Sowing continues with annuals including wild flowers, and peak planting season approaches, including late summer flowers. Monitor greenhouse problems and prepare strawberries for cropping.
1. Wild flowers and annuals
Garden annuals are more colorful and flower longer than native annuals such as cornflower, common poppy, corn marigold and corncockle. Meadows of garden annuals – California poppy, cosmos, larkspur, love-in-the-mist and phacelia, for example – are sometimes confused with native annuals. But the latter, though not as bright, are somewhat more beneficial to wildlife. There
is room for both in gardens, but native annuals not only provide nectar and pollen but can support native insect larvae so, if possible, have some natives.
2. Planting time
It is peak planting time until mid-June, as newly bought and home-raised plants can be planted out. Water potted plants, ideally with diluted liquid fertilizer, before planting into moist soil. If time and water are short, take out a planting hole, fill with water and allow the water to sink in before planting. Firm the soil for good root and soil contact. Allow about a finger width of soil over the root ball of transplants. Avoid smothering the stem with mounded earth.
3. Sowing more flowers
Fill gaps with spreading annuals that will prevent weeds from taking root. Try sowing alyssum and candytuft, smaller clarkia and godetia. Daisy family flowers – cosmos, gazania, sunflowers and zinnia – can be sown now, either where they are to flower, or in cell trays to plant out later. Warm soils promote quick germination. Dry soils should be watered the day before sowing. Most of these plants can be bought by mail order as plugs – it costs more, but gains several weeks.
4. Greenhouse monitoring
Yellow sticky traps give early warning of the arrival of pests such as whitefly and aphids, so that biological controls can be ordered before the intruders get numerous.
Aubergine plants are especially vulnerable and pests occur first on these, giving early warning. A minimum-maximum thermometer is almost indispensable in managing high temperatures, over 30°C, which reduce growth, stress plants and encourage pests and diseases. Generous ventilation and shading is needed on burning days, but much less so on cool days.
5. Strawberry care
Mulch strawberries with straw (inset below) once the risk of frost
has passed. Bare soil retains warmth and releases it at night, protecting the vulnerable flowers. Straw keeps soil from splashing on to the fruits and spoiling them. Alternatively, use strawberry mats sold for the purpose. Slugs and snails thrive beneath straw – but a drench of anti-slug nematodes can prevent damage. Bird netting, kept taut with no loose flaps to avoid entangling birds, is usually necessary as fruits ripen.
Guy Barter is the chief horticultural adviser for the Royal Horticultural Society. The Royal Horticultural Society is a charity working to share the best in gardening and make the UK a greener place. Find out more at rhs.org.uk