The general rule of thumb is to plant seeds and bulbs approximately two to three times as deep as their size. So a seed that measures 1/8 of an inch could be planted 1/4 to 3/8 of an inch deep. Bulbs by their size, are buried much deeper and can go even lower.
Many gardeners plant spring spring bulbs like daffodils as much as six inches deep! While it takes a bit longer for them to emerge in the spring, this practice allows the gardener to plant annuals with roots closer to the surface, without disturbing the perennial bulbs below.
This also works great for hiding the bulbs foliage once their bloom period is done.
While daffodils, tulips and alliums look fabulous in bloom, once the blossoms are spent the foliage can look a tad unsightly. An understandable impulse is to just hack the stems and leaves down to the ground, but put down those snippers and step away from that plant! The bulbs need the nutrients it gathers through its foliage – ugly or otherwise – to build up energy in its bulb to produce next spring’s blooms.
Tucking appropriately sized annuals around the spring bulbs will allow the spring bloomers to still soak up all the nutrients they need, while the annuals provide a clever dose of camouflaging beauty.
Having the roots at different depths mean neither are being disturbed by the other or having to compete for valuable nutrients.
It’s a Win Win Combination!