Viola Growing Calendar: Sowing in Late Summer for Autumn Through Spring Flowers

The shape of the viola year

Violas are cool season plants and the whole calendar follows from that. They germinate in cool conditions, root through autumn, flower whenever the weather is mild, keep opening buds through cold spells that stop most bedding, surge in early spring, and slow when summer heat arrives. Everything in the schedule is arranged either to give them enough cool weather at the start or to reach the heat with a big established plant that can be sheared and shaded through it.

There are two viable patterns. In mild climates, sow in late summer, plant out in early autumn, and take a display from mid autumn through to early summer with only a brief quiet spell in the coldest weeks. In climates with hard winters, sow in late winter under cover, plant out in early spring, and take a display from early spring until the heat. The late summer sowing is much better value where it is possible, because it produces months of flower when almost nothing else is doing anything.

The difference from a pansy is worth stating plainly, because it changes how much the schedule returns. A pansy shuts down below about 40F (4C) and collapses above 75F (24C), so its useful season is bracketed at both ends. A viola keeps producing smaller flowers through cold snaps and holds on to around 80F (27C), and it is far more likely to survive the summer and flower again in autumn rather than being cleared. From the same sowing date you get several more weeks at each end, and sometimes a second year from the same plants.

Late summer: sowing for the long autumn to spring display

Sow ten to twelve weeks before your first expected frost. That produces a plant with a solid crown and a working root system by the time cold arrives, and it is the whole basis of autumn planting. Sow later and you get a small plant that spends winter surviving rather than flowering. Sow much earlier and the seedlings must be nursed through the hottest weeks of the year.

The difficulty is that you are germinating a cool season seed in the warmest part of the year. Viola seed germinates best between 60F and 68F (15C and 20C) and germination falls away sharply above 75F (24C). Sow in trays in the coolest shaded place you have, not in open ground. Cover the seed lightly, an eighth of an inch (3 mm) of compost, because violas germinate better in darkness. Keep the compost just damp and expect seedlings in ten to fourteen days, sometimes spread over three weeks.

Transplant at the first true leaves into plugs or small pots, handling seedlings by a leaf and never by the stem. Grow them cool and as bright as you can manage; warm and dim gives long floppy seedlings that never make decent plants. Half strength liquid feed weekly from about two weeks after transplanting seedlings, and pinch each tip out once to get two shoots instead of one. Violas branch more readily than pansies after that pinch, so the plant you set out is noticeably bushier.

Autumn: planting out and the first flush

Plant out in early autumn while the soil is still warm, ideally above 45F (7C), so plants root out over four to six weeks before the weather turns. Space them six to eight inches (15 to 20 cm) apart, set the crown level with the surface, water in once thoroughly, and put slug protection down on the same day. Shear off the open flowers as you plant.

Flowering starts within two to three weeks of planting and builds through the mild part of autumn. This is when the routine starts: a quick weekly pass to pull off fat seed pods and clear spent flowers out of the crowns, and a light shear over the whole plant every three to four weeks. Feed at half strength every two weeks. This autumn flush is the reward for the late summer sowing and is often the heaviest flowering of the year.

As nights turn properly cold, growth slows and the flower count drops, but on a viola it rarely stops. Expect a scatter of smaller blooms through mild days all winter, which is the main reason to grow these rather than pansies where the cool season is long. Clear fallen leaves off the plants, because a viola buried in wet leaf litter rots at the crown, and stop feeding once growth has visibly stopped, since nutrients applied to a resting plant just wash through.

Note your sowing date and the date the first flower opened after planting. That gap is remarkably consistent in one garden, and once you know it you can work backwards from when you want the autumn display and sow to hit it.

Winter and spring: holding on, then the surge

Through the coldest weeks the plants mostly hold rather than grow, and they hold better than pansies do. Established violas take hard frost and come back; the foliage goes limp and dark during a freeze and stands up again as it thaws, which alarms people every year and is normal. The two jobs are to keep dead material cleared out of the crowns and to check after each freeze and thaw cycle for plants heaved partly out of the ground, which are pressed gently back and firmed in on the next mild day.

At the first sustained mild spell in late winter, resume the half strength feed every two weeks and go over everything. Anything that has sprawled and opened in the middle is cut back by half, above leaf joints, and will be flowering again inside two to three weeks. Doing this at the start of the mild weather rather than in mid spring is what gives you a dense plant for the peak season instead of a sprawling one.

Spring is the heaviest flowering and the heaviest shearing. Take the top inch (2.5 cm) off the whole plant monthly, keep pulling pods weekly, and keep feeding every two weeks, because a plant flowering this hard in soil leached by winter rain runs short faster than it looks. Aphid numbers climb quickly through mild spring weather, so check buds and shoot tips at the same time. This is also the best moment to take cuttings, from the soft shoots that break after a shear.

Early summer: carrying them through, or clearing them

When daytime temperatures settle above about 80F (27C) the stems lengthen, flowers shrink and the display goes downhill. With a viola you have a genuine choice at this point, which you do not really have with a pansy. Shear the plant hard, back by half, move containers into afternoon shade, water deeply twice a week and drop to a quarter strength feed, and a healthy viola will often sit out the summer as a green mound and flower again when the nights cool. In a hot summer it will not, but the attempt costs nothing.

Clear plants that are clearly finished rather than leaving them in place. Exhausted violas become a reservoir of leaf spot, mildew and aphids for whatever follows, and any left to ripen seed will scatter it several feet. Tip out container compost rather than reusing it, and avoid replanting violas into the same ground next autumn, because black root rot builds up in soil that grows them repeatedly. Since violas self seed, that also means pulling the volunteers out of any patch that has carried them for several years.

If you want seed from a plant you liked, this is the one situation where you deliberately stop shearing. Let one plant set pods, wait until the capsules turn upward and start to pale, and collect them before they split, which they do explosively. Accept that this plant will more or less stop flowering as a result, and keep it away from the ones still on display. Remember that the seedlings will not match the parent; for that, take cuttings instead.

Record the week the plants stopped flowering in the heat, alongside the week you planted them and whether you tried to carry them through. Over two seasons those dates give you the real length of the useful display in your own garden, which is what decides whether carrying plants over is worth the summer watering where you are.