Marigold Myths

Although the sunny annuals have been used in this capacity for many generations, little documentation exists showing marigolds actually repel insects. In fact, they may attract harmful pests damaging not only the marigolds but also your vegetables.

While marigolds are rumored to deter certain beetles, they are more widely known for their effects on nematode populations in the soil. Nematodes are microscopic worm-like organisms that destroy the root systems of plants.

Certain species of marigolds release compounds from their roots that are toxic to some species of nematodes. Unfortunately, the great variety of nematode species in many soils significantly reduces the potential for adequate control.

When the right combination of marigold and nematodes species does exist, visible results can take up to four months to appear. During this time, if the marigolds are planted around or intermingled with your vegetable or ornamental plants, they can act as weeds, competing for water and essential nutrients and causing additional stress for the plants. Also, the marigolds don’t draw nematodes away from the other plants, so the plants still run the risk of nematode infestation and damage. The greatest disadvantage to using marigolds is they attract large populations of spider mites to many gardens and landscapes.

If you enjoy growing marigolds, French dwarf varieties have shown the most consistent control (of nematodes, not insects. Plant these marigolds in an infested garden and maintain a solid stand for three to four months to reduce nematodes. After the appropriate amount of time, plow the plants under as green manure. The nematode population should be decreased and the garden ready for planting. Be sure to keep the garden weed-free until planting time.

Winterizing With Mulch

Just about the time the soil is freezing, it is time to pile on the mulch.  Mulch does not keep your plant warm through winter, it helps the soil to maintain a more constant temperature and also helps it to retain moisture.  Soil that freezes, thaws, and freezes will eventually damage roots and may heave your plants up out of the soil.

Plants and perennials that require additional protection to survive your winter will need a deep layer of mulch added by mid- November or later, when the ground is beginning to freeze.  Do not add deep mulch too early or your plants will not be slowly exposed to colder temperatures, allowing them to acclimate for winter.  Leaves, other than oak or beech, are not recommended for mulching.  They tend to mat down and prevent air from reaching the soil, damaging your plants.  Grass clippings are also less effective than other mulching materials.

Certain tender perennials just can’t be resisted even in northern climates. Before selecting a tender perennial, shrub or tree for your garden, be sure to check special methods for protecting them through winter.

When considering tender perennials, as well as tender shrubs, for your Midwest garden it is important to understand the preparations required for winter. A perennial is considered tender if it is not fully hardy in your zone, or may not be recommended for your zone at all. Look for information on the garden tag such as “hardy in (your zone) with winter protection”. What that winter protection is generally is not on the tag, so a little research may be required. Your garden center staff should have some basic information, and often some very good tips. Extra mulch or compost mounded around the base of the plant may be enough.  Some will require up to 8 inches of soil mounded at the base.  A little creativity and experimentation will often produce excellent protection methods.  Mulching material covered and held in place by a porous covering is the primary objective.  Soil mounded up several inches at the base of the plant first will add more protection.  It is not advisable to select a plant more than one zone away from yours. Survival chances are diminished.

When it comes to flowering shrubs, the same protections are generally successful if the shrub flowers on new wood.  If they shrub forms flower buds on old wood in summer or fall, the possibility of success is diminished.  The flower buds are not always evident, but they are there. The plant should be covered with mulch right up to the tips of the branches. The easiest way to do that is usually by forming a chicken wire cage around the plant.  Then fill it to entirely cover the plant with leaves or other mulching material. Soil mounded at the base of the plant first will give you added protection to the roots.  These are common methods for rose protection.  You can use this method for Rose of Sharon, Rhododendrons, tender Hydrangea, as well as tender perennials.

Protecting larger shrubs and trees that bloom on old wood is more challenging due to size. It is difficult to build a large enough structure to protect an entire plant that grows beyond 2 or 3 feet.  If you are determined to try a tender shrub or tree, be prepared to lose it.  However, there are a few things you can do to help.  First, select a planting site that offers some protection.  Planting on the North or East side of a structure or screen of tall evergreens or a large tree will protect your plant from winter sun and wind.  But be sure the site will allow enough summer sun.  Planting close to a heated building will provide a warmer micro-climate, but beware of sun reflection from light colored surfaces.  And sometimes to get close enough to the warmth, your large shrub or tree will be quickly overgrown for the space.  Only a healthy plant has a chance of survival.  Give the shrub or tree perfect growing conditions (proper soil, drainage, sun, water and fertilizer).  Do not fertilize after mid- August, and water thoroughly in fall, gradually decreasing the water in September to allow the plant to naturally prepare for winter.  And take heart that if you can properly protect a young shrub or tree until it is well established, many will begin to acclimate to its’ growing conditions.  If it adapts and thrives, your attention was worth the effort.

Colors & Insects

Insect behavior can be influenced by color. Trap manufacturers make extensive use of color research to design more efficient ways of attracting, capturing and killing insects. If color can attract insects, then it is possible that color could be used to repel insects, but there is little evidence to support this hypothesis. For most insects, if an object is not attractive, it is simply ignored. Specific color avoidance behavior is rarely reported.

Some home owners believe that painting their porch ceiling blue will discourage wasps from building nests in the entryway. While it is unlikely that blue paint actively repels wasps, the color may not be particularly attractive to them.

Research on wasps lends limited support to this theory, insofar as research on one species of wasps can also apply to totally different wasp species in another country. The study results showed that the most effective wasp traps were yellow or green. Blue lures were one of the least effective. However, researchers also found that the same species of wasps showed changes in color preference that were dependent on the location of the trap. Black lures were the least successful at trapping wasps in two locations but were the most successful lures at a third location.

Some homeowners purchase yellow light bulbs with the expectation that the bulb will drive away moths and mosquitoes. Unfortunately, yellow light bulbs do not actively repel insect, the bulbs simply attract fewer insects. Most insects are unable to see light with a wavelength longer than 650 nanometers; red light is invisible to a moth, and yellow light, at about 580 nanometers, is difficult for most insects to see. A red bulb would attract even fewer insects, but red light also appears dim to the human eye, making it an unpopular choice for outdoor lighting.

According to the U.S. Department of Agriculture, honey bees will attack objects that resemble nest-raiding predators such as skunks and bears. Any object that is dark, furry or leathery, including a person wearing dark clothes, may be seen as a threat to bees protecting a nest. The bees may respond to the threat with aggression. Bees perceive the color red as black, so red is included on the list of colors to avoid when approaching a bee. Light-colored clothing won’t repel a honey bee, but it may be less likely to attract its attention.

Flies may be one of the few insect families that are actively repelled by a color, at least enough to avoid a fly trap. Research published in the Proceedings of the Royal Society reports that near-ultraviolet light and blue light attract tsetse flies, whereas UV-reflecting surfaces, or objects with green-yellow reflectivity, repel them. While exploring the effectiveness of house fly traps, a team of researchers at the University of Florida noticed a similar reaction to color in house flies. Blue attracted house flies, whereas yellow actively repelled them.

Unfortunately, the results of these tests may have no practical use beyond designing more effective fly traps. A yellow tablecloth on a picnic table might repel house flies but could attract more wasps.

Winterizing Perennials

Perennials that are not cut down after the growing season not only provide winter interest in your garden, but also weather the winter better. This may, in part, be because the plants hold on to some leaves in fall and snow through the winter. Ever notice that plants that are left through the winter are the last areas to lose snow in the spring? That snow is preventing the soil from warming rapidly, keeping the perennials dormant until growing season has truly arrived.  Protecting hardy perennials is good insurance against a harsh winter.

The one thing all experienced gardeners can agree on regarding this subject is never cut a perennial to the ground while the foliage is still green.  The plant is still working on reserving energy for spring growth.  Wait until all foliage has died back naturally or until after a hard freeze to remove top growth.  Some plants that are cut back too soon may try to regrow in warm fall periods, not leaving enough energy to survive winter, or to produce a plant in spring.

The difference of opinion among gardeners relates to when foliage should be cut back, spring or fall.  Much research has made it clear that, at least with marginally hardy plants, old growth should be left through winter.  The stems catch and hold leaves and snow which are nature’s natural protective mulch.  The old plants will also provide some winter structure and interest.  Some are more attractive than others, with interesting seed capsules or dried seed heads.  However, any diseased or damaged foliage should be removed and disposed of to help control the problem next year.  Cutting back plants that were afflicted with insect problems such as borers or insects that lay their eggs in or on the plants will also reduce the likelihood of insect infestation next year.

The hardiest of perennials can be cut back to the ground in fall without much concern for survival.  If you have had any problems with disease or fungus, it is best to remove all old top growth before winter to help reduce the possibility of the disease recurring.  Even with marginally hardy plants, persistent disease may be eliminated if the infected foliage is removed.  Be sure to heavily mulch instead, or mound protective soil at the base, and then mulch.

Late Fall & Your Clematis

There are many clematis hardy enough for the northern zones that need no winter protection other than, perhaps, some extra mulching. But clematis is often a special plant for a special spot. Finding the perfect one may take you out of your zone, and you may be quite willing to make an exception to a “no special care” policy.

Clematis twist their stalks around a support. If you use a mesh such as chicken wire around/over your support structure, the tender plant will be attached to the mesh rather than the structure. Before winter remove the mesh with the vine attached and lay it flat on the ground. Mulch the base heavily and cover the entire plant. If you need to lay your mesh out over the lawn, cover it with leaves and stake down burlap over.  Or just pile your bagged leaves from the lawn on top.  In spring, remove the mulch and reattach the mesh. When growth starts, prune back to a few strong shoots and remove the dead vines. (Note that pruning times can be different for hardy clematis, based on whether they flower on new or old growth.)

If your clematis was afflicted with a fungal disease, remove all infected vines and dispose of them by bagging or burning.  Cover the crown with a few inches of soil so it is now “deep planted”.  The most damaging fungus to clematis attacks at the soil line.  Then cover with at least a few inches of mulch.  Your clematis may regenerate, but could take a few years to fully recover.  Apply a sulfur based fungicide in spring.

Fall Color Suggestions

Arrowwood viburnum bears white flowers in spring. In autumn, Arrowwood viburnum shrubs give you a 2-for-1: nice fall foliage and blue berries. They can range anywhere from 6 feet tall to 15 feet tall.

Fothergilla (Fothergilla major) is a spherical multi-stemmed shrub with white flowers in spring that carry a fragrant aroma. In fall the dark green foliage of summer changes to colors of yellow, orange and scarlet. Reaching ten feet in height and spreading up to nine feet it should be planted in a sunny or partially-sunny location on your landscape.

‘Tor’ spirea (Spiraea betulifolia ‘Tor’) reaches a height of 2-3′ and spreads out 2-3′. It requires full sun. The shrub’s foliage is dark green in summer, but its fall color is red. In May the plant bears small, white flowers in clusters.

Blackhaw viburnum (Viburnum prunifolium) is similar to the shrub Hawthorn in the way that it grows except it has no thorns. The shrub yields white flowers in May, which become an edible fruit at harvest time. Fall color is offered not only by these bluish-black berries but also by colorful leaves. Dark green foliage morphs to purple to reddish-bronze to a crimson in fall. It achieves a height of 12-15′ and a spread 8-12′.

Oakleaf hydrangea (Hydrangea quercifolia) offers white flowers in summer that fade to a pinkish-brown in fall. But the plant’s inclusion on this list is due to its foliage, not its flowers. Its oak leaf-like foliage turns reddish, bronzy-orange or purplish in the fall. Tolerant of light shade, they achieve a height of 4-6′ and a spread of 4-6′.

American bittersweet is a must-have for those serious about providing the landscape with fall color. The berries, green in summer, bear a yellow husk in early fall. Even at this stage, they provide a truly striking display of fall color. But this initial treat is merely a foretaste of the splendor to come. For, as autumn progresses, the husk peels back, revealing an orange berry within. And as if that weren’t enough, the numerous leaves of the vine turn a vivid yellow.

Red chokeberry (Aronia arbutifolia) reaches a height of 6-10′ and a spread of 3-5′. This shrub has white flowers in early spring, which become glossy red berries in the summer. In autumn the berry color can turn deeper, almost to purple, providing interesting fall color. Although this shrub tolerates poor soil and shade, landscapers seeking maximum fall color from its berries should plant it in a sunny location.

Viking black chokeberry (Aronia melanocarpa ‘Viking’) bears white flowers in May with dark green foliage. The foliage morphs first to red, then to purple in the fall. Reaching a height of 3-5′ and spreading out to 3-5′, the plant tolerates wet soil better than most. The berries produced by this shrub grow in clusters and are a blackish-purple. Although not edible for humans, the bitter-tasting berries remain on the shrub well into the winter and serve as an emergency food source for birds.

When & Why Winter Mulch

The main idea behind winter mulching is to keep the ground frozen by shielding it from the warmth of the sun. A steady temperature will keep the plant in dormancy and prevent it from triggering new growth during a brief warm spell. Tender, new growth too soon will just result in more winter die back. Mulching now will also help conserve whatever water is in the soil, so hopefully you’ve been keeping your garden beds watered right up until the hard frost.

Protect Crowns & Surface Roots: (Especially newly planted plants) Mulching to protect most perennial plants is done when the soil has started to harden, which is generally after the first hard or killing frost. A hard frost is usually defined as when temperatures drop to below 25 degrees F., but you’ll know it when you see the last of the hardy annuals crumbled and brown in the morning. At this point, your perennials should be well into dormancy and mulching around them won’t encourage tender new growth. The ground has had time to chill and absorb fall moisture. Go ahead and spread a 2-4″ layer of mulch around the base of the plants.

Grafted plants, like hybrid tea roses, benefit from being mulched more heavily. These are usually mulched with compost or soil and are actually buried to just over the graft union. You can pile the soil up around the stems or you can use some wire fencing and fill with compost.

Prevent Dessication: Some shrubs that are evergreen or somewhat evergreen, like rhododendrons and viburnums, can become desiccated by harsh winds. You can protect the branches and buds by wrapping them with burlap or by spraying on an anti-desiccant, like Wilt-Pruf. (Anti-desiccants are handy to have around. You can prolong the life of your Christmas tree with a spray. They’re also good for coating carved pumpkins.) If you choose to wrap your shrubs, make certain there is space between the branches and the burlap or the burlap will freeze onto the branches and cause its own problem. You can also fill the space between the shrub and burlap with leaves, for additional insulation.

Woody plants don’t require as much protection as herbaceous perennials. However, a 2 – 4″ layer of shredded bark mulch or compost does help conserve the ground moisture. Just be sure not to pile it around the base of the plants. Keep it several inches from the stems or you’ll invite rodents, like voles and mice, who like the cover of mulch while munching on bark. Mulching up against the stems also holds too much moisture against the plant, providing ideal conditions for diseases to take hold.

Prevent Heaving: When the ground repeatedly freezes and thaws, it expands and contracts. When a plant is sitting in ground that expands and contracts, its roots get loosened from where they are anchored underground and the plant eventually gets pushed up through the surface of the soil, exposing its crown and roots to freezing temperatures and drying winds, which brings us right back to Reason to Winter Mulch #1. Again, you would wait until the top of the plant has died back and the ground has frozen, before applying a layer of mulch.

Prevent Erosion: (Especially important for fallow gardens, like vegetable gardens during winter.) Mulching unplanted garden beds can be done at any time in the fall. Ideally, you would plant a winter cover crop and let it sit until you till it under in the spring. If you choose not to plant a cover crop, it would still be beneficial to spread a layer of compost, manure or shredded leaves. I use my vegetable garden as a corral for my shredded leaves. They mulch the vegetable garden all winter and in the spring, I spread them as mulch in my flower beds.