Gadenin日本語Get the appSlugs and snails on young plants
Nothing removes a viola planting faster than slugs. The plants are soft, sit low to the ground, and go out in the cool damp conditions that suit slugs best, so a tray planted in the evening can be chewed to stubs by morning. The damage is easy to recognize: ragged irregular holes eaten inward from the leaf edges, small plants grazed off at ground level, buds hollowed out, and dried silvery slime trails across the leaves and soil.
The vulnerable window is the first three to four weeks after planting. An established viola with a thick crown takes slug damage and carries on, and its dense low mound actually recovers faster than a pansy's looser one because there is more growth in reserve. A plant that has just gone in has no reserve and is simply eaten. Cover that window and you rarely need to do anything for the rest of the season.
Go out with a torch an hour or two after dark on the first mild damp evening after planting and collect by hand. One or two sessions usually clears most of the population working that bed, because slugs concentrate on the newest soft growth available. Then remove the flat damp hiding places within a few feet of the plants: upturned pots, boards, thick mulch pushed against the crowns, and last season's leaf piles. Ferric phosphate pellets work and are safe around wildlife, but only if scattered at planting rather than after the leaves are shredded.
- Water in the morning, not at dusk Slugs feed on damp nights. A bed watered at dusk is far more attractive than the same bed watered at dawn and dry by nightfall.
- Hunt after dark on the first three nights A torch an hour after dark shows them out on the plants. Three consecutive nights of hand collecting after planting removes the bulk of the local population.
- Pull mulch back from the crowns Leave a clear two inch (5 cm) ring of bare soil around each plant. Mulch heaped against the crown is both a slug refuge and a direct cause of crown rot.
- Scatter ferric phosphate at planting Apply thinly on the day you plant, not once damage appears. Reapply after heavy rain through the first month, then stop.
Aphids on the shoot tips and buds
Aphids gather on the flower stalks, unopened buds and newest leaves, and on violas they are usually green or gray green and small enough to be missed against the fine foliage. The first signs are indirect: buds that open lopsided or fail to open, a sticky honeydew film on the leaves below the infested growth, and later black sooty mold growing on that film. Ants running steadily up and down the plant are a reliable indicator, because they farm the aphids and drive off the predators that would otherwise handle them.
Aphids matter more on violas than on many plants because they transmit viruses. A plant with mottled, puckered, distorted leaves and streaked or broken flower color that does not improve once the aphids are gone is almost certainly virused, and there is no treatment. Pull it out, bin it rather than composting it, and wash your hands before touching healthy plants. Because violas self seed so freely, also pull any seedlings that came up directly around an infected plant.
For a colony that is still small, a firm jet of water into the shoot tips on three consecutive days knocks it down with nothing else. For a heavier one, insecticidal soap sprayed until it runs off both leaf surfaces works, but only on what it actually wets, so the undersides and the crowded center of the mound matter more than the tops. On a viola that center is dense, which makes thorough coverage harder than on a pansy and makes shearing the plant first a sensible first step.
Leaf spot, downy mildew and powdery mildew
Three different leaf problems all get called mildew and they behave differently. Powdery mildew appears as a dry white dust on the upper leaf surface, in warm dry weather, on plants that are dry at the root. Downy mildew appears as pale yellow blotches on the top of a leaf with a gray purple fuzz on the underside directly beneath, in cool wet weather with still air, which is exactly viola weather. Leaf spot appears as distinct round brown or purple spots with defined edges, often paler in the center, that spread and merge until the leaf dies.
All three are managed the same way and it is mostly not a spray. Space plants so air moves between them instead of packing a container to look full on planting day, which matters more on a viola than on a pansy precisely because the mound is so dense. Water at the base and in the morning. Pick off and bin affected leaves as soon as they appear and clear all dead foliage from the crown, because that is where every one of these overwinters and restarts. Do not compost the material.
A light shear also helps and is worth using deliberately. Taking the top inch (2.5 cm) off a viola removes a large share of the infected tissue, opens the middle of the plant to moving air, and costs you only a fortnight of flowers, since the plant regrows so readily. If a whole planting is badly affected, though, the honest answer is to remove it and start again in fresh compost elsewhere rather than nursing plants that will never look right and will infect what you put beside them.
| Symptom | Likely cause | What to do |
|---|---|---|
| Ragged holes and slime trails | Slugs and snails | Hunt after dark; ferric phosphate at planting |
| Sticky leaves, distorted buds, ants | Aphids | Water jet three days, then insecticidal soap |
| Mottled leaves, streaked flowers | Virus spread by aphids | Remove and bin the plant; no treatment exists |
| White dust on the upper leaf surface | Powdery mildew | Improve airflow, water the root zone, remove leaves |
| Yellow blotches with gray fuzz beneath | Downy mildew | Space plants, shear lightly, water at the base in the morning |
| Round brown spots with defined edges | Leaf spot | Pick off affected leaves, clear crown debris |
| Rusty orange pustules under the leaves | Rust | Remove affected leaves; thin the planting for airflow |
| Sudden wilt, soft brown stem at soil level | Crown or root rot | Not recoverable; remove and do not replant there |
A plant that wilts and never recovers
A viola that goes limp and stays limp after watering has a problem at the base, not the top. Lift it and look at the stem where it meets the soil. A brown, soft, sometimes water soaked patch there is crown rot, caused by the crown sitting wet: planted too deep, mulch heaped against the stems, a container without free drainage, or a run of cold wet weeks in heavy soil. There is no cure. Remove the plant, take out the soil immediately around it, and do not put another viola in that spot this season.
Black root rot is the related problem below ground. The plant is stunted, older leaves yellow, growth stalls, and when lifted the roots are blackened and brittle rather than white and firm. It builds up in soil where violas or pansies have grown repeatedly, and violas make this easy to fall into, because their self sown seedlings keep the same ground occupied year after year without anyone deciding to plant there. If a patch has produced two poor generations in a row, pull the volunteers out of it, use it for something else, and start the violas again from seed in fresh compost.
The difference from simple drought is the commonest misdiagnosis and it is easy to settle. A viola short of water wilts in the warm part of the day and is upright again by the following morning; one good soak fixes it, and violas recover from this more reliably than pansies do. A viola with rot is limp at dawn as well, and every further watering makes it worse.
Keep a note of which bed or container each planting went into and how it did. Rot problems build up in one specific place over years, and with a self seeding plant that quietly stays put, a two line record of where things went badly is what stops you leaving the next generation in the same soil.