UNDERSTANDING THE GROWTH OF HERBS
Herbs are a fantastic addition to your garden beds or containers. With herbs, your amount of gardening experience and the size of your herb garden really don’t matter—you can expect lots of fresh leaves from even the smallest of spaces with minimal tending.
Whether you’re growing herbs from seed or potting up herbs purchased from your local plant nursery, you might be wondering just how long you have to wait before your first leaf harvest.
If you purchased a mature plant, you can begin cutting your first leaves that very same day (just go easy)! But if you’ve sown seeds or placed a cutting in some water to see if it’ll grow roots, you’re in for more of a wait. Just how long that wait will be depends on both the type of herb you’re growing and how you’re growing it.
FACTORS AFFECTING HERB GROWTH TIME
One of the most important factors is the type of herb plants you’re growing.
Annual herbs (any herb that completes its life cycle in a single growing season) like dill typically grow to the point where you can begin harvesting leaves quickly. Perennial herbs (herbs that live more than two years) like rosemary are slower to grow and will need a bit more grow time before harvesting.
Your annual herbs will produce seeds and die at the end of their growing season, while perennial plants can spend years giving you leaves. It’s a bit of a tradeoff. An annual plant gives you quicker harvests but won’t stick around nearly as long in your vegetable garden.
Biennial herbs, like parsley, complete their life cycle in two years and are an interesting compromise in this tradeoff between time to harvest and length of life cycle. Parsley takes about a week longer than its annual cousins dill and cilantro to sprout; the typical time to parsley germination is 2 to 3 weeks, though apparently there are parsley seeds that have taken 60 days! From there, it grows relatively quickly, ready for its first harvest in about 3 months, and will spend up to two years in your garden space before producing seeds.
Other Factors that Affect Herb Growth
Besides herb type, here are some other factors that also affect herb growth:
- Sunlight – Herbs that get more than 4 hours of sunlight per day will grow faster than those in a shadier spot. That’s because sunlight gives them the energy they need to form new leaves.
- Water – Herbs in the mint family come from drier regions and like the top of their soil to dry out a bit before they’re watered again. Dill, cilantro, and parsley prefer a moist soil.
- Soil – Herbs like a well-drained soil with some nutrients. Herbs growing in a more fertile soil, such as potting soil amended with compost, will grow faster.
- Space – Herbs don’t require a lot of space in your garden, but they do feel the effects of being overcrowded. They will slow their growth or become “leggy” (tall and spindly) if their neighbors are too close. Basil plants bought from the store are the perfect example of this. You might think you’re getting one very full basil plant, but in reality, it’s several herbs planted much too close. If you pull them apart and replant, the herbs will grow much faster.
TYPICAL TIMELINE FOR HERB GROWTH
Some herb seeds take longer than typical veggies to germinate, or sprout. Basil seeds typically sprout within a week, while parsley seeds could take up to three weeks. Seeds for a hardy perennial like rosemary, mint, sage, oregano, and thyme typically need between 4 and 14 days.
Herbs that are started by seed indoors about 6 to 8 weeks before your last frost date are typically ready to harvest about 1 month after they’re transplanted outdoors. When I say ready though, I mean very small harvests, just a few leaves at a time. A good rule of thumb is to never cut more than a third of an herb at one time. You could be looking at many months more before your plants are large enough to give you sprigs and sprigs at a time.
HERBS THAT GROW QUICKLY VS HERBS THAT TAKE LONGER
Some of the fastest-growing herbs are basil, cilantro, and dill. Basil (which is actually a tender perennial that we often treat like an annual) takes just 5 to 7 days to germinate (assuming the soil is nice and warm), and you’ll be able to cut your first leaves within about two months, when the plant has grown about 6 to 8 inches tall. Similarly, dill can grow taller than a foot within just a couple months. Thanks to such rapid growth, these are easy herbs to grow from seed yourself.
Mint, thyme, and oregano need a fair amount of time to grow to maturity, but from there, they grow very quickly, as much as 4 inches per month.
Rosemary is known for being one of the slowest-growing herbs. For this reason, it’s a great idea to buy a healthy rosemary plant from your local nursery or root cuttings instead of trying to grow rosemary from seed. The same goes for other perennial and biennial plants if you’re looking for a harvest sooner rather than later.
Perhaps the slowest-growing herb you might want to grow is bay laurel. The seeds spend so long in the soil that many of them rot before they ever germinate, and cuttings require up to 9 months to root. The good news is that once you have a bay laurel plant, it will live for years and grow into a small tree as long as you protect it from frost. (One harsh winter will do it in.)
Keep the speed scale of basil to bay laurel in mind when deciding whether to sow seeds or buy young plants from the store. Herbs that take a long time to grow are worth the investment.
TIPS TO ENCOURAGE FASTER HERB GROWTH
#1 Know Best Soil Temps for Herb Seed Germination
If you’re growing herbs from seed, make sure to keep soil temperature in mind. Some herbs like chamomile and chives actually germinate best when the soil and air temps are a bit on the cooler side. Other herbs, basil in particular, need warmer weather; this is why many gardeners start basil from seed indoors while it’s still cool outside so they can have more control over its environment and move it out as soon as the weather warms.
#2 Choose Correct Planting Depth for Herb Seeds
Another tip when starting herbs from seed is to pay attention to the planting depth noted on the back of the seed package. Many herbs like to feel a little light on their seed coat as they’re germinating. They’ll take much longer to sprout—if they sprout at all—if you cover them with too much soil. Herbs that like light to germinate should just be pressed into the soil instead of covered with more soil.
#3 Pick a Sunny Location to Grow Herbs
If you have mature herbs that you’d like to grow faster, move them to a sunny windowsill (a south-facing window is best) where they will receive full sun, or at least more sun than they’re currently getting. Herbs can survive with as little as 4 hours of sunlight per day, but that will slow their growth. You can still have an indoor herb garden even if you don’t have a sunny spot; you’ll just need to supplement with LED or fluorescent lights that are kept on for 10 to 12 hours a day (light from a grow light isn’t the same as natural light).
#4 Prune Your Herbs Regularly
This last tip might seem a little counterintuitive, but it’s true: Lightly prune your herbs regularly to encourage them to grow bigger. For woodier herbs, that means cutting older and outer stems each week. For herbs like basil, that means tipping, or cutting the tips of each stem just above a leaf node so the plant will grow bushier. “Lightly” is the keyword here. Regular pruning keeps the plant healthy and encourages new growth, but being too heavy handed with the pruners can stunt the herb’s growth.
5 BEST PRACTICES FOR GROWING HERBS
#1: Prioritize Good Drainage
Make sure your pot or container has at least one good drainage hole for your herbs. Root rot is a common problem that can arise when herbs are left sitting in stagnant water and is one of the fastest ways to kill your herbs, or at least make them very unhappy.
#2: Give Herbs Space
Give perennial herbs plenty of room to grow to maturity. Since perennial herbs are plants that can live for many years, it’s important to give them enough space to develop and thrive. By providing ample room for their roots to spread out, these herbs can establish a strong foundation and give you many harvests. Proper spacing can also help prevent overcrowding and promote good airflow, which can reduce the risk of disease and pest infestations.
#3: Provide Enough Light
Make sure your herbs have access to plenty of sun. If you’re growing herbs indoors on a windowsill, it’s important to rotate them regularly (such as every time you water) to prevent them from growing toward the light source. By doing so, you can encourage even growth and prevent your herbs from becoming leggy or spindly.
If you observe water pooling on top of the soil surface before it’s absorbed, it may be time to repot your herbs in a container that has proper drainage holes with some new potting mix. When repotting, use fresh potting soil mixed with construction sand or fill sand to provide a well-draining growing medium for your herbs. The sand will help to loosen the soil, allowing excess water to flow through more easily and preventing it from pooling on the soil surface.
#5: Prune Regularly
Regularly prune your herbs to promote good air circulation around each plant. Adequate airflow is essential, as it can help to prevent the growth of mold, mildew, and other fungal diseases that can harm your herb plants. By pruning your herbs, you thin out the foliage and allow air to circulate more freely around each plant. This will also help to ensure that each herb has access to sufficient sunlight and nutrients.
By the way, when it comes to herbs, pruning is really just harvesting!
PATIENCE AND PERSISTENCE IN HERB GARDENING
Herbs are overall easy to grow and keep alive, but these two qualities—patience and persistence—are key. Good things, after all, take time, and culinary herbs are some of the best good things you can grow. We’re also very fortunate here in Austin in that we can give our perennial herbs some protection from cold snaps and keep them happy and producing all winter long so they don’t die back and have to regrow.
Fresh herbs all year? Now that’s what we signed up for!
Lettuce know if you have any questions about herbs. We’re here to help you grow!