Question — Does a plum tree need a cross-pollinator?
Answer —Many fruit trees need a cross-pollinator (that is another variety of the same type of fruit tree) in order to set fruit. Most apples, pears and sweet cherries (except ‘Stella’) need a cross-pollinator. For cross-pollination to occur, the trees need to be planted within 100 feet of each other and bloom at the same time.
Some fruit trees are self-pollinating (sometimes referred to as self-fruitful). These trees do not need pollination by another variety for successful fruit set; however, they often produce better when cross-pollinated by another variety. Most apricots, nectarines, peaches and sour cherries are self-pollinating trees.
Plums are a mixed bag. Japanese plums (Prunus salicina) (including ‘Beauty,’ ‘Methley,’ and ‘Shiro’) need a cross pollinator. European plums (Prunus domestica) (including ‘Italian,’ ‘Mirabelle,’ and ‘Stanley’) are self-pollinating.
European and Japanese plums typically cannot pollinate each other because their bloom times do not overlap; European plums bloom much later than Japanese plums.
Q — Recommendations for planting a vegetable garden usually suggest that crops be rotated. What is crop rotation?
A — Crop rotation is the practice of growing crops from different plant families in succession in a particular spot in your garden.
The main reason to rotate crops is to limit the establishment of plant pests and diseases but there are other benefits. Because different crops have roots at different soil depths and use certain soil nutrients in higher amounts than other crops, crop rotation also helps maintain soil fertility and prevent depletion of important nutrients. This also helps keep plants healthier and better able to counter pests and diseases.
Most sources recommend a three to four year rotation cycle that is waiting three or four years before planting a crop from the same family in the same place again. This length of crop rotation can be difficult to achieve in small gardens, but even changing plant families from year to year is helpful.
You can find information on plant families online but here are the most common ones planted in the vegetable garden.
• Tomato family (Solanaceae) (eggplant, peppers, potatoes and tomatoes)
• Cabbage family (Brassicaceae) (arugula, broccoli, Brussels sprouts, cabbage, cauliflower, kale, kohlrabi, mustards, radishes and turnips)
• Beet-spinach family (Chenopodiaceae) (beets, chard and spinach)
• Pea family (Leguminosae, also known as Fabaceae) (beans and peas)
• Carrot family (Umbelliferae, also known as Apiaceae) (carrots, celery, cilantro, dill, fennel, parsley and parsnips)
• Squash family (Cucurbitaceae) (cucumbers, melons, pumpkins and summer and winter squash)
• Onion family (Amaryllidaceae) (chives, garlic, leeks, onions and shallots)
To help in planning crop rotations, keep a garden log or map as a reminder of where vegetables are planted each year. Be sure to include cover crops (such as clover) when determining your crop rotation cycle.
Have more questions?
Visit a Clallam County Master Gardener Plant Clinic for gardening advice and help with garden problems. Plant Clinics are held from 9:30 a.m.-12:30 p.m. on Mondays at the Clallam County Courthouse in Port Angeles, and on Saturdays at the Master Gardener Demonstration Garden (2711 Woodcock Road) in Sequim.
You can also call the Master Gardener Helpline at 360-417-2514 and leave a message.
Jeanette Stehr-Green is a WSU-certified Clallam County Master Gardener.