Here’s What you Need to Know to Grow Herbs
If you’ve never had any kind of garden before, herbs are a great place to start. Even if you have a lot of experience growing other plants, here’s what you need to know to grow herbs.
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What’s the difference between perennial herbs and annual herbs?
Herbs (or any plant, really) that remain in the ground and either maintain foliage or re-grow foliage each year are perennial. In many cases, they will increase in size each year until they reach the limits of their planting location or hit the maximum size for their variety.
Annual herbs will generally only grow for one season. While they can (and do!) drop seeds which germinate and grow in the same spot year after year, the plants are new each season.
It’s very important to realize that for many herbs, whether it grows as an annual or a perennial is determined by the climate. This is commonly referred to as a growing zone, which is broad and not very precise term. Even within a growing zone there are microclimates and that can impact how an herb will perform. Microclimates can exist even within a garden or yard. In many cases, it will take a few growing seasons before you fully understand the microclimate of your own particular garden.
Why does it matter if an herb is an annual or a perennial in my zone?
There are a few reasons you need to worry about this. The first is because, given sufficient space, a perennial herb will keep growing. That means the cute little rosemary plant you put in the ground can potentially grow to a 4 foot tall shrub in a few years. Now that can be a great thing but it’s definitely something you want to plan for in advance. The second reason this matters is because you don’t want to invest in what you assume are long-living herb plants only to have them all die off at the end of the summer.
Finally, herbs that grow as annuals in your area will spend the whole season trying desperately to make flowers. Producing flowers leads to the production of seeds, which is the plant’s primary purpose. This isn’t bad, per se, but once an annual flowers, it generally puts all of its energy there and the foliage may wither and even die off. The flavor of the leaves typically changes, often for the worse, once the herb flowers. To ensure a continuing harvest, it’s important to keep pinching or cutting off leaves so the plant can’t produce flowers. If you want to harvest seeds at the end of the season, you can keep pinching the plant back (and enjoying the delicious leaves!) until you’re ready to let it set seeds.
Note that some annuals are inherently short lived, and even with regular harvesting will still complete the full cycle. Others will grow well in the cooler spring or fall weather but ‘bolt’ to flowering and seed setting as soon as the temperature starts to climb. Look for varieties (more on that below) that are especially suited to the seasonal temperature patterns of your area to minimize this and/or plan to sow multiple rounds of plants.
Two more points about perennial and annual herbs:
Although many herbs ARE perennials in a lot of places, you don’t have to grow them as perennials. If space is a concern or you’re not sure your garden is well-suited to overwinter plants, you can simply regard all of your herbs as annuals and plan to put new plants in each year. This isn’t necessarily the most cost effective way to garden but it can be more manageable in some cases.
Even though an herb is perennial, it can, of course, still die due to disease, drought or harsher than usual winter conditions. Or sometimes for seemingly no reason at all. And although perennials live longer than annuals, they do still have lifespans, which can range from 2 years to decades. Here again, research is the key to selecting the best option for your growing space, needs and microclimate.
There a lots of different varieties of most herbs
This is one of the things you need to know to grow herbs successfully. Beyond the very broad “perennial or annual” categorization, herbs also have cultivators. These are different varieties of the plant that have either been selectively bred for certain characteristics or have evolved naturally. Common selected varietal characteristics are taste, aroma, zone hardiness, size, height and drought tolerance.
Why does it matter which cultivator an herb is?
In the broadest sense, it doesn’t. If your goal is to grow ‘basil’ then you might be equally happy growing Genovese or Sweet. But you would probably be surprised by the flavor of Thai basil compared to either of those. And Tulsi basil is even more dissimilar – though wonderful and something you should definitely consider growing!
‘Hardy Hill’ and ‘Arp’ rosemary are both cold hardy varieties, which makes them far better suited to zones 6 and colder than other types. French lavenders (like Provence) and English lavenders (like Munstead) have distinctly different flowers and aromas. Within those types, some are specifically bred for colder, wetter climates (like the ‘Grosso’ or ‘Phenomenal’ varietals).
Finally, some cultivators are designed to bloom earlier or later, or to have a heavier yield of flowers. Some are intended to grow well in compact areas, like containers or small spaces. And some are better able to tolerate more soil conditions.
So although your goal might be to simply grow common culinary herbs like basil, thyme, rosemary and mint, understanding the options available and how they will fare in your zone and garden can make a big difference in how well the herbs grow. And in whether you get your intended use from them.
So how do I know which variety of herbs to grow?
The best thing to do is examine your growing area, including frost dates, high and low temperatures, average sun, typical rainfall and soil type (sandy, loamy, clay, container). Then consider what you most want out of the herb. Is it a specific flavor? A particular size or shape? Are you growing for aroma or essential oils? Do you want to grow the plant as a perennial? Are you planning to harvest a lot of the plant parts?
All of these will determine the best variety or varieties for you to grow. And you can grow more than one variety of an herb, if you have room for it.
Different parts of herb plants serve different purposes
And the time of day and year you harvest those parts makes a big difference in the properties of the plant!
Some herbs bring to mind distinct things – the pungent scent and flavor of mints, rosemary’s crisp, piney flavor or lavender’s purple flowers and aroma. On a basic level, any part of most herbs will bring the signature flavor or scent of the plant. But for certain uses, you’ll need to harvest the correct part of the plant at the correct time.
Using all the parts of the plant – but make sure it’s the right part for the job
Take fennel. It’s feathery leaves have a distinct licorice flavor that makes it a popular culinary herb. And so do the flowers. If your only goal in growing fennel is to sprinkle a bit on fish, then snip off whatever is convenient. But the leaves will change flavor once the plant has flowered. And the bulb, aka the root, can be harvested, cooked and eaten and offers a completely different flavor. In order to maximize your fennel harvest, you need to know if your priority is a supply of fresh leaves, a big harvest of flowers to dry or the bulb.
Chamomile, which has both an annual (Roman) and perennial (German) variety, produces gorgeous green foliage that smells wonderful. But it’s the flowers that make the tea. So in this case, you’d want it to flower and you’d harvest them to dry. Conversely, mint tea is made from dried leaves, and once mint flowers, the leaves can lose the desired flavor.
Growing herbs for tinctures or infusions
If you’re growing an herb in order to make infusions or tinctures, it’s often necessary to use the stems, and sometimes the roots, to fully harness the herb’s properties (whether for medicinal or culinary use). Generally, harvesting too much of an herb’s leaves and stems will kill the plant, as will digging up and harvesting the roots or tubers. In order to have enough plants to take stems or roots, you should plan for more plants, and be prepared to put replacements in the ground for next year. Luckily, herbs are very easy to propagate.
To learn more about growing and using medicinal herbs, check out
Growing herbs for simple kitchen use
For a simple culinary herb garden, you can usually just snip off bits of leaves or flowers as needed. Regular, minimal harvesting won’t harm most herbs, and can actually be beneficial to some, like basil. Basil, like most annual herbs, must have leaves pinched off regularly in order to keep the plant producing leaves instead of going to seed. Small, routine harvests will keep perennial herbs like rosemary or thyme from flowering. Though the flowers are pretty and edible, once an herb flowers, the leaves can change flavor and even become bitter.
For best flavor, harvest herbs early in the day.
Growing herbs to dry or preserve
Though nothing beats the flavor of freshly harvested herbs, you may want to dry, freeze or otherwise preserve some herbs for the colder months. Dried or frozen herbs take up less space than fresh herbs and their flavor is more concentrated. It’s possible, however, to pick a massive pile of fresh leaves, dry them and discover they only yield a couple of tablespoons. If you plan to put up herbs, especially enough to get your through the cold season, it’s best to grow several extra plants.
To ensure the maximum flavor, harvest first thing in the morning and don’t rinse the herbs unless there is visible dirt or other soiling on the plants. Learn more about drying herbs and preserving herbs through butter, oil or salt.
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