Autumn:

Yard Cleanup Can Control Insects

Cleaning up gardens and flower beds in the fall can be an effective way to control various pests - weeds and diseases of course, but insects especially. Removing any debris on the soil will cut into the ability of many insects to survive.

In winter, the soil temperature is higher than the air temperature. This is because various components in the soil act as a buffer against severe freezing temperatures. Any trash or debris allows the insects to settle in and overwinter, emerging next spring to raise havoc with emerging leaves, flowers, or other freshly planted crops. In essence, the removal of debris allows the soil to freeze to a greater depth, resulting in a more complete insect kill.

The cleanup is best done in early October, generally around Columbus Day. By this time a sufficient number of frosty days and nights have passed to discourage further insect activity, usually forcing them into the soil, preferably starting under any existing trash. With lawns, simple raking of the fallen leaves will suffice; in gardens, a light roto-tilling will do the trick. This later activity will be effective in checking the beet leaf miner, cabbage root maggot, Colorado potato beetle, flea beetle, imported cabbage worm, and onion maggot. Tilling organic matter (be careful of the source!) into the soil at this time is also good for improving tilth for next growing season.

Raking and cleaning up around shrubs and herbaceous perennials will do wonders in controlling the following insect pests: Currant fruit fly, imported currant worm, pear slug, rose curculio, and spring cankerworm. While some foliage can remain behind to help trap snow, it should be selectively done. Foliage on mums or Russian sage is acceptable, but with hostas, it is a definite no-no.

Controlling Slugs

This is probably the most detested pest found by homeowners in the garden. The frustrated gardener often resorts to whatever insecticide is on hand, which results in further frustration because of poor or non-control. Our garden slug is related to (think about this next time you have some...) clams, oysters, and of course, snail (escargot).

Slugs love shady, damp places. The denser the landscape, the more water applied, the better they like it, and the more they will proliferate! Slugs secrete a slimy mucous that protects their bodies against drying out and abrasion. The mucous also provides a slippery trail on which the slug can slide smoothly along. These highly visible trails are a good indication of slug activity in the garden.

While they are voracious feeders, they have their preferences too! They tend to prefer decaying plant and fungal material, but when the supply is limited or competition becomes heavy, they are not above digging into succulent growth such as found on lettuce, tomatoes, and pepper leaves. They also will feed on potatoes and carrots, with most of their dining taking place at night.

They are most active in a warm, moist environment. Temperature extremes and dry conditions slow their feeding and development. The shade of trees and shrubs, perennials, and even heavy thatch in lawns have been known to be breeding places for these creatures. Slugs start out small in life, hatching in late spring or early summer, feeding heavily, and getting larger, until their damage and presence becomes noticed by the average home gardener in late summer or early fall.

It is during this time that eggs are laid just below the soil surface in clusters of 200 to 300 . Unfortunately, they can tolerate severe temperature conditions in this stage, easily surviving winter.

To combat slugs, carry on with the following:
      Don't allow the landscape to become overcrowded
      Don't over-water
      Cleanup methodically every fall before the ground freezes
      Keep weeds to a minimum
      Place a circle of crushed egg shells or Diatomaceous earth around plant material being harassed by slugs. This penetrates their soft body tissue, causing dehydration and eventual death
      Use the usual tricks: stale beer in a shallow saucer (non-alcoholic will do), laying a board down in a damp area, then hand pick those that collect under it.
      Also use the usual mollusicides - Metaldehyde and Methiocarb - in the appropriate manner and places.

The Fall Frost Questions

It happens every autumn (or late summer, in some cases!) in ND - we get killing frosts! What to do with the vegetables and apples? Well, the answer lies in many little nuances of nature. How cold it will actually get; how long it stays that cold; the condition - the degree of hydration of the plants and fruits/vegetables in question - whether there is surrounding protection from buildings and other plant materials; if the tree or garden is located in the lowest part of the property where cold air drains; and whether or not a cloud cover or wind exists.

Now let's examine the freezing terms or cold snaps our plant materials can experience:

Radiation Frost: Occurs on cloudless and relatively quiet nights. Ground heat radiates to the sky; air near the soil level is cooled and the heavy cold air will drift to low spots. Humidity and clouds will vary the heat loss from the ground during the night, peaking just before sunrise.

Advective Freeze: An arctic cold air mass that is dry, often accompanied by winds.

Inversions: An inversion occurs when a warm air mass floats over cold air close to the ground. The sun warms the earth during the day, with the air becoming cooler at higher elevations. On a cool, clear, quiet night, some 50 to 500 ft above, the air is warmer than at ground level, hence an inversion.

Dewpoint: This is the temperature at which moisture begins to condense from the air mass. The more water vapor in the air, the higher the dewpoint temperature. As water vapor condenses and changes back to liquid water, it releases stored latent heat. When the dewpoint temperature is above the critical temperature - freezing of tissue - the fruit tree owner benefits by a slower temperature drop due to latent heat being released from water vapor as it condenses to dew or frost.

Typically, the dewpoint gets lower the further west one goes in the state. Hence more damaging frosts can occur in Dickinson or Williston than in Valley City or Fargo, because of the more rapid drop in temperature and the longer exposure to that low point.

The first frost on apple trees will usually begin leaf color change and defoliation. As that occurs, the apples increase in vulnerability to future hard frosts. The sugar content will protect them from soft or light frosts, but when the temperature gets into the mid 20's, it is time to protect or harvest shortly, and begin making applesauce.

Tomatoes will need to be harvested immediately after frost. Green, mature tomatoes can be collected, kept inside at room temperature, and develop a nice red blush. Squash and pumpkins - assuming a good foliage canopy cover - can take the first frost, but are then vulnerable to future frosts, and need to be protected or harvested before the next one arrives. Root crops like carrots, beets, turnips and others can stay in the soil until the snow flies or to just before the soil freezes.

Hardy Bulb Planting Time

Fall is bulb-planting time! A visit to the garden centers and a review of the fall catalogs will reveal the potential beauty that one can enjoy the following spring with a little effort before the soil freezes. Bulbs consist of a growing tip or bud surrounded by fleshy layers of tissue containing stored food. All are held together by a hardened disk which is old stem tissue, referred to as a plate. This plate is the area where the roots develop from during the active growth phase of the bulb. When the bulbs are purchased at this time of year, the roots are not present. The flower buds were formed during the summer, as the leaves were dying down. Unless the grower has provided them with a cold treatment (a common practice to bulbs that are sent to the deep south) they will not bloom. Hence, they need a northern prairie winter treatment to bloom their best next spring.

Generally, the bigger the bulb for the species, the better the blooming vigor. Reject any bulbs that are not firm to a slight squeeze. Plant them as soon as they hit the market for maximum establishment time. This may be a problem with some mail order catalogs, but plant them even if they arrive with snow flying - just as long as the soil is not frozen. Plant them deep enough - roughly eight inches for tulips and narcissus in sandy soils, and about three inches shallower in heavier soils. Bulbs have the ability to survive many adverse conditions, except poor drainage.

Set the bulbs about six inches apart, keeping the varieties and colors separate for best effect. Keep in mind also, the height of the flowers when setting them out. Small, minor bulbs such as grape hyacinths, squill, or puschkinia can be lost on large properties or beds dominated with other shrubs or flowers. These smaller bulbs are best used as "vest pocket" points of interest closer to the entry or patio areas.

Plant the bulbs with the flat side down and the pointed tip up. Make sure they are firmly set in place, carefully back-filling with soil. Careless dumping of soil over the bulbs can cause them to be knocked off vertical with something less than an attractive showing next spring. Water thoroughly immediately after planting, and again until the soil freezes.

Soil conditioners such as peat moss, or compost are good additions, but stay away from manure. It is believed to be the source botrytis and other fungal diseases, to which tulips and other bulbs are very susceptible.

Saving Geraniums For Next Year!

The first frosts of fall bring the growth and beauty of annuals to a halt. With geraniums, usually the top inch or two is damaged, but the rest of the stem, being protected by the leaves is usually unscathed by these initial frosty periods. Many gardeners, being a frugal lot, want to save them to grow on the following year. How can they do it?

First, discard any obviously diseased plants. Make sure too, that none will be stored that are harboring insects - adults, pupa or larvae. Then, cut the plants back to about three to four inches after shaking most of the soil off the roots. They can then be stored in unwaxed brown paper bags, and hung in the coolest part of the basement. Check them on at least a monthly basis thereafter to be sure they have not shriveled to a major extent. If they have - and this is likely at least once or twice through the long winter months - soak them in tepid water until they appear re-hydrated. Allow them to sit on a bench or counter until they are surface dry, then re-bag them again. It is found that the bag enclosure helps to slow the drying out of the plants too rapidly. Under no circumstances should the plants be placed in plastic bags.

Around the first week in February, pot them up and place in a sunny south or west window, or under some Gro-Lights. If you can give them long days (12+hours) of light, they will come into flower sooner. They will generally remain vegetative otherwise. Fertilize as they show active growth, and move outdoors when danger of frost is past.

Fall - Best Time For Tree Fertilization

From mid-September until freeze-up is a good time for tree fertilization. This is the time period when root activity is high and top growth is declining or has ceased altogether. There are several ways to carry out this task. One is to drill holes in a grid pattern around either side of the tree's dripline. The holes should be done with a two inch soil bore - either gas powered or by hand - and spaced about two feet apart. Go down about 18 inches, then place about two tablespoons - or four ounces - of a balanced fertilizer into each hole. A formulation of 10-10-10 (N-P-K) or something similar would be acceptable.

If the soil is heavy or compacted, fill the holes with sand/peat (50/50), or pea gravel, otherwise replace with the same soil. This will help get oxygen into the root zone, making more effective use of the fertilizer being applied.

After fertilization, soak the soil around the tree with a slow trickle. Try to avoid any runoff. Repeat this unless ample rains follow, until the ground freezes.

There will most likely be noticeable green rings around the tree next spring from the grass's reaction to the presence of the fertilizer and aerated soil. This can act as a friendly reminder to fertilize the rest of the lawn, which will help to make the grass more uniform in color.

Fall - Best Time For Planting Trees and Shrubs

Fall is the perfect time to plant woody plants - trees and shrubs - in the home landscape. The outdoors is particularly enjoyable for gardeners after the first killing frost because mosquitos are finally out of commission, and the temperatures are usually moderate during the daylight hours. There is also still plenty of residual soil heat and ample moisture that will help to get the plant established through continued root activity.

First on the agenda is to select where and what to plant. The most common mistake made by homeowners is to select the "perfect" tree, but place it in the landscape improperly. This is usually not realized until the tree begins to mature, and an overcrowded landscape becomes apparent. What looks cute when small, can become overpowering and dominant if the tree, house and property are not synced to scale.

Dig the hole at the site where the tree is to be located, and fill it with water. Observe how well the hole drains. If it is not completely empty in 48 hours, plan another location for the tree or do something to correct the poor drainage. When the hole is completed and checked for drainage, be sure it is the right depth - so that the tree is slightly above the depth it was at the nursery, and plenty wide. Never try and cram roots or root ball into a small planting hole!

After placing the tree in the hole, refill with the soil that was originally removed. As it is refilled, gently firm and water the soil to be sure no air pockets remain. Keep the root system well watered until freeze-up.

Winter:

Plants Make The Perfect Holiday Gift

Why are more and more people giving plants as gifts for the holidays? Perhaps because plants meet all the criteria for easy and thoughtful gift-giving. They are long-lasting, distinctive, and appropriate for both business associates and close personal friends.

Many houseplants will live for years with minimal care, reminding the recipient of the giver long after the holidays have passed. Not only are plants a living reminder of a meaningful friendship or family relationship, they make an unusual gift in this age of fast-changing electronic gadgets. Perhaps the best reason to give plants for the holidays is that they can either be as business-like or personal as you choose. The simple dignity of a poinsettia, paper-white narcissus or amaryllis, in a white ceramic container with a satin bow, is hard to beat for customers or co-workers.

To tweak the heart strings, give your spouse the showiest, most fragrant gardenia you can find! Other more personal gift plants might be kitchen herb gardens, backyard wildflower seeds, or garden planner kits for nature lovers who can hardly wait for winter to end!

Understanding Light Requirements For Indoor Plants

Daylength or photoperiodism, and light intensity are extremely important factors in growing quality indoor plants. Our indoor home environment can be a jumble of messages for the houseplants to interpret. Consider: Everyone is gone from the house on a typical Monday through Friday, either at school or work. A couple of nights a week the kids stay up late working on a homework project, or mom or dad have found a book that is difficult to put down until the wee hours; on weekends everyone tries to sleep in, and Saturday night everyone has an agenda for late hours. Most home interiors have a preponderance of incandescent light - the wrong end of the spectrum for good plant growth - and some people like their homes at 80º F, while others try to keep it below 70º. Sometimes the kids are the last ones to bed, leaving a majority of lights on for the entire night. Any wonder then, why houseplant problems exist and are difficult to isolate?

Plants grown under poor or low light intensity will usually exhibit etiolated growth - weak, spindly, and pale. With adequate light intensity from the correct light spectrum, plants will be stocky, strong, and have good color. Unfortunately, there are many confusing terms used to express light intensity: Footcandle - the amount of light received from a standard candle on a one square foot surface, one foot away from the source. Lux - a metric term often used, to state the amount of light received from a standard candle on a square meter of surface at a distance of one square meter. Then, there's the Lumen - a term used to express the intensity or brightness of the light being given off by the source. One lumen is the total light given off from a standard candle.

The best source of artificial lighting for the homeowner is through the use of a pair of fluorescent tubes. Beneath these, as much as 1000 fc (foot candles) can be achieved. This would have the lights about six inches above some flats for germinating seeds. 320 - 400 fc would be the "usual" at foliage height of typical potted plants. Intensities can be boosted somewhat by using fixtures with reflectors, adding additional lights, or by placing reflecting surfaces behind, around, or under the plants. Where low light intensities may still be a problem, they can often be compensated for by increasing the duration (length of time) of the light. This can easily be accomplished through timers connected to light banks.

Fluorescent tubes - the cool white type typically used in commercial buildings - would provide adequate light spectra for foliage growth, but very poor for flower development. Adding incandescent bulbs to the bank of lights would provide the wavelength in the red end of the spectrum for flower development. This combination, although archaic, does an adequate job for most situations and is considerably less expensive than the special plant light bulbs on the market. The inverse square law applies to light intensity, which decreases by the square of the distance between the light source and the receiving surface (See Illustration 1.).

Plants with the same light requirements should be grouped together to achieve success. Keep in mind that even a seemingly minor relocation of a plant, the opening or closing of curtains, and the age of the light bulbs can have an impact on the light intensity and quality. Refer to Table 1 and Illustration 2 and 3 for clarification.

Spring:

Selecting and Planting Bedding Plants

As spring planting season approaches, here are some pointers on the selection and planting of bedding plants.

Selection: First, big is not always better. This is especially true when selecting vegetable seedlings. Select stocky plants with healthy, dark green foliage. Avoid any tall or spindly plants. Larger plants don't necessarily lead to earlier production or higher yields. Large plants will be subject to greater transplanting shock and will take longer to get established. While initially behind in size, the smaller plants will often catch and surpass the larger plants quickly.

Hardening: Bedding plants which have been raised indoors or purchased from a greenhouse should not be planted directly into the garden or landscape. The hot/cold winds and strong sun of our prairie environment may damage the young tender seedlings. Instead, they should be hardened before transplanting. Initially place the plants in a protected location during the day, away from the direct sun, and sheltered from high winds. Then gradually, expose the plants to these elements, being sure to bring them inside each night to protect from spring frosts. Check for water, as the potting soil will dry out quickly on a warm or windy day, making these young plants vulnerable to permanent wilt and death. After about a week to ten days of this routine, the plants will be ready for planting in their final location.

Starter Fertilizer: When setting transplants into the garden, the use of a starter fertilizer will aid establishment. Generally a water-soluble material is the most effective, with several brand options being available on the market. When transplanting, set the plants deep into a "saucer" of soil for protection and to collect water. Water in well, then add about a cup of fertilizer solution to each plant. If the area is accessible by garden hose, use a material that can pass through a hose-on sprayer, such as Miracle-Gro.

Dead Grass In Shady Areas

Homeowners are often dismayed to find a large portion of their turfgrass dead beneath the canopy of their trees. Many suspect it to be a disease - such as snow mold - vole damage - or insect problems - such as grubs. While any of the above are possibilities, it is often found to be a combination of tree and turfgrass species, shade, drought, and over-fertilization.

In some cases, such as under mature maple, elm or willow trees, the shade is too dense for even shade-tolerant grass species to grow. This dense canopy can cause drought stress, weakening the turf going into the winter months, making it vulnerable to winter kill. In some cases, the grass was over-fertilized. Shade-grown grasses need about 1/2 the amount of nitrogen per 1000 square feet that sun grown grass needs. In most cases also, the grass is a Kentucky bluegrass cultivar. Even those that tout shade tolerance such as Glade and Ben-Sun (A-34) will succumb if the shade is more than 50%.

The answer is to not fight it and grow something else, or simply put a mulch under a portion of the tree canopy, with a minimum of 10 feet in diameter on mature trees. Next, seed between the mulched area with a shade tolerant species such as one of the fine leaf fescues. They are not only best for heavy shade situations, but they can tolerate (and look pretty good too) droughty and infertile soils.

Some suggestions would be:

Remember: Shade-grown grasses - any species, require just half the amount of nitrogen, and are more traffic intolerant than the sun grown counterparts.

Diseases That Thrive In Wet Weather

Wet spring weather is likely to give a boost to diseases of fruits, ornamentals, and turf. Important diseases to look for are: scab on apples, Botrytis on strawberries, and black rot on grapes. Also look for cedar-apple and cedar-hawthorn rust to appear on their respective alternate hosts, leaf spot on iris, and anthracnose on ash and maples. As the weather warms and especially if the moisture remains, look for Fireblight bacterium outbreaks on apples, crabapples, Juneberries, Mt. Ash, and others. Spring dead spot, a crown rotting and root destroying fungus gets started under these ideal conditions as well. It then manifests itself later in the summer when the weather is hot, and the lawn is stressed from the heat and lack of natural rainfall.

Last season, many samples of Prunus came in with shothole fungus. This disease gets a lot of attention at the time it hits, then is forgotten when the leaves drop. It is one of the easiest fungus diseases to control while the plants are still dormant. A spray with lime-sulfur or Captan while still dormant will take care of the overwintering spores in the lesions and bud scales on the tree. The previous season also saw a heavy infection of black spot on hybrid roses. Here again, the dormant spraying of the canes after the spring pruning with lime-sulfur will initiate good control. Follow up from there as the leaves unfold with Daconil 2787. If peonies had a history of leaf spot the previous year, it was likely a Phytophthora fungus. This can be controlled with a fungicide containing maneb, mancozeb, or zineb.

Summer:

Early Reminders:

To get through a spring or early summer without some sort of storm related damage to the landscape plants is more of an exception, rather than the rule. Hail, of course, is the worst culprit for sudden and unpredictable damage to flowers, vegetables, and ornamentals. Most plantings will recover if the damage is not too severe, and the plants are given a little extra care. Try a light fertilization with a water-soluble material and see if any perking up occurs. If nothing shows response in 7 to 10 days, then it is time to replant or give up for the year.

Heavy rains will often cause the soil to crust over, resulting in poor emergence and the eventual stand of vegetables or flowers. Mulching lightly with cured sawdust, compost, peat moss, or grass clippings right after planting, will help to reduce this problem.

High winds are most seriously destructive on older, and usually boulevard planted trees where root systems are limited or in a state of decay from age, salt accumulation, compaction, etc. These trees should have corrective pruning, bracing, cabling, or removal carried out by professional arborists who know what they are doing, and are insured against property or personal liability. Younger trees that have been heaved can be re-set and watered in; where the leaves are shredded from the wind/rain/hail combination, the damage is mostly aesthetic, with recovery taking place later in the season. Be on the lookout for disease or insect damage to follow up on the storm damaged plants and control accordingly.

Mushrooms also usually make their appearance after a period of rains, and no, there is nothing to "spray" to get rid of them. Normal, routine mowing will eliminate, or they can be easily picked or raked up.

Effects of Flooding And Compaction On Plant Growth

Trees, shrubs, and turfgrass all perform at a poorer rate when their roots are flooded or are subjected to compacted soil for any extended period of time. In essence, flooding is a basic form of compaction. On gallon of water weighs 8.33 pounds; one cubic foot of water, which is 7.48 gallons, weighs 62.4 pounds. Worse yet, this flooding water carries sediments, silt and clay particles, which contribute to the sealing of the soil surface and the micropores within the soil profile.

This cuts down on oxygen diffusion into the soil, and the migration of the carbon dioxide from the root zones when extensive flooding or waterlogging takes place over plant roots. The effect is the same with simple mechanical compaction: lack of gaseous exchange and mechanical impedance prevents good root development. The symptomatic response of the plants to these two stresses is likewise the same. Stunted, yellow foliage, a curling of the leaves, and in extreme cases, even death. Plants that are not actively growing are subject to disease activity.

The universal antidote is core aeration. This will increase the surface area of the soil which in turn, increases evaporation. It also gets the oxygen to the root system, which improves root respiration.

Iron in the form of ferrous sulfate, or as a chelate, is often added to the root zones to re-green the yellowed trees or turf. Generally, this element tends to be limiting in our high pH soils anyway, and when flooded, compacted, or cold conditions are added, the limitations become readily apparent in many planting locations.

Gall Forming Insects And Mites

Galls formed by insects or mites are swellings or deformities of plant tissue resulting from the irritation caused by feeding, or the injection of a plant tissue growth altering substance during prolonged feeding. Such abnormalities show up as blisters or projections on leaves, stems, petioles, buds, roots, and fruit. Don't expect to become expert in this area unless one wants to devote the rest of their life in studying this fascinating phenomenon of nature, as it is estimated that there are more than 2,000 gall insects or mites - gall forming wasps number over 800, some 700 by midges, 80 by aphids, and the rest by sawflies, beetles, and mites.

Their presence may causes appropriate concern for the homeowner, as some are genuinely harmful, while many are not. For example, the spruce gall aphid will cause swelling and in some cases defoliation at the ends of the conifer branches, many times leading to eventual death of the branch. The maple bladdergall mite causes a blister like growth on the leaf surfaces which could be red, green, or black, and often causes deformation of the leaves.

A particularly attractive gall forming on maple leaves has been noted in our area. This is the erineum gall caused by eriophyid mites, showing up as a red discoloration either in distinct spots or massed into a large area. This is one of the harmless galls to infest our local trees.

The take-home message on galls is that by the time they are noticed by the homeowner, the damage is already done, and the culprit insect or mite is gone. Spraying at this point would be useless and wasteful. Chances are the gall-maker will be gone the next year. If a spray is desired, then use dormant oil combined with lime-sulfur next spring to kill overwintering eggs in the bark and bud scale crevices.

Understanding Light Requirements For Indoor Plants
Ronald C. Smith, PhD
NDSU Extension Horticulutrist/Turfgrass Specialist

Daylength or photoperiodism, and light intensity are extremely important factors in growing quality indoor plants. Our indoor home environment can be a jumble of messages for the houseplants to interpret. Consider: Everyone is gone from the house on a typical Monday through Friday, either at school or work. A couple of nights a week the kids stay up late working on a homework project, or mom or dad have found a book that is difficult to put down until the wee hours; on weekends everyone tries to sleep in, and Saturday night everyone has an agenda for late hours. Most home interiors have a preponderance of incandescent light - the wrong end of the spectrum for good plant growth - and some people like their homes at 80º F, while others try to keep it below 70º. Sometimes the kids are the last ones to bed, leaving a majority of lights on for the entire night. Any wonder then, why houseplant problems exist and are difficult to isolate?

Plants grown under poor or low light intensity will usually exhibit etiolated growth - weak, spindly, and pale. With adequate light intensity from the correct light spectrum, plants will be stocky, strong, and have good color. Unfortunately, there are many confusing terms used to express light intensity: Footcandle - the amount of light received from a standard candle on a one square foot surface, one foot away from the source. Lux - a metric term often used, to state the amount of light received from a standard candle on a square meter of surface at a distance of one square meter. Then, there's the Lumen - a term used to express the intensity or brightness of the light being given off by the source. One lumen is the total light given off from a standard candle.

The best source of artificial lighting for the homeowner is through the use of a pair of fluorescent tubes. Beneath these, as much as 1000 fc (foot candles) can be achieved. This would have the lights about 6 inches above some flats for germinating seeds. 320 - 400 fc would be the "usual" at foliage height of typical potted plants. Intensities can be boosted somewhat by using fixtures with reflectors, adding additional lights, or by placing reflecting surfaces behind, around, or under the plants. Where low light intensities may still be a problem, they can often be compensated for by increasing the duration (length of time) of the light. This can easily be accomplished through timers connected to light banks.

Fluorescent tubes - the cool white type typically used in commercial buildings - would provide adequate light spectra for foliage growth, but very poor for flower development. Adding incandescent bulbs to the bank of lights would provide the wavelength in the red end of the spectrum for flower development. This combination, although archaic, does an adequate job for most situations and is considerably less expensive than the special plant light bulbs on the market. The inverse square law applies to light intensity, which decreases by the square of the distance between the light source and the receiving surface (See Illustration 1.).

Plants with the same light requirements should be grouped together to achieve success. Keep in mind that even a seemingly minor relocation of a plant, the opening or closing of curtains, and the age of the light bulbs can have an impact on the light intensity and quality. Refer to Table 1 and Illustration 2 and 3 for clarification.