Growing Violas: A Guide to Sowing, Care and Harvest

Violas are a low-growing perennial plant under the Violaceae botanical family. With somewhere around 600 species, Violaceae has given rise to numerous hybrids. Often crossed with Viola tricolor (wild pansy), their most famous descendants are horticultural pansies.

The plant grows rapidly by rhizomes under the soil and easily self-seeds in gardens. They are ideal for low beds and borders, as well as pots and window boxes, where they can be combined with other spring and summer flowering plants. (forget-me-nots, primroses, botanical tulips, asters...).

Most species are found naturally in the temperate Northern Hemisphere; however, some are also found in areas such as Hawaii, Australasia, and the Andes.

Violas thrive in full sun due to the light offered rather than the heat given. High temperatures can be offset with regular watering and a mulch to prevent the tubers from drying out.

Many viola species contain antioxidants and have been used for medicinal purposes both topically and for ingestion. Don't hesitate to decorate your plates with a flower or two, or even place a few on your salads to give them a touch of color!

The Basics

Height at maturity: 15-30 cm (depending on variety)
Spread at maturity: 15-30 cm (depending on variety)
Light needs: Full sun to part shade
Hardiness: down to -20C°, fully hardy perennials in Zones 6-10 but can grow just fine in zones 3-11
Type of soil: humusy, moist garden soil heavily amended with organic material
Soil pH: Slightly acidic soil; peat moss as a soil additive will help acidify garden soil
Where to plant: Garden beds and containers, landscaping
Features: Attracts Bees and butterflies, very fragrant, frost tolerant (depending on variety)
Pruning: not needed
Pests: Fungus gnats and shore flies, aphids, thrips, mites and whiteflies can be a problem
Diseases: Damping-off, black root rot, foliar leaf spots and Botrytis blight are common
Plant type: Cool-weather annual
Difficulty: Low maintenance

Starting your seeds

Light is not required for germination.

Pansies do best when you grow them in nutrient-rich, well-draining potting mix. Fill containers that are 9 to 12 inches deep with sandy loam soil that is amended with 2 to 4 inches of organic matter, like manure or peat moss. Lightly water the starter plants before planting. Water the pansies again once they are in the pots to replace any lost moisture. Lightly spread the roots of your pansies and press them firmly into the soil, pushing the potting mix up to the bottom stem of your plants. Place your planted pansies near a window that receives direct sun throughout the day.

Prefers a humus-rich, moist but well-drained soil in full or partial sun. Water well until established.

Use a well-drained, disease-free seedling medium with a pH of 5.4 to 5.8.

Spring sow for flowers the same year. Autumn sow for flowers the following year. Autumn sow under glass. Fill a pot with 90% compost 10% sand. Sow 2mm deep and cover lightly with soil.

Ideal temp: 22°C

If seed germinates straight away transplant otherwise seed will be dormant but ready to germinate the following spring. Spring sowing as above, if seeds have not germinated in 2-4 weeks cold stratify. Move to 4°C. for 6-8 weeks then return to warmth at 10°C. When seedlings have 2 true leaves transplant to 8cm pots.

A medium covering of coarse grade vermiculite is recommended to help maintain high humidity around the germinating seed for better germination performance. Bench germination takes 3 to 4 days. Chamber germination will yield better results.

Temperatures

Germination, week 1: 68°F (20°C)
Week 2: 65° to 70°F (18 to 21°C) days; 60°F (15°C) nights
Week 3: 65°F (18°C) days; 60°F (15°C) nights
Week 4: 60°F (15°C) days; 55°F (13°C) nights

At Week 3, reduce the moisture level in the media once the seedlings are established. Stage 4 plugs can be grown under wet/dry cycles to tone the seedlings and avoid soft growth. Maintain 95 to 97% relative humidity.

A month after they sprout, you can start using a fertilizer once a week from 14-0-14, alternating with a 20-10-20 type fertilizer for pH balance.

A high pH (greater than 6.0) can induce boron deficiency and also encourages fungal black root rot, caused by Thielaviopsis sp.

Growing On

Transplant the plugs “on time” to avoid initiation in the plug stage. Plugs that are initiated will not fill out the finished container well at the time of flowering.

The level of starter nutrient charge incorporated into the growing mix influences crop quality. A starter charge that is too low can result in a viola crop that will flower before enough foliage has grown to fill the packs/container. Incorporate a medium level of supplemental nutrient charge in the growing media mix to encourage good foliar growth before the crop flowers.

Provide day temperatures of 60°F (15°C) and night temperatures of 50 to 55°F (10 to 13°C) for greenhouse production.

A week after transplant, begin fertilizing once a week when grown in the greenhouse. Additional fertilization may be needed if grown outside. Alternate between an acidic fertilizer, such as 20-10-20, and a basic fertilizer, such as 15-5-15 calcium/magnesium for pH balance. Temperature is the best natural growth-controlling factor. Minimal to no plant growth regulators are needed when the crop is produced at lower temperatures.

To produce the best-quality violas, grow them outside beginning a week after transplant under cold frametype conditions. Optimal outside growing temperatures are 60 to 70°F (15 to 21°C) days, and nights in the low 50s°F (11 to 15°C) for the first few weeks. Violas can also tolerate lower night temperatures – in the 40s°F (5 to 9°C).

Care

For optimal germination performance, maintain the plug media at “wet” moisture levels, i.e., the media is glistening, but water will not ooze out from the bottom of the tray and will penetrate only slightly from the top around the fingertip. Avoid germination temperatures above 70°F (21°C) to prevent seedling stretch. Pansies need regular water or they will fail to thrive. Test the moisture of your soil two to three times a week with a moisture meter — a device with a long metal probe you insert into soil that gives you a readout of water levels — or with your finger. When the soil is dry, give your pansies 1 inch of water, making sure to remove any standing water from under the pot.

Sow to transplant: 4 weeks in a 406-cell plug tray
Transplant to finish in 606 jumbo cell pack: 3 to 5 weeks seasonally
Total crop time to flower: 7 to 9 weeks seasonally

When flowers are in bloom, apply fertilizer once every three to four weeks to get larger, longer-lasting flowers.

Pansies will grow in any container that holds soil and allows water to drain. You may want to grow your pansies in small terra cotta pots and group them together on a table. You can also plant pansies in a hanging basket placed near a window. Nontraditional containers, like galvanized buckets, decorative bowls or fish bowls, can add a creative flair to your pansy display. To use a nontraditional container, first plant your pansies in a pot with drainage holes. Place the pot into your container and bury it in soil. This helps prevent overly wet soil in the pot.

Remove spent flowers to encourage further blooms.