What Is Grosso Lavender – How To Grow Lavender “Grosso”


By: Darcy Larum, Landscape Designer

Nothing pleases the senses quite like a mass planting of lavender– the velvety spikes of purple blooms set against silvery blue fine foliage, the busy bees, butterflies, and hummingbird moths flitting from flower to flower, and the heavenly scent of those blooms that can undo all the stressors of the day with just one whiff.

However, many gardeners have difficulty growing lavender, as they have a reputation of being somewhat picky about where they are grown. Fortunately, we live in an age where plant breeders recognize problems and swiftly create new, tougher varieties. One such tough, reliable hybrid is Grosso lavender. Continue reading for all the perks of growing Grosso lavender plants.

What is Grosso Lavender?

Grosso lavender, scientifically known as Lavendula x intermedia ‘Grosso,’ is a woody perennial hybrid of English lavender and Portuguese lavender. Lavender hybrids of these parent plants are generally known as lavadins, and incorporate all the beauty and fragrance of English lavender with the resistance and tolerance of Portuguese lavender.

Not just a favorite for beds, borders, or mass plantings in the home landscape, Grosso lavender is also the most widely cultivated lavender variety for its essential oils. Its long lasting blooms and fragrance are excellent for cut flowers, dry flowers, oil infusions, potpourri, and other crafts as well as in culinary and herbal recipes.

This is also an excellent plant to grow for honeybees. Harvest the large, deep purple to blue blooms of Grosso lavender from mid to late summer, just as the buds open, on dewy mornings when blooms are laden with natural essential oils.

Growing Grosso Lavender Plants

Like all lavender, Grosso lavender plants require full sun and well-draining soil. However, Grosso lavender does not struggle quite as much as English lavender in the cool, wet conditions of spring or fall in cooler regions. It also can stand up to the hot, arid summers of warm regions better than other lavenders.

Hardy in zones 5 through 10, Grosso lavender plants will grow best when planted in slightly sandy to rocky soil, with excellent air circulation. Even this tough hybrid cannot handle extremely humid regions or overcrowding and shading from other plants.

Grosso lavender plants are rabbit and deer resistant and drought tolerant once established. They seem to thrive in poor, infertile soils where other perennials suffer. To keep plants looking their best, water deeply but infrequently and apply a general slow release fertilizer in spring. For tidy looking plants deadhead spent blooms.

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Despite its Mediterranean origin, English lavender was so named because it grows well in that country's cooler climate and has long been a staple in English herb gardens. The gray-green foliage and whorls of tiny flowers make this one of the most attractive lavenders in the garden. It’s one of the most cold-hardy varieties and the best for culinary use because of its low camphor content.

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Also called fringed lavender, this showy variety is distinguished by narrow, finely-toothed leaves and compact flower heads topped by purple bracts. While the flowers have less aroma than English lavender, the fleshly leaves are more fragrant, with an intoxicating rosemary-like scent.

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This variety is prized for its unusual pineapple-shaped blooms with colorful bracts, or “bunny ears,” that emerge from each flower spike. Although the flowers are not especially fragrant, the light-green leaves are very aromatic.

Photo by: Peter Radacsi / Shutterstock.

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This popular hybrid combines the cold hardiness of English lavender with the heat tolerance of Portuguese lavender (L. latifolia). It typically starts blooming a few weeks later than most English lavenders and features long spikes of highly fragrant flowers. Although not considered edible (due to high camphor content), the flowers and foliage are often added to sachets and potpourris.

Although all lavender (Lavandula) is native to the Mediterranean, there are many varieties offering a vast selection of bloom times, colors, flower forms, and sizes. “Bloom time can vary drastically between different locations—where one lavender blooms at the start of June, only 20 miles away could be a very different outcome,” says Kristin Nielsen, president of the Lavender Association of Western Colorado.

Contrary to the name, not all lavenders are purple. Some hybrids come in other lovely pastel hues such as violet blue, rose, pale pink, white, and even yellow. The leaves can also vary in shape and color. To extend the bloom season as well as the color palette, consider planting several varieties.


How to Plant Lavender

SOIL

  • Use well-drained soils or raised beds and containers (outdoors only).
  • Soil should be well draining. There is no need for a special soil, just one that is not compact. If gardening in clay soil, the soil must be amended. Use 50/50 1″ rounded stone or pebbles to native soil.
  • Soil should have low fertility.
  • Lavender prefers alkaline soil. pH should be 6.5 or higher and is easily measured with a simple soil test (a soil test is not absolutely necessary since typical southern clay benefits from the addition of lime – and a lot of it – to boost and retain an increase in the pH level.)

Lavender is a perennial herb. If you are concerned about winter survival, protect the plants by covering with a straw mulch until the danger of extremely cold temperatures has passed. Be mindful that lavender does not like moist conditions, so planting with sharp drainage is especially crucial if planting lavender in areas that are not appropriate for the growing zone.

If lavender plants are in pots, it will be 15 degrees colder in the pot than if it were planted in the garden. Bring the pot indoors, drag it to a warm side of the house with protection from the winter wind, cover the pot, sink it in the ground and/or wrap the pot. Lavender prefers to be an outdoor plant, with maximum access to sunlight and warmth. Remember that this herb is native to the Mediterranean. Lavender is not a house plant.

SOIL PREP

  1. Create an 18″ – 24″ mound with well cultivated soil and 2 heaping shovelfuls of 1″ round stone worked into the mound. Err on the side of too much stone. May create a French drain by placing fist sized rocks in mound base.
  2. Using a trowel, dig a hole just deep enough for the plant.
  3. Blend together equal parts of bone meal, lime and well composted manure. Add ½ cup in the bottom of hole and mix well. The stone will allow the soil to drain, the lime will improve the pH, bone meal and compost for a healthy start.(Remember that lavender prefers arid conditions, both beneath and above the soil. The humidity in the south will benefit from a light colored, reflective mulch, Since hardwood mulch holds in the moisture, one that encourages excellent drainage and light reflection to keep the plant dry is highly recommended.)

PLANTING & TRANSPLANTING

As long as the soil can be cultivated, plant lavender. You may wish to avoid planting in July, August, December and January. (July and August will require more attention and watering as they establish their root systems and December and January will require tamping down the plants due to soil heaving, exposing the roots to the air leaving them vulnerable to freezing temperatures.) Lots of lavender goes into French lavender fields in February!

LAVENDER IN POTS

Please follow the same instructions for planting lavender in containers. Be sure to know the mature diameter of the lavender and choose an appropriate container. Remember that lavender is shallow rooted, so the pot does not need to be a tall one. Average depth and spread of the root system is 8-10 inches. Excellent drainage is key to success with lavender be it in the ground or in a pot. The pot will need to be watered more frequently in the heat of the summer as they dry out quickly. This could mean nearly every day in July. Keep in mind that lavender prefers to live in the garden or in a pot outdoors. Requiring significant sunlight, it is nearly impossible for them to thrive as a houseplant. So, it is best to find a sunny, well-draining location in the garden, or a pot, for your lavender.

Potted lavender will need to be protected over the winter since it is 15 degrees colder in a pot than in the ground. Please do the following …

1. Drag the pot to a warm side of the house to protect it from winter wind.
2. Wrap the pot with a layer of bubble wrap and burlap or similar.
3. On really cold nights, below 32 degrees, toss an old blanket over it.
4. Or, sink the pot in your compost heap.
5. Or, plant your lavender in the garden!

  • Water your lavender well in its nursery pot every day. Soak it deeply in the evenings, daily until planted, then water again for about an hour before planting, and of course, after as well.
  • Prune the top of the plant to ensure a productive plant.
  • Loosen the roots from the potting soil by working the trowel teeth into the soil block.
  • Place plant just above the blend of stone/ lime / bonemeal / compost, not allowing the roots to touch the blend and gather soil around base of plant. Water deeply.
  • Space largest plants 5 – 6 feet from one another for good air circulation.
  • Lavender blooms at its peak in its third year producing about 1000 stems


'Grosso' Lavender

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'Grosso' Lavender

'Grosso' lavender (Lavandula x intermedia 'Grosso') is a hybrid variety that is a cross between English lavender (Lavandula angustifolia) and broadleaf lavender (Lavandula latifolia). It has both excellent heat and cold tolerance, plus boasts huge flower heads and a rich fragrance.

Include a more heat-tolerant English lavender hybrid in your landscape by planting ‘Grosso’ lavender. This lavender hybrid brings an improvement to traditional English lavender by blending cold hardiness with heat tolerance. ‘Grosso’ lavender also brings flowers that have larger heads, a darker purple hue and intense fragrance.

In botanical-speak, ‘Grosso’ lavender is Lavandula x intermedia ‘Grosso’. That “x” in the name reveals that ‘Grosso’ is a hybrid, the result of breeding two different lavenders. In this case, the parents are English lavender (Lavandula angustifolia) and a Portuguese lavender known as spike or broadleaf lavender (Lavandula latifolia).

Quite a few English lavender hybrids have these plant parents. Collectively, the hybrids are known as lavandins. The list includes ‘Grosso’, ‘Provence’, ‘White Grosso’ and ‘Hidcote Giant’. Lavandins are well-known in gardening circles for their strong garden performance and stems that are covered with long, gray-green leaves that are roughly twice the size of English lavender leaves. These hybrids also stage a heavy flower show.

‘Grosso’ lavender fits this description, opening an impressive number of flowers about midsummer. After the first heavy flush of blooms, plants send up additional flower wands throughout summer. ‘Grosso’ lavender flowers are so prolific and laden with essential oils that it’s the primary commercial variety grown for producing lavender oil.

In the home garden, ‘Grosso’ lavender blooms are favorites for crafting, with flower stems being gathered for lavender wands and bouquets. The strongly scented blossoms make wonderful additions to sachets and potpourris. The purple blooms of ‘Grosso’ lavender not only offer a deeper violet hue, but they’re contained in a bract that’s also purple (instead of green, like other lavenders). That makes these flowers even more desirable for craft purposes.

The rich perfume that ‘Grosso’ lavender blooms offer also works well in culinary applications. Use ‘Grosso’ flowers as you would any other culinary lavender to season desserts and savory dishes, as well as teas and spreads.

‘Grosso’ flower stems are elegantly long, extending far above the mound of silvery leaves. Clip stems of faded flowers to put the foliage in the spotlight. ‘Grosso’ lavender grows to form a mound that’s roughly 24 to 36 inches tall and wide at maturity. The plants tend to be compact, which makes them an ideal choice for a hedge or driveway edging. Just allow plenty of elbow room for the flower stems.

Like other lavenders, ‘Grosso’ thrives in full sun in well-drained, even rocky or sandy soil. This lavandin hybrid tolerates cold and summer humidity, surviving in regions where traditional English lavender cannot. Despite its sturdier nature, ‘Grosso’ won’t survive if it’s shaded or even crowded by other plants. Give it good air flow for best growth. Prune after flowering to shape the plant.


Watch the video: Robertas 6-piece Fat Budded u0026 Bushy Grosso Lavender on QVC


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