Grow more plants from the ones you have with propagation
Who doesn’t love a good bargain at the garden center? I know I do! But it’s even better when you can get more plants without having to open your wallet at all. Knowing a few easy propagation techniques can increase your collection of annuals, perennials or shrubs without putting a strain on the budget.
When annuals get lanky and leggy, cutting them back helps improve the look of the plant and why not turn a few of those stems into cuttings? If a perennial isn’t flowering like it used to, it might be overcrowded. Division helps it grow more vigorously again and adds more colorful flowers to your border. Or maybe you have an heirloom shrub that you don’t want to lose — layering is a sure-fire way to keep it going and share with others.
These propagation techniques are super simple and most of what you’ll need is probably already in the garden shed, so let’s get started!
1. Propagate plants with stem cuttings
If you’ve cut a stem of your favorite coleus and plunked it in a jar of water, you’ve taken a cutting. It’s a simple and sure technique that works for other plants, such as alternanthera and purple heart, too. But you can actually skip this step and go right to potting mix to get transplant-ready cuttings like the one at left in as little as a few weeks.
Before you start cutting stems you’ll want to get a few containers and some potting medium. A mix of equal parts coarse sand and peat, perlite or vermiculite is great, but premoistened potting mix works just fine for most plants and still drains well.
When to cut
Cut stems any time during the growing season. Just be sure to water the parent plant the day before and harvest your cuttings early in the morning to ensure that the stems are well hydrated and in peak condition.
Where to cut
Look for pliable new growth near the stem tip. Older woody growth found near the base of the plant isn’t as likely to root. Use pruners or scissors to cut a 2- to 6-inch-long piece just below a leaf joint and remove the flower two to three sets of leaves.
Apply rooting hormone
This is the time to apply rooting hormone if you’re going to. It’s not essential, but it can help some plants take off more quickly. Rooting hormone is available as a powder, gel or liquid and in different strengths, depending on the type of plant you’re propagating. The weakest strength —0.1—is suffi cient for stem cuttings like these. Stick the exposed leaf joints in the potting mix and firm the mix in place.
Plants that propagate well from stem cuttings
You can grow all kinds of plants from stem cuttings, but the tender perennials that most of us grow as annuals are the most common.
- Alternanthera Alternanthera spp. and hybrids
- Basil Ocimum basilicum
- Coleus Plectranthus scutellarioides
- Cuban oregano Plectranthus amboinicus
- English ivy Hedera helix
- Iresine Iresine herbstii
- Penstemon Penstemon spp. and hybrids
- Purple heart Tradescantia pallida ‘Purpurea’
- Salvia Salvia spp. and hybrids
- Wallflower Erysimum hybrids
How to care for plant cuttings
Place the cuttings-filled container under grow lights or in the indirect sunlight of a south-facing window. Keep the growing medium moist but not soggy and the temperature between 65 to 75 degrees F. Use a nursery flat with a plastic lid or create a tent with a plastic bag to provide extra humidity. You’ll know the stems have formed roots when a gentle tug meets with some resistance. This can take a few weeks or a few months, depending on the plant.
Once the roots are at least an inch long, transplant the cuttings to a slightly larger container. When there are three or four new sets of leaves, they’re ready to be hardened off and planted outdoors.
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2. Divide perennials to get more plants
When you want more perennials, division is the fastest and simplest method. All you need is a spade or garden fork. You can divide most perennials, but those with taproots, such as butterfly weed (Asclepia tuberosa) or false indigo (Baptisia spp. and hybrids), don’t bounce back as reliably as those with fibrous root systems, such as garden phlox (Phlox paniculata) or daylily (Hemerocallis spp. and hybrids).
Best time to divide plants
Spring is a great time to divide. It’s cooler and there’s usually plenty of rain so plants aren’t stressed out before or after being dug. Plus, new growth is just getting started. Fall is also a good time: Temperatures are cooling down and the sun isn’t as intense, so plants can recover more easily. Be sure to allow 4 to 6 weeks before your expected first frost so plants have time to put on a few roots before the soil freezes. This will help them survive winter.
How to divide perennials
You can either slice pieces off the edge of the plant or lift the whole clump and divide it. Some plants will just fall apart once they’re out of the ground, while for others you’ll need a sharp spade or soil knife to create divisions. Just be sure that each piece has some roots and a few leaves.
Get the new divisions planted at the same depth they were growing in the ground or in a pot right away. You’ll want to keep them watered if it doesn’t rain so new roots get going and the foliage doesn’t get crispy. If your new division is in full sun, create some temporary shade so it doesn’t get cooked by the heat: Attach landscape fabric to a tomato cage and leave it in place for a week or so until the plant settles in.
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3. Propagate shrubs with a simple layering technique
Some shrubs will do this on their own if they have a low-growing branch touching the soil. This technique works for lots of woody plants, such as vines and shrubs. Look for flexible stems —roots form more easily on young growth.
When to layer shrubs
Any time of year will work, but fall or early spring is best because cooler temperatures and rain help them take off more quickly.
How to layer shrubs
- You may be able to anchor a stem to the soil with a rock and the plant will root on its own. But to ensure growth, find a low-growing stem that’s 2 to 3 feet long.
- Dig a shallow 3- to 4-inch-deep hole just under the spot where you can bend it over to touch the ground. If there are leaves, strip them off of the portion that will be underground.
- Then cut a shallow 1-inch-long wound in that spot on the stem like you see in the photo above. Brush some rooting hormone on if you’d like and use a large landscape staple to pin the stem in place.
- Bend the tip upward and secure it to a stake to encourage upright growth. Refill the hole with soil and water thoroughly.
- Make sure the soil has settled in to cover the wound so it doesn’t dry out.
Give them time to root
It can take up to a year for roots to form, depending on the plant and the growing conditions. To check progress, carefully brush away the soil and pull up the landscape pin. Ideally, after a year of growing, there should be a nice cluster of roots and you can cut your new shrub away from the mother plant. But if you only see one or two roots, it’s a good idea to cover the stem and keep it attached for another season.
Shrubs that propagate effectively through layering
- Azalea Rhododendron spp. and hybrids
- Boxwood Buxus spp. and hybrids
- Clematis Clematis spp. and hybrids
- Climbing rose Rosa spp. and hybrids
- Common lilac Syringa vulgaris
- Forsythia Forsythia x intermedia
- Honeysuckle Lonicera spp. and hybrids
