autumn, consider what the garden will look like at the height of spring, but also once spring is over: by planting spring bulbs in-between or behind perennials, their dead foliage will be hidden by the growing shoots of perennials in early summer. Then when comes summer, use your annuals to match and reinforce the colour scheme of your existing perennial borders (for instance adding pink-flowering annuals to a white and purple perennial border for a ‘cold’ border effect).
Finally, don’t forget your patio pots, windowsills and containers: it helps to see the garden as a series of ‘vignettes’ which evolve over time, of which pots are an essential part. Colourful containers can also be moved around the garden to lure the eye away from areas where foliage is predominant, or placed in key locations within the line of sight to make a statement.
Thank you for reading and here is to a bright and colourful summer in the garden!