How to grow houseplants without ever having to buy one

Many houseplants are simple to propagate, offering a greener and cheaper way to add plants than ordering online. Photo / Sarah L. Voisin, The Washington Post

Sharing plant cuttings is a free and environmentally friendly way to grow your plant collection. You just have to know where to cut.

House plants have got something of a bad rap lately, with climate advocates citing the energy-intensive greenhouses they’re grown in, the harmful emissions produced from shipping them long distances and the environment-depleting peat they are often packed in.

But there’s a greener – and cheaper – way to expand your plant collection. Local plant swaps offer a chance to trade plants and get tips for how to care for them. You may also have a friend, neighbour, relative or co-worker who has the plant you want and will give you a cutting free.

“They’re the ultimate renewable resource,” said Chad Husby, chief explorer at the Fairchild Tropical Botanic Garden in Coral Gables, Florida. “You can take one piece of a plant and get a whole new plant. It’s miraculous.”

Some species can be grown from saved seeds, divided bulbs or offshoots. But many common house plants can be propagated by cutting. Here’s what to know before you break out the shears.

When is the best time to take cuttings?

Cuttings intended for propagation have the best chance of thriving when there’s plenty of warmth and sunlight. Photo / Sarah L. Voisin, The Washington Post

Spring is the ideal time. Plants respond best to pruning at the beginning of their growing season, and cuttings intended for propagation have the best chance of thriving when there’s plenty of warmth and sunlight to fuel quick root growth.

After you cut, be prepared to move quickly to the next steps.

“Once you take a cutting, it basically has to rely on whatever sugars it has stored until it can start to … generate roots to supply leaves with nutrients,” Husby said. “You’re working against time. The more you extend the process, the more chance there is your cutting will get exhausted or infected because it’s in a weakened state.”

Where should you cut your plant?

Snip right above a growth node: one of the knobby joints along a plant’s stem that leaves or buds grow from. You don’t want to cut so close that you damage the node – that’s where a new branch will form. But any stem beyond that point will wither, so you don’t want to leave too much, either.

You should also think about the cutting you’re creating. Ideally, you’ll have a few leaves near the tip of the stem, which will collect sunlight and give the plant energy to grow roots.

“Save the tips because those are the best things to root,” said Tim Pollak, plant production manager at the Chicago Botanic Garden. “They’ll grow faster than some of the older parts of the stem.”

You also want to leave one or two bare nodes at the bottom of the cutting that new roots can grow from. You might have to cut off leaves at the bottom to clear space for roots to grow.

How to root a plant in water

Some hardy plant cuttings root well in water, but most do better in soil. It depends on the species, so you should look up what works best for your plant.

“There are some plants, for instance a pothos, begonia or coleus, that, given enough time and the right conditions, they’ll root on a wet floor,” said Marc Hachadourian, director of glasshouse horticulture at the New York Botanical Garden. “They really don’t need much to propagate.”

If you’re rooting in water, your job is pretty easy: just fill a glass or jar with enough water to cover the growth node you’d like to grow roots from, and then change the water every two or three days.

Soon you should see pale roots starting to poke out. When the roots are an inch or two long, you’re ready to put your new plant in a pot with soil.

How to root a plant in soil

If you’re rooting your cutting directly in soil, you’ll need to dote on it a bit more. Fill a pot with dirt, use your fingers to clear a hole and place the cutting so that the lower nodes roots will grow from are covered with soil.

Over the next few days, you’ll have to keep the soil moist – but not too wet. Using a pot with drainage holes helps avoid overwatering. You can raise the humidity around your cutting by misting it a few times a day – or you can place a clear plastic bag over the plant and its pot to create a miniature greenhouse. Just keep it out of direct sun to avoid overheating.

You won’t be able to see the roots grow beneath the dirt, but you can look for signs they’ve arrived. If you see new shoots or leaves growing above the soil, the plant has probably rooted. Or you can take a more hands-on approach.

“Just take your fingers and right at the base of the stem, where it meets the soil, you give it a little tug – lightly,” said Pollak. “If you feel there’s some resistance, that means it’s probably starting to root.”

At that point, your cutting is established in its new home and you can start treating it like any other house plant. Don’t worry if some of the old leaves fall off.

“As long as new leaves continue to grow, you’re going to be fine,” Husby said.

Other propagation techniques

Everything you’ve just read about taking stem cuttings and rooting them in water or soil will work for most common house plants. But there are other propagation methods.

Pothos will sometimes grow roots at the nodes along its long, trailing vines. Photo / Sarah L. Voisin, The Washington Post

Pothos will sometimes grow roots at the nodes along its long, trailing vines. You can bury these roots in a new pot while the vine is still attached to the mother plant, in a technique called “layering”. Once the new roots are established, you can cut the vine and split the plant in two.

The succulent known as mother of thousands will grow fully formed baby plants, complete with leaves and roots, in a ring along the edge of its leaves, and drop them when they’re ready to grow on their own.

Some succulents will grow fully formed baby plants in a ring along the edge of their leaves. Photo / Sarah L. Voisin, The Washington Post

“Some plants, like begonias, can be propagated from leaf cuttings,” Hachadourian said. “If you did that with a monstera, you’d wind up with a dead leaf.”

So, look up your particular plant before you start cutting. And if you want to learn much more about propagation, the botanists say, you may be able to find a hands-on class at a botanical garden, nursery, garden centre or park near you.