How to propagate herbs and other perennial plants
One of the coolest things about growing perennial plants, like herbs and flowers, is that it’s really easy to make more of them! Here’s how to propagate perennial herbs to make your garden bigger or increase your harvest. While I’m focusing on herbs (because herbs are my thing) in this post, these propagation methods apply to all perennials.
Propagating just means using some part of an existing plant to create a new, independent plant. There are three ways to propagate perennials – taking cuttings, layering and division. Some of the methods work better for some plants than others.
Collecting seeds and planting them is also a way to make more plants, but I’m focusing solely on propagation by splitting, rooting and cuttings for this post.
Growing perennial herbs and flowers
Many herbs are perennials, which means they come back year after year in most growing zones. Perennial plants are simply plants that die back in the fall and become dormant over the winter. Herbaceous perennials are leafy and typically lose most or all of their foliage after a hard freeze or two. Woody or shrubby perennials lose their leafy foliage as winter sets in but their bare branches remain above ground. Many gardeners plant leafy and shrubby perennials together so they have at least some ‘winter interest’ from the shrub’s branches.
In the spring, perennials begin to create new foliage as the weather warms up. By summer, the plant is the same size, or larger, and covered with new growth.
It’s very easy to grow completely new plants from perennials you (or friends or family members) are already growing.
Growing annual flowers and herbs
Some herbs, like basil, are annual in many places, meaning they live only one growing season. But because they can grow so vigorously, these non-perennial herbs can be very easy to propagate during their short life. Therefore, I’ve included those in this guide. But even if you are able to propagate annuals during the growing season, the new plants will still die at the end of their growing season. They’re simply intended to live only a few months, at least in many growing zones. In most cases, you’ll need to buy new plants the following year or start them from seeds. That’s outside the scope of this post but I wanted to clarify the difference between growing perennials and growing annuals.
For further information on basil propagation, check out Making More Basil.
Keep in mind that most perennial plants want to spread and replicate themselves. Some even NEED to be divided every so often to maintain vigor. Knowing this, it’s better to start with just a few plants and a plan to turn them into more. You’ll save money and you won’t run out of garden space as quickly.
HOW TO PROPAGATE PERENNIAL HERBS WITH CUTTINGS:
Many plants will happily grow roots from a single cut stem or stalk. Generally referred to as ‘taking a cutting’, this is one of the easiest ways to create new plants.
For best results, take cuttings from established perennials that have at least one full growing season under their belts.
Once the plant has started to grow in the spring, it’s ready to donate a cutting. Clip off a small section, at least 3-5 inches tall. This is best done just above where two stems fork. Use clean, sterilized pruners or scissors.
Seasonal Timing – when to take perennial cuttings
Both spring and fall are great times to take cuttings to propagate perennials. Early in the year, it’s best to take the cuttings from new growth on the plant. Later in the season, you can take cuttings from new or older growth. Old growth is typically woodier and usually takes longer to produce roots but can ultimately make a stronger new plant.
Can you take cuttings for propagation in the summer?
While you can take cuttings for propagation in the summer, doing so can stress the plant. Taking a cutting during active growth will also limit the production of fruit or flowers, which can be real drawback for some plants. Cuttings taken in the middle of summer will also need more water and to be more carefully tended. While mid-summer isn’t the ideal time to take cuttings, you CAN do so and propagate new plants successfully – just be prepared to baby those new plants for a few months.
How to use cuttings for propagation in soil
After you’ve taken the cutting, remove most of the foliage along the stem. This allows the plant to focus energy on making roots instead of supporting leaves. Leave at least two pair of leaves, however, as the plant needs to be able to photosynthesize. Plant the cutting in a small container filled with moist soil. Be sure to bury at least 2-3 inches of stem to help new roots form. The buried stem will develop new roots over time. Keep the soil moist and keep the container out of direct sunlight. Cuttings are vulnerable, especially in the first week or two. Too much sun or extreme temperatures will kill them before their roots can establish.
The advantage to rooting cuttings in a container is that it’s easy to move the container to keep the fragile cutting out of harsh weather or searing sun. You can also optimize the soil to make root development easier for the cutting.
Make sure the soil is tightly packed around the cutting. If the cutting isn’t in contact with the soil, it won’t form vigorous roots.
The best soil for propagation of cuttings
I make my own propagation soil mix by using 1 part coconut coir (an awesome product that’s more environmentally friendly than peat moss) and 1 part horticultural vermiculite, plus a scoop of my worm compost. Coconut coir holds moisture well, which is very important for developing roots. The vermiculite ensures air can circulate and that water can pass through easily. While it’s important for the soil to stay moist, it’s equally important water can’t build up. Standing water can rot the cutting. The worm compost also helps retain moisture and provides nutrients to the growing plant.
This is the same soil I use for seed starting, by the way. If you don’t want to mix up your own garden soil, buy a bag of soil labeled for ‘container use’ at your local garden center. Strictly speaking, you can make cuttings root in just about any type of soil but using loose, well-draining soil will make it easier for the roots to develop.
Why make your own garden soil?
Creating your own garden soil allows you to control every component and customize the soil to your needs. Mix more coir in if you’re concerned about plants drying out. Use more vermiculite if drainage is important. Add a little more compost for plants that are heavy feeders.
And in larger quantities, buying the components and making your own soil is usually cheaper than bags from the garden center.
What perennials can be propagated with cuttings?
Honestly, most of them. If the perennial grows into stems, branches or vines, it will likely form roots on cuttings. Here’s a short, incomplete list – hydrangeas, anything in the mint family, tarragon, thyme, rosemary, lavender, honeysuckle*, many deciduous shrubs, sage, Russian sage, yarrow, chamomile, milkweed and some roses.
Perennials that grow from a central, leafy rosette, taproot or rhizome will be difficult, if not impossible, to propagate via cutting. These includes things like hostas, lilies, spiderwort, chives, parsley (actually a biennial) and bronze fennel.
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Propagating plants in water
It’s also possible to root cuttings in water. Take the cutting as described above and simply plunk it into a glass of water. Keep the water fresh and abundant and the cutting will eventually develop roots.
Is it better to root cuttings in water or soil?
It depends on the plant, honestly. Some people feel that plants develop better roots and are generally stronger if they are rooted in soil instead of water.
In my experience, basil and oregano both love to make new roots in water and do so quickly. Thyme and rosemary, and other plants with thicker, woodier stems, seem more resistant to rooting in water. It is possible but it takes a lot longer. Since most woody plants are happy to make roots wherever their stems have contact with soil, I choose the path of least resistance and propagate stiff stemmed and woody plants in soil.
The benefit to rooting in water is that you can tell if the plant is making new roots. It’s also very easy to simply stick a cutting in a glass and wait.
A big benefit to rooting cuttings in soil is that transplanting the new plant is less stressful. The roots won’t be as disturbed because you can scoop out the soil and put it straight into the hole you’ve dug.
Knowing when the new plant is ready to go in the ground
Whether you use water or soil, wait to see new growth develop on the plant before moving it to the garden. New growth is a sure sign the plant has formed roots and that the roots are working to take up nutrients. Think of new growth as a literal green light to transplant!
Note that many people use rooting hormone when putting cuttings into soil. This is an inexpensive powder that can help roots form more quickly. It’s helpful but not at all essential. Try it and see if you like it, but if you don’t have any, go right ahead and root your cuttings without it.
If you root cuttings in soil:
Keep in mind that the rate of new root development will vary from plant to plant. Woodier plants, like thyme, rosemary or lavender typically take longer to start making roots. By contrast, plants like oregano, mint and chamomile both form new roots very quickly. The best course of action is to take several cuttings and carefully monitor their development.
HOW TO PROPAGATE PERENNIAL HERBS BY LAYERING EXISTING PLANTS:
Layering, is very similar to taking cuttings, but with a key difference. The section of plant you are rooting isn’t cut off of the original plant. Instead, you take a small branch, stem or section of the parent plant, bend it gently over to the soil and then cover it with more soil.
Remove any growth from the section you’re burying so it doesn’t rot. Leave the growth on the end of the section intact.
The parent plant continues to provide nourishment for the section, but the soil around it encourages it to make roots. Once the section starts to make new growth and resists being (gently) tugged, assume it’s made roots. At that point, cut the section off just before the buried portion, carefully dig the section up and admire your new plant!
Seasonal timing for propagation by layering
What’s great about layering is that the parent plant does most of the work in nourishing the section. That means you can do this at any point in the growing season. The buried section doesn’t need special care or extra watering. If you aren’t ready to remove and transplant the new plant, you can even leave it on the parent plant over the winter.
What to know about propagating perennials by layering
The biggest drawback to using layering for propagation is that you have to work with a section of plant that is low to the ground or otherwise easy to force (gently) into contact with soil. There’s also a limit to how many pieces you can try to root at a time, since space usually ends up being a concern. This method can also take longer. But if you’ve got time and a little extra room around your parent plant, this is a great way to start new plants. Layering is a great way to turn existing plants into a dense hedge, too.
Which perennials can be propagated by layering
Layering works great for propagating woody plants like rosemary, lavender, or thyme. Plants that spread by sending out runners are already using layering, so it’s a given that oregano, mints, Roman chamomile and other creeping or ground covering plants can be propagated with layering. Tarragon will also make roots via layering.
It’s not a good choice for plants with very rigid, upright stems or plants that are large and leafy.
While it’s often easiest to bury the section in the ground, you can also put a pot full of soil next to the parent plant and bury the section in that. Using this method of layering makes it easier to propagate taller plants and herbs.
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HOW TO PROPAGATE PERENNIALS BY DIVISION:
This is the most violent way of making more plants but it’s also very effective! One simply takes an existing plant and splits it into chunks. The chunks get planted in new holes. In no time at all, each split piece of plant will grow and become a new, full-sized plant.
The other methods can be used on younger plants, but a plant should be mature and well-established before being divided. For most plants, that means at least two full growing seasons. The parent plant needs to have ample, healthy roots and foliage in order to survive the process.
Seasonal timing – when to divide perennials
Division should be done only at the beginning of the growing season or the very end. It’s very stressful for the parent plant, so it’s best to avoid extreme temperatures or expected dry periods.
If possible, plan to divide and plant your perennials just before rain. The cloudy sky and extra moisture can help them recover and establish.
How to divide perennials
Most of the time, you have to dig the parent plant up completely, even if you intend to leave part of it in the same spot. Water the plant thoroughly the day before division. If it’s been very dry, it’s best to give supplemental water for a few days in advance of division and a couple of hours before digging the plant up. Once the plant and its roots are unearthed, use a sharp shovel, shears or a knife to cut the root system in two. Some plants with softer growth and roots can be pulled apart, but older, tougher plants will require a tool.
The goal is to separate the plant quickly and cleanly, with the least amount of damage to the roots. Some roots WILL end up severed or damaged, but the majority need to survive intact in order for the plants to survive. Work quickly. The longer the plants are out of the soil, the harder it will be for them to recover.
It’s best to divide plants early in the day when temperatures are mild. All of the plants need to go back into soil as fast as possible, so dig the planting holes or fill the containers before you dig up the parent plant.
Planting the new sections of divided perennials
Dig a hole that is large enough to accommodate the entire root ball or structure. If your soil is very compacted or heavy clay, loosen the soil around the planting hole. If appropriate for the plant in question, work in compost or organic matter before putting the new plant in the hole.
Quickly, but carefully, put the roots into the hole, fill solidly with soil and then water thoroughly. Even if it’s raining, give the new plant water. It will settle the soil around the roots and help the plant recover. If possible spread a little mulch over the soil around the new plant to keep soil temperature more consistent and conserve moisture.
Water the new plants daily the first week or two. Division is very stressful for plants and stressed out plants can’t tolerate dry conditions or harsh weather the way other plants do. The newly divided plants will look rough for awhile. In some cases, it will take a full growing season for them to fully recover and start making robust new growth. The bigger and healthier the parent plant, the faster all of the plants will recover.
Should you divide damaged perennials?
No. Don’t divide a plant unless it’s very healthy. An unhealthy or diseased plant may not survive the stress of division. Worse, dividing a diseased plant can spread the disease.
If a plant is wilted or has a lot of discolored leaves or has sun scald or other damage, don’t divide it. Figure out what’s causing the damage. If it’s a nutritional deficit, amend the soil or apply fertilizers to help the plant recover. Do not divide the plant until it has regained its full health, which may take a full season.
If the issues are from disease or pests, you may be able to ‘cure’ the problem by removing damaged foliage or applying topical remedies*. Some plant diseases, like asters yellow and other forms of bacterial disease can’t be cured, however. The only way to remedy those types of plant disease is to remove the plant entirely.
*if you must use insecticides or fungal remedies, please do so sparingly and use the least aggressive option possible. Too often, gardeners reach for harsh chemicals which harm beneficial insects, birds, and the soil itself.
What happens after re-planting
Once the plants have been divided and planted, they’ll need to be carefully monitored. Don’t be shocked if they collapse limply within a couple of hours. Being dug up, severed and reburied takes a lot of out of a plant! Within a day or two, they’ll perk back up, provided you keep them watered and avoid doing this in hot weather.
If you are dividing plants at the end of the growing season, sheer back the top third of new growth before you dig the parent plant up. A haircut means there’s less foliage for the plant to support while its roots recover from the indignity of being cut and replanted.
Benefits of propagating perennials by division
What’s great about dividing plants is that you immediately double your plants, at least. Very large plants can be split into three or four new plants, but the parent plant should several years old and have a substantial root system. Each new plant need to have good roots and plenty of leaves to survive the process, so if you’re in doubt, it’s better to divide into fewer new sections.
Which perennials can you divide?
Remember all the perennials that don’t make roots by cutting or layering? Most them are very happy to be divided! In fact, a lot of them need to be divided eventually to make sure they’re not overcrowded.
Any perennial that grows in shoots or clumps, like hostas or coreopsis, can be divided. Plants which spread by rhizomes can be divided. Chives and other perennial alliums can be divided. All plants that grow from bulbs or tubers can be divided.
Don’t try to divide plants with woody or shrubby growth, like rosemary or winterberry holly, because it will kill the plant. Some smaller perennials with slightly woody stems, like thyme, will tolerate division but it’s much easier to propagate those through cuttings. You can also divide robust plants that like to spread, such as mint or oregano. Their roots are so shallow that you can simply pull sections off the parent plant and put them in new soil, as long as there are some existing roots. Though as noted, those sorts of plants will also make roots readily if you take cuttings.
Basically, you can propagate through division any perennial that has multiple root systems. If a perennial has a single central ‘trunk’, like most shrubs, division will likely kill the parent plant.
What’s the best method of propagating perennials?
There’s not a clear winner. Knowing how to use each propagation method will give you the most options when it’s time to expand your garden. In general, woody plants or shrubs won’t tolerate being divided. Large, leafy plants will rot if you try to layer them. Rooting cuttings is probably the most versatile technique but it’s still not a universal solution.
Some herbs and perennials really don’t seem to care how you treat them, they’ll make new roots and keep on going. Others are more delicate or more resistant. And sometimes you can do everything right and the new plant just doesn’t survive. For that reason, it’s always best to have multiple new plants going.
Perennials that root well from cuttings:
- Thyme, rosemary, lavender, oregano, mint, tarragon, chamomile, basil (technically an annual in most zones, but super easy to propagate), lemon balm
- hydrangeas, mist flower, yarrow, sage
Perennials that propagate well via layering:
- Thyme, rosemary, lavender, mint, oregano, tarragon
- Most shrubs or vining perennials
- Any plant that grows low and wide with soft stems, like Russian sage
Perennials that are easy to divide:
- Thyme, oregano, mint, chamomile, tarragon
- hostas, coneflowers, black-eyed Susans, most non-culinary mints, lobelia
- any plant that spreads via rhizomes
- perennial alliums
How to choose a propagation method
In general, the method you pick will depend on both your preference and the age and condition of the parent plant. Younger plants won’t handle division very well but many older perennials actually NEED to be divided once in awhile for optimal health.
Some herbs are very prolific, like mint, oregano and thyme, so it is very easy to propagate them. Others, like rosemary, need more time and patience.
Propagating via seeds and reseeding
Some perennials are challenging to propagate with any of these methods. They may be very slow growing or resistant to setting new roots and division may kill them. For those plants, propagation at home may be nearly impossible, unless you can start them from seeds.
Many herbs will flower and then set seed. This can be a great way to make more plants, but you should wait until the end of the season or until you’re done harvesting from the plant. Flowering changes the flavor of the herb and often saps the plant’s vigor. The plant will put all of its energy into making flowers, which generally leads to very lanky plants with less foliage.
Letting herbs go to seed is great for annuals and biennials, like basil or cilantro, once they’ve reached the end of their season’s growth.
Flowering perennials can also set seeds but may re-seed too vigorously. If you end up with more volunteer plants than you can keep, dig them up and sell or give them away. You can curb volunteers by deadheading flowers before they go to seed.
How to grow a perennial garden
Now that you know how to make more plants, here’s a few tips for caring for your perennials and tending to your garden.
The best way to grow a perennial garden is to pick sturdy plants that are native to your region or well-suited to your microclimate. Start with a handful of perennials that will thrive in the growing conditions of your own unique garden. That means selecting perennials that will tolerate the levels of sunlight in your garden and that won’t need tons of extra water or fertilizer just to survive. It also means choosing plants that can grow in your soil or amending your soil to ensure it will support the plants you’ve chosen.
If you choose the right perennials, they’ll thrive without a lot of care from you. Healthy perennials will spread happily on their own or you can use these propagation methods to speed the process along. Because of that, choose just a few plants at first. While it isn’t as fun to see gaps in your perennial garden for the first few years, it’s better to leave room and fill in the gaps with new plants or by propagating the ones you already have.
Caring for perennials
Most perennials are actually very low maintenance, especially those native to your region. In general, they need to be cut back in the fall or spring to manage their growth and keep them healthy and vigorous. Some perennials may need soil amendments or even fertilizers during the growing season, but many will do just fine without. Once perennials are well-established, they don’t generally need supplemental water. Watch for signs of pests or disease and take gentle but appropriate action to address those issues before they spread. Your perennial herbs and plants will reward you with years of beauty and a thriving ecosystem.