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Lavenders in gardens come from three main lines: English lavender, the lavandins that are its hybrid with spike lavender, and the French or Spanish group with the tufted flower heads. They look similar enough on a nursery bench that people buy them interchangeably, then treat them all the same way and lose the tender ones over winter.
You can tell them apart at flowering without knowing a single name. English lavender has short flower stalks and a plain, narrow flower spike. Lavandin has long stalks, often eighteen inches (45 cm) or more, and a longer spike that opens later. The French and Spanish group carry a squat, pineapple-shaped head with two or four upright colored bracts sticking out of the top like rabbit ears.
| Group | Flower head | Cold it takes | Main flowering |
|---|---|---|---|
| English lavender | Short stalk, plain narrow spike | Down to about minus 15F (minus 26C) | Early to mid summer, often again in late summer |
| Lavandin | Long stalk, long spike, strong scent | Down to about 5F (minus 15C) | Mid to late summer, one flush |
| French and Spanish | Squat head with upright bracts on top | Down to about 20F (minus 7C) | Spring, then on and off until autumn |
| Fringed and woolly types | Loose spike, gray cut or felted leaves | Not below about 30F (minus 1C) | Almost continuous in frost-free conditions |
English lavender is the hardy, forgiving one
English lavender is the group to grow if your winter drops below 20F (minus 7C). It comes through hard frost in the open ground, and unlike the others it will often give a second, smaller flush in late summer if you cut the first flowers off promptly.
It is also the group that stays compact longest. Plants sit at twelve to twenty-four inches (30 to 60 cm) tall and wide, which means a single yearly hard trim is enough to hold them in shape. The flower color on this group ranges from deep violet through pink to white, and the paler forms are usually a little weaker growing, so give them the driest, sunniest position you have.
Hardiness figures assume sharp drainage. The same plant that survives minus 10F (minus 23C) on a gravelly slope dies at 25F (minus 4C) sitting in wet clay. Cold rarely kills lavender on its own.
Lavandin is the big, late, strongly scented one
Lavandins are the ones grown commercially for oil, and in a garden they are the largest of the three groups, often three feet (90 cm) across within a few seasons. The flower stalks are long and straight, which makes them the group to grow if you want bunches to dry. The scent is sharper and more camphorous than English lavender, because of the spike lavender parentage.
The trade-off is a slightly shorter cold limit and a single flowering. Once the flush is over, no amount of deadheading brings a second one, so the late summer cut is about shaping the plant for next year rather than chasing more flowers. Because they are big and vigorous, lavandins also go woody and open faster than English lavender if you skip a year of pruning.
French and Spanish lavender flower first and freeze first
The tufted group starts flowering weeks before the others, often as soon as spring warms up, and carries on in flushes into autumn if you keep cutting the spent heads off. That long season is why they sell so well in spring, and why so many are dead by the following spring.
They are the least hardy of the common types. Below about 20F (minus 7C) they are at risk, and a wet winter at that temperature will finish them. In a cold area, grow them in pots and move them into an unheated but bright frost-free space for the winter rather than fighting the ground. They also flower on new growth in a way the others do not, so light trimming through the season keeps them going instead of setting them back.
Choose by winter first, pruning nerve second
Decide which group you can grow before you look at flower color. Start from your coldest normal winter night, subtract the effect of wet soil, and only then pick on looks. If you already have plants and do not know what they are, note the flower shape and the week they open, and you will know by the end of one season.
This is the one thing worth writing down early. Record which plant is where, what its flower head looked like, and the date it opened. Two seasons of that and you will know without guessing which plants need a spring check for frost damage, which need cutting in late summer, and which ones to lift into shelter before the first hard frost.
- Look at the head, not the leaf Leaves overlap too much between groups to be reliable. The flower head separates them in one glance: bracts sticking up on top means the French and Spanish group, a long bare stalk means lavandin, a short stalk means English lavender.
- Note the opening date The order of flowering is fixed. Whichever plant opens first in your garden is in the tufted group, the last to open is a lavandin. Recording the date once settles the identity permanently.
- Match the group to the position Put the hardy English types in the open ground, keep the tufted types in pots or against a warm wall, and give lavandins the space they will actually fill so you are not cutting them back hard to make room.