Propagating new plants for free and watching them thrive is hugely satisfying. Whether it is to add more to your own garden or to give away to family or friends, propagating is a skill every gardener should learn.
With the last of the hot weather behind us, conditions in September are ideal for cuttings and divisions to take root. Furthermore, with frosts not that far off, now is the perfect time to create some back-ups in case some tender specimens do not make it through the winter.
That being said, if you spot any gaps in the borders or vegetable patch, there is still time to plant flowers and crops in September. If the ground is still baked hard, a Nisaku hori hori (available from Amazon), with its pointed tip and slim profile, can make short work of any digging or planting.
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1. Hardy Geranium
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Hardy geraniums, or cranesbills as they are also called, are a great investment as they can flower for months on end and, as a perennial, reliably regrow every year.
However, over time, cranesbills can form large clumps and become overcrowded. To prevent this, you can divide plants every 3-5 years to revitalize them. And, as well as being a good time to plant hardy geraniums, September is also the perfect time to propagate them by division.
To divide hardy geraniums, carefully dig up the plant and split it into sections, making sure each division has some roots, using a sharp tool such as a hori hori knife or Berry & Bird perennial spade, available from Amazon.
Plant out the new divisions or pot up and water regularly until established.
2. Sweet Pea
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A stalwart of cottage gardens and cut flower patches, sweet peas (Lathyrus odoratus) are renowned for their beautiful and scented flowers that look as good scrambling up a wigwam support as they do cut in a vase in a home.
One of the easiest plants to harvest seeds from, all you need to do is let the spent flowers form pods and dry out before collecting and storing.
As hardy annuals, sweet peas can be sown anytime from late September to April, so planting them directly later this month in USDA zone 8 and above will allow them time to establish strong roots before winter sets in and bloom early next year. In zones 7 and below, sow late winter to early spring or start seeds undercover 4 to 6 weeks before your last frost.
Encouraging deep and strong root systems, Haxnicks rootrainers are available to purchase from Amazon.
Whether you gift young plants or a posy of flowers, sweet peas are always gratefully received. Perfume Delight sweet peas are available to purchase from Botanical Interests.
3. Rose
(Image credit: Future/Edward Bowring)
The easiest way to propagate roses is by taking rose cuttings. If you missed the opportunity to take softwood cuttings earlier in the spring and summer, do not worry, as you can propagate your favorite roses from semi-hardwood cuttings now or from hardwood cuttings later this winter.
To take semi-hardwood rose cuttings in September, cut a section of stem 6-8 inches long early in the morning using clean and sharp secateurs, such as a Felco 2 bypass hand pruner, available from Lowe’s. For the best chance of success, select only healthy, disease-free material with a firm base and a flexible tip.
Cut the selected stem straight across at the bottom, just below a leaf node and remove all leaves except one set at the top. Dip the end in plant rooting hormone, available from Amazon, and insert into a pot prefilled with equal amounts of potting compost and sand.
Water well and place in a greenhouse under a propagator dome where it will receive indirect light. Once rooted, pot up and grow on under cover until ready to harden off.
4. Lamb’s Ear
(Image credit: Sviatlana Zyhmantovich/Alamy Stock Photo)
Grown for its pink-purple flowering spikes and soft and furry silver-green foliage, lamb’s ear (Stachys byzantina) is a solid choice for dry gardens and hot borders, due to its drought-tolerant nature.
A low-maintenance perennial, it sprawls across the soil, making lamb’s ear an excellent ground cover that thrives on neglect.
You can propagate lamb’s ears through collecting and sowing its seed, but lifting and dividing it in the fall or spring is easier and a faster way of producing new plants. To divide Stachys byzantina, carefully dig up a healthy mature plant and separate using a sharp spade or knife (I find an old bread knife works perfectly), making sure each clump has a section of roots attached.
Pot up the divisions or replant in the garden and water regularly. With the soil still holding its warmth in September, new roots will develop and establish quickly.
Whichever method you use to propagate plants, labeling is essential for their identification and ongoing care, especially if you are propagating large numbers or giving them away to friends. As an alternative to plastic, you can purchase wooden plant labels, available from Amazon, or make your own.
5. Lemon Verbena
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Another plant to propagate in September is the slightly unusual aromatic herb, lemon verbena (Aloysia citrodora). Used in herbal teas and desserts, lemon verbena produces narrow, pointed green leaves and small, delicate white flowers over the summer months.
Given time, it can reach 6 feet tall and wide, but is well suited to a herb garden planter, where its size is restricted.
Grown as a perennial in USDA Zones 8-11, it is usually treated as an annual in colder parts. Nevertheless, for growers in Zone 7 and below, you can take semi-ripe cuttings in September to overwinter undercover and grow on before hardening off and replanting outside in late spring or early summer.
To use in teas, snip off leaves or the tips of stems with sharp, clean scissors or Felco F322 pruning snips, available from Amazon.
6. Pelargonium
(Image credit: Future / Edward Bowring)
Adored for their scented foliage, long flowering season, and low maintenance, pelargoniums are highly collectible and one of my favorites. They are available with white, pink, orange or red flowers and often have attractive foliage, which, when crushed or rubbed, can release delightful scents.
However, unlike hardy geraniums, pelargoniums are tender and rarely overwinter outdoors in zones 8 and below. As a result, they tend to be grown as annuals or brought indoors for the colder months, making them a great plant to propagate in September.
As a backup and to provide more plants for free, you can take pelargonium cuttings, 3-4 inches long and place them in pots filled with free-draining soil, such as plant propagation potting mix available from Lowe’s, to encourage initial rooting.
To give your cuttings the best chance, remove all but the top few leaves using a sharp, sanitized pruning knife, available from Amazon, and place them under a humidity dome to reduce moisture loss.
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Along with those listed above, if you want to grow more plants for free this year, there is still time, as you can take hardwood cuttings anytime from mid-fall to late winter.
Used for propagating most deciduous climbers, shrubs and trees, taking hardwood cuttings is perhaps the easiest method to try and can be used for butterfly bushes, roses and dogwoods.
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