How to Plant, Grow, and Care For ‘Grosso’ Lavender

Lavender’s scent is a popular one for everything from skincare to candles to cleaning products. Its cool, clean, crisp smell is both refreshing and relaxing. No wonder so many people are fond of this delightful plant. Lavender is also an edible herb, and the flowers of some varieties are delicious baked into cakes and cookies. 

The plants are low-maintenance and easy to care for. They not only thrive on neglect; they prefer it. The long history of their use dates back more than 2,500 years, with records of their value to the Egyptians and the Romans. Some used them for their aroma, and others for their medicinal powers. They have also been used as decorations in the home and in the garden. There are over 450 recognized varieties, but if you particularly desire the decadent smell of lavender, you will want to grow ‘Grosso.’

We could spend hours discussing lavender’s many applications and specific types. The list is long, especially in and around its native range. For now, let’s discuss how to grow and care for the especially fragrant ‘Grosso’ variety of lavender. 

‘Grosso’ Lavender Overview

Plant Type Evergreen semi-woody shrub Family Lamiaceae Genus Lavandula Species X intermedia ‘Grosso’	Native Area Mediterranean region Exposure Full sun Height 3’ Watering Requirements Low	Pests & Diseases Aphids, whiteflies, root and crown rot, and shab disease Maintenance Low Soil Type Sandy, loamy, well-drained, slightly alkaline Hardiness Zone 5-9

What Is ‘Grosso’ Lavender?

‘Grosso’ is a French hybrid lavender variety, the product of breeding English lavender with spike lavender. It has the hardiness of its English parent and the ultra-concentrated scent of its spike parent. The general consensus is that this is the most fragrant variety of lavender, which earns it a top spot in essential oil making and perfumery. It is also among the more commonly cultivated types. 

Characteristics

As lavenders go, ‘Grosso’ is impressive in many ways. For one thing, it’s the most fragrant type, which makes it exceptionally popular for extracting essential oil from. Those oils are added to cosmetic products, home cleaning agents, medical preparations, and in most other areas where heavy scent is desirous. 

The plants are large and vigorous. They are easy to grow if you get the conditions right and don’t pay them too much attention. They reach about three feet tall and wide, which is on the larger side. 

The colors are vivid among other varieties with brighter green foliage and deeper, more vibrant purple flowers. This paired with its fragrance makes it more attractive to pollinators. The flower spikes are longer than average, up to six inches, and robust. It often goes by the nickname Fat Lavender. 

Native Area

Lavender, in general, hails from the Mediterranean region, including the bordering countries of the Mediterranean Sea, western Asia, northern Africa, and the Middle East. It is well adapted to places with hot, dry summers and cool to mild winters. ‘Grosso’ is a hybrid from France. 

Planting

In cool climates, it’s best to plant your ‘Grosso’ lavender in the spring, providing it some cool weather to establish roots and time to settle in before the following winter. In warmer climates with hot summers, early fall is a good time to plant. This gives it some cool weather to establish roots, without the heat stress of summer coming directly afterward. 

Transplanting

When it comes time to transplant, choose a sunny spot with excellent drainage. Lavender doesn’t tolerate wet feet. Dig a hole that is twice the size of the root ball. Backfill so that when you set your plant in the hole, the root ball is at the soil surface level. Backfill with native soil and water thoroughly. 

Growing From Seed

Growing ‘Grosso’ lavender from seeds is a bit tricky and requires some patience. The seeds have better germination with cold stratification, which you can achieve by putting them in the refrigerator for three to six weeks before planting. Lavender seeds are tiny, and they require light to germinate, so while you can directly sow them, you’ll have a better result if you start them in a more controlled environment. 

When starting indoors, use a well-draining seed starting mix and gently press the seeds into the surface. I find it’s easier to start with moist soil so the seeds don’t wash away when you water. 

Place your seeds in a warm, brightly lit location, out of direct sun. Indoor room temperature is just about right for their germination needs. It can take up to two months for lavender seeds to germinate, so be patient. Keep seeds and then seedlings moist, and transplant outside after the threat of frost has passed.

How to Grow

Overall, lavender is easy to grow and requires little attention once it’s established. The greater concerns with this plant stem from being overly attentive and giving more care than it needs. 

Light

Lavender is a sun worshipper and will tolerate about as much light as you give it. It needs a minimum of six to eight hours of sun if you want busy, compact growth and maximum flowering. A lack of sun will lead to reduced flowering and leggy growth. 

In hot climates, some afternoon sun won’t hurt, as long as there is sufficient exposure in the early part of the day. In fact, this is preferable in places with hot, humid summers. 

Water

When you first plant it, you’ll want to water your lavender regularly. Every two to three days for the first three to four weeks will help it establish roots. It’s best to water deeply and less frequently than the opposite. Once established, this is a drought-tolerant plant that prefers to be on the dry side. 

Only water your established plants in times of prolonged drought. They will only need water once every one to two weeks. For container plants, water about once every 10 days, and less in the winter. 

Soil

Lavender is naturally adapted to soil that is sandy, gravelly, and loamy. It doesn’t tolerate compacted soil types like clay. It needs proper aeration and drainage to prevent root rot. 

Adding organic matter is a subject of debate, as this evergreen prefers soil that is slightly alkaline. Since organic material lowers the pH of your soil, adding too much is bad for your lavender. A little won’t hurt if you have poor soil, but in general, you’re better off with poor soil than that which is particularly rich. 

In a container, aim for a loose, well-draining mixture of potting soil with perlite or coarse sand mixed in. The medium should drain freely, especially in a pot. 

Temperature and Humidity

While it loves the sun, heat is not your lavender plant’s best friend. It dislikes extreme fluctuations and performs best when the temperature stays between 60-85°F (16-29°C). Slightly cooler temperatures are fine at night. Indoors, keep it away from drafts.

‘Grosso’ is evergreen to about 15°F (-9°C), so in most of its range, it remains green all winter. It flowers best between 70-85°F (21-29°C). It tends to have better cold and heat tolerance than most varieties. 

Lavender typically dislikes humidity. You may have difficulty keeping this one alive in regions with hot, humid summers. Heat and humidity often result in fungal issues. You can combat this by making sure that it has adequate air circulation and thinning the interior. 

Fertilizing

Lavender thrives in dry, somewhat poor soil and doesn’t require fertilizer. In fact, fertilizer can often lead to an abundance of green growth and poor flowering. If you apply fertilizer at all, use a bloom booster one time in the spring. 

Maintenance

Pruning your ‘Grosso’ lavender is important to maintain its attractive shape and size. The ideal time to prune is in spring and late summer, after your plant has finished blooming. Neglecting to prune will result in an overgrowth of woody stems, which will, over time, cause a leggy, unattractive appearance. 

In early spring, remove any dead or damaged foliage, but avoid a complete overhaul at this time. In late summer, after it finishes blooming for the year, shape and rejuvenation pruning are appropriate. 

Identify the place where stems become woody. Count upwards about two to three inches above that point. This is where you should make your cuts. Avoid cutting into the woody portions of the stems, as this may result in stunted regrowth. 

While it is in bloom, you should consistently deadhead your lavender flowers to keep the plant producing more. This helps to maintain a nice shape, stimulates growth, and improves the overall blooming ability. 

Propagation

When it comes to propagation, growing from cuttings is the safest and most reliable method. You can grow it from seeds, but it tends to be less reliable this way. Division is also risky, as lavender is a sub-shrub with a single trunk and root system. Dividing may land you with a couple of dead plants on your hands. 

Spring and early summer are ideal times for propagating by cuttings. Semi-hardwood cuttings can work, but softwood cuttings are ideal. You want to use that healthy new growth that pops up at the beginning of the growing season. 

Choose stems between four and six inches long and cut them with a clean, sharp pair of scissors or harvesting snips. Remove the leaves from the bottom half and dip the cut end in rooting hormone to help it root faster. 

Fill nursery pots with a well-draining mixture of sand, peat moss, or perlite mixed with potting soil. Keep the soil moist during the rooting process, but don’t allow it to become waterlogged. Keep it in bright but indirect light and at a stable temperature around 70°F (21°C). 

It should take between four and six weeks for your cuttings to root. You can test them by lightly tugging on the tops to see if the bottoms catch in the soil. Some resistance, along with new growth, indicates that they have rooted. You can plant them in their permanent location at this point. 

Common Problems

Despite its usefulness to humans, lavender is typically not attractive to insects and can repel them. A few may cause an issue, but it’s unusual. In terms of diseases, most of them affect lavender and are fungal in nature. 

Pests

Most insects don’t like the way this member of the mint family smells. It’s actually recommended to help repel common garden pests. However, a couple of pests will brave the scent to get to the sap. Whiteflies and aphids are the most common issues and some of the most common garden pests in general. 

Both of these insects suck the sweet sap from your plants, depleting them of moisture and nutrients. Both are also prey for some beneficial, predatory insects that you can attract with nectar plants. Spray down plants with a strong stream of water from a hose. Neem oil is also an effective way to treat both of these. Make sure to spray them in the late afternoon or early evening so they have time to dry by morning. 

Diseases

There are several fungal diseases that you may encounter when cultivating lavender. This is one of the reasons it is important to avoid overwatering this plant. Root and crown rot are the most common, and are most often cause by overwatering and a lack of proper air circulation. 

High humidity and a lack of air circulation are other common causes of fungal disease.  If you go through a period of high humidity or extended rainfall, you could end up facing fungus. If you live in a humid climate, consider thinning out the interior of your shrub to allow light and air to reach the center. 

To reduce the occurrence of fungal rot, avoid overhead watering, and don’t water too often. While some molds are not curable, others may be, so it’s worth it to try. Repotting a lavender plant with root rot and removing the damaged tissue may work in milder cases. 

There are some diseases such as shab, that you can’t treat, and it’s best to remove and dispose of these plants. It’s best to destroy these by burning them to avoid transmission to other plants. For milder fungal infections, you can treat with neem oil and remove the affected tissue. This is not a sure thing, but often works and preserves part of the plant.