How to Grow Phalaenopsis Orchids on a Windowsill

When I first started growing orchids, I started with Phalaenopsis plants that I fell in love with in the grocery store or big box stores. They looked lovely for awhile, but invariably languished and died, and I thought it was that I just didn't have a green thumb. 

A few years ago I was determined to crack the orchid code. I killed a record number of poor grocery store phalaenopsis that year! What finally worked was pretty simple, and might work for you too. 

Keep in mind that plant culture is closely connected to where you live, and the conditions you are growing your plants in-- you might have different challenges based on where you live and grow. I live in the Northeast, in Central New York State, and it gets cold and dark here in the winter. My house was built in the 1920s and was renovated in the 1980s, which means it is cozy, but far from hermetically sealed, and we are cost-conscious about how much heat we use in the winter. 

Phalaenopsis orchids are tropical plants, with many coming from breezy, perpetually warm islands closer to the equator. The plants we buy in the grocery store are bred to flower prolifically with minimal care, but they still expect some basics!

Phalaenopsis philippinensis in the National Orchid Garden of Singapore

First Rule of Windowsill Phalaenopsis Culture: Warmth

Phalaenopsis orchids are happiest between 65 and 80 degrees F (18-27 degrees C). That means they'll tolerate 65 degrees (or lower), but they don't want to be 65 degrees all the time. During the day, they really want to be at least 70, preferably mid 70s, even in the winter. At night a dip to 65 is tolerable, but keep in mind that if your thermostat is set to 65 at night, your windowsill is probably a few (or more than a few) degrees colder. 

Phalaenopsis Sweet Memory

In addition, when locating your orchids, watch out for drastic temperature shifts. Early on, one of the windowsills I put my orchids on was 25 feet away from the door, but in a direct line to receive the drafts when it opened or closed-- receiving blasts of freezing air was not welcomed by my tropical plants. 

A phalaenopsis kept too cool won't die immediately, but its growth will stall and it will languish for months. It will be much more likely to experience root and crown rot. 

How to keep your phalaenopsis warm?

Our thermostat in winter is set to 68 degrees, which means that temperatures in the house might range from 65-70 during the day. To a tropical plant, these temperatures are barely tolerable, so seedling heat mats are an economical solution to make Phalaenopsis orchids a lot happier. The long skinny 3"x20" are perfect for windowsills.

Double layer pots help provide additional protection and humidity for the roots. It is likely your grocery store phalaenopsis came with a double layer pot-- it is potted in a (usually) clear inner pot with holes inside a decorative plastic or ceramic pot without holes. The outer pot will help hold the heat and humidity near your plant's roots. 

If your plant doesn't have a liner pot or you've repotted it and it no longer fits in the decorative pot, then you can make one out of recycled plastic food containers. You can see in the above photo that I've made some out of a recycled sour cream container and a hardware store mixing container with the rim cut off. 

Won't the leaves get cold?

In the winter, keep the leaves from touching the cold window directly, and protect your plants from drafts. But if the plant's feet (roots!) are warm, it will be much happier!

Can't I put my plant near a heater?

No, this is generally not a good idea! You might think putting your orchids near a heater or vent might help, but the intense dry heat of an air vent or baseboard heater can be very damaging to their delicate leaves and roots-- it can cause rapid decline of a plant. Yes, it has happened to me!

Will seedling heat mats work in all areas?

Unfortunately, heat mats are not a magical solution... you still might have rooms or windowsills that are too drafty for your phalaenopsis. For example our kitchen windowsill is just too chilly for phalaenopsis orchids, but cool-loving paphiopedilums from the mountains of China and Vietnam love it there. In my drafty office in the attic of an old carriage house, the only way I can keep my phalaenopsis alive is in a plastic terrarium with a seedling heat mat under it. 

Second Rule of Phalaenopsis Culture: Light

Phalaenopsis are often said to be low light plants. They live in the understory of tropical forests, and only receive filtered light, rarely direct sunlight. However, that's TROPICAL filtered light, from islands near the equator. So even though it isn't direct sunlight, there are may more hours of it, and it is much more intense before it gets filtered through tree leaves and atmospheric moisture. 

The average hours of daylight in Singapore on the shortest day of the year is 12 hours. The hours of daylight on the shortest day of the year at the latitude where my plants live is 9 hours. But it is worse than that, they don't see all those 9 hours of sunlight. For one, the angle of the sun changes so that less of that light makes it into our windows, for less hours of the day, since it is blocked by our building and the structures around us. In addition, our area frequently experiences stormy weather and cloud cover, further blocking the light. 

A phalaenopsis orchid that doesn't get enough light won't die immediately, it might hang out for YEARS growing very slowly, if at all, and never blooming. This is no fun... we grow orchids to see them grow and bloom! 

There is a very simple solution for northern houses without exceptional natural light: add light with LED plant lights. So many different energy efficient plant lights are available now, and most of them would be better than nothing as far as your plants are concerned.

LED plant light bulb that fits a standard socket. I bought a socket and made a shade from a galvanized bucket, but you could use any lamp that takes a standard bulb.

LED clip lights with 3 heads. This one has an integrated timer that I have to reset every month, but otherwise it has been very effective for 3 years!

These LED light strips were bought at a local hydroponics store on clearance. 

A 24-inch LED light strip from the company Botanical LEDs, hung across two windows held up with string supported by nails.

You'll also probably want a plant light timer. Some lights come with an integrated timer, for others you'll need to purchase a timer and plug the light into that. 

Will any light bulb work?

Plants prefer full-spectrum lights. All of the things marketed as LED plant lights that I have bought have worked to supplement weak window light and get phalaenopsis orchids to bloom regularly, they are not picky. When I got into Cattleyas I did buy some "special" LEDs which I'll talk about in another post. 

How long should your supplemental lights be on?

Phalaenopsis come from near the equator, so 12 hours is ideal. If you have good window light, you could have them on only for the hours needed to add up to 12 hours. 

If you have supplemental lights, do your plants even need to be near a window?

Actually, no! If you have true full-spectrum plant lights, phalaenopsis will grow and bloom with just LED light. Some of my phals grow on shelves and never see real daylight. Windowsills are just convenient plant shelves 😁.

Can you give a plant too much light?

Yes, you should protect your phalaenopsis from direct sunlight, it can burn the leaves. Reportedly this happens in south windows and sun rooms, move your phals away from direct light or use translucent window shades. (It's not a problem around here!) 

I have not had a problem with hybrid phalaenopsis orchids suffering from too much LED light... theoretically it is possible, and you might want to take care when introducing a new light, moving the plants gradually into the light. (Certain phalaenopsis species are truly lower light plants and can suffer stress from too much light, which I'll talk about in other posts-- but hybrids have a wide range of genetics that make them flexible about the amount of light they receive). 

 Third Rule of Phalaenopsis Culture- Water

If you are keeping your plants warm and giving them good light, they will be growing well and you'll need to water them regularly.

How much water is a bit complicated by several factors-- what kind of potting medium your plant is in, what kind and size pot it is in, and the ambient temperature, humidity, and air movement. Generally, phalaenopsis orchids want to be in airy media that experiences cycles of wet to (almost) dry. 

The most common media to grow hybrid phalaenopsis orchids is in bark (orchiata). When watering a phalaenopsis in bark (or mixes that are mostly bark), use use the outside pot without drainage holes as a soaker pot and fill the pot with water. Allow to soak for 5-15 minutes, then empty the outer pot. Water when the roots are approaching dryness- phalaenopsis roots are greener when wet, and turn silvery when dry. For larger pots (5 inches and larger) you might only need to water once a week, but smaller pots might dry out and need watering twice or three times a week. Fresh bark holds less water and needs to be watered more frequently than older, more broken down bark. 

Phalaenopsis growing in a mix of large bark and perlite, with a recycled yogurt container as a liner pot.

If your plant is in spagnum moss, you need to water differently. Don't soak the spagnum (if you do it by accident it is not a tragedy, just let it dry out)! Instead, put a couple tablespoons of water into the soaker cup and let it soak up into the pot. If you feel the moisture in the top of the pot, then this is enough, otherwise give it a little more water. Properly watered spagnum should feel damp and springy, not soggy. Water the plant in spagnum moss again when the moss has gotten dryer, but not bone dry and crispy. The goal of a plant in spagnum is to keep the moss evenly moist. 

Doesn't spagnum cause root rot?

This is a common perception, and I used to believe this too, but no, I no longer believe spagnum causes root rot. What changed my mind? I learned to water with the above method, which allows the spagnum to stay airy. If you soak the spagnum on a regular basis, you are removing the natural air pockets and the roots could end up rotting. This is especially a problem if you are also keeping your phals too cold. 

What about semi-hydro and inorganic media?

Semi-hydro works great for phals also! With this style of growing, you use an inorganic media like expanded clay (leca) or volcanic rock, and keep a reservoir of water that the roots grow into and that wicks up into the pot. I use this method also. Reportedly this keeps the roots cooler, so I'm a bit hesitant to move all my windowsill phals to this method, but I have a couple in semi-hydro and they are doing great, even on my cool windowsills. 

Repotting a phalaenopsis grown in semi-hydro. Great root growth!

Other factors:

Air movement

All of my grow areas have small fans set up to provide air movement. This probably isn't essential to phalaenopsis growth, but it does seem to generally keep plants happier, reduces problems with some pests (mites), and helps pots dry out more quickly. 

Humidity

Humidity can be on the low side when the heat comes on in the winter in my house-- sometimes 30 or 40 relative humidity. However I haven't found humidifiers or pebble trays to be very effective for my windowsill culture-- humidifiers affect such a limited area and I neglect to refill them and pebble trays have almost no measurable effect. What I have found to be effective is the use of double pots-- in combination with heat mats, they hold humidity near the roots where orchids need it most. (I grow mounted plants on tented shelves with misters which keep the humidity between 50-70 percent, but that isn't necessary for hybrid phalaenopsis and many other potted orchids).

A sour cream container with the rim cut off as a liner pot. 

Under the liner pot, roots are happily trying to escape the pot!

Don't you need a temperature drop to induce spiking?

No, you do not! Happy phalaenopsis orchids will produce spikes WITHOUT any temperature drop, especially grocery store phals which are selected for their readiness to bloom. When they produce spikes is determined by the plant having sufficient energy and the genetics of the plant. Some plants will only spike once a year, while others will produce spikes almost continuously. 

You definitely can induce spikes on hybrid phalaenopsis orchids with a night drop in temperature, and this is how the orchid industry times the delivery of blooming orchids to vendors. Whether you choose to experiement with this is up to you- personally I prefer to let my plants bloom on their own schedule.

Should you cut spikes after plants are done blooming?

This is a matter of preference. If you leave the spike, some plants will rebloom on that spike, sometimes immediately and sometimes later, after producing another spike. Sometimes plants will make a keiki (baby plant) on an old spike. At some point the plant will re-absorb the nutrients and chlorophyll from the spike and it will dry up, and then you can definitely cut it. 

I love to leave the spikes to see what the plant will do, all outcomes are interesting to me 😁.

Grocery store phal that I've had for many years, blooming on a new spike in February, producing a classic Phalaenopsis cascade of blooms. 

 

The same phal re-blooming on old spikes in April in an untidy explosion of new blooms. 

Should you repot Phalaenopsis immediately when you bring them home?

In most cases, no! It is best to let the plant acclimate to its new growing conditions (hopefully warm and bright!) and start growing roots. If it is in a clear liner pot inside of its decorative pot, you can observe the roots. Use the methods described above for watering--if it is in bark, soak and empty when approaching dryness, and if it is in spagnum, moisten but don't soak. Wait until you see new growing root tips, then either decide to keep the current media or change to the media and pot you prefer. 

If you do need to repot, Phalaenopsis orchids are usually pretty forgiving and adjust well, but in my experience they adjust best to their new pots when they are actively growing. 

What about pests in the soil? Should I spray roots with Hydrogen Peroxide or other products?

No, please do not ever put hydrogen peroxide on orchid roots. It damages them, even at the "suggested" three percent solution that some people recommend on social media. There is a study that looks at this issue in great detail and concludes that it is not helpful and is likely harmful to orchid roots. 

I bought this Phalaenopsis at Walmart in May. It's in a decent pot with nice bark and growing well... I'm leaving it alone for now, no need to disturb it. It does have active root tips so I could repot it now if I wanted to. 

Should you fertilize your orchids?

Yes, please do! There are many thoughts on fertilizers and fertilizing schedules, and honestly, if you did all of the above and didn't fertilize, your plants would probably grow and bloom fine for a year or more. But if you fertilize, it can only help growth and blooming! My current theory is to fertilize at every watering, very weakly-- that way I don't have to think about when I fertilized last 😌. With my fertilizer (K-Lite), you would use 1 tsp per gallon once a week, so I do 1/6 of a tsp per gallon on every watering. I am not precise about it. 

Do you use any other products?

Yes, I do use Kelpmax when repotting and I add it to the water every couple of months. My plants grew fine before I started using Kelp, so I don't think it is necessary, but it probably does help stimulate growth. 

Can you grow phalaenopsis outside in the Northeast?

Yes, you can! You need to be aware of keeping within the 65-80 degrees F temperature range, and keep them in bright but not full sun. And watch out for pests. 

While I grow other orchids outside in the summer, I keep my Phals inside. I did try them out on the porch one year, but I had trouble with vine beetles feasting on them and I decided to keep them protected inside after that. For me they do so well inside, there didn't seem to be a huge benefit to risking them outside.