How Much and How Often Should You Water Rosemary?
Did you recently bring rosemary into your garden, but aren't sure how much water it needs or how often you should be watering? In this article, gardening expert and former organic farmer Logan Hailey shares exactly how much moisture your rosemary plants need.
Rosemary is a resilient herb with a bold fragrance and an array of culinary uses. Known for its drought tolerance and pest-repellent properties, rosemary is also easy to grow in the garden. It doesn’t require much fertilizer or attention, but it does have specific preferences regarding soil and irrigation.
As a native to the Mediterranean coastline, rosemary enjoys dry, hot summers and wet, mild winters. However, it is also highly adaptable to hardiness zones 7 to 11, as well as indoor growing.
As long as rosemary has sunshine and well-drained soil, this tender perennial only needs occasional watering. Whether you’re growing in a pot or outdoors, here is everything you need to know about watering rosemary.
The Quick Answer
The easiest rule of thumb with rosemary is to only water when the top inch of soil feels dry to the touch. With most perennial herbs, there isn’t an exact interval for watering. Instead, you need to use your hands to feel the soil and assess the moisture level. Wait until the soil dries out before watering again.
Like its cousins lavender and sage, rosemary absolutely despises having “wet feet.” A soggy, saturated root zone is this herb’s worst nightmare! That’s why overwatering is often the biggest problem with this drought-tolerant herb.
The Detailed Answer
In general, rosemary is not a thirsty or needy plant. You should only water it when the soil feels dry or the plant appears slightly droopy.
However, remember that these two symptoms need to show up together; if the soil is soggy and the plant appears wilted, it could be caused by overwatering and/or root rot.
Beginner gardeners are more likely to struggle with overwatering than underwatering. When in doubt, let the herb enjoy periods of dry soil.
Here are a few more scenario-dependent guidelines for watering rosemary:
|Container Rosemary||For container-grown plants, water 1 to 2 times per week when the top inch of soil is dry. Container plants need more water than those planted outdoors.|
|New Transplants||Water newly transplants and freshly propagated rosemary cuttings every few days during the first 1 to 2 weeks to help it get established.|
|Wet Regions||If your region gets regular rainfall throughout the season, mature plants likely won’t need irrigation.|
|Dry Regions||If you live in a dry region, give rosemary a deep watering just 3 or 4 times per summer. It only needs moisture during the hottest, longest droughts.|
|Clay Soils||If you are growing in heavy soil with high clay content, your plant may rarely need water. In fact, it probably needs more drainage! Add horticultural sand, gravel, or vermiculite, and only water once or twice during the driest months of the year.|
Irrigating this tender perennial has some nuances based on your garden location and the plant’s life stage. For a more detailed growing guide on rosemary from start to finish, check out the video below.
Plant Age: Young Plants Need More Water
Like most perennials, rosemary needs the most water when it’s young. Fresh transplanted plants need more frequent watering than grown shrubs.
Provide young plants with water every 2 to 3 days during the first week or so after planting. The plant needs this water to fuel its root establishment and prevent transplant shock.
However, you should still be very careful not to overwater. Check that the soil is never soggy or oversaturated for long periods of time. Young plants can quickly succumb to root rot. The easiest prevention is proper soil preparation, as described below.
Beware not to continue watering after the initial transplant adjustment phase is complete. Ease off the watering in the second week and observe.
The plant should look perky, robust, and able to withstand longer droughts. Think of weaning a baby off of milk; slowly reduce your watering frequency and let the herb dig for water on its own, just like it learned in the wild.
Once the shrubs mature and adjust to a new planting area, they rarely need water in most U.S. climate zones.
Climate: Wet Regions Need Less Water
Rosemary’s deep roots help it withstand long periods without water. It is often grown as a shrubby landscape plant without irrigation. It especially thrives in all areas of California, where the plants can grow to 7 feet tall! These regions most closely mimic rosemary’s Mediterranean home with hot, dry summers and rainy, mild winters.
Gardeners in moderate to dry climates only need to water a few times per year once the plant is established. Yes, per year! Commercial rosemary farmers rarely irrigate.
In areas with hot summers and no rainfall, farmers may only irrigate 3 to 4 times during the summer. On the other hand, if your region gets regular rainfall throughout the year, you may not ever need to water. In warmer zones of the southern and eastern states, summer rains provide plenty of moisture for this herb.
For most gardeners, it is not necessary to install an irrigation system around rosemary plants. Because these plants so rarely need water, I have found it is much easier to water with a hose.
Plant rosemary alongside lavender, sage, thyme, and oregano for a drought-tolerant rock garden that you can water all at once on the rare occasions that these Mediterranean natives need an extra boost. Save your drip lines for the vegetables and thirsty perennials like roses.
Season: Water More Frequently in Summer
Scorching summers are the only time when mature outdoor plants need irrigation. Indoor pots will require the most frequent watering (up to twice per week) during the brightest, warmest months.
But you should lay off the watering can in the winter. Rosemary is most susceptible to root rot during the winter, especially in a container! No matter the location, it’s best to reduce or stop watering all rosemary plants during the winter months.
The plant typically slows its growth or goes dormant, so very little water is needed. Potted plants are also more subject to root rot during the cool, less sunny winter months. Outdoor rosemary is likely getting its share of moisture from winter rainfall.
Seasonal fluctuations in rainfall will also affect your rosemary’s needs. During rainy summers in the south, you probably won’t need to water at all. And even when there hasn’t been rain, you should pay attention to the leftover moisture from a rainy spring.
For example, the Pacific Northwest receives a lot of rainfall in the winter and spring. The soil tends to be more clay-like, which means it holds onto lots of water.
Rosemary’s roots can dig deep into the soil and access those soaked soil layers to sustain it through most of the spring and early summer. The plant usually needs sparse watering only during the driest parts of late summer and early autumn.
If you are growing rosemary indoors, you will need to water it once or twice a week during the summer months. When herbs are grown in containers, their roots are unable to reach deeper into the soil for extra moisture. In the winter, cut back to once a week only when the soil feels dry.
Soil: Let Soil Dry Out Between Waterings
While all of the above factors are important, proper soil preparation is the easiest way to ensure that plants don’t get too much or too little water. The frequency and volume of water are highly dependent on the soil that this herb is growing in.
As a Mediterranean plant, it naturally prefers very well-drained soil that is sandy or gravelly. Water should be able to move through the root zone fairly quickly and never “pool up” at the base.
Properly prepare your soil by:
- Double digging and loosening the surrounding areas
- Amending with pea gravel, limestone gravel, or horticultural sand
- Mixing perlite, vermiculite, grit, and/or horticultural sand with heavy clay soils
- Adding a small amount of low-fertility compost (avoid anything with manure because high nitrogen can actually harm rosemary)
In a container, a succulent or Mediterranean soil mix and a breathable pot are key. Choose a well-drained soil with lots of pumice, gravel, or perlite. Opt for a natural earthen pot like clay or terracotta.
It is especially important that the pot has a hole at the bottom where the water can escape into a catchment tray. Without a drainage hole, the soil can become stagnant and soggy at the bottom of the pot. This is the most common cause of root rot in potted rosemary.
Water Stress Symptoms
If you are unsure about your plant’s water needs, pay attention to the signs it is showing you. Sometimes overwatering and underwatering can look similar, so here are a few ways to differentiate between them:
|Wilting leaves or drooping stems that look dry||Wilted, soft stems with a yellowing appearance|
|Top few inches of soil feels very dry||Soil feels soggy and wet|
|Brown leaves that look twiggy and brittle||Brown tips and leaves that eventually turn black with a diseased appearance|
|Dry, hardened roots||Foul-smelling, rotten roots|
The most important thing to remember about rosemary is that it doesn’t want to sit in water. Give it a generous soak, then let the soil dry out before you water it again. Rosemary is naturally drought-resistant, but if the weather is extra hot and dry, you can give it a boost with a generous watering a few times per season.