A L A B A M A A & M A N D A U B U R N U N I V E R S I T I E S
`
`Hobby Greenhouse
`Operations and Practices
`
`The Plant Environment
`Even though a greenhouse
`is an enclosed space, it is not
`isolated from the outside envi-
`ronment. Conditions within the
`greenhouse are constantly
`changing. Learn not only to see
`but also to feel changing condi-
`tions. Watch weather forecasts
`so that preemptive steps can be
`taken to compensate for chang-
`ing outside conditions. Day
`length, light intensity, tempera-
`ture, humidity, and precipitation
`frequency change hour to hour,
`day to day, and season to sea-
`son. Greenhouse owners should
`be able to recognize these
`changes and alter environmental
`control equipment to keep the
`greenhouse environment opti-
`mum for plant growth.
`Variations also exist within
`a greenhouse. Look and feel for
`patterns of light or shadow, low
`or high humidity, and stagnant
`or moving air. These patterns
`create microclimate differences
`from the greenhouse center to
`the walls. Take advantage of mi-
`croclimate differences by placing
`plants in areas within the green-
`house suitable for their growth.
`
`Light
`During the day, leaves of
`plants use the energy from sun-
`light combined with carbon
`dioxide from the air and water
`from the soil to manufacture
`sugar and oxygen in a process
`called photosynthesis. At night,
`plants burn sugar produced dur-
`ing the day and release the ener-
`
`gy for maintenance and growth
`in a process called respiration.
`Photosynthesis and respiration
`can be viewed as opposing
`processes, one capturing energy,
`the other using it. Plants must re-
`ceive enough light during the
`day not only to meet the needs
`of maintenance but also to have
`enough left over for growth.
`Every plant species has its
`own requirement for light inten-
`sity. Most vegetables, cut flow-
`ers, and many flowering potted
`plants require high light intensity
`to grow well. Most foliage plants
`and some flowering potted
`plants require lower light intensi-
`ty to grow. Under light intensity
`that is too low, plants exhibit
`slow growth, spindly, slender
`elongated stems, yellow lower
`leaves, and soft succulent
`growth. In some cases, they ex-
`hibit larger, thinner leaves and in
`others they exhibit smaller
`leaves and stem bending toward
`a light source (called phototro-
`pism). Under light intensity that
`is too high, plants exhibit small-
`er, light-green thick leaves, short
`thick stems and, in extreme
`cases, burned leaf margins or
`scorched blotches on the leaves.
`Light intensity in the green-
`house is measured in foot can-
`dles (f.c.). A clear summer day
`may measure 10,000 f.c., while
`an overcast, winter day may
`measure 500 f.c. The amount of
`light needed for a person to read
`comfortably is about 20 f.c.,
`while the light of a full moon is
`less than 1 f.c. Measuring the
`light available to plants requires
`
`Visit our Web site at: www.aces.edu
`
`ANR-1153
`
`Introduction
`Perhaps there is no greater
`joy than owning a hobby green-
`house and entering a warm, dry
`room filled with green plants
`when there may be frost, wind,
`or rain outdoors. For many peo-
`ple, tending to a greenhouse is
`like entering a relaxing, private
`world, isolated from workaday
`worries as well as the weather.
`A greenhouse can be an absorb-
`ing hobby with the satisfaction
`of growing fragrant flowering
`plants, foliage plants, ingredients
`for fresh-picked salads in winter,
`transplants for the spring garden,
`or bouquets of cut flowers.
`Do not be fooled, however,
`into believing that a hobby
`greenhouse does not involve
`some work. Constant attention
`is required at most times of the
`year. This often means every day
`during the summer unless auto-
`matic watering and ventilation
`systems are installed. During the
`year, there are always jobs to be
`done. But none of these chores
`have to be strenuous or tedious
`if tasks and the materials needed
`to accomplish them are arranged
`intelligently. The purpose of this
`publication is to provide infor-
`mation about tasks that should
`be done to have a well-run, effi-
`cient hobby greenhouse, one
`that is satisfying for the owner
`and a joy for the entire family.
`Information on hobby green-
`house construction and environ-
`mental maintenance equipment
`can be found in Extension publi-
`cation ANR-1105, “Hobby
`Greenhouse Construction.”
`
`SCOTTS EXHIBIT 1004
`
`

`

`a simple, convenient tool called
`a light meter. It is the only way
`to be sure plants are receiving
`the correct amount of light. Light
`meters can be purchased from
`greenhouse supply companies
`for $70 to $120. Recommended
`light intensity ranges for specific
`plants can be found in books
`under the additional reading sec-
`tion of this publication.
`The purpose of glazing (the
`transparent or translucent materi-
`al such as glass covering a
`greenhouse) is to capture sun-
`light as well as to separate the
`interior greenhouse environment
`from the outside environment.
`During the summer, high light
`intensity can burn low-light re-
`quiring plants and raise interior
`temperatures excessively. Light
`intensity and heat load in the
`greenhouse can be reduced
`using one of several means of
`shading.
`Shade fabric is a woven
`polyethylene cloth that can be
`purchased from greenhouse sup-
`ply companies. It comes in
`weave densities ranging from 20
`to 90 percent. It is more effective
`in heat reduction to purchase a
`size large enough to drape over
`the outside of the greenhouse
`rather than hanging the fabric in-
`side. One problem with draping
`fabric over the outside of the
`greenhouse, however, is that it
`can interfere with vent opera-
`tion. During the summer in
`Alabama, high light requiring
`plants can benefit from 30 to 40
`percent shade while low light re-
`quiring plants may need 50 to 80
`percent shade. Purchase shade
`fabric with grommets along the
`edges so the cloth can be tied
`down in case of strong wind.
`One simple and inexpensive
`alternative is to purchase shade
`paint from a greenhouse supply
`company. Mix the paint with
`water according to the manufac-
`turer’s directions. Shade paint is
`a weak- binding latex paint that
`
`is diluted and sprayed on the
`outside of the glazing. It is often
`applied in two applications, one
`light application in mid to late
`March and a second application
`in mid to late April. Shade paint
`is designed to weather off the
`glazing gradually over the sum-
`mer and fall. However, it is fre-
`quently necessary to wash the
`glazing in late fall with soap and
`water and a long-handled brush
`to prevent unwanted light reduc-
`tion in the winter.
`Greenhouse blinds are re-
`garded by many owners as the
`best shading alternative. Blinds
`can be purchased in a wide se-
`lection of roller types made with
`wood, plastic, or plastic-coated
`aluminum slats. Many owners
`mount blinds on the outside of
`the greenhouse that aid in heat
`reduction but like shade fabric
`can interfere with vent opera-
`tion. Blinds designed to be
`mounted inside the greenhouse
`can be adjustable.
`Most methods for increasing
`light intensity after a greenhouse
`is constructed are drastic, such
`as cutting down trees or remov-
`ing other outdoor obstacles, or
`expensive, such as installing arti-
`ficial light sources. However,
`plants can be spaced farther
`apart and objects such as hang-
`ing baskets can be taken down
`in the winter to reduce competi-
`tion and shading. Painting as
`many interior surfaces as possi-
`ble with white semigloss or gloss
`paint can also increase light in-
`tensity. Exterior latex works well
`but epoxy paint is even better.
`Paint benches, walls, doors,
`glazing supports, and even the
`floor, if possible, to reflect light.
`Another solution is to use a her-
`bicide to kill all vegetation with-
`in 10 to 15 feet around the out-
`side of the greenhouse and to
`spread white rock on the outside
`to reflect light into the green-
`house.
`
`2 Alabama Cooperative Extension System
`
`Temperature
`Each plant species has an
`optimum and tolerable tempera-
`ture range for growth. Plant
`growth and flowering are rapid
`within the optimum temperature
`range. Tolerable temperatures,
`which may be higher or lower
`than optimum, allow the plant to
`grow but at a reduced rate.
`Growth usually stops and plants
`may be damaged at tempera-
`tures outside the tolerable range.
`Recommended growing temper-
`atures can be found in books
`such as those listed under the
`additional reading section of this
`publication. Generally, these rec-
`ommendations are for minimum
`night temperatures because heat-
`ing is required to maintain a
`minimum temperature for
`growth.
`Most plant species grown in
`greenhouses are tropical or sub-
`tropical in origin and heating,
`when needed, to a 60 to 65 de-
`grees F minimum night tempera-
`ture works well. Exceptions to
`this recommendation include
`many cool-season plants such as
`primula, pansy, and some or-
`chids. Cooler than optimum
`night temperatures will slow
`growth while warmer tempera-
`tures will speed growth. Daytime
`temperature should generally be
`5 to 10 degrees F warmer on
`cloudy days and 10 to 15 de-
`grees F warmer on sunny days
`than the night temperature.
`Excessively warm temperatures
`during the day or night, espe-
`cially during cloudy weather, can
`reduce growth because respira-
`tion is increased and plants use
`sugars faster than photosynthesis
`can manufacture them.
`Temperature requirements
`can also change with a plant’s
`stage of growth. Generally, ger-
`minating seed and seedlings and
`rooting vegetative cuttings re-
`quire warmer temperatures,
`plants growing vegetatively per-
`form better under somewhat
`
`

`

`cooler temperatures, and flower-
`ing plants need under even cool-
`er temperatures. With a mix of
`plants at different stages of
`growth in the greenhouse, it
`may be difficult to select an
`ideal temperature; nonetheless,
`provision should be made for
`germinating seed and rooting
`cuttings in a warmer setting.
`Greenhouse temperature
`maintenance equipment (fans,
`heaters, etc.) is commonly regu-
`lated by installing one to several
`thermostats depending on the
`number of devices that require
`control. Thermostats controlling
`heating equipment are set to the
`minimum desired temperature
`and cooling devices are set to
`the maximum desired tempera-
`ture. Do not depend, however,
`on the accuracy of commercial
`thermostats. Instead, install a
`high/low thermometer next to
`the thermostats and adjust the
`thermostat set points according
`to the high/low thermometer.
`High/low thermometers record
`the low temperature at night and
`the high temperature during the
`day. They have two liquid-filled
`glass stems and a metal bar
`within the glass stems that
`moves as the temperature
`changes, but stays in place at the
`lowest and highest temperature
`readings. Record the tempera-
`tures and reset the high/low
`thermometer daily. The ther-
`mometer is reset by moving the
`metal bars with a magnet or by
`pressing a button on the face of
`the thermometer.
`
`Relative Humidity
`Relative humidity (RH) is a
`measure of how much water is
`dissolved in the air at a particu-
`lar temperature expressed as a
`percentage. Generally, growth of
`many plants is relatively unaf-
`fected by RH between 45 per-
`cent and 85 percent. Plants
`growing at RH below 45 percent
`may grow slowly, have smaller
`
`leaves, require watering more
`frequently, or develop burned
`leaf margins or leaf tips. Plants
`growing at RH above 85 percent
`are susceptible to fungal
`pathogens, especially if water
`condenses on the foliage.
`Several conditions can occur
`in a greenhouse that result in
`problems caused by high or low
`RH. During the summer, high
`light, high temperature, and
`rapid air movement from fans
`can reduce RH to unacceptable
`levels. Shading to reduce light
`and temperature and using evap-
`orative cooling (cooling pads)
`are the best solutions. RH can be
`raised for a short time by using a
`hose to wet down interior sur-
`faces (walks, side walls, and
`open bench areas, but not
`plants). It is also advisable to
`keep the greenhouse full of
`plants because plants generate a
`lot of RH.
`During the spring and fall,
`warm days followed by cool,
`clear nights cause rapid heat loss
`from the greenhouse, especially
`from the glazing material. Warm,
`moist interior air moving next to
`cool glazing material can drop to
`the dew point temperature and
`cause water to condense in
`droplets on the inside of the
`glazing material. These droplets
`run down the slope of the roof,
`grow larger, and then rain down
`on plants below creating ideal
`conditions for the growth of fun-
`gal pathogens. Two ways to re-
`duce this problem is to avoid
`watering plants late in the day
`and to make sure the green-
`house floor drains well with no
`standing water or constant wet
`spots. The best way, however, to
`alleviate this problem is to wire
`a fan to a 24-hour time clock
`and set the fan to turn on for 30
`to 60 minutes (depending on the
`size of the greenhouse) starting
`at 9:00 or 10:00 PM. The goal is
`to exchange the warm, moist in-
`terior air with cool, moist out-
`
`side air, then allow the heating
`system to warm the air to its set
`point, thereby reducing the
`amount of water in the green-
`house air. Ironically, high RH
`and condensation are generally
`not a problem during the cold of
`winter because heating reduces
`the amount of water in the air.
`
`The Root Environment
`Underneath every healthy
`plant is a healthy root system.
`Although most of us know what
`a healthy plant looks like, few of
`us bother to learn what healthy
`roots look like. Learning the
`characteristics of healthy roots is
`one key to successful growing
`and diagnosing of plant prob-
`lems. Drop plants out of their
`pots periodically and examine
`the roots. Roots may be thin, fi-
`brous, and many-branched or
`thick and straight with few
`branches depending on the plant
`species. However, they should
`be more or less white, not
`brown or black. There should be
`root hair development just be-
`hind the root tip. Root hairs
`should be straight, not curled,
`discolored or absent. Roots
`should grow toward the bottom
`of the pot and, when mature,
`cover the entire soil volume.
`Disease, incorrect watering prac-
`tices, poor soil, excessive fertiliz-
`er, or a combination of these fac-
`tors can cause root problems.
`
`Potting Soil
`The major function of pot-
`ting soil is to provide air (oxy-
`gen and carbon dioxide), plant
`support, and a constant supply
`of water and fertilizer nutrients
`to the roots. Roots take up oxy-
`gen and give off carbon dioxide
`in respiration to carry out their
`functions. Therefore, potting soil
`must have a sufficient number of
`large channels or pores to allow
`water to move through quickly
`and to allow air to exchange
`with the atmosphere. It should
`
`Hobby Greenhouse Operations and Practices 3
`
`

`

`or composted byproducts (leaf
`mold, sewage sludge, etc.) can
`also be used. The drainage com-
`ponent improves the potting
`soil’s ability to drain water and
`exchange oxygen and carbon
`dioxide with the air. Perlite and
`vermiculite are widely used, but
`sand (washed river sand) can
`also be used. Chemical additives
`can be blended in the potting
`soil when the organic and
`drainage components are mixed.
`The pH of a potting soil is a
`measure of the acidity or alkalin-
`ity of the mix. The pH scale
`ranges from 1 to 14 with 7 being
`neutral. Kits or meters for testing
`potting media pH can be pur-
`chased from garden centers or
`greenhouse supply catalogs.
`Most plants grow well in a soil-
`less potting soil with a 5.5 to 6.5
`pH. However, a potting soil
`using peat moss as an organic
`component will have an unac-
`ceptably low pH. Dolomitic
`limestone, which also supplies
`calcium and magnesium needed
`for plant growth, is added to the
`potting soil at the time of mixing
`to raise the pH. It is both conve-
`nient and economical to add
`some fertilizer to the soil at the
`time of mixing. Superphosphate
`(rock phosphate), a commercial
`micronutrient formulation and a
`source of nitrogen and potassi-
`um can be added at mixing.
`Keep in mind that these rates
`will get plants off to a good
`
`start, but additional fertilizer will
`be needed once plants establish.
`Four cubic feet is a conve-
`nient amount of potting soil to
`mix at a time. This amount will
`fit into a 30-gallon, new or clean
`garbage can for storage and will
`fill approximately 171 4-inch
`pots, 93 5-inch pots, or 56 6-inch
`pots. Begin by constructing a
`box from plywood with a 1-
`cubic foot inside dimension.
`Measure the organic and
`drainage ingredients according
`to Table 1 and mix them with a
`shovel on a clean surface to pre-
`vent contamination by root
`pathogens (cover dirty surfaces
`with plastic). Add just enough
`water to the mix to barely dark-
`en the color. Turn the soil as
`you add water. Measure the fer-
`tilizer and limestone using an ac-
`curate scale and mix them to-
`gether in a bucket. Add some of
`the fertilizer/limestone mix and
`turn the soil, repeat until all the
`fertilizer/limestone mix is uni-
`formly blended.
`
`Watering
`Miswatering, typically over-
`watering, is probably one of the
`major causes of failure with
`plants in a greenhouse. Despite
`all that has been written, water-
`ing plants comes down to two
`critical decisions: when to water
`and how much to apply at a
`time. How much water to apply
`at a time is relatively easy as
`long as plants are growing in
`
`High moisture
`
`High drainage
`Intermediate
`
`Table 1. Three Soilless Potting Soils for Hobby Greenhouse Culture
`Type
`Ingredient
`per 1 cu. yd.
`per 4 cu. ft.
`131⁄2 cu.ft
`Peat moss (50 percent)
`2 cu.ft.
`131⁄2 cu.ft.
`Vermiculite (50 percent)*
`2 cu.ft.
`OR
`Perlite (50 percent) OR
`Vermiculite (25 percent) *
`+ Perlite (25 percent)
`Dolomitic limestone (ground)
`Superphosphate (0-20-0)
`Potassium nitrate (13-0-45)
`
`131⁄2 cu.ft.
`6: cu.ft. each
`
`8 to 10 lb.
`2 lb.
`1 lb.
`
`2 cu.ft.
`1 cu.ft.
`each
`19 to 24 oz.
`5 oz.
`21⁄2 oz.
`
`also have a sufficient number of
`small pores to hold adequate
`water and fertilizer between ap-
`plications. In addition, potting
`soil should be initially low in fer-
`tilizer, free from toxins or herbi-
`cides, standardized and uniform
`for consistent results, and free
`from diseases, insects, and weed
`seed. Soil from the yard cannot
`meet many of these criteria, es-
`pecially once confined to a pot.
`Therefore, it should not be used
`in a potting soil for the green-
`house.
`Most of the potting soils used
`in greenhouse growing are called
`soilless mixes. As the name im-
`plies, they do not contain soil
`from the ground. There are two
`choices for obtaining sufficient
`potting soil, either mix your own
`or purchase it commercially al-
`ready prepared in bags from re-
`tail sources. Commercial potting
`soil is convenient and inexpen-
`sive, but unfortunately, no stan-
`dards exist for content or quality.
`There may be a high variation
`among brands. Look for a brand
`with “Professional Potting Mix”
`on the label, then look for a list
`of contents. The potting mix
`should contain predominately
`peat moss, perlite, and/or vermi-
`culite. Run a test in your green-
`house with several brands using
`different plants to see which one
`performs best. The advantage of
`mixing your own potting soil is
`that you have control over the
`content and quality. Recipes for
`three soilless potting soils are
`found in Table 1. Ingredients for
`mixing your own potting soil can
`be purchased from garden cen-
`ters or greenhouse supply cata-
`logs.
`Soilless mixes are composed
`of two categories of compo-
`nents. The organic component
`gives potting soil the ability to
`absorb large amounts of water
`and fertilizer. Peat moss is used
`more than any other organic
`component, but composted bark
`
`Minor elements (manufacturer recommendations)
`*Medium or coarse grade
`
`4 Alabama Cooperative Extension System
`
`

`

`well-drained potting soil. Apply
`an amount of water that will sat-
`urate the entire soil volume in the
`container plus enough for a small
`amount to run out the drainage
`hole in the bottom of the pot.
`The decision of how often to
`water should not be based on
`habit, nor should watering sim-
`ply be done at certain time inter-
`vals. Always check plants to de-
`termine if they require water.
`One advantage to a soil contain-
`ing peat moss is that it changes
`from dark brown when wet to
`light tan in color when dry. This
`color change can be used to de-
`termine when to water. Like-
`wise, soil containing peat moss
`changes from heavy when wet
`to much lighter in weight when
`dry. With practice and experi-
`ence, lifting pots periodically can
`help you determine when it is
`time to water. This method is es-
`pecially useful for hanging bas-
`kets. Sticking your finger into
`the soil about a half-inch to feel
`for moisture can also be used.
`Many plants develop a gray-
`green cast to the foliage when
`dry. This can be used to judge
`when to water. The goal, how-
`ever, is to water before plants
`wilt. Wilting damages plants,
`often causing lower leaf loss,
`stunted growth and delayed
`flowering.
`Hand watering is probably
`the most common watering
`method used in hobby green-
`houses. Hand watering should
`be done early in the morning so
`that water on the foliage dries
`before nightfall. A watering can
`with a water breaker fitting is
`useful for watering dry spots or
`an occasional water-hungry
`plant but for larger jobs, a hose
`will be needed. The hose usually
`has a thumb valve to control
`water flow, a water wand to ex-
`tend reach (usually a 2-foot
`wand is sufficient) and a water
`breaker nozzle (21⁄4-inch diame-
`ter has wide application) at the
`
`end to soften the flow water im-
`pacting the soil surface. A one-
`half gallon per minute mist noz-
`zle is also handy for watering
`seedlings.
`When watering, go through
`the greenhouse systematically so
`that plants are not missed. Apply
`water gently so that the soil does
`not puddle, wash excessively, or
`knock-over young seedlings. This
`may require repeated light appli-
`cations, especially to flats. When
`done, wind the hose close to the
`faucet so it is not under foot and
`hang the watering wand and
`breaker up off the floor to pre-
`vent the spread of diseases.
`Hoses last longer if the water is
`turned off at the faucet and the
`hose is drained after use.
`
`Fertilizer
`Fertilizer requirements for
`plant growth can be classified
`into two groups according to the
`amount used by plants. The
`macronutrients nitrogen, phos-
`phorus, potassium, calcium, mag-
`nesium and sulfur are needed in
`relatively large quantities while
`the micronutrients iron, man-
`ganese, boron, zinc, molybde-
`num, copper, and chlorine are
`needed in very small amounts.
`Calcium, magnesium, and sulfur
`are generally supplied by adding
`dolomitic limestone and super-
`phosphate to the potting soil at
`the time of mixing. Adding mi-
`cronutrients at the time of mixing
`supplies plant needs for these nu-
`trients for three to four months.
`The macronutrients nitrogen,
`phosphorus, and potassium are
`highly soluble and wash from
`the potting soil easily. Therefore,
`they must be applied frequently,
`often in liquid form. There is a
`wide range of water soluble fer-
`tilizers available in garden cen-
`ters and mass market outlets, but
`all will provide the percentage
`of nitrogen, phosphorus, and
`potassium (example: 20-20-20 is
`percent N-percent P-percent K)
`
`on the front label. When shop-
`ping for a fertilizer, purchase a
`water soluble, general plant fer-
`tilizer with the three percentages
`either very close or identical in
`value. Generally, it is more cost
`effective to purchase the highest
`analysis available (highest value
`for N-P-K).
`Water soluble fertilizers can
`be applied by mixing a mea-
`sured amount of fertilizer, ac-
`cording to the product label,
`with water in a watering can and
`drenching the potting soil.
`However, this method can be-
`come a time-consuming task if
`you have a large number of
`plants. A simple fertilizer injector
`that delivers fertilizer into the
`water line can be purchased
`from garden centers and mass
`market outlets. Common brands
`are Siphon, Siphonex, and
`Hozon. These units attach be-
`tween the faucet and hose and
`have a siphon tube that is placed
`in a bucket filled with concen-
`trated fertilizer solution. The
`concentrated solution is drawn
`into the hose, diluted in water,
`and delivered to plants during
`the normal watering operation.
`Follow the manufacturer’s direc-
`tions for mixing the concentrated
`fertilizer solution.
`How often to apply liquid
`fertilizer depends on the growing
`environment, the plant type, and
`how rapidly the plant is growing.
`Plants in high light and tempera-
`ture during late spring, summer,
`and early fall can be fertilized
`about once a week, especially
`annual flowers, flowering potted
`plants, and vegetables. Medium
`growth rate plants and plants in
`moderate light and temperature
`during early spring and late fall
`can be fertilized about once
`every two weeks. Slow growing
`plants and plants under shade
`can be fertilized about once a
`month. Many plants that stop
`growing in the winter should not
`
`Hobby Greenhouse Operations and Practices 5
`
`

`

`be fertilized until growth resumes
`in the spring.
`
`Propagation
`Every hobby greenhouse
`owner either already has an inter-
`est in propagating plants or will
`soon develop one; there is some-
`thing fascinating about becoming
`involved in starting a new life.
`Besides always purchasing estab-
`lished plants to meet your needs
`can be expensive.
`
`Seed Germination
`Start with good quality, fresh
`seed of known parentage. Seed
`collected from the wild or from
`the neighbor’s yard often does
`not produce plants like the origi-
`nal. For flowering annuals and
`vegetables, purchase named vari-
`eties from reputable sources. Mail
`order sources and reputable gar-
`den centers are the best sources
`because they often carry the best
`varieties adapted to your area
`and they turn over their invento-
`ries fast enough so the seed are
`not too old. Stay away from bar-
`gain basement seed sales.
`There are many different
`types of containers for germinat-
`ing seed. They include plastic
`pots, paper pots, peat pots, peat
`blocks, multi-cell trays, and open
`flats. The container to choose de-
`pends on seed size. Large seed
`probably perform best sown indi-
`vidually in pots; medium and
`small seed perform best sown in
`multi-cell trays; and very small
`seed perform best sown in rows
`in open flats. Seedlings in open
`flats will require transplanting
`soon after germination. The con-
`tainers should be filled with a
`potting soil designed for seed
`germination. Generally, seedling
`mixes are finer textured than
`general potting soils so they can
`accommodate small seed.
`Seedling mixes can be purchased
`from garden centers and mass
`market outlets.
`
`Seed should be sown in
`moist, but not wet seedling mix.
`In the process of sowing, do not
`place seed too close together or
`competition for space will result
`in spindly, weak seedlings.
`Resist the temptation to sow
`more seed than you really need.
`Follow the directions on the
`seed package for seed spacing
`and sowing depth. Large seed
`are placed in holes dibbled in
`the soil—a good rule is to make
`the hole no deeper than twice
`the diameter of the seed. Small
`seed are often sown directly on
`the soil surface and covered by
`sifting a small amount of fine
`vermiculite (fine or super fine
`grade) or seedling mix over the
`seed. A good way to water sown
`containers without washing the
`seed out of place is to submerge
`the container in a shallow pan of
`water so moisture can be ab-
`sorbed by the soil through the
`drainage holes. Be sure to label
`the containers to identify what
`was sown. Store leftover seed
`sealed in labeled zip-lock plastic
`bags placed in the vegetable
`keeper of a refrigerator for fu-
`ture use. Note any instruction on
`the seed package for how long
`seed will remain viable under
`storage conditions.
`Seed require a warm, moist
`environment to germinate.
`Tenting is an easy way to pro-
`vide high humidity during ger-
`mination and to prevent seed
`from drying out. On a small
`scale, slip the sown containers in
`a plastic bag (large zip-lock bags
`work well) and seal the open
`end. On a larger scale, construct
`a tent over a greenhouse bench
`from plastic pipe and clear sheet
`plastic. Do not expose the tents
`to direct sunlight. A piece of 40
`to 60 percent shade fabric or
`cheesecloth can be used to
`shade the tents.
`Germination temperatures
`vary greatly depending on the
`plant species, but a soil tempera-
`
`6 Alabama Cooperative Extension System
`
`ture of 70 to 80 degrees F works
`well for many seeds. Check the
`seed package for temperature
`information. Soil temperature can
`be monitored with a soil ther-
`mometer, which you can pur-
`chase from greenhouse supply
`company. Placing sown contain-
`ers on an electric germinating
`mat (soil warming mat designed
`for propagation) that can be pur-
`chased from greenhouse supply
`companies can accelerate seed
`germination. Remove the tents as
`soon as the majority of the
`seedling unfold cotyledon leaves
`and place them at growing light
`intensity. Seedlings should be
`transplanted to larger containers
`before they begin to crowd, es-
`pecially those sown in open flats.
`Seedlings with one or two mature
`leaves survive transplanting better
`than older seedlings, so do not
`delay transplanting!
`
`Rooting Cuttings
`Growing plants from cuttings
`involves removing a plant part
`and placing it under conditions
`that favor development of a new
`root system. This is a form of
`cloning, often called vegetative
`propagation, because the new
`plant will be genetically identical
`to the parent plant. Vegetative
`propagation is often less expen-
`sive and faster than starting
`plants from seed.
`Many plants are easy to root
`from cuttings. Some can be root-
`ed directly in a glass of water
`placed in a bright window that
`does not get direct sun. In gener-
`al, herbaceous annuals and
`perennials and tropical foliage
`plants are easier to root than
`woody trees and shrubs. Select a
`healthy disease- and insect-free
`parent plant, preferably one that
`does not have flowers. With a
`sharp knife, remove a 3- to 5-
`inch cutting from a stem tip of
`the parent plant. This type of cut-
`ting is called a terminal cutting. If
`the cutting has flowers or flower
`
`

`

`buds, remove them. Trim the
`larger leaves from the lower end
`of the cutting so that three to four
`smaller leaves remain toward the
`cutting tip. Dip the cut end of the
`cutting into a rooting powder
`(purchase from garden center or
`greenhouse supple company)
`and tap off the surplus. Rooting
`powders come in different for-
`mulations for different types of
`plants so select a formulation
`based on the plant type being
`propagated. Removing portions
`of the stem below the shoot tip
`of the parent plant can also make
`subterminal cuttings. However,
`cuttings taken from too low on
`the stem may be too woody and
`root slowly, if at all.
`Cuttings can be started in any
`of the containers discussed for
`seed germination. Generally, a
`coarse, well-drained potting soil
`such as the 50 percent peat moss
`and 50 percent perlite mix out-
`lined in Table 1 promotes rapid
`rooting. Poke a hole in the soil
`and insert the cut end of the cut-
`ting into the soil up to the lowest
`leaves. Do not stick the cuttings
`all the way to the bottom of the
`container. Stick them just deep
`enough to stand up. Water the
`cutting immediately. During this
`process, do not allow the cuttings
`to wilt. If cuttings must be trans-
`ported or sticking the cuttings
`must be delayed, seal them in a
`plastic bag with wet paper tow-
`els, place them in a cooler or re-
`frigerator and protect them from
`high light.
`Because cuttings do not ini-
`tially have roots, they must have
`a high humidity environment to
`prevent desiccation until roots
`form. If a few cuttings are stuck
`in a pot, cover the pot with a
`clear plastic bag, seal the bag
`with a rubber band and place
`the pot in bright, but not direct
`light. On a larger scale, construct
`a tent over the cutting containers
`on a greenhouse bench from
`plastic pipe and clear sheet plas-
`tic as discussed for seed germi-
`
`tions of the science of how to
`grow plants. However, the artis-
`tic side of a hobby greenhouse
`is to choose plants that look and
`grow well and that please the
`owner. Choose a reasonable va-
`riety of plants and then arrange
`the plants and the interior space
`in a way that is pleasing, com-
`fortable, and functional for all
`who visit.
`
`Additional Reading
`American Horticultural Society.
`1982. Gardening under Glass and
`Lights. The Franklin Library/Ortho
`Books, Franklin Center, Pennsylvania.
`D.G. Hessayon. 1997. The
`Greenhouse Expert. Sterling Publishing
`Company, New York, New York.
`Shane Smith. 1992. Greenhouse
`Gardener’s Companion: Growing Food
`& Flowers in Your Greenhouse or
`Sunspace. Fulcrum Publishing, Golden,
`Colorado.
`Ian G. Walls. 1996. The Complete
`Book of the Greenhouse. Sterling
`Publishing Company, New York,
`New York.
`
`nation. Cuttings may require
`from 2 weeks to 6 months to
`root depending on the species
`and plant type, so be patient.
`Another method for rooting
`cuttings that is used by serious
`hobby greenhouse owners, espe-
`cially for cuttings of woody shrubs
`and trees, is intermittent mist
`propagation (Figure 1). During
`propagation, a film of water is
`maintained on the leaves by ap-
`plying a fine mist from mist noz-
`zles attached to a plastic water
`line installed