1. Indoor Plants

2. Environmental factors affecting plant growth
Light - most houseplants are understory plants
Water – very tricky
Nutrients- match to the needs of the plant and time of year
Temperature – warmer days cooler nights ( tropic to subtropic)
Air – clean, not too dry

3. LIGHT/ Photosynthesis
Light descriptors: intensity, duration, quality
All green living plants need light to grow
When grown in too little light plants will be etiolated (spindly)
The brighter the light the more color develops in leaves ( coleus, begonia)
Flowering usually depends on light levels and day length

4. Light intensity
Light intensity is measured in Foot Candles, Lux or Lumens. 1 foot candle is the light cast by a standard candle at the distance of 1 foot.
Light intensity influences:
Photosynthesis
Stem length
Leaf size and color
flowering

5. Light Intensity Factors that influence intensity of sunlight
Curtains, trees in the landscape, uv filters on windows, weather, season, cleanliness of the glass, low E glass, paint color of the room…
Too much light can sunburn a plant

6. Houseplant classification
Houseplants are listed as High, medium or low light, and some plants can be in several categories.
In a Duluth house, the south windows with have the strongest sunlight, E and W = 60% and N=20%
The southern exposure also generates the most heat followed by W, then E, then N

7. Light Duration Most plants need some darkness at night 3-4 hours.
If the light in the house is a bit low longer hours of illumination can compensate.
Plants are generally divided into long day, short day and day neutral when describing initiation of flowering

8. Light Quality= wavelength
Photosynthesis required red and blue light
Sunlight has all the right parts of the spectrum
Electric lights may or may not
Incandescent lights lack blue, and add too much heat
Fluorescent “Grow lights” are more expensive than they are worth
Cool white fluorescent or a mix of cool white and warm white are the best deal – 12 “ above plants

9. Coping with low natural light
Choose “low light” plants: Philodendron, Pothos, Aglaonema, Cast Iron Plant
Rotate your plants into the better lit areas for a few weeks to rev them up
Put plants outdoors in summer in a “bright indirect” light place

10. Watering
Let your plant tell you- Observe closely and the plant will let you know when it is at “incipient plasmolysis” ( the leaves turn a little dull colored)
Check the weight of the pot, lighter=less water in the soil.
Scratch the surface if you see no damp soil down ½ inch, it may need watering

11. Watering
Plant roots do not function when a plant is overwatered ( the roots need Oxygen)
Symptoms of over or under watering:
Lower leaves and scattered leaves turn yellow from root rot ( over watering)
Oedema ( corky bumps on the leaves) usually on succulents when the plant is overwatered
Adventitious roots on the soil surface = overwatering

12. Watering
Leaves will wilt if the plant is in dry soil OR in saturated soil
Letting plants wilt then snap back when watered can cause slow growth, flower drop and leaf drop.
Make sure you have drainage in the pot- a hole in the bottom. Don’t let the pot sit in water ( in a full saucer)

13. Watering The general rules
use air temp water
water until excess water comes out the bottom of the pot, then dump out the saucer.
Don’t use softened water
Some plants are bottom watered, however you should remove the pot once the wetness reaches the surface of the soil

14. Potting Soil Potting soil needs more air than garden soil
A good mix contains a combination : peat, vermiculite, perlite, compost , sand, loam
Soil mix may contain nutrients ( plant food) but that will be used up in a month.
If your mix is mostly peat, it can shrink away from the sides of the pot and be heard to re-wet.

15. Nutrients
Plants make their own food from photosynthesis but they need a source of essential minerals. You will learn these later.
Most house plant fertilizers are water soluble salts
The label recommendations are usually too strong so use ½ of the label directions.
Fertilize most houseplants in spring and summer only

16. Nutrients Time release fertilizers will last for several months
ORGANIC fertilizers take longer to become available in the soil and less likely to “burn”.
INORGANIC fertilizers are immediately available to the plant but more likely to burn.
Only fertilize when plants are actively growing.
Don’t fertilize a bone dry pot

17. Fertilizers are salts. salts can accumulate in potted plants
If you see a whitish or yellow crust on the surface of the soil it is probably a salt buildup
You can scrape off the top ¼ to ½ inch of soil and replace with fresh soil.
You can leach the soil in the pot with fresh water to remove excess salt( run water through the pot).

18. Temperature
Most house plants like people temps 75 day and 65 night, most can adapt a few degrees either way.
Respiration (burning food) in plants happens 24hours a day and high temps speed up the process. Light allows photosynthesis to make more food.
Houseplants suffer when they have low light and high temps

19. Temperature
Most flowering plants will have higher qualit flowers if they have cooler nights (55-60)
In Duluth the temps next to a window can be quite cold on a winter night, you may have seen house plant leaves frozen to a window.
Move plants farther into the room and off a cold floor

20. Cleaning plant leaves lets in more light
The leaves will get dusty
Wash with warm water and a soft sponge
Don’t use wax products or mayonnaise

21. Air quality Plants use CO2 and O2 Air circulation is beneficial
Gas leaks can kill plants, products of incomplete combustion ( ethylene) can make houseplants grow strangely or drop flower buds
If all your plants twist up at the same time –
It could be an air quality problem

22. Insect pests Observe plants closely
Prune the worst looking parts of the plants
Spray plants with products that won’t kill you or your pets, insecticidal soap, Ivory soap, alcohol
Keep checking the plants because insect eggs are usually un affected by sprays