The very first flowers of a few angustifolia cultivars are open in Simcoe (Norfolk County). This is a few days later than the average, probably delayed by the long stretch of cold and cloudy weather at the end of May. Bloom will begin later farther north. The peak appearance of lavender plants is usually about 10 days into the bloom, which will be around July 1 in the south. Lavandin cultivars are about 10 days later than the angustifolia cultivars.

Harvest Time

For new growers, it is important to know the optimal harvest timing, which will depend on what you will be doing with the lavender:

Dried bundles and buds: Harvest near the beginning of bloom when, on average, the flower stalks have only a few buds open, but before too many blooms start to wilt. If you wait too long, the dead petals (corollas) will turn brown (Figure 1). These remain on the flowers after drying and are difficult to remove through the bud cleaning process. Some cultivars have more of a staggered bloom, meaning that some flower stalks bloom much later than others. You may have to delay bloom in these cultivars to a point when most stalks are close to flowering. This will result in more dead petals on the most advanced flower stalks.

Figure 1. A dried ‘Melissa Lilac’ bundle showing how the appearance of dried buds degrades as they go through the bloom cycle.

Fresh bundles: If you have a market for fresh flower bundles, it is best to wait to harvest for an extra few days to allow more buds to open.

Oil: Oil yield and quality peaks between the middle and end of the bloom period (approx. 2 to 4 weeks after the beginning of bloom). After that time, yield and quality gradually decrease as buds begin to fall off the flowers and the oil begins to oxidize or buds decay. Most growers wait until after bloom to harvest for oil to allow for a long agritourism season, and this only marginally reduces yield and quality.

Recovering from Winterkill

For plants with extensive winter damage, it is best to harvest for bundles so the plant has a long period to grow vegetatively. Waiting to harvest could add further stress to the plants and prevent regrowth from the base of the plant. If they need to be harvested for oil, consider harvesting right at peak bloom rather than waiting until bloom is finished. After harvest, it is best to allow for some regrowth and then do a hard pruning to force the plant into a more rounded shape. A hard pruning means about 50% of the new growth. This could be more than 50% of the branches that stick way out of the plant, and less than 50% of any new shoots coming from the base of the plant.

Irrigation

Rainfall has been highly variable so far this spring, with some areas seeing considerable rainfall and others very little. Delhi in Norfolk County, for example, has only had 8 mm of rain in the past 4 weeks. Most other areas have received 40-60 mm. With the coming heat wave being timed for the beginning of bloom, it is important to monitor soil moisture and irrigate if necessary. Dry conditions during bloom can cause sudden wilting of flowers in the afternoon, potentially reducing stem length, lowering flower yield, and reducing the appearance for agritourism.

As a plant adapted to dry conditions along the Mediterranean, why is this a problem here? Due to our high water table over the winter, the root system on our plants is not nearly as extensive as plants would be in the Mediterranean region. In fact, flooding of the root system in some fields caused extensive winter damage this year due to root dieback, and those plants will be very prone to wilting in the first heat of the summer. Plants will likely live through a dry period, but the goal of a farmer is to maximize yield, not just ensure the plant survives.

Pests

Garden fleahoppers have completed one generation, and most are adults in the plot in Simcoe. The next generation can be much larger, with the third generation in August being the most destructive. Monitor plants closely to ensure you do not have a major outbreak.  Controls applied early will be more effective than waiting until a major issue develops. This is more of a localized pest, so insect controls are only warranted if scouting indicates significant populations and damage.

Four-lined plant bugs are in the adult stage now. Feeding will continue for a few weeks, but it is too late to apply any controls. For more information insect pests of lavender, visit the lavender module of Ontario Crop IPM.