Now that the ground is starting to warm up, we can think about planting out some summer colour in the form of seeds and bulbs. Whether you’ve been working in the greenhouse already - bringing plugs on and growing from seed, or you’re thinking of planting bulbs for some perennial colour, we’re heading into the prime time for outdoor planting.
During April and May the soil temperature increases dramatically with longer days, warmer overnight periods and reduced risk of frost. You can even fleece or cloche ground to trap warmth in, driving the heat back down into the soil ready for root systems to develop. The regular rain showers also mean that your new plants, seeds and bulbs get the right mix of daylight, warmth and water – the perfect growing conditions. So, what should you be planting now?
Summer flowering bulbs to plant in Spring
It’s not too late to plant summer flowering bulbs, in fact those that do best in summer should only really be going into the ground now as that warmth continues to build. Many of the best summer bulbs do well when they’re lifted at the end of the previous season, carefully stored over winter and then gradually awoken from their dormancy in the green house or cold frame during the spring. Examples of these bulbs and root tubers are bearded iris and dahlias which if looked after, will flower for many years and continue late into the season giving strong, bright, tall blooms.
If you’re planting root tubers, be aware that the tuber itself is unlike a bulb in that it too likes some warmth and light to hit it. Normally, you’d plant a bulb deeper into the soil, but tubers prefer to be on or just below the soil – like an engine room needing fuel. Bearded iris in particular like to sit with around half the tuber above the soil, whilst dahlias will sit just below – both sending roots out and down into the soil to create an anchor.
More traditional bulbs may include summer lilies, gladiolus and Ranunculus which will put on foliage and then provide a burst of strong bright colour through July, August and September. If you’ve already started bulbs off in plugs or pots during the spring, or over wintered them in the greenhouse, shed or cold frame, be careful to introduce them slowly, so they harden off and become acclimatised. Whilst there is less chance of hard frosts in April and May there’s truth in the saying ‘Ne’er cast clout ‘til May is out’ and the nights can still get down to very low temperatures.
Summer flowering seeds to plant in Spring
In addition to bulbs, there is a host of summer flowing plants that you can sow direct outside now for a burst of colour this year. Many will be annuals, but you can always capture seed heads when they set, creating your own supply for next year too.
Cosmos, Nigella and Sweet Williams can be scattered directly where you want them to grow. Simply give the soil a dig over, sprinkle liberally and then gently water in or pull a fork or rake lightly over the soil to bed them in. You should see growth within a few weeks if planted into sunny south or west facing plots. These will grow vigorously and provide lots of multi-headed blooms throughout the summer. Remember to dead head spent blooms if you want to keep the plant flowering and the garden looking nice – but leave a few to set seed if you want that important supply for next summer.
Agapanthus grown from seed can take a few years to develop into strong flowing plants. For best results, sow the seeds into pots and keep the young plants relatively pot bound as they develop. Agapanthus ‘like it tough’ and so if you transfer to a bed, make sure it’s got a few things to compete with. They’ll flower in June and July and if you leave the heads on, not only will you get some seed to propagate for the future but their bulbous, waterfallesque heads will provide a beautiful feature in late summer, adding height and structure. You can also cut and dry stems and heads, like large alliums, to create decorative flower arrangements indoors during the autumn and winter.
If you’re looking for long flowering and late summer colour you cannot go wrong with Rudbeckia. If you can, choose mixed varieties so you get everything from the synonymous mini sunflowers to the deep rich colour of Rudbeckia Cherry Brandy. Perfect in pots or beds, dead heading through the season will keep these flowering late into the year. Some varieties may provide a second year of flowers but in most cases rudbeckia will not over winter.
Where to place summer flowing plants
One obvious point that's worth remembering is that summer flowering plants like it hot and dry. Most summer blooms will prefer south or south-west facing beds. Obviously if they’re in pots you can move them to maximise their time in the sun. For annuals pots are great as they allow you to build and arrange individual pockets of colour and then reuse the pot again in the autumn or winter. Perennials like agapanthus, once established, can happily go in beds, but as noted, these particular blooms like quite constrained root systems, so put them into busy beds whether there is a bit of competition.
Root tubers need lifting and storing over winter, so again, pots are ideal growing mediums for these, not least of all because you can remember where you planted them! It also makes moving and storage easier. If you have sweeps of root tuber plants (think dahlias and iris) in beds, it is possible to cloche, mulch or protect the bed over winter to save you having to lift and store them, but if the plants are intermingled with others, this might be less than straight forward.
The majority of summer flowering plants prefer free draining, loose soils that allow air, warmth and water to flow through the root system. This is another reason why pots can be a good idea because they allow better management of the water levels and soil structure, creating unique environments suited to each plant.
The one thing to be said for summer flowering plants is they provide a real burst of colour, structure and scent to a garden, so enjoy playing around with different combinations or colour themes each year and work out what grows best in your garden. But don’t forget to sit down and enjoy your hard work too!
We hope this blog has helped you to decide on what summer flowering bulbs to plant in spring! Earth Cycle has everything you need to give your summer flowers all the nutrients they need to grow including topsoils, soil conditioners and compost. We also have some handy tools and accessories available, so you have everything you need in one place!
Be sure to check out our handy Garden Planner for 2023 blog that includes lots of handy tips on how to plan for the year ahead.