Advice and care
Describe what you see on the plant, or choose a common symptom.
Powdery mildew
A whitish to greyish powdery coating on the leaves (and sometimes the stems). Affected leaves turn yellow and brown and dry up; later, tiny black fruiting bodies appear in the coating. It spreads by spores (conidia).
Cause
Golovinomyces orontii (syn. Erysiphe cichoracearum) and other powdery mildews. It is favoured by warm, dry days without sun, high humidity at night and fluctuating temperatures.
What to do
- preventive: use resistant varieties, thin out the planting and ensure air circulation, water at ground level (not on the leaves)
- direct: treat with a fungicide
Grey mould (botrytis)
Browning, rotting patches on leaves, stems and especially flowers; in damp conditions they carry a grey mould coating. A polyphagous disease that gets worse in damp, close conditions.
Cause
Botrytis cinerea (teleomorph Botryotinia fuckeliana).
What to do
- preventive: reduce humidity, thin out the planting, do not overwater, remove faded and affected parts promptly
- direct: fungicide under heavy disease pressure
Root and crown rot
Brown patches on the root crown, with the rot spreading into the roots; the plant wilts and dies. Young plants collapse (damping off).
Cause
Soil fungi, Thielaviopsis basicola, Pythium sp., Fusarium sp., Phytophthora sp. They are encouraged by waterlogging and contaminated substrate.
What to do
- preventive: do not overwater, ensure drainage, use uncontaminated substrate and healthy planting stock, treat seed, remove sources of infection
Viral diseases
Varied symptoms: mosaics, yellowing, vein clearing, necrotic spots, distorted or reduced flowers and stunted plants. Can be confused with a nutrient disorder.
Cause
Plant viruses; they are transmitted mainly by sap-sucking pests (aphids, leafhoppers, thrips) and by tools.
What to do
- preventive: healthy seed and planting stock, disinfection of tools, prompt removal and destruction of affected plants
- direct: focus on controlling the carriers (vectors)
Bacterial diseases
Water-soaked or oily spots on the leaves, often with a yellow margin; the bacteria break down the tissues and cause rots. Spread by water (rain, irrigation), insects and people (infected seed, tools).
Cause
Bacteria that attack plant tissues.
What to do
- preventive: hygiene and phytosanitary measures, healthy propagation material, careful watering
- no bactericides are available in Czechia; copper-based products have only a limited effect
Spider mite
Tiny mites feed on the leaves, causing pale spots (stippling); if neglected, fine webbing appears at the shoot tips. Worse in warm, dry conditions.
Cause
Two-spotted spider mite (Tetranychus urticae).
What to do
- direct: biological control with the predatory mite Phytoseiulus persimilis; in greenhouses, an acaricide at least 3× at intervals of 3–5 days
- preventive: raise humidity, do not let plants dry out
Thrips
Small sap-sucking insects. Pale whitish-yellow spots on flowers and leaves, black droplets of excrement left behind, distorted flowers.
Cause
Thrips (Thysanoptera).
What to do
- direct: insecticides; in greenhouses, biological control and sticky traps (blue)
- preventive: remove weeds and affected plant debris
Slugs and snails
Holes in leaves and stems that may merge, often starting from the edges; a silvery slime trail is typical. Active in damp conditions and at night. (Many other pests also make holes in leaves, see below.)
Cause
Garden slug (Arion hortensis), marsh slug (Deroceras laeve), grey field slug (Deroceras reticulatum) and others.
What to do
- preventive: keep the surroundings free of hiding places, collect them in the morning, release natural enemies
- direct: molluscicide products (pellets) when numbers are high
Chlorosis: iron deficiency
First, on young leaves, the tissue between the veins turns pale (the veins stay green); the leaves then gradually turn brown from the edges.
Cause
A lack of iron in the substrate, or the iron in the soil is unavailable (often in chalky/alkaline soil).
What to do
- a fertiliser containing iron (chelate)
- for sensitive species, adjust the soil pH towards slightly acidic
Leaf spot diseases (fungal)
Well-defined spots on the leaves, brown to black, often with a pale margin or a dark centre (in some, black dots of fruiting bodies are visible). The spots enlarge and merge, and the leaf dries up and falls early.
Cause
Fungi of the genera Septoria, Phyllosticta, Ascochyta, Colletotrichum, Coniothyrium and others. They spread in damp conditions.
What to do
- preventive: remove fallen leaves and affected parts, open up the planting, do not water onto the leaves
- direct: spray with a suitable fungicide
Rose black spot
From May, brownish to brown-black spots of various sizes on the leaves; the leaves then turn yellow and fall, and the plant gradually weakens.
Cause
A fungal disease (Diplocarpon rosae). Encouraged by damp conditions.
What to do
- preventive: more resistant varieties, remove and destroy affected leaves, improve air circulation
- direct: fungicides (e.g. Discus, Dithane DG Neotec, Sylit)
Rust (on ornamental plants)
Orange to brown spore pustules, most often on the underside of the leaves; there may be yellow spots on the upper side. A heavy attack distorts and dries out the leaves.
Cause
Rusts of the genera Puccinia, Phragmidium, Cumminsiella and others. The hosts are roses and many perennials. They spread by water and wind.
What to do
- preventive: remove and burn affected leaves, reduce humidity
- direct: fungicides
Tospoviruses (INSV, TSWV)
Necrotic rings and line patterns on the leaves, blackening, stunting and distortion of plants. Widespread on ornamental plants in greenhouses.
Cause
Tospoviruses: impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TSWV). They are transmitted by thrips.
What to do
- preventive: control thrips (the vectors), remove and destroy affected plants, check new plants
- viral diseases cannot be cured: prevention and removal of sources are the basis
Bacterial soft rot and leaf spot
Dark, water-soaked spots on the leaves; in fleshy parts the tissues break down into a foul-smelling mush. The bacteria enter through wounds and stomata and spread by water.
Cause
The bacteria Pectobacterium (Erwinia), Xanthomonas and others.
What to do
- preventive: dry conditions, careful watering, hygiene and disinfection of tools, remove affected plants
- bactericides are not commonly available in Czechia; copper has a limited effect
Caterpillars (of butterflies and moths)
Irregular holes and bite marks in the leaves; in a heavy attack only the veins remain. Some species roll the leaves or mine them (tunnels). The caterpillars can usually be seen on the plant; tortrix moth larvae hide in rolled leaves.
Cause
Caterpillars of butterflies and moths (e.g. the tortrix moth Cnephasia spp.), looper caterpillars.
What to do
- direct: hand picking, biological control with Bacillus thuringiensis, insecticides while the caterpillars are young (instars 1–2)
- caterpillars have many natural enemies: encourage them
Cutworms (soil-dwelling caterpillars)
The caterpillars live in the soil and come out at night. They eat leaves and crowns at ground level, cut through young plants and also damage roots. During the day they hide at the base of the plants.
Cause
Turnip moth (Agrotis segetum) and related species.
What to do
- preventive: thorough soil cultivation, weed control
- direct: registered insecticides when young caterpillars are present; encourage natural enemies
Vine weevil / weevil (Otiorhynchus)
At night the adults eat characteristic curved notches in the leaf margins. The most dangerous, however, are the white larvae in the soil, which eat the roots and crown; the plant then wilts and dies (often begonias, primulas, rhododendrons and container-grown perennials).
Cause
Black vine weevil (Otiorhynchus sulcatus) and related species.
What to do
- direct: against the larvae, biological control with the parasitic nematode Heterorhabditis (watered into moist soil); against the adults, contact insecticides in the evening
- preventive: check the root balls of new plants
Flea beetles and other beetles (small holes in leaves)
From spring, small round holes (a "shot-hole" look) from the feeding of small beetles; the larvae of some species damage underground parts. Larger irregular holes are made by leaf beetles.
Cause
Mallow flea beetle (Podagrica malvae) and other flea beetles, leaf beetles.
What to do
- direct: insecticide spray against the beetles when numbers are higher
- preventive: remove affected parts and weeds (overwintering sites)
This is general information. When using plant protection products, follow the label.
Planting step by step
- Set out the pots by number
Do not plant anything yet. Set the pots out on the border exactly by the numbers in the planting plan, tall ones at the back (framework), low ones at the front (edge). - Check the spacing
Step back and look from above. There should be gaps between the plants. They will fill them once they have grown together. The recommended spacing is given for each plant (spacing in cm). - Photograph the layout
Before you start planting, photograph the border from above. If something does not fit, now is the time to move it, not after planting. - Plant in groups
Start with the framework (the tallest, at the back), then the filler, and finally the edge. Plant to the depth of the pot, firm in and water at the roots. - Water and mulch
After planting, water generously (~10 l/m²) and mulch the surface between the plants 5–7 cm deep. This holds moisture and suppresses weeds. - Note the planting date
Make a note of the planting day. We will use it to prepare a care plan for the first, most sensitive season.