The most reliable way to propagate alstroemeria is by dividing the rhizomes of an established plant. This produces identical copies of the parent and yields flowering plants much faster than growing from seed. Seed propagation works too, but the resulting plants may not look like the parent, and the process takes longer. Here’s how to do both successfully.
Rhizome Division: The Fastest Method
Alstroemeria grows from a network of fleshy, tuberous rhizomes underground, similar in appearance to dahlia tubers. Each rhizome has visible growing points, or “eyes,” much like a potato. To propagate, you’re separating this root network into smaller clumps, each with its own set of eyes and healthy roots.
Wait until your plant is at least two years old before dividing. Younger plants haven’t developed enough rhizome mass to split successfully. The Royal Horticultural Society recommends dividing in April, as the plant is waking up from dormancy and actively pushing new growth. Late fall, after flowering has finished, is the other window. Avoid dividing in summer when the plant is in full bloom and under heat stress.
Step by Step
- Dig wide, not deep. Use a garden fork rather than a spade to lift the entire clump. Alstroemeria rhizomes are brittle and snap easily, so start 15 to 20 cm out from the base of the plant and lever gently upward.
- Shake off excess soil. Once the clump is out of the ground, brush or rinse away enough soil to see the rhizome structure clearly.
- Separate into sections. Each division needs at least two or three growing eyes and a decent amount of root attached. You can pull some sections apart by hand where natural separations exist. For denser clumps, use a clean, sharp knife. Wipe the blade with rubbing alcohol between cuts to avoid spreading any soil-borne pathogens.
- Replant immediately. Alstroemeria rhizomes dry out quickly. Get divisions back into the ground or into pots the same day. Plant them about 5 cm deep, with the eyes facing upward.
Soil and Drainage for New Divisions
Good drainage is non-negotiable. Sitting in waterlogged soil is the fastest way to lose new divisions to root rot. Alstroemeria is vulnerable to several soil-borne fungi, including Pythium and Fusarium, and poor drainage creates exactly the conditions these pathogens thrive in.
Keep soil pH below 6.5. Higher pH can trigger iron and manganese deficiencies, which show up as yellowing between the leaf veins. If you’re planting in containers, a general-purpose potting mix with extra perlite works well. In garden beds, work in compost and grit if your soil is heavy clay.
Water consistently but lightly. Alstroemeria produces a lot of lush top growth that demands steady moisture, especially in warm weather. Short, frequent watering is better than occasional deep soaking, particularly in sandy soils where nutrients leach quickly. The goal is evenly moist soil that never stays soggy.
Growing From Seed
Seed propagation is slower and less predictable, but it’s the way to go if you want to grow species varieties or experiment with new plants. Keep in mind that hybrid alstroemeria (the type most commonly sold at garden centers) often won’t come true from seed, meaning the offspring may look quite different from the parent.
Collect seed pods from the plant as they turn brown but before they split open. The pods burst with surprising force, scattering seeds in all directions. A good trick from the RHS: slip a sealed paper bag over ripening pods and let them explode inside the bag. Sow the seeds as soon as possible after collection, ideally in autumn.
Cold Stratification
Alstroemeria seeds have a built-in dormancy mechanism that cold stratification helps break. This mimics the winter chill the seeds would experience naturally. Research on the genus tested stratification at both 1°C and 13°C for four weeks, with both temperatures proving effective at overcoming dormancy. In practical terms, placing your sown seeds in the refrigerator (around 1 to 4°C) for four weeks before moving them to warmer conditions works well. Some growers sow in autumn and let winter do this work outdoors naturally.
What to Expect During Germination
Alstroemeria seed viability is generally high, around 91% in lab conditions. Actual germination rates are lower. Research found that untreated seeds on a suitable growing medium germinated at roughly 49%, while seeds given an optimal pre-treatment reached about 64%. For home growers without lab setups, expect somewhere in that range or a bit below, which is why sowing generously is a good idea.
The good news is that once germination starts, it happens quickly. Seeds typically sprout within about 4 to 7 days of being moved to warm conditions. Sow them in a free-draining seed compost, cover lightly (about 5 mm deep), and keep the surface moist but not wet. A temperature around 18 to 20°C encourages sprouting once stratification is complete.
Seedlings grow slowly at first. Don’t expect flowers in the first year. Most seed-grown alstroemeria take two to three growing seasons before they bloom, which is why division remains the preferred method for gardeners who want results sooner.
Protecting New Plants From Disease
The biggest risk during propagation is fungal root rot. Pythium, Rhizoctonia, and Fusarium are all known to attack alstroemeria, and freshly cut or transplanted rhizomes are especially vulnerable because the wounds provide an entry point for pathogens.
Prevention is far easier than treatment. Use clean tools, fresh or sterilized potting mix, and containers with drainage holes. Avoid overwatering in the first few weeks. Some growers dust cut surfaces with sulfur powder before planting, which helps dry the wound and discourages fungal growth. If you’re dividing in the garden, avoid replanting in the exact same spot if the original plant showed any signs of disease.
Watch for yellowing, wilting, or mushy stems at the base in the weeks after planting. These are early signs of rot. Removing affected plants quickly prevents the pathogen from spreading to healthy divisions nearby.
Division vs. Seed: Which to Choose
- Division produces an exact genetic copy of the parent, flowers within the same season or the next, and has a high success rate. It requires an existing mature plant.
- Seed is inexpensive, lets you grow species or new varieties, and doesn’t require a parent plant. But it takes two to three years to flower, results are genetically variable with hybrids, and germination rates are moderate.
For most home gardeners, dividing an established clump every three to four years is the simplest approach. It keeps the parent plant vigorous (alstroemeria can become congested and flower less over time) while giving you new plants to spread around the garden or share. If you’re starting from scratch and can’t source rhizomes, seed is a perfectly viable route, just one that rewards patience.