Tips for Planting Summer-Blooming Bulbs

Discover some easy design tricks and practical pointers for planting summer bulbs.
Blue Storm Agapanthus

Blue Storm Agapanthus

Blue Storm agapanthus forms a tidy mound of foliage topped with blue flower clusters. It’s hardy in Zones 8 to 10.

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Blue Storm agapanthus forms a tidy mound of foliage topped with blue flower clusters. It’s hardy in Zones 8 to 10.

Bulbs are one of nature’s gifts to gardeners. Goof-proof and amazingly easy, bulbs make every gardener look good. Most folks know the familiar faces of the spring bulb chorus—tulip, daffodil and crocus. But few realize there’s a host of summer bulbs that can keep the color show going strong deep into sizzling August days.

The summer bulbs category encompasses true bulbs, such as Asiatic and Oriental lilies, as well as corms, like gladiolus and crocosmia. Tubers, including tuberous begonia, caladium or dahlia, fall into this group, along with the rhizome crops, such as agapanthus and canna.

As you decide where to place summer-blooming bulbs in your garden, do a little homework to make sure you’re providing ideal conditions. This is especially important for bulbs that perennialize or are hardy in your zone. Many of the tropical summer bulbs prefer toasty, sun-bathed sites, but still strut their stuff in partial shade. Some, like canna or elephant ear, thrive with as much moisture as you can give them and will even grow in shallow standing water.

Others, including all the lilies, gladiolus and crocosmia, need soil that holds moisture but drains well. That sounds contradictory, but what it means is this: These bulbs will rot in clay soil, where water never drains, but they’ll thrive in soil that’s rich in organic matter, such as compost, which has the ability to hang onto moisture droplets for thirsty roots. 

Aim to plant bulbs right side up, which means roots should be on the bottom of the planting hole. With some, like caladium, it can be tricky to tell which end is up. Always look for where any roots attach to the bulb—that’s the bottom. Many tubers have a cup shape; the concave bowl of the cup is usually the top side. The plants can recover if you tuck bulbs into soil upside down, but you’ll have best results if you get things right.

You’ll often see tiny sprouts of new growth that are pink or white. Try not to break these off as you handle bulbs. In general, plant bulbs at a depth equal to two to three times the fattest part of the bulb. Double-check planting instructions that come with the bulb just to be sure.

If you know plants will need staking, insert stakes at planting time. This helps prevent accidentally spearing the bulb later in the growing season. If for some reason you can’t insert a full size stake at planting time, slip a shorter one into position. Later in the growing season, when stems need support, push a taller stake into soil outside the shorter one.

In the garden, summer bulbs look best when planted in drifts or clusters, as opposed to soldier-straight rows. If you’re using bulbs to skirt a patio or deck, plant in a staggered row arrangement for more eye appeal.

Do not plant summer bulbs into garden soil until it has warmed sufficiently. In colder regions, spring air temperatures are often warm enough to jump-start summer bulbs outdoors in pots. Use black nursery pots to absorb the sun’s heat and warm soil. Don’t shift bulbs into garden beds until you’re sure soil is warm enough. Summer bulbs tucked into chilly soil often rot.

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