Also known as giant lemon, the Ponderosa lemon (Citrus "Ponderosa") is a citrus variety of unknown origin that is believed to be a hybrid between a lemon (Citrus × limon) and a citron (Citrus medica). Reaching heights of between 10 and 25 feet tall, the thorny tree produces enormous, thick-skinned fruits that may weigh between 2 and 4 pounds. The Ponderosa lemon requires similar cultural conditions as other citrus plants, and does particularly well when grown indoors.
Choose a Sunny Site
Though the Ponderosa lemon will grow in light shade, the tree will produce its best growth in full sunlight. Ponderosa lemon is hardy in U.S. Department of Agriculture plant hardiness zones 9 to 11, tolerating brief periods of temperatures as low as 32 degrees Fahrenheit.
To provide protection against chilly weather, plant the tree near the south or southeast side of the house or building. Avoid planting near large shade trees, which may block too much light. Space the tree at least 12 feet away from structures and other trees.
Ponderosa lemon isn't particular about soil so long as it is well draining. Problems may occur in heavy clay soils.
Boost growth by fertilizing in early spring and late fall with a specially formulated citrus fertilizer, such as a 9-12-12 fertilizer spike. With a hammer, drive spikes down into the soil in a circle around the tree, keeping the circle at least 30 inches away from the trunk. When the spike is level with the soil, remove the cap and hammer until the spike is 2 inches or more below the surface. Use 2 spikes for a tree with a trunk diameter of 1 or 2 inches, and up to 5 spikes for a tree with a trunk diameter of 5 inches. Store unused spikes away from children and pets.
Ponderosa lemon can benefit from occasional irrigation, though excessive watering can lead to rot and prevent oxygen from reaching the roots. During dry periods, water your Ponderosa lemon every 2 to 6 weeks with 3 to 6 inches of water, aiming to wet the top 3 feet of soil. Avoid getting the trunk wet, as this encourages diseases such as gummosis.
Retain moisture by layering 2 to 3 inches of organic material such as wood chips or compost over the soil, keeping the mulch at least 12 inches away from the trunk.
Grow Indoors in Cool Climates
Gardeners in chillier climates can grown Ponderosa lemon indoors in a container. Purdue University notes that the tree is one of the citrus types best suited to growing indoors. Plant in a high-quality potting soil in a container with a hole in the bottom for drainage, and set the plant in front of a bright, south-facing window. Move tree outdoors in late spring or summer and move indoors when temperatures drop below 50 degrees Fahrenheit. Water deeply on a regular basis, re-watering when the soil has begun to dry out between waterings.
- Texas A&M Aggie Horticulture: Home Fruit Production -- Lemons
- Master Gardeners San Diego: Citrus for the Home Garden
- Tradewinds Fruit: Ponderosa Lemon: Citrus Limon 'Ponderosa'
- Purdue University: Growing Citrus Indoors In Cool Climates
- Missouri Botanical Garden: Citrus 'Ponderosa'
- University of California: Growing Citrus in Sacramento
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