No Greenhouse? Convert a Sunny Window into a Seedling Nursery

Starting plants from seed can be intimidating. Purveyors of gardening supplies will suggest that you need a pre-fab greenhouse and all kinds of special trays, soil mixes, heating mats, and grow lights to ensure success. While those conditions might be optimal, you can still grow seeds indoors without any special equipment whatsoever. Don’t miss out on the magical experience of growing from seeds! It is the most rewarding thing a gardener can do.

Water, warmth, light, and a growing medium — those are the only ingredients seeds really need to germinate and grow. But you also need a fifth element, and that is a location that has all these things.

I have two big, sunny, south-facing windows in my kitchen. When we first moved in to our apartment, I looked at those windows and envisioned SHELVES. Specifically, clear acrylic shelves, with baby seedlings perched atop them in neat rows, high enough that my cat couldn’t reach.

Because everyone’s windows are unique, this post is intended more to inspire your own DIY journey than provide a step-by-step guide. My project required almost no carpentry experience, but it did involve going outside my comfort zone and some creative pivoting. It would have gone a lot more smoothly for an engineer or handyperson. But if I could figure it out, so can you! 

Assess Your Windows

My kitchen windows are tall, almost floor-to-ceiling, and recessed into the wall by about three inches. They were begging to be converted into a seedling nursery.

Assess the windows in your home. Do any of them receive full sun, creating a nice toasty environment for baby plants to thrive? If so, I advise you to be brave and creative, and find a way to maximize their growing potential.

Finding Materials

As I mentioned, I received a vision of clear acrylic shelves. I didn’t want them to block out light or look obtrusive. Our building is from the 1960s, so the windows aren’t standard sizes; in fact, after measuring them, I realized one was slightly wider than the other (always measure!).

How was I going to find pieces of acrylic the exact width, length, and depth to fit perfectly into my weird windows? Well, it turns out there are PLASTIC STORES. Yes, businesses specifically dedicated to selling all sorts of plastic, cut to size, for any project! The preeminent local outfit in the Bay Area is called TAP Plastics, but you can google “plastic fabrication company” to find the equivalent in your area.

I don’t know about you, but I have to work up a lot of courage to step foot into places like this. I feel like the staff can automatically tell that I’m an idiot who knows nothing and has never custom-ordered her own plastic before.

But I pushed through my discomfort, and I have to say, the folks at TAP Plastics really hooked me up. I brought all my measurements with me and explained my project to a non-judgmental staff person who helped me choose the thickness and quality of acrylic. I never could have figured it out by myself trying to order the materials online. I love that places like TAP exist!

I won’t say it was cheap — it cost about $70 for four pieces — but it was a lot less expensive than the portable greenhouses, grow lights, and other gadgets they try to sell you on gardening websites.

Next, I needed a mechanism for supporting the shelves. You know those little thingies that hold up the shelves inside your bookcase or kitchen cabinets? They are called shelf brackets and are available at your local hardware store. I picked out some brass ones at Ace that seemed sturdy enough.

Installation: Tears, Compromise, and Victory

I try to approach “home improvement” projects thoughtfully and deliberately, the way my dad taught me. He always says, “go slow, it’s faster.” And yet, no matter how many times I measure or how carefully I plan, unexpected problems inevitably arise and my zen outlook unravels.

Immediately, I discovered a problem with my measurements. I had measured the width of the window openings, but had not accounted for the few extra millimeters that the shelf brackets would take up. This meant that my all of my shelves were too big.

I had to go back to TAP, ashamed. Of course, since they’re the best, they kindly shaved off a fraction of each piece. I brought them home. The ones for the smaller window still didn’t fit. I cried. 

But then, my husband suggested installing all four of the shelves in the larger window, in which they did all fit, instead of two and two as I had originally planned. I agreed this was a good solution, stopped crying, and moved forward.

Then there came the saga of trying to insert two shelf brackets per shelf edge on the exact same level. Each time I tried so hard, marking the wall with my pencil exactly where the hole needed to go, and each time the brackets were at slightly different levels. 

But you know what? When I slid the acrylic shelves onto the wonky brackets, they stayed put. They wobbled a little, but they’re not for displaying priceless artifacts in an archeological museum. For holding a bunch of egg cartons filled with dirt, they would work perfectly fine. 

Installation was complete! I couldn’t believe it. It was perhaps my proudest small-space gardening moment of all time.

The Fun Part: Starting the Seeds!

The sweet, sweet reward of this DIY endeavor: my plan to create a miniature greenhouse to grow seeds indoors in my kitchen actually worked!

Egg cartons fit perfectly on the shelves and worked great for my initial sowing. I started tomatoes, peppers, basil, and cucumbers. As the plants grew, I potted them up into larger containers, re-using plastic nursery pots and yogurt containers until they outgrew their shelves.

I ended up with way more plants than I had space for and foisted the extras upon friends and neighbors. For my balcony, I kept eight tomato plants, three pepper plants, and one cucumber, but my rollercoaster of a vegetable growing season that summer is a story for another day. 

Addicted to growing seeds indoors even after my vegetables had graduated to the balcony, I later sowed nasturtiums, asters, and snapdragons, to varying degrees of success. The asters and nasturtiums were favorites and I’m definitely going to sow them again this year.

A few words of caution if you’re starting seeds in a sunny window:

• In the midday sun, the soil can dry out really fast and form a crust, which you don’t want. Before the seeds germinate, keep the soil continually moist by spraying with a water bottle. Once the seedlings have sprouted, water the soil at the base of the plant whenever dries out.
• For seeds that need heat to germinate and grow, place the tray/egg carton/plugs in a plastic bag with holes in it for extra warmth. A plastic produce bag for apples and such works well here. Once the seedlings are growing strongly, stop using the bag to avoid mold problems.
• In the beginning, especially if you’re starting seeds in February or March, the nighttime temperatures near the glass window may be too low for some seeds, like peppers and tomatoes. Move them somewhere warmer at night. If you have a dishwasher with a “heated dry” setting, the countertop above it works great as a heated surface!

You, Too, Can Grow Seeds Indoors!

I fervently hope that no one comes away from reading this post frustrated at the size, shape, and orientation of their windows. The point is not that you should replicate my creation or feel pressured to take on an ambitious DIY project. 

On the contrary, I hope you feel empowered to realize a vision you have for your space, whatever it may be. Go to that intimidating store and ask for help! Google what that obscure piece of hardware is called so you can ask for it! Don’t despair when things go awry; take a deep breath, pivot, and embrace imperfection! 

Most importantly, do what you need to do to start those seeds. Witness the miracle of life unfurl from your kitchen table and nurture it into its full glory!