Caja Frequently Asked Questions

Do You Have Recommended Suppliers for Soil Media, Potting Mix, Seeds, and Transplants?
For the soil media/substrate, investing in a high-quality soil mix is important for optimal plant growth. Most people will use the soil over multiple cropping cycles and for many years, amending it each time with some additional fertilizer, dolomite, compost, or other soil amendments to ensure the plants have the appropriate nutrients. We’ve had great results with the Young Urban Farmers’ Potting Soil Mix. When working on international projects, we like to find local suppliers instead of shipping heavy and bulky soil.

For seeds and transplants in Southern Ontario, we’ve had great results with Freeman Herbs, Richter’s Herbs, Urban Harvest Seeds, and William Dam Seeds. Talk to your local independent garden center for seedlings and for your other gardening needs.

Note, The Growing Connection does not receive any financial compensation from our Recommended Suppliers. We suggest them because we believe in what they do and we’ve had great results with their products.

Can You Deliver One or More Cajas Already Planted and Ready To Grow?
Contact us directly, or contact Young Urban Farmers if you are in the GTA (Greater Toronto Area) – let’s see what can do to help you get your Caja planted, setup, and delivered if you are in southern Ontario.

Where Can I Setup Caja To Grow My Edibles?
You can grow almost any type of plant in your Caja as long as you have sufficient light. For most people, they will be growing outdoors during the spring/summer growing season. If you have a greenhouse, a very sunny window, or want to use growing lights, Caja can be used inside all year round.

Can I Use Regular Soil From My Backyard In My Caja?
No. The Soil Media is very important to the proper growth and health of your plants. We recommend using a commercial potting soil mix or creating your own using materials like cocopeat or peat moss (these two ingredients facilitate in the wicking of water from the reservoir to the roots of the plants) along with natural organic compost like worm castings.

What Can I Grow In My Caja?
Caja was originally developed by a commercial tomato grower, and people all over the world have grown a wide variety of crops with it including herbs, greens, cucumbers, melons, zucchini, and even corn. Check out our planting guide for spacing and variety suggestions.

Can I Plant More/Less Than The Recommended Plants In My Caja?
Our recommendations are based on years of experience, to maximize yields, minimize pests and diseases, and to make maintenance as easy as possible. If you plant more than the recommended guide, each plant will have to compete more for space, sunlight, and water, which can decrease overall yields, increase the chance of fungal issues and pests, and make maintenance more time consuming.

Can I Mix and Match Plant Types In My Caja? For Example, Can I Plant One Tomato Plant With Three Chard Seedlings?
We recommend following our guidelines and growing one type of plant per Caja (ex. two tomato plants per Caja, 6 chard plants per Caja, etc.). For advanced growers, you can mix and match plants as long as you provide each plant with enough water, nutrients, and growing space. This is easiest when you select plants that grow to a very similar mature size (ex. 3 chard plants and 3 cabbage plants in one Caja) to avoid one type of plant outgrowing, overcrowding and shading out the smaller sized plant(s). For beginners, we recommend following our planting guide.

Can I Use Liquid Fertilizer Instead Of a Granular Fertilizer When Setting Up My Caja?
No. Liquid fertilizers generally provide an immediate nutrient feeding to your plants while granular fertilizers are slow acting and release their nutrients on a consistent basis over time. Caja makes growing easy by allowing you to setup your nutrients once at the beginning of the season and not have to worry about subsequent fertilizing and feeding later on.

For advanced growers, if you are growing heavy feeding plants like tomatoes, melons, onions, etc, you can provide additional nutrients during the growing season using compost tea or a diluted liquid fertilizer. Be careful not to over feed or feed the wrong balance of nutrients. For beginners, we suggest using the granular fertilizer as instructed during the setup of your Caja as the plant’s source of nutrients for the growing season.

Do I Need To Add Dolomite When Setting Up My Caja?
Dolomite is a translucent mineral consisting of calcium and magnesium (two important plant nutrients). These nutrients are critical for plants like tomatoes, peppers, and other fruiting plants in order to promote good plant health, and high yields. We strongly suggest adding in dolomite whenever you are setting up your Caja.


What Is The Size, Weight, and Dimensions of My Caja?
Caja measures 74cm x 34cm x 28cm (29″ x 13.4″ x 11″). The water reservoir capacity is 10 litres (2.6 gallons) and the planting area holds 57 litres (2 cubic feet) of Growing Media/soil.

Caja weighs 2kg (4.4lbs) empty. When planted with heavy plants like tomatoes and a full water reservoir, Caja can weigh up to 36kg (80lbs).


What is Caja Made Of?
Caja is made from food-grade, BPA-free, UV-stabilized HDPP plastic. It is all safe for gardening and growing your own food, and can withstand temperatures from -40C to 40C. It will last you for many years of growing.

How Does Caja Work
Caja is a sub-irrigated growing container. Through the cutouts in the corner of the aeration screen, water gets wicked up into the Soil Media. Once your Caja is planted and assuming the reservoir doesn’t run dry, water continually cycles through the box, bringing with it nutrients from the fertilizer and dolomite directly to the plant roots. Water loss through evaporation is minimized as it condenses against the Mulch Cover. As a result, plants stay hydrated longer, plants are less stressed (which can lead to tough/bitter vegetables with lower yields), plants grow bigger and faster, water and fertilizer use is minimized, and maintenance and watering is super easy. It really is a winning combination when it comes to an easy solution to grow your own veggies.

Is Growing With Caja Really Weed Free?
Yes – provided you start with healthy transplants and use the Mulch Cover as directed. However, if you grow without the mulch cover, there is a chance weed seeds can blow into the Caja.

What Is The Purpose Of The Mulch Cover? Do I Really Need To Use it?
The mulch cover serves 3 important purposes. The first is to keep weed seeds out of the growing media. While you may think weeds won’t get into your box if you leave it uncovered, we’ve seen weeds germinate on a downtown Toronto balcony 30+ stories in the air.

The second reason is to minimize water loss from evaporation. Water is continually cycling through the growing media (assuming the reservoir hasn’t run dry) and the mulch cover provides a surface for the moisture to condense and continue cycling through the growing media without being lost to evaporation in the air. The holes you cut for your plants as well as air coming from the watering tube and reservoir will provide enough oxygen and air flow to prevent harmful mould and other fungal organisms from growing underneath the mulch cover.

The third purpose of the mulch cover is to keep the soil warm in the spring and fall. In cooler climates like Canada, placing the black side of the mulch cover facing up will help to warm up th soil faster in the spring and fall shoulder seasons. By the time the heat of summer comes along, the plants should have grown big enough to shade out the mulch cover and prevent the growing media from becoming too hot.

When and How Much Water Do I Add?
Caja’s reservoir should not be allowed to run dry. As long as there is some moisture in the reservoir and soil media, your plants will grow just fine. The amount and frequency of watering will depend on how big the plants are (bigger plants typically drink more water than smaller plants), the ambient day and night temperature (warmer weather usually means faster plant growth and more water usage), the type of plants you grow (tomatoes drink up much more water compared to herbs and greens), how much precipitation has fallen recently if growing in an outdoor environment, and other factors like your microclimate and sun conditions.

In general, we recommend creating a watering schedule every 2-3 days to begin with, and then assessing the water needs of your plants as they develop. Early in the growing season, we’ve gone up to 1 week between watering. In the summer with tomatoes, we’ve often had to water every day or every other day to ensure the box doesn’t dry up. Morning, afternoon, evening or nighttime doesn’t make a difference when it comes to filling up the water reservoir.

When watering, you want to water only through the watering tube and until you see water coming out of the overflow hole(s). The water reservoir capacity is 10 litres (2.6 gallons). You cannot overwater your plants.

Can I Over- or Under-Water My Plants?
You can’t over water your plants as the overflow holes ensure the soil will not get waterlogged. Too little water and plants can dry up and die.


Can I Order Extra Mulch Covers For My Caja?
Yes. You can order as many as you need from our online store.

What Should I Do With Caja In The Winter?
Your Caja is frost-proof, and can be left outdoors throughout the winter. For best results, we suggest you remove all plant material growing above the mulch cover, drain the excess water from the reservoir, and place the box in a sheltered and/or protected area.

How Do I Replant My Caja After The First Year Of Growing?
Please see our Caja replanting guide for more information on how to reuse your Caja for another growing season (coming soon).

Can I Use My Own Mulch Cover Instead Of The One You Provided?
Yes, if you have something similar and suitable, you can definitely use it to make tending to your plants easier. Our mulch cover has been designed specifically for your Caja in terms of ease of use by having an elastic edge, the right thickness, and a double sided option.

Can I Reuse The Mulch Cover For Subsequent Growing Seasons?
Yes, as long as the cover is in good condition, you can continue to use the mulch cover until it tears or wears down and is no longer as functional as before.