Illuminating indoor gardens

Posted by: John Stolzle, Jefferson County Extension 

One of the great challenges I’ve faced with my indoor garden is light, or rather the lack thereof. At times, I view my indoor garden as low productivity time sink; but at other times I've noticed that it can be pretty fun to have such a variety of plants to tinker with and train from the comfort of home. An indoor garden can offer (a few) fresh tomatoes and herbs, and green colors in the middle of winter. And personally, in my apartment, in the middle of a city, I definitely enjoy the extra connection with nature that it brings.

My indoor garden is often a disorganized mess of green. On the bright side, I am able to harvest a few small bunches of cherry tomatoes every month.

When plants don’t receive adequate light, they become more susceptible to disease, their leaves can become pale and discolored, some will even drop leaves which further reduces their ability to absorb light. This low-light leaf drop feedback loop has resulted in the failure of many of my indoor plant experiments. Light intensity also plays an important role in a plant’s production of lignin, a scaffold-like component which plants produce to support themselves. Without proper light, many plants will often flop over due to weak structural support. Twine, twist-ties, or string can be used to help support a weak plant. 

This 'Purple Passion' (Gynura aurantiaca) bolted earlier in the spring. Using some twine and makeshift stakes, it has now become a 'spiraled' purple passion.

Compounding the issue of inadequate support structures, many plants can exhibit strong shade avoidance mechanisms. These mechanisms often manifest in a plant putting more energy towards the development of fast-growing elongated shoots and can result in spindly or “leggy” plants. The Purple Passion in the image above, for example, bolted and grew many inches within a just few weeks.

Increasing light (or PAR - photosynthetically active radiation) to adequate levels for a given plant can resolve these issues. Grow lights can be used to accomplish this or to mitigate the effects of low light conditions.

Even with these lights, the plants in my garden do not receive as much light as they would if they were planted outdoors. The lights just help mitigate some of the problem. 

Light Types:
Many options such as LEDs and fluorescents are available for homeowners to purchase. Decisions regarding 'which light is best' should be based upon individual situations, and factors such as the needs of the plant, energy consumption, heat, quantity of ambient light, and position of the to-be-installed grow light in relation to the plants. Below, I have provided links to pages which discuss these topics in more detail: 

  

• A great general overview on indoor lightning from Missouri Extension: https://extension2.missouri.edu/g6515
  
• Comparison of different types of lighting: http://factsheets.okstate.edu/documents/hla-6450-led-grow-lights-for-plant-production/
  
• A more technical introduction:  https://ipm.missouri.edu/MEG/2012/10/Lighting-the-Way-to-Gardening-Indoors/  
  
• This page provides some great lists on low, medium, high light level plants: https://extension.umn.edu/planting-and-growing-guides/light-requirements-houseplants   
• Another list of plants and their light/water requirements:https://www.uaex.edu/yard-garden/home-landscape/docs/Light%20and%20Moisture%20Requirements.pdf 

  

A few last minute tips:

• Help the plants support themselves. A small trellis, cage, or other structure can give the plants something to climb on.
• It is very easy to overwater indoor plans. A general recommendation is to only water when the top 1-2 inches (2-5cm) of soil are dry. 

• Scan with some regularity for pests and disease. Indoor plants often face significant challenges regarding pest infestations (especially of spider mites & aphids) due to a lack of natural predators that could otherwise help keep pest populations in check. Catching a problem early on can save lots of headache and potentially prevent the loss of a plant.

If you are interested in indoor gardening, you may appreciate these other posts in this indoor blog series: 

1. https://csuhort.blogspot.com/2019/09/reflections-on-season-of-indoor.html
2. https://csuhort.blogspot.com/2019/11/trials-of-indoor-gardening-pt1-spider.html

Trials of Indoor Gardening pt.1: spider mites, aphids, and thrips oh my...

Posted by: John Stolzle, Jefferson County Extension

One of the best things about indoor gardening is being surrounded by green foliage during winter. But this also brings a potential for pests to thrive 365 days a year.

The indoor garden remains unaffected by an early season blizzard; fresh produce as of this publication date!

One of the greatest challenges my garden has faced has been a battle against aphids and spider mites. In outdoor environments, natural predators do much to keep populations of pests (like aphids and spider mites) in check. But in the climate-controlled world of an indoor garden or greenhouse pests can reproduce unchecked by predators and lead to imbalanced (aka. out of control!) populations.

Where did they come from?
With a few exceptions, plants which I started from seed have remain unscathed; however, a few plants which were placed next to incoming nursery stock encountered problems.

Damage from inadequate watering and spider mites on a Jalapeño

Case in Point: one poor Jalapeño (photo above) that was started from seed caught a bad case of spider mites from another pepper plant which was purchased from a commercial nursery/greenhouse. Initially things in the garden were great but while I went away on vacation, insects were busy chowing down on my pepper plants. I returned to what you see in the picture.

Some time after this, I purchased a sad looking (#discount) Taro plant. I placed it in the garden, wiped off its leaves and stalks with a damp paper towel, and watched it closely. After some weeks, I began to notice many tiny glistening, sticky spots on its leaves; the spots were honeydew, evidence (waste) left by aphids. I took a closer look (picture below) and saw tiny green insects (aphids) moving around the leaves.

Aphids on a Taro leaf

A lack of patience.
One pepper which had become infested with spider mites appeared to stop growing after treatment. I became frustrated because it hadn’t produced a new leaf over the course of two months! So, I decided to rip out the pepper and use the pot for something else.

Pepper plant after 3 months of growth in an 18cm (7in) diameter pot.

Little had I known that the plant had been developing a very robust root system. Sigh.. a root system that would have been able to support many specialty peppers. On the flip side, now I know the plants are growing and that this container was likely too small for the plant anyway. Recommendations for adequate container sizes can be found here: https://cmg.extension.colostate.edu/Gardennotes/724.pdf

What can be done... aside from tearing out a plant?

It is important to first know what may be attacking a plant. For example, after looking for some time (phone cameras, magnifying glasses, hand lenses, and microscopes can be helpful!) I observed not only spider mites but also thrips on my pepper plants! These two insects require slightly different management strategies. Note: Information on thrips is linked-to at the end of this post.

Spider mites and aphids lay eggs on plant material and go through a roughly 2-week life cycle (important to know when planning follow-up treatments). A jet of water is often enough to dislodge these pests from many plants. Have a spider plant (‘Chlorophytum comosum’) with spider mite webbing between its leaves? - Give it a shower in the sink!

It is easier to battle 10 insects than it is 10,000. Washing a nursery plant upon its arrival can save headaches  by preventing major outbreaks from ever occurring. Note: Not all plants like to have wet leaves. It can be helpful to look up a plant’s general care recommendations.

Insecticide products do exist for treating spider mites, aphids, thrips, and other various plant pests. Insecticidal Soaps with the active ingredient Potassium Salts of Fatty Acids, and Horticulture Oils (e.g. Neem, Cottonseed) can be effective parts of an integrated pest management strategy. It may not seem like it, but Insecticidal Soaps and Horticultural Oils can be harmful to humans and pets and other non-target organisms. Pesticide product labels should always closely be followed and adhered to. Note: when applying an insecticidal soap (active ingredient: 'Potassium Salts of Fatty Acids') any insect not completely wetted (e.g. an aphid hidden in a rolled up leaf) will not be affected.

What I wish I would have known.

• That placing plants in the shower or sink or (even better!) taking them outdoors prior to treatment can make cleanup a much easier process.
• Some plants can react poorly to Insecticidal Soap and/or Horticultural Oil treatments. It can be mildly traumatic to see a plant drastically defoliate a day after being treated.
• Yellow sticky pads can be incredibly effective at managing indoor populations of fungus gnats (sometimes mistakenly referred to as fruit flies).
• Patience is key (in reference to the pepper I tore out).

For more information on a variety of topics, please see the links, below.

• More info on managing Houseplant Pests: https://extension.colostate.edu/docs/pubs/insect/05595.pdf
• Insect Control: Soaps and Detergents: https://extension.colostate.edu/docs/pubs/insect/05547.pdf
• Insect Control: Horticultural Oils: https://extension.colostate.edu/docs/pubs/insect/05569.pdf
• Spider mites: https://extension.colostate.edu/docs/pubs/insect/05507.pdf
• Fungus Gnats: https://extension.colostate.edu/docs/pubs/insect/05584.pdf
• Thrips lifecycle: http://ipm.ifas.ufl.edu/applying/Biology_of_Thrips.shtml
• Western Colorado Thrips: http://www.wci.colostate.edu/shtml/ot.vs.wft.shtml

As a fun aside, insects (like 'Lady Bug' and Lacewing larvae) which feed on spider mites, aphids, etc. can be purchase from locations around the USA. Here is a very impressive list of BioControls and example locations from across the US where they can be acquired: https://webdoc.agsci.colostate.edu/bspm/InsectInformation/Factsheets/BioControlSuppliers.pdf

For an introduction to this indoor garden, please see this blog post: https://csuhort.blogspot.com/2019/09/reflections-on-season-of-indoor.html

 Best of Luck in all your gardening endeavors! 
- John 

Reflections on a season of indoor gardening

Posted by: John Stolzle, Jefferson County Extension
This post details what can happen when a plant enthusiast with a will to tinker moves into an apartment. In this post, I have overviewed some of the setup, challenges, current outcomes, and tips gleaned from my trials with indoor gardening. 

I moved into an apartment about a year ago. It had one large south facing window which was light limited by surrounding structures. It had no patio, nor space to grow plants outdoors, nor were there open community garden patches nearby. Slowly, in the back of my mind, the urge to cultivate my apartment space grew. I eventually purchased a few houseplants, yet, I was unsatisfied. I wanted to tinker, I wanted a challenge, I wanted to pick fruit and see flowers. 

One morning, I decided that I wanted a garden and that apartment life was not going to stand in my way. I had grand visions of tomatoes and peppers in winter. I wanted a challenge and a challenge is what I got. 

Early March 2019 - Late September 2019 (Click to enlarge)

Stage 1: The Set Up

Plants need a whole bunch of things to thrive, but for the sake of this post I am going to drastically simplify them as: Soil, Water, Light, and Space. 

I began with a garden plan in my mind; however, most of my plans went out the window as soon as I first arrived at a nursery. There were just too many possibilities and so I opted to make a game out of my garden – What could I keep alive in this plant-unfriendly environment? 

Due to ad hoc planning and prep, I made multiple trips to hardware stores and nurseries; it was fairly inefficient, but I eventually ended up with a selection of plants, containers, and soil. I drilled drainage holes in the bottom of 5 gallon HDPE buckets (for tomatoes and peppers) and purchased short lipped storage bins to catch water. Beneath the storage bins and lids, I placed paper towels to help monitor for moisture and facilitate sliding the containers around. I have heard reports that moisture can seep from terracotta/clay containers and damage floors, and so all of the plants were placed on plastic lids or in bins. 

Note: If I were to restart the project, I would use boot/shoe trays sold at hardware stores. They would likely be less expensive, and I believe that they would be easier to position in such limited space. 

Note the white growth on the soil in the picture on the right; this a type of saprophytic fungi which feeds on decaying plant matter (generally not a major concern for plants). 

Here are some references for starting out

* Container Gardening (Great Overview); https://extension.colostate.edu/docs/pubs/garden/07238.pdf

* Vegetable Gardening in Containers (Space); https://cmg.extension.colostate.edu/Gardennotes/724.pdf
* Soil (Potting soil is important!); https://web.extension.illinois.edu/containergardening/soil.cfm
* Watering: https://planttalk.colostate.edu/topics/houseplants/1318-houseplants-watering/
* Light: https://planttalk.colostate.edu/topics/houseplants/1352-interior-plants-light/
* Insect Control: https://extension.colostate.edu/docs/pubs/insect/05595.pdf

Stage 2: Environmental Modification

After a month, many of the plants began to show significant stress. Some were spindly (in search of sunlight), the Asiatic Lilies were succumbing to disease and hadn’t grown but 2 millimeters, and the Lamb’s Ear was slowly losing its leaves. The plants had been carefully watered, planted in decent potting soil with room to grow, but needed more light. 

I thought it would fun to try growing a Mammoth Sunflower (Helianthus giganteus); the kind that can grow 10ft+ tall. It grew 3 feet with artificial support, flowered and then died shortly thereafter.

I eventually acquired and installed a broad spectrum led grow light; the plants didn’t rebound quickly but they did show signs of increased vigor… And then I began to notice the insects. 

I had attempted to avoid an insect outbreak by rinsing the foliage of each plant in my kitchen sink and then spraying some of the plants with Neem oil and/or insecticidal soap. Despite my best efforts, I have found myself locked in battle with aphids and spider mites. In this protected environment, the pesky bugs are able to feed and reproduce without a check or pressure from predators. At one point, I considered releasing predatory insects but then had visions of Cane Toads in Australia… I have so far opted to not venture into this territory, though I am very tempted.

Wiping down and then spraying the plants does seem to provide a brief reprieve from the infestation. I currently believe my challenge of aphid and spider mite management to be two-fold: 1, I occasionally re-infest my garden with new insects as I add different/new plants (to replace those which didn’t make it), and 2, my soap and horticultural oil treatments need to be better timed.  

Additional References

* Horticultural oil; https://extension.colostate.edu/docs/pubs/insect/05569.pdf
* Spider Mites; https://extension.colostate.edu/docs/pubs/insect/05507.pdf

Additionally, I have learned that many potting soil mixes come pre-packaged with fungus gnats eggs. Upon adding water, these eggs hatch, and adults will soon be flying all around indoor environments.  These insects are very minor plant pests, but can be an incredible nuisance. I have had huge success managing the insects with yellow sticky paper; noted in this factsheet on Fungus Gnats: ://extension.colostate.edu/docs/pubs/insect/05584.pdf.

To any adventuresome gardeners considering an indoor garden, I had the greatest struggle with: Asiatic Lilies, Snap Dragons, Sunflowers, Sweet/sugar Peas, Daffodil bulbs, and ornamental grasses. The grasses struggled and failed in the most spectacular fashion.

The tomatoes and peppers seem to struggle up to a certain point of development, after which they grow quite rapidly. The Scotch Bonnet (nursery started) has done amazingly well. It did have a significant set back due to an insect outbreak and me burning it with oils, but three weeks later, it is now flowering again. I have also been surprised by how well the Bougainvillea, Mandevilla, and Pineapple have done.

Stage 3: Success?

What does success look like in a mad-gardener’s laboratory?  I have lost many plants along the way and have added some fun new players such as Purple Passion Gynura aurantiaca, Lavender, and Taro. It has been a worthwhile experiment in my mind. Yields have been low, but my vegetables are just starting to produce... And who knows, maybe I’ll have fresh tomatoes in winter. 

A bit of gardening chaos; perhaps it's time for a mid-season prune.

I have many tales to tell from my trials with indoor gardening: of tomato training, of the importance of wind and humidity, supplemental lighting, container rotation, fertilizing, and manual pollination...  Perhaps this will be the first in a series of indoor gardening blog posts.  

For more information on houseplants, check out this blog posted last Monday: https://csuhort.blogspot.com/2019/09/plant-parenthood-rise-again-of.html

 Best of Luck in all your gardening endeavors! 
- John