Have limited space in your garden? Consider planting potatoes

Charles M. asks: I have limited space in my garden beds but would like to grow potatoes. Can I plant them in a container?

Answer: Yes! Potatoes are well-suited for growing in containers. One option is a grow bag, a fabric pot that is easy to move for optimal sun. The porous fabric allows the bag to breathe, which can prevent overheating and overwatering. March is an ideal month to plant potatoes; for a continuous harvest, you can plant them every month from March to August.

Buy seed potatoes from a nursery that displays a Certified Seed Potato tag, to ensure they are free of disease. Avoid grocery store potatoes; often they are treated with sprout inhibitor.

If you are new to potato cultivation, try a variety recommended on our Master Gardener website (bit.ly/3kjn6k8): ‘White Rose’ (high-yield, large; white waxy flesh with moist texture), Kennebec (high-yield, white flesh, stores well), ‘Norgold Russet’ (medium-yield, white flesh), ‘Red Lasoda’ (red skin, white flesh, stores well) and ‘Yukon Gold’ (gold flesh with dry texture).

If your seed potatoes are small, you can plant them whole. Cut larger seed potatoes into pieces weighing 1½ to 2 ounces. Make sure each piece has at least one eye. Then store the freshly cut pieces at room temperature for one to three days to allow the cut surfaces to dry and form a callus, which decreases rotting.

Potatoes grow best in well-drained, loose soil. A good potting soil or a mix of soil and compost works well. Add about 3 to 4 inches of soil to the bottom of each grow bag. Place four to six small or cut seed potatoes onto the soil. Then cover them with an additional 3 to 4 inches of soil.

When the plants reach about 4 inches tall, add more soil to cover. This is called “hilling” or “dirting.” Continue hilling as the plants grow until the bag is full. By covering the base of the plants as they grow, you prevent the potatoes from getting too much sun exposure, which can cause greening, a toxic condition.

Soil in a grow bag or container can dry out quickly. Regularly monitor the moisture content of the soil; it should feel moist, but not soggy. In the hottest part of the summer, you may have to water every day. Note that excessive watering may cause rotting. If the soil is alternately wet and dry, the potatoes may become rough and knobby.

Monitor your plants for pests such as the flea beetle and aphids. Hose off aphids with water or spray with an organic insecticidal soap. For a good reference on pest identification and control, go to bit.ly/3pPjjft.

Harvest your potatoes when their vines die, in late July or August, or approximately 90 to 120 days after planting. Carefully empty the bag, plants and soil to unearth your potato bounty. Brush off most of the soil, then store the potatoes in a cool, dark place.

What to do about weeds

Laura S. asks: How can I get rid of all the weeds sprouting in my yard? I don’t want to spray and don’t have time to pull.

Answer: You can use all of the paper grocery bags and home delivery boxes you’ve accumulated during COVID-19 to make “sheet mulch,” an easy and effective way to kill weeds while enriching your soil. Winter and early spring is a great time to use sheet mulch.

Weeds rule the plant kingdom for three reasons: weed seeds germinate easily when exposed to light, garden soil is teeming with weed seeds and weeds easily adapt to difficult conditions. Sheet mulching stops weed seeds from germinating by blocking them from the light.

To start sheet mulching your weeds, cover the ground with layers of overlapping paper bags, cardboard or newspaper. Cover the paper with 2 to 4 inches of mulch; wood chips and shredded leaves are great choices.

To reduce the risk of fire spreading, maintain a 5-foot border around your house of noncombustible rock, gravel or pavers. Make sure that area is free of flammable mulches, such as wood chips, straw or paper.

If you want to add plants after sheet mulching, push aside the top layer of mulch, expose the paper and cut an “X” large enough for your plant. Fold back the flaps, dig a hole and add your plant. When you’re done, lay the flaps back in place. You may have to trim them to make sure they don’t touch your new plant. Then, re-cover the paper with mulch. When mulching plants with woody stems, especially trees, leave a few inches of bare earth around the trunks.

What’s up with our Christmas camellia?

Donna A. asks: We fertilized our Christmas camellia several times leading up to Christmas with camellia food — and no buds. Zero! What’s up with that?

Answer: Unsuitable growing conditions or fertilizing at the wrong time of year are possible reasons your camellia did not bloom.

Our Mediterranean climate is not ideal for camellias, although they can flourish if their growth requirements are met. Camellias, including various cultivars known as Christmas camellias, originated in eastern and southern Asia, where they thrive beneath cool, humid forest canopies in well-drained acidic soils that are rich in organic matter. Camellias do best when sheltered from full sun and dry winds.

While camellias are somewhat drought-tolerant, a lack of water in late summer, when buds are forming, may limit the following season’s bloom. Overwatering may also inhibit blooms. An early or severe frost can kill maturing flower buds, while poor soil conditions may inhibit bud formation.

To promote bud and flower formation, the best time to apply fertilizer is in the spring and summer. We recommend an organic fertilizer formulated for acid-loving plants, applied in accordance with package directions.

If it is difficult to replicate prime growing conditions for camellias in your garden, don’t despair. See our list of recommended plants for Sonoma County at bit.ly/3kmSQET.

For more information on this week’s topics, follow these links:

Mulch, a Gardener’s Best Friend: bit.ly/3pMktIp

Good Gardening Practices: bit.ly/3uqq5eW

Year-round Food Gardening: bit.ly/3sn1q9y

Vegetable Planting Summary: bit.ly/3dGBXnh

Contributors to this week’s column were Janet Bair, Kim Roberts and Debbie Westrick.

The UC Master Gardener Program of Sonoma County (sonomamg.ucanr.edu) provides environmentally sustainable, science-based horticultural information to Sonoma County home gardeners. Send your gardening questions to scmgpd@gmail.com. The Master Gardeners will answer in the newspaper only questions selected for this column. Other questions may be directed to their Information Desk: 707-565-2608 or mgsonoma@ucanr.edu.