Urban Agriculture | April 21, 2020

A Beginner's Guide to Starting a Windowsill Garden

NYRP Public Events Manager Matthew Dain's windowsill garden. From left to right on windowsill: potatoes buried in milk carton, avocado pit in clear plastic container, and green onions in plastic container. All other plantings are pawpaw tree seedlings. Credit: Matthew Dain.

Author: Tess Wenstrup, Environmental Educator

Gardens come in all shapes and sizes, including containers on a windowsill. For this garden, we will salvage produce ends you might otherwise toss to grow potatoes, green onions, and even avocado pits.

First, make some space on a window sill that gets a good amount of sun (you can also place a table or shelf near the window if the sill is small). A north or south facing window is always best, but these plantings will still work if you get just morning or afternoon light; the more light you get, the faster they will grow.

Second, you can of course try this with produce you get in any store, but you will probably have better luck if the scraps were from organically grown produce. This is because on-organic farms will sometimes spray crops with chemicals that inhibit regrowth.

Have any questions? Need a plant expert’s advice? Email us at [email protected]—we’re happy to help!

Equipment and materials:

A bag of indoor potting mix: Any type will do.
3 separate containers: This is a good chance to recycle your old milk cartons or take out containers. For example, we use a half-gallon cardboard milk container for both the green onions and potatoes and a plastic take out container for the avocado pit.
A few toothpicks
A vessel for watering

Green onions

Green onions are very easy to regrow at home with just a few simple steps. Instead of throwing out the inch or two of the plant after using the green tops, you can plant it, roots down, to grow another edible stem! This way you can keep a supply of green onions in your house until the bulbs exhaust, which can sometimes be up to three years!

  1. After using the tops of the green onion, keep at least an inch or two above the bulb and roots. You can keep and replant all of the green onions that typically come in a single bundle.
  2. Find a container in your home that has room for the roots to grow. We suggest something about six inches deep, such as an old half gallon milk container or empty pot.
  3. You have a couple options for drainage: Poke a few holes in the bottom of the container and place it on a plate to catch the extra water OR fill the bottom of the container with a layer of small rocks if available.
  4. Leaving about an inch at the top, fill the container with your indoor potting soil.
  5. Using your finger or pencil, poke holes in the soil deep enough so the roots and most of the white part of your individual cuttings are covered. You still want to be able to see about half an inch of the cutting above the soil.
  6. Continue making holes and planting the rest of your green onions. Don’t worry if you have a bunch of cuttings as they grow well even when placed close together.
  7. Give the planted cuttings a sprinkle of water (your soil should be moist, not wet) and place the pot (plate included, if you chose it) in a sunny window.
  8. Water your green onions enough so the soil never completely dries out, but also doesn’t turn into a puddle. In a few weeks (or sometimes even days!), you should see new green growth! Harvest with a pair of scissors (or other cutting tool) by just snipping off what you need and leaving the roots planted in the soil. Be sure to leave about a half inch above the soil so they’ll keep regenerating!


Potatoes are such a satisfying vegetable to grow yourself. Except for sweet potatoes and yams, you can choose any type of potato including russet, wax, purple, or red. Above the soil, the potato will grow into a tall vine-like plant before flowering. It will then slowly turn yellow as it completes its life cycle. When this happens, and the plant starts to brown, you know it’s time to harvest your new potatoes under the soil. The timing will vary depending on your growing situation and could take anywhere between 2-5 months to get new potatoes. This is a good reminder that with gardening, sometimes the journey is the destination.

  1. While looking at a potato, find the small indents called “eyes” on your potato. It should have many eyes and possibly some growth coming from them.
  2. If it is a smaller potato, you can plant it whole, but if it is a large potato you could cut it in half or even quarters as long as each piece has at least one eye. More than size, whether or not the piece has at least one eye is most important. Leave it out overnight so the fresh cut can heal over.
  3. Find a container that works with your space. If you are only going to be planting one potato, a smaller container like the half gallon milk jug will work. If you want to plant more than one though, you must keep in mind they need to be planted about 6 inches apart. If you want to grow more, you can use a 5-gallon bucket that sits on the floor.
  4. Fill ¾ of your container with soil.
  5. Place potato pieces so that the eyes mostly face up towards the light.
  6. Cover the potatoes with a two- to three-inch layer of soil and place in a sunny spot. Don’t forget to water them! Like the green onions, the soil should be moist, not flooded.
  7. Depending on the light and location, as the potato plant grows, it may be pretty tall and leggy. In this case, use a stick or some twine to keep the plant supported and upright.
  8. When the plant starts to die back, pull the whole plant out of the pot and search the roots for your new baby potatoes!


Growing an avocado from seed takes patience and dedication but nothing beats the satisfaction of knowing that you can grow a whole tree from something you may usually toss. While it’s not likely to grow fruit for about a decade, avocado trees are still beautiful plants in their own right.

  1. Trying not to leave any knife marks, carefully remove the pit from the avocado. Wash off any remnants of the green fruit and leave the pit to dry for a few days. You can tell the pit is dry when you can feel the outside layer crackle.
  2. Carefully peel off that dried layer exposing a lighter and more delicate inside.
  3. Next, look at your pit. Instead of it being perfectly round, you can see that one side is a little more pointed and it is more in a tear drop shape than perfect sphere. That pointed side of the pit should be pointing upward throughout the planting process.
  4. Only inserting the very tip, poke three toothpicks into the sides of the avocado (remember pointed end up!) so that it can balance in the center of a cup without touching the bottom.
  5. Balance the avocado in the cup and fill the cup with water. The pit should be at least half way submerged in water. You can reposition the toothpicks if needed.
  6. Set the cup in a sunny window and keep the cup filled with water so the avocado is always half-submerged.
  7. After a few weeks the pit will start to crack open and send down a single root. When the root reaches to the bottom of the cup, you can transplant the pit into soil while being careful to make to hole deep enough to not damage the root. (We would suggest planting in a pot at least ten inches deep to start. Eventually, you will want to upgrade to bigger pots as it grows.)
  8. Place the pit in indoor potting soil so that the top-facing pout of the pit is still exposed. That way you can monitor the growth of your tree.
  9. Keep the soil moist and the plant in partial light. At this stage, the avocado plant is prone to sunburn, so should not receive direct sun.

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