Late Spring Flower Garden Tasks: Staking, Deadheading, Feeding, and Greenhouse Shading

Staking and Training

Herbaceous perennials growing fast — many need supports. Just as many don't, but older popular ones usually do: delphinium, erigeron, some euphorbias, lupin, peony, poppy, pyrethrum, Michaelmas daisies (if advanced).

Supports: bushy twigs (pea sticks), bamboo canes, dahlia stakes, extending wire rings + fillis (soft string), plastic-covered wire, sweet pea rings, twist-ties. Apply at ~30 cm (12 in) growth, attach so plants don't look bundled, grow naturally — quickly masked by leaves.

Some lilies need staking — single cane per plant. Chrysanthemums, dahlias, sweet peas already staked at planting/sowing.

Indoor plants with long growth: achimenes, begonias, seed-grown freesias, climbers. Pendula begonias, some achimenes = natural trailers, great for hanging baskets. Most pot plants: split bamboo canes. Double-flowered begonias: special extending wire stakes ending in cup/half-ring for flowers — adjustable length, multi-variety use.

Sweet peas: attention every 3–4 days — remove tendrils, attach stems, remove side shoots. Tendrils replace leaflets; side shoots grow at main stem/leaf stem join.

Cutting Back and Deadheading

Remove spent flowers from spring bulbs and herbaceous perennials. Rock plants (aubrieta) → shear trim. Far from brutal — clears 'dead wood' so well some flower again, especially with post-cut feeding.

Feeding

Finished-flowering hippeastrums ripening bulbs → liquid fertilizer higher in potassium than nitrogen/phosphorus encourages next year's flowers. Potassium = maturity nutrient, partly compensates for lack of sun. Other container spring bulbs (daffodils, hyacinths) → same until die down. Frequency/quantity per manufacturer.

Mulching

1–2.5 cm (⅓–1 in) rotted organic matter around annuals, herbaceous perennials (especially peonies, hellebores) prevents soil water loss in heat. Don't mulch dry soil — it keeps soil dry. Wait for rain or soak with hose first.

Shading the Greenhouse

Late spring: greenhouse needs shading, especially ¾-span or lean-to on south wall. Ideal for heat but gets extremely hot/glaring — only cacti like it.

Shading essential: hessian, chain laths, plastic sheet, Venetian blinds — temporary, can be automatic or manual. Or glass wash: quicklime/hydrated lime + water to milk consistency + little size to stick. Proprietary washes: one turns transparent when rained on, opaque in sun (unfortunately also in dull dry weather).

Weeding

Vital among small plants for good bedding/annual display mid-summer to autumn. Watch biennials in nursery bed. Systematically eradicate perennial weeds in herbaceous borders while tiny — else never rid of ground-elder, bindweed, oxalis. Hoe and handfork = allies for cultivated ground. Paths, drives, patios, steps → chemical weedkillers.

Compost Heap Making

Material: lawn mowings (heat fast), weeds, cut-back spring plants. Pool excess growth to clear. Leaves fall year-round. Build: alternate vegetative layers with activator/sulphate of ammonia or, better, thin animal manure layer.

Watering

Unless unseasonably hot, watering = greenhouse plants, daily. Water at air temp best — tank in greenhouse. Galvanized iron, covered (excludes light) → clean, no algae/dirt/insects/disease/small mammals. Outdoor water-butt for drainpipe overflow → covered, but hard to keep clean. Pipe strainer helps but floods if not cleared. Polythene/plastic butts → algae. Same for watering cans — galvanized/painted best.

Ventilating

Roof ventilators → open permanently. Side ventilators → open day, doors open on really hot days. Lower temp by damping down: sprinkle floor, staging, walls, plants 2–3× daily.

Frames must ventilate — critical for young plants wanted for late spring/early summer planting. Warm sunny days → lights fully back. Rising night temps → prop open nights, gradually more until off altogether (unless <10°C/50°F at night).

Pest and Disease Treatment

Greenfly, caterpillars = main problems. Capsid = unseen nuisance from now on. Green insect, sucks sap from young leaves, shoot tips, flower buds → flowers misshapen, lopsided, stunted. Dahlias, chrysanthemums especially vulnerable.

Capsids ~10× greenfly size, quick, drop to ground when disturbed → often missed. Damaged leaves: pin-prick holes → rapidly tattered, new shoot growth stops. Precautionary spraying advisable: start late spring, repeat per manufacturer.

Narcissus bulb fly: adults lay eggs near bulb neck, maggots bore in, feed center ~2 months from early summer. Even if bulbs survive, next year = few short leaves. Dust soil around bulbs with insecticide mid-late spring, repeat 2× at ~2-week intervals.

Slugs/snails → trap/treat. Greenhouse grey mould → hand removal works.