Starting leek seeds indoors using repurposed toilet paper rolls is a popular method among home gardeners. This technique utilizes readily available, biodegradable containers to give seedlings an early start on the growing season. This approach is favored because it addresses a common challenge with Allium species like leeks: their sensitivity to root disturbance.
When a plant is moved, it can experience transplant shock, which slows growth and may cause wilting. This stress occurs because the fine root hairs responsible for water and nutrient absorption are often damaged during the process of pulling a seedling out of a traditional seed tray.
The cylindrical cardboard container allows the leek seedling to be planted directly into the soil without handling the roots. The cardboard eventually breaks down in the moist garden soil, permitting the roots to grow naturally into the surrounding earth. This seamless transition bypasses root damage, promoting faster establishment and more vigorous growth in the garden. Repurposing paper rolls is also a cost-effective and sustainable way to provide individual, deep cells, which leeks favor for their vertical root development.
Why Biodegradable Rolls Work Best for Leeks
Leeks are particularly susceptible to the effects of root trauma, a condition that compromises the plant’s ability to take up water and nutrients. Traditional transplanting, which involves separating crowded seedlings, inevitably tears some of the fine root structures.
The design of the toilet roll pot provides a deep column of soil, which is beneficial for the leek’s long, slender root system. This vertical orientation encourages a strong, downward root run from the start, unlike shallow trays that can lead to circular root growth. Once placed in the ground, the moist soil and microbial activity quickly cause the cardboard to soften and disintegrate. This decomposition process ensures the roots are entirely undisturbed, allowing them to extend into the garden soil naturally.
Preparing the Rolls and Sowing the Seeds
To prepare the containers, gather the paper rolls, a waterproof tray, and a specialized seed starting mix. For stability, you must create a closed bottom on each roll to hold the soil in place. Begin by cutting four short slits, approximately one inch deep, into one end of the cardboard tube.
The four resulting flaps are then folded inward, overlapping one another to form a secure base for the pot. This folded bottom keeps the soil contained while still allowing water to drain and roots to penetrate once the roll is planted. Once all the rolls are prepared, pack them tightly together in a shallow, waterproof tray. Grouping the pots closely provides mutual support and prevents the thin cardboard from collapsing when saturated.
Fill each prepared roll with the seed starting mix, pressing it down gently to remove any large air pockets. Leave about a quarter of an inch of space below the rim for watering. The seed starting mix should be fine-textured to provide an optimal environment for germination.
Sow one or two leek seeds in the center of the soil in each roll. Cover the seeds lightly with a thin layer of soil, no more than half an inch deep. Water the tray from the bottom by pouring a small amount of water into the tray itself. The soil will wick up the moisture, ensuring thorough and gentle saturation without dislodging the seeds.
Timing and Technique for Transplanting
Leek seedlings are typically ready to be moved outdoors when they have reached a height of about six inches and their stems are roughly the thickness of a pencil. Before permanently planting them, the seedlings must be gradually acclimated to the harsher outdoor environment, a process known as hardening off. This involves placing the tray outside for increasingly longer periods over one to two weeks, protecting them from direct sun and wind initially.
Once hardened off, the entire toilet roll, complete with the seedling, is ready for planting directly into the garden bed. Leeks thrive when planted deeply, as this technique naturally blanches the stem, which is the prized edible white portion. Dig a trench or individual holes approximately seven inches deep in the prepared garden soil.
The simplest method is to use a dibber or the end of a broom handle to create a deep, narrow hole, often referred to as ‘dibbling’. Gently drop the entire cardboard roll into the prepared hole. Ensure the top edge of the roll sits slightly below the surrounding soil level.
Any exposed cardboard above the soil line can act as a wick, drawing moisture away from the roots and drying out the soil inside the pot before the cardboard fully decomposes. After planting, water the area thoroughly to settle the soil around the roll and fill the remaining space in the hole. Plant the leeks about six to eight inches apart to allow sufficient room for each stem to mature into a thick shaft.