Author: digman

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Dandelions & Potassium

Spring is here and our lawns look like they have the horticultural counterpart of the measles, but the spots are yellow, not pink. This leads to the stratification of gardeners into three groups. There are those who reach for an herbicide to get rid of dandelions, then the more environmentally concerned who pinch off seed pods and dig up what they can – and lastly those who simply accept things as they are since after all, it’s only Taraxacum officinale, alias dandelion. The first group of gardeners may receive some relief as a result of what American ecologists saw at the Rothamsted Experimental Station in England. They noticed there was a mosaic of plots in this grassland. Some plots, yellow with dandelion blooms, were bordered by plots where dandelions were almost absent despite the heavy rain of dandelion seed received annually. They found that the dandelion population was related to whether potassium had been applied.

Following tip on this observation the Minnesota group studied the effects of potassium on dandelions and five lawn grasses in a greenhouse environment and the relationship between the amount of potassium in plant tissue and the density of dandelions of lawns in Minnesota. In the greenhouse study potassium was highest in dandelion tissue, suggesting dandelion has a hearty appetite for this element. They also found that in pots given a low potassium fertilizer the dry weight of dandelion, fescues and orchard grass all decreased BUT dandelion suffered the greatest loss, down to 81% of its weight in pots given a complete mineral supplement.

The lawns selected for study were restricted to those that had not been fertilized, treated with herbicide or hand-weeded for several years. The amount of cover as well as the density of dandelions correlated with the tissue potassium content. When the plant tissue level of potassium was low, the dandelion density and cover in the lawns was low. Based on these results it is suggested that one step gardeners could take right now is to use a fertilizer of ammonium sulfate or ammonium phosphate, However, this would not be good for lawns of Kentucky bluegrass which is almost as greedy for potassium as dandelions.

At this time it is unclear how widely applicable the strategy of controlling weeds through nutrient limitations will turn out to be. In the opinion of agricultural and weed scientists, it appears to be an area that is worthwhile to follow up, for the relationship between soil characteristics and weeds is only beginning to be understood.

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Integrated Pest Management

Hawthorn lace bugs plague many plants in the rose family including hawthorn, apple, cotoneaster, and firethorn. Adults have partially transparent wings with an intricate lacy pattern and opaque areas. Look for a whitish speckled appearance on the tops of leaves. The lower surfaces of the leaves are often discolored with excrement and cast skins of the developing nymphs. Use horticultural oil or a pesticide containing acephate and be sure to spray thoroughly on the underside of the leaves if large numbers of lace bugs are present.

During periods of dry weather, allow your lawn to go dormant to avoid turf diseases and to discourage weeds. If a green lawn is a must, water early in the morning and adjust your mowing height above two and a half inches.

Adult Japanese beetles feed on the foliage and flowers of over 300 different plants during the hot, summer weeks of July. These beetles have a metallic green body with reddish-bronze wing covers and are the size of a coffee bean. After mating, adult females lay eggs in turf. Dry soil conditions kill many of the eggs, so avoid watering lawns in July and August. To prevent serious damage, handpick the beetles daily in the early morning when they are less active and drop them into a bucket of soapy water.

Powdery mildew, a fungal disease that attacks the leaf surfaces of many flowers, shrubs, and trees, is a growing problem for dogwoods. Look for white powdery patches on the upper surface of new growth. This disease can cause the new growth to be curled and deformed, and often reduces the growth of very small trees. Loss of photosynthesis can also weaken the trees making them more susceptible to dogwood borers and canker diseases. To prevent powdery mildew, avoid heavy doses of nitrogen fertilizer, overhead watering, and excessive pruning. These practices can force tender new growth that is more susceptible to the fungus. Provide your trees with good air circulation, prune out dead wood, and place a thin layer of mulch over the root system. There are disease-resistant flowering dogwood cultivars available also such as ‘Cherokee Brave’ and ‘Sweetwater’.

Monitor your boxwoods for boxwood mites. These spider relatives are small, red, and slow moving. Yellowish stippling in a linear pattern appears on old foliage when mite populations are high. Beat test by tapping a stem onto a piece of white paper. Consider spraying with horticultural oil when the count exceeds twenty or more mites per beat. Do not spray if faster moving predatory spider mites, or small, jet-black mite destroyer ladybugs are present.

Monitor your plants for thrips. These very small insects may be found in the flowers and leaves of many plants. Thrips are orange to brown in color and they scrape leaves and petals with their mouthparts. Look for white streaks, curled leaves, and stunted growth. Find thrips by using the beat test. Gently tap a branch of the plant onto a piece of white paper and look for the thrips on the paper. If you count more than five thrips and the foliage shows signs of damage, you may want to consider spraying with a pesticide labeled for thrips. Before spraying, look for minute pirate bugs, small black insects that feed on thrips. They also feed on pollen, so look for them on the flowers. Refrain from spraying if these predators are present.

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Butterflies and Caterpillars in Your Garden

There is no more delightful decoration for a garden than nature’s own–butterflies. On a warm sunny day these visitors provide color and motion that doubles the pleasure of gardening. How fortunate for the gardener that it takes very little effort to make the yard attractive to butterflies!
Butterflies will visit, and possibly stay to lay eggs, wherever there is a variety of plants for food and shelter, some moisture, and an absence of pesticides. While there are typically more species in warm climates than in cooler ones, there are butterflies almost everywhere in the country. Their appearance in your backyard ultimately depends on whether their favorite plants are growing there–certain ones to support their larvae, many others to support adult butterflies.

Larvae (Caterpillar) Host Plants

The typical garden is not likely to incidentally have plants that host the larvae of most butterflies. The caterpillars of each species are usually are pretty picky, favoring the foliage of specific plants or plant groups at this stage of their lives. Larval host plants are often unattractive, weedy and wild, generally unfit for cultivated gardens [see box]. Yet, adult female butterflies choose these particular plants (Monarch moms must have milkweed!) to lay their eggs on. This assures that newly hatched caterpillars have appropriate food immediately at hand.

Typically, young caterpillars begin voracious feeding immediately after hatching, virtually skeletonizing host plant foliage. Watch a parsleyworm, (a swallowtail caterpillar) devour the foliage of Queen Anne’s Lace, carrots, or parsley! Butterfly larvae grow as they eat, shedding their skins 4 to 6 times before achieving maximum size for pupating. Only then do they desist, becoming immobile in a hard chrysalis suspended from a leaf or stem of the larval host plant until emerging as an adult butterfly.

All-time Butterfly Flower Favorites

-Aster
-Black-eyed Susan
-Butterfly bush
-Butterfly weed
-Coreopsis
-Joe-Pye weed
-Lantana
-Liatris
-Pentas
-Purple Coneflower

Butterfly Host Plants

Fortunately, adult butterflies have more cosmopolitan palates. The flower nectar they need for energy is available in lots of different flowering plants. They will visit your yard in search of those that are most easily accessed by their long, coiled tongues, or proboscis, which enables them to reach deeply into the center of flowers where the glands that produce the sweet nectar are located. They are particularly attracted to hot-colored, fragrant flowers. They get further nutrition from moisture from puddles and raindrops, rotting carrion and other liquids–even human perspiration if you stand very still–that provide traces of minerals and nutrients not in nectar.

Butterfly Garden Design

The butterfly gardener’s challenge is to provide diversity of plants in communities throughout the property to support both larvae and adults. Variety is the key. Choose lots of kinds of plants–herbs, annuals, and perennials as vines, groundcovers and in beds, plus shrubs and trees. Wildflower meadows featuring native plants are ideal. Food crops add to the diversity too. Assure that blooms are available to visiting butterflies for the entire season. The greater the variety of suitable plants, the greater the potential number and variety of types of butterfly visitors.

It is not necessary to integrate larval and adult plants throughout landscape. Just allow some part of your yard or nearby property to remain weedy and undeveloped to lure female butterflies to lay eggs. Somewhere in the yard, let fresh water accumulate to support communal “mudpuddling”, so butterflies get soil salts and minerals as well as moisture. Overripe fruit that has dropped from trees also provides nutritious moisture. Finally, butterflies like some flat stones for basking, or sunbathing, to gather warmth to power their wings.

Butterflies visit flowering plants that are in full sun and in sites sheltered from wind in beds or containers. Protect garden beds exposed to the wind with a hedge of glossy abelia or butterfly bushes or a wall or pergola covered with honeysuckle or passionflower. Flowering shrubs provide shelter for roosting too. The more fragrant, the better. Plant at various heights, because like birds, certain butterfly species prefer to feed at certain heights. (Some species are even quite territorial and try to chase others from favorite plants).

Finally, unlike the famous monarchs which migrate to Mexico and other points south, most butterfly species overwinter nearby. This means that their eggs, chrysalises, or larvae are likely to be in or near your yard during the non-gardening months. Some will even hibernate as adults. Do not mow weedy sites and dismantle woodpiles which provide them safe shelter in the off-season.

Caterpillars: Distinguishing Friend From Foe

Butterfly larvae tend to be solitary, or sparsely distributed, whereas pest caterpillars such as fall webworm make tents and hatch in the hundreds. The latter are best handled by pruning the tent out of the tree or breaking it open so that the birds can eat the immature larvae.

However, even in sparse numbers butterfly caterpillars can damage ornamentals or food plants. For example, the ubiquitous white cabbage butterfly lays lots of eggs that turn into destructive green worms which devour cabbage and broccoli and their relatives. An insecticide product containing Bt (Bacillus thuringiensis) sprayed onto plant foliage will handle feeding worms that threaten to destroy crop yields. In the case of parsleyworms on parsley, simply moving them to a non-essential plant such as wild carrot will both save the crop and preserve the eventual butterfly.

Favorite Larval Host Plants:

-Asters
-Bermuda grass
-Clover
-Hollyhock
-Lupine
-Mallow
-Marigold
-Milkweed
-Nettle/thistles
-Parsley
-Passionflower
-Plantain
-Snapdragon
-Sorrel
-St. Augustine grass
-Turtlehead
-Violet

The Best Butterfly Blooms Are:

-composites, umbels, and panicles, whose clusters of small florets provide many sips plus a place to pause. -brightly colored in lavender, purple, red, orange and yellow. -single-flowered types where the nectar is more accessible. -flat or tubular in varied lengths. -planted in drifts and clusters for efficient grazing. -fragrant.

Flowering Plants Whose Flowers Attract Adult Butterflies:

Common Name Botanical Name
Aster, New England Aster novae-angliae
Beebalm Monarda sp.
Black-eyed Susan Rudbeckia sp.
Blanket flower Gaillardia sp.
Blazing star Liatris sp.
Butterfly bush Buddleia sp.
Butterfly weed Asclepias tuberosa
Candytuft Iberis sempervirens
Cardinal Flower Lobelia Cardinalis
Catmint Nepeta
Coneflower, Purple Echinacea purpurea
Daisy, Ox Leucanthemum sp.
Gas plant Dictamnus Fraxinella
Goldenrod Solidago sp.
Globe thistle Echinops Ritro
Hyssop, Anise Agastache Foeniculum
Joe-pye weed Eupatorium purpureum
Jupiter’s beard Centranthus ruber
Lantana Lantana Camara
Lavender Lavandula sp.
Lupine Lupinus
Milkweed, Swamp Asclepias incarnata
Milkweed, Common Asclepias syriaca
Mountain bluet Centaurea sp.
Pentas Pentas lanceolata
Phlox, Garden Phlox paniculata
Sneezeweed Helenium autumnale
Sage, Scarlet Salvia coccinea
Tickseed Coreopis sp.
Turtlehead Chelone glabra
Verbena Verbena bonariensis
Yarrow Achillea sp.
Zinnia Zinnia sp.

Provided by the National Garden Bureau www.ngb.org.