Stock plants (Matthiola incana) are cherished for their enchanting fragrance and classic cottage garden aesthetic. Often found in shades of white, pink, lavender, and purple, these blooms are popular for their visual appeal and delightful scent. Their upright growth and dense flower clusters make them stand out in garden beds and floral arrangements.
Planting Stock Flowers
Stock flowers are cool-season annuals. In most regions, plant seeds in early spring after the last frost. In mild climates, sow seeds in fall for spring blooms. Starting seeds indoors 6-8 weeks before the last frost can give them a head start in shorter growing seasons.
Choose a proper location for healthy growth. Stock plants prefer full sun (at least six hours daily), though they tolerate light shade. The soil should be well-draining and fertile, ideally with a slightly alkaline pH between 7.0 and 7.5. Amending the soil with compost or well-rotted manure before planting improves fertility and drainage. Space seeds or seedlings 12-18 inches apart for good air circulation, which helps prevent fungal issues.
Ongoing Care for Healthy Growth
Stock plants thrive in cool environments, requiring consistent care for a robust display. While they enjoy full sun, they are sensitive to high temperatures (above 80°F) and can decline or stop blooming in hot, humid conditions. Cooler night temperatures, ideally below 60°F, encourage abundant blooms.
Well-draining soil is crucial, as stock plants are susceptible to root rot in waterlogged conditions. They prefer a soil pH ranging from neutral to slightly alkaline (6.8 to 7.5). If your soil is acidic, adding lime can help raise the pH.
Consistent watering is necessary to keep the soil evenly moist, but avoid overwatering. Allow the top inch of soil to dry slightly between waterings to prevent saturation. Watering in the morning allows foliage to dry before evening, reducing fungal disease risk. During hot or dry periods, stock plants may require more frequent watering.
Stock plants generally do not require heavy fertilization if planted in fertile soil. However, a balanced, slow-release fertilizer applied every 4-6 weeks during the growing season can promote healthy growth and blooming. Alternatively, a water-soluble fertilizer with a balanced NPK ratio like 10-10-10 can be used according to package instructions.
Managing Pests and Diseases
Stock plants are relatively resilient but can encounter common garden pests and diseases. Aphids, small sap-sucking insects, are a frequent nuisance on leaves and stems. Flea beetles and cabbage white caterpillars also feed on stock plants. For minor infestations, handpicking pests or spraying them off with a strong stream of water can be effective. Organic insecticidal soap or neem oil can provide further control if needed.
Diseases affecting stock plants are primarily fungal, often linked to excessive moisture or poor air circulation. Common fungal issues include powdery mildew, gray mold (botrytis), root rot, leaf spot, and fusarium wilt. Preventing these diseases involves ensuring proper plant spacing for good airflow and avoiding overhead watering, which keeps foliage dry. If fungal diseases appear, fungicides may be necessary, and removing affected plant parts can help contain the spread. Maintaining well-draining soil is the best defense against root rot.
Pruning and Harvesting Stock Flowers
Pruning stock plants primarily involves deadheading spent blooms to encourage continued flowering and maintain vigor. Removing faded flowers prevents the plant from expending energy on seed production, redirecting it to new flower buds. This practice can extend the blooming season and keep the plant looking tidy.
To deadhead, make a clean cut just above the first set of healthy leaves or a new side bud on the spent flower spike. While deadheading encourages more blooms, some varieties may not rebloom extensively after the main flush.
For cut arrangements, harvest stems when about one-third to one-half of the florets on the stalk have opened. Cut stems in the coolest part of the day, ideally early morning, and place them immediately into deep water to condition, preferably overnight. This helps prolong their vase life, which typically ranges from 7 to 10 days.