Spring Care of Overwintering Herbs
Answered by: Richters Staff
Question from: Penny Parr Eccles
Posted: Before April 1998

The year before last (I think) I successfully grew some lavender from seed. I transplanted it outside and it survived. Last year it bloomed. I am wondering if there is something I should be doing to it in the spring. Should I be cutting it back as I do with other perennials??

First of all, not all lavenders are winter hardy. The hardiest lavenders are what are called the ‘English’ lavenders. Botanically, these are known as Lavandula angustifolia, or sometimes in older books as L. vera or L. officinalis. There are many varieties of English lavender, such as ‘Munstead’, ‘Hidcote’, and the 1994 All-America winner, ‘Lady’. The flowers of the English types are known for their fine fragrance.

The commercial lavender industry prefers to grow a hybrid called ‘lavandin’ because the English lavenders are susceptible to disease and are generally lower in oil yields. Lavandin is thought to be a cross between the English types and another species called ‘spike lavender’ (L. spica). The botanical name is L. x intermedia, where the ‘x’ refers to its hybrid parentage. The flower and oil yields of these lavenders are enormous, but the quality of the oil is lower because of the resinous influence of spike lavender. There are several strains available, such as ‘Provence’ and ‘Grosso’. Since spike lavender is not hardy in our area (zone 5) we were surprised to discover that at least one lavandin strain, ‘Provence’, is perfectly hardy in our area.

There are many other Lavandula species in cultivation, all of which are not hardy in zones 5 or lower. These include the spike lavender already mentioned as well as French (L. stoechas), Spanish (L. dentata), sweet (L. heterophylla), woolly (L. lanata) and fernleaf (L. multifida) lavenders. All of these tend to be grown for their strongly scented leaves and not for their flowers. The oils from these are not used for perfumery because they are ‘coarser’ and more ‘piney’ compared to oils from the English types and the lavandins; but since English lavenders and lavandins do not normally flower indoors, their fragrant leaves make these other varieties very desirable for indoor gardens.

At risk of confusing most casual herb gardeners who just want a basic good lavender for the garden, let me recommend the generic ‘English’ lavender or possibly English cultivars like ‘Munstead’ and ‘Hidcote’. These perform admirably in temperate zones.

One word of caution: the famed All-America winner, ‘Lady’ lavender is not as hardy as other English types. Some experts are beginning to think of ‘Lady’ as better suited as an annual, not a perennial. It is a wonderful variety that flowers reliably the first season from seed while other English types require two years to start flowering. It also flowers more abundantly. Certainly, the commercial potplant growers like this variety because it grows quickly from seed and can easily be produced for the spring bedding plant market.

Now to the question of pruning overwintering lavenders. We prefer to wait until spring when we see new growth appearing at the bases of the plants and along the overwintering woody branches. Cut back the dead branches and trim the live branches back by about a third. The pruning should be done with an eye to shaping the plants to whatever shape your landscaping aesthetic demands. Do not cutback too much otherwise flower production will suffer.

Older lavender plants can get quite crowded. It is a good idea to thin some of the oldest branches out, otherwise various diseases can cause rot in the centre and eventually death of the plant. Deaths of this sort commonly occur over winter.

I also have a rosemary which survived the winter. Do I cut that back?? Fertlize or anything?

You are obviously located in a zone warmer than our zone 5, because we cannot winter rosemary at all. Probably the lower limit for rosemary is zone 7, with some people reporting success in zone 6. The rosemary variety ‘Arp’ is the hardiest variety we carry, often persisting through winters outdoors. The plant dies back to the ground and new growth starts from the roots in the colder zones. In warmer zones like 7-9 rosemary does not die back to the ground and it then becomes necessary to prune the overwintering branches in spring much like lavender.

We recommend a high nitrogen fertilizer, such as bloodmeal or well-rotted manure applied to the base of the plant in spring, after new growth appears.

Last but not least I have a sage plant that was transplanted last fall and which looks a bit droopy. Should this be cut back as I would do with most of my perennials.

The droopy leaves are dead, so remove them. New growth will come from the base and branches like lavender and you would prune it the same way. Since sage is suceptible to centre rot, it is a good idea to divide the plants every three years.

I guess the over-riding question for all of these is ... what should I have done last fall. And since I didn’t do anything and now have plants with old foliage on them, should I be cutting them back and giving them anything to spruce them up.

Since you are in a warm zone, not much is necessary. You can do some of the pruning (cutting back by a third) after the killing frosts, but it is not really necessary. For gardeners in colder zones, from 7 or lower, a winter mulch may be necessary depending on the herb in question. Certainly, those trying to grow lavender, rosemary and sage in the coldest zones must mulch. Dead leaves or straw make good mulches. We like to apply the winter mulch after the ground is frozen but before the first permanent snow fall. About 15 cm (6") is adequate.

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