Horticulture Report

October 2018

Sherrie Eoff

Bulbs and More…

When to Plant: You can plant most fall-planted bulbs when soil temperatures in your area drop to about 60°F. You can also keep planting, as necessary, LONG after the first frost, as long as the soil remains workable. This is much later than many people realize, requiring many nights below freezing. However, since small bulbs dry out in storage more easily and their shallow planting depths subject them to earlier freezing, they should be planted in most zones IMMEDIATELY. This is also true of all lilies, Fritillaria, Hyacinthoides, and Camassia. Hyacinths root better in not-too-cool soil, so plant them next, then narcissus, and finally tulips, which prefer the coolest soil. Don’t wait too late, though, because if the soil freezes down to the bulbs before they root well, health and performance will be impaired. To keep soil warmer longer, apply a thick, light winter mulch such as straw or pine needles — but not if you have bulb-eating voles. 

Soil and Drainage: Most bulbs need well-drained soil to thrive, and soils that stay too damp for too long are a leading cause of bulb death. Rich sandy loam is ideal for most bulbs, though soil that’s too sandy can cause bulbs to suffer from a lack of water and nutrients. Adding organic matter will help. Clay or “heavy” soil is usually a bigger problem. Clay soil drains slowly and will cause problems for most bulbs, especially tulips and hyacinths which need to be as dry as possible when dormant in summer for best return. Clay soil also makes it difficult for bulbs to expand and multiply underground. Imagine trying to push your fist into a bucket of clay rather than sand and you’ll understand why this is so. You can improve clay soil by adding lots of organic matter to it (compost, peat moss, etc.). Adding sand and gypsum can help, too. Planting in raised beds is another way to improve the drainage of heavy soil and make it more bulb-friendly. 

Sunshine and Shade: In general, for best performance year after year, plant your bulbs in full sun. However, some bulbs — especially daffodils, snowflakes, and small early bulbs such as crocus and Siberian squill — can do well with a bit of shade — and seem to prefer it in the South — especially if it’s from deciduous trees that don’t leaf out till later. Some bulbs need cool, moist conditions and actually grow best in light shade. 

Planting Depths and Spacing: Advice on planting depths varies, so we recommend you do what has worked well for you. A few basic guidelines are (1) plant larger bulbs deeper, smaller bulbs less so (three times the height of the bulb is often recommended), (2) plant deeper in sandy soils, less so in heavy soils, (3) plant deeper in the North, less so in the South. Deeper planting is said to enhance longevity and to keep bulbs from dividing into so many smaller bulbs that blooming suffers. Full-size tulips, hyacinths, and daffodils can all be planted about 6-8 inches deep, measured to the bottom of the hole. Varieties with smaller bulbs such as ‘Rip Van Winkle’ should be planted 4-6 inches deep. Even-smaller bulbs such as crocus and snowdrops should be planted 2-4 inches deep. Full-size bulbs are usually spaced about 6 inches apart from center to center, though many gardeners like the lush look gained by closer planting. Smaller bulbs are planted 3 or 4 inches apart, or even closer for more immediate impact. Don’t guess. Take a ruler into the garden, or mark off inches on your trowel with a permanent marker. Your bulbs will thank you by growing and blooming better. 

Fertilizing: Just like other plants, most bulbs do better in fertile soil. Though bone meal was a popular fertilizer for bulbs in the past, the way it’s processed today saps most of its nutrients, and it can attract animals. Bulb fertilizer is a better choice, or any relatively balanced mix (aim for 10-10-10, but just about any rose, tomato, or flower and vegetable fertilizer will work). Many experts now recommend a slow-release fertilizer scratched into the surface soil every fall. Beware, though: as we’ve learned the hard way, fertilizing year after year can cause nutrients such as phosphorus and potassium to build up in the soil to counter-productive levels. That’s why we always recommend getting a soil test before you fertilize. Testing is available through your county Cooperative Extension Office and simple kits are sold at many garden centers. 

Water: After planting, water well. Fall-planted bulbs need good soil moisture from fall through spring — whenever the soil isn’t frozen — while they are rooting, growing, and flowering. In the summer, however, many fall-planted bulbs like to dry out — and will suffer from normal watering. Tulips, hyacinths, crown imperials, and a few others  often return best when kept very dry in summer, so consider planting them where you never water or where shrubs or trees will soak up most of the moisture. In the South, keeping daffodils dry in the summer when soil temperatures are high will help protect them from basal rot. On the other hand, snowflakes, snowdrops, snake’s-head fritillaries, lilies, and a few other fall-planted bulbs — including daffodils in the North — can suffer from too little summer moisture. 

Protecting from Animals, Insects, Etc.: Most bulbs (and especially heirloom bulbs) are relatively untroubled by insects and diseases, and the best way to avoid problems is to give your bulbs what they need to thrive As for animal pests, daffodils and snowflakes (Leucojum) are very animal-resistant, and other bulbs that are rarely eaten include hyacinths, Crocus tommasinianus, many of our Fall-Planted Diverse bulbs (alliums, winter aconites, glory-of-the-snow, snowdrops, Spanish bluebells, grape hyacinths, silver bells, and Siberian squill), and spring-planted iris, and crinums.Tulips and lilies, unfortunately, seem to be a favorite on most animal menus. 

If animals dig your newly-planted bulbs — including ones they won’t eat, like daffodils — try covering with plastic bird-netting, wire-mesh, a window screen, or burlap bags for a couple of weeks till the inviting smell of freshly-dug earth disappears. 

If animals burrow to your bulbs, either plant them in PermaTill crushed shale (also sold as VoleBloc), wire-mesh boxes, buried plastic pots covered with chicken-wire, or miniature plastic laundry baskets with their bottoms replaced with wire mesh. 

Moles often disturb bulbs as they dig for grubs. Killing the grubs (try beneficial nematodes or spraying your lawn with bitter, organic Mole-Med) will reduce the moles — and this will discourage voles and mice which often use mole tunnels to munch on bulbs. 

If animals eat spring growth, cover it with chicken wire for a few weeks (while they are hungriest), sprinkle blood meal around it, fence them out, or — my most successful solution — spray it with bitter, non-toxic Repels All Animal Repellant, available at many garden centers. Bulbs can be dipped in Repels All before planting, too. 

Blasting: Why Good Buds Go Bad: When buds form but fail to develop into flowers it’s called blasting. This usually happens because the plant wasn’t getting enough of something it needed. In most cases that’s water — especially for newly planted bulbs — but late planting, high temperatures, too little sun, and improper storage can also be to blame. 

How to Make Maturing Foliage Look Beautiful: It’s important to leave all foliage to mature, since this is what builds up the bulb for next year’s flowering. Leave stems, too, since they also photosynthesize, but snap off spent flower heads so seeds don’t form — except for bulbs you want to self-sow. Leaving the foliage for at least six weeks after blooming may not be convenient or pretty, but it is essential. Even braiding or tying the foliage will diminish future bloom. You may remove the foliage as soon as it yellows. This often leaves holes in the soil where the foliage used to be. Lightly cultivate the soil to prevent insects from using these as routes to attack your bulbs. It’s not that hard to camouflage maturing bulb-foliage with annuals (old-fashioned forget-me-nots, corn poppies, and larkspur are favorites of ours) or nearby perennials. Planting your bulbs in narrow, foot-wide drifts or ribbons rather than in broad patches helps the maturing foliage “disappear,” too (a suggestion from Gertrude Jekyll herself). Reminding yourself of the important work the foliage is doing, and the beautiful flowers that will follow next spring, is sure to make it less of a problem, too! 

Other Ways to Make Bulbs Last: Daffodils are generally long-lived. When they increase to the point of being crowded, however, their bloom often diminishes. It is then time to dig, divide, and replant them. This can be done “in the green” — right after bloom — or wait till the foliage yellows and then dig and store the bulbs until fall. Put a sticky-note on your calendar so you don’t forget them! Tulips: Back when tulips were more of a luxury, people often dug them after the foliage yellowed and stored them through the summer. This dry rest promotes good increase, and I recommend it for any truly rare tulip you may be growing — though it is a lot of work. Happily, many antique and species varieties are long-lived even when left in the ground year-round, especially if you keep them as dry as possible. After all, they were bred for gardens, not greenhouse and cut-flower production as most modern tulips have been. Parrots and doubles are the hardest to make last, however, requiring near-perfect conditions. Hyacinths are usually left undisturbed and are often slow to increase. Dry summers but rather cool, rich soils seem to suit them best. Some varieties do better in different conditions, so experiment! Crocus usually multiply happily when well-sited, though they can be smothered by fallen leaves or thick turf. Lilies: Our lilies are generally long-lived when planted in humus-rich, well-drained but well-watered soil, their roots cool but their heads in the sun. Although most prefer slightly acid soil, Madonna, Henry’s, and tiger lilies do best in neutral to alkaline soil. 

Tulips Can Live Forever: Well, almost. Though they have a reputation for being short-lived, we know of tulips that have been blooming beautifully for decades. Here’s how to get the most out of yours. For a start, you need to be in zone 7 or colder, or zone 8 or colder on the West Coast where winter temperatures stay cool longer. (Gardeners in warmer zones can grow tulips as annuals, but you’ll need to pre-cool or pre-chill them in the refrigerator for 8-12 weeks before planting.) Then most important, we’ve learned from experience, is keeping them DRY in SUMMER (as in their native homes). Try this: plant a few where you never water in summer — or near a thirsty shrub or tree — and see how well they return. Beyond that, the basics include well-drained soil (improve heavy soil, or try raised beds), lots of sun, regular fertilizing, and — this is very important —letting the foliage ripen to yellow to feed the bulbs for next year’s bloom. Some authorities recommend deep planting, especially in the South — to 12 inches — but we say 6-8 inches is plenty. Then there’s this age-old method: dig them up every summer, store them in a cool dry spot, and replant them in the fall. You’ll end up with more bulbs every year, guaranteed. Some varieties just last better, too — often Single Earlies, Single Lates, Lily-flowered tulips, and species. And there’s a good reason why OLD VARIETIES OFTEN PERENNIALIZE BETTER: they were bred for gardens, not for commercial pot-flower and cut-flower uses as most modern tulips have been. Tulips do best when planted in mid- to late fall, after the soil has thoroughly cooled. Later is better than earlier with tulips. If necessary, store in open bags in a cool, dry spot (or the refrigerator — NOT the freezer). Neutral to slightly alkaline soil is ideal, though tulips are very adaptable. Set bulbs about 6 inches apart from center to center (or closer for a lush look). For each, scratch a tablespoon of bulb fertilizer into the surface soil (slow-release 10-10-10 is ideal). Use no manure. Water well and make sure the bulbs have reliable moisture throughout their growing period, from planting in the fall through the ripening of their foliage the following summer. 

From Old House Gardens website: www.oldhousegardens.com

A Few Special Fall Blooming Bulbs

FALL CROCUS

FALL CROCUS speciosus

The elegant, goblet-shaped blooms are violet blue to mauve. This is the easiest to naturalize, most floriferous, and least expensive of the fall Crocus. Plant by the 100s for lovely pools of rich, glowing color. Heirloom, 1800.

Perhaps because the sun is so low in the sky after the autumn equinox, the blooms of fall crocus positively glow in the landscape. They appear between September and January (depending on your climate) on stems 3–6″ tall and have the same refined goblet-shaped flowers of their spring cousins.

When  bulbs are planted in September, they may go about the business of rooting and preparing to flower, a process that generally takes 4–6 weeks. Fall Crocus grow best in a sunny, protected site.

COLCHICUM autmnale ‘Pleniflorum’