Planting Violas: Choosing Plants, Spacing and Getting Them Established

Pick short bushy plants, not the ones already covered in flower

The tray that catches your eye is the one smothered in open blooms, and it is usually the wrong one to take. Violas flower young and hard, so a cell pack in full flower has put its energy into those blooms rather than into roots, is very often pot bound, and will sit and sulk for weeks after planting while a plant that went in carrying buds only gets straight on with growing. Choose short, dense, dark green plants with plenty of unopened buds, and shear the open flowers off as you plant.

Turn one plant out of its cell before committing to a whole tray. You want white roots visible through the compost but not a solid mat circling the outside. Violas root quickly and go pot bound faster than pansies in the same size cell, so this check matters. If the roots have set into a hard spiral, tease the bottom third apart with your fingers, or the plant will keep the shape of its cell and never root out into the bed.

Reject anything with yellow lower leaves, stretched pale stems, spotted foliage or a soft brown patch at the base. Violas are inexpensive and quick to raise from seed, so there is no reason to plant a compromised one, and a plant carrying leaf spot or rot brings it into soil that you will very likely be growing violas in for years, since they self seed and stay put.

Soil, drainage and the timing of planting

Violas want free draining soil with plenty of organic matter and a position that does not stay waterlogged after rain. Fork a two inch (5 cm) layer of well rotted compost through the bed before planting. On heavy clay, plant into a raised bed or a container rather than trying to fix the drainage in one season, because a viola sitting in cold standing water through winter rots at the crown however carefully it was planted.

The timing that matters is soil temperature, not air temperature. Plant while the soil is still warm, roughly above 45F (7C), so roots have four to six weeks of active growth before cold shuts things down. Violas root faster than pansies and will make useful growth at soil temperatures a few degrees lower, which buys you perhaps a fortnight of extra planting window at the end of the season, but the principle is unchanged: plants that root out before the cold flower through it, and plants that go into cold soil sit there, lift out when the ground freezes and thaws, and are often dead by midwinter.

In practice that means planting in late summer or early autumn for an autumn to spring display in a mild climate, or in early spring as soon as the ground can be worked where winters are severe. Because violas keep flowering through cold snaps that stop pansies, and hold on for several weeks longer into summer heat, the same planting date gives you a noticeably longer display.

Set the crown level and space wider than looks right

Dig each hole slightly wider than the root ball and the same depth, so the top of the root ball finishes flush with the surrounding soil. The crown, where the stems emerge, must sit at soil level. Half an inch (12 mm) too deep and soil and mulch collect around the stems, stay wet, and the plant rots at the base in the first long damp spell. Planted proud of the surface, the root ball dries faster than the soil around it and the plant rocks loose in wind.

Space six to eight inches (15 to 20 cm) apart in open ground. On the day that looks far too sparse, and it is still the correct distance. This is where people who have grown pansies get caught out: a viola spreads at least as wide as a pansy and does it faster, so a bed that looked thin at planting is a closed mat in three or four weeks. Plant at three or four inches (7 to 10 cm) for an instant effect and you get a dense airless cushion with no wind moving through it, which is where downy mildew and leaf spot begin.

In containers you can plant closer, at four to six inches (10 to 15 cm), because the display is wanted for one season and the compost is fresh. Accept that a tightly planted container exhausts its compost faster and needs feeding from about six weeks after planting, and that it must have free drainage holes and must never stand in a full saucer through a wet cold spell. Raise it on pot feet or bricks before winter rather than after.

1. Prepare the whole bed, not each hole Fork two inches (5 cm) of well rotted compost through the top six inches (15 cm) of the bed. Improving individual planting holes in heavy soil just creates sumps that fill with water.
2. Tease out circling roots If the root ball comes out as a solid spiral, pull the bottom third apart with your fingers. A plant left in the shape of its cell pack never roots out into the bed.
3. Plant with the crown at soil level The top of the root ball sits flush with the surrounding soil. Firm gently around it with your fingers, never with your heel, which compacts the surface and sheds water away from the roots.
4. Water in thoroughly, once One proper soak at planting settles the soil against the roots. Repeated light sprinkles over the following week wet only the surface and encourage shallow rooting that heaves out in frost.
5. Shear off the open flowers Take the top inch (2.5 cm) off each plant as it goes in, removing every open bloom. The plant spends that fortnight on roots instead and flowers harder and far longer as a result.
6. Keep mulch clear of the crowns Mulch the bed to hold moisture and steady the soil temperature, but leave a two inch (5 cm) ring of bare soil around every stem.

The first month after planting

For the first three to four weeks the plants are rooting out and are at their most vulnerable. Keep the soil evenly damp over that period, checking with a finger rather than watering to a schedule, and water in the morning so the foliage is dry by nightfall. This is also when slugs do their worst, so put protection in place at planting rather than after the leaves are shredded.

Hold off feeding for the first two or three weeks. A newly planted viola given a strong feed puts on soft top growth before it has roots to support it, and that growth is the first thing frost damages. Start a half strength liquid feed once you can see new leaves being produced, then continue every two to three weeks through the flowering season.

Pinch or shear the growing tips once when the plants are established and clearly growing. Two shoots break below each pinch, giving a bushier plant carrying far more flower stalks, at a cost of about two weeks. On plants set out in autumn for a spring display that delay costs nothing at all, and on a viola it pays back more than on a pansy, because the extra shoots each carry buds at nearly every joint.

Record the planting date, the spacing you used and the position of each group. Violas are planted when little else in the garden is happening, so notes are easy to skip, and the comparison between a bed planted early and one planted three weeks later is the single most useful thing you will learn about your own ground.