If you’re gardening in zone 8, figuring out when to plant sweet potatoes is your first step to a great harvest. This guide covers the optimal timing for planting and all the details you need to succeed.
Sweet potatoes are a warm-season crop that love heat. Planting them at the right moment ensures they have a long, warm growing season to produce those tasty tubers. Getting the timing wrong can lead to disappointing results, so let’s get it right.
When to Plant Sweet Potatoes in Zone 8 – Optimal Timing for Planting
For most of zone 8, the ideal time to plant sweet potato slips is in the spring, after the danger of frost has completely passed and the soil has warmed up. You should aim for a planting window between mid-April and late May.
The single most important factor is soil temperature. Sweet potatoes will not thrive in cold soil.
- Target Soil Temperature: A consistent 65°F (18°C) or warmer. Use a soil thermometer to check at a 4-inch depth.
- Air Temperature: Daytime temperatures should be reliably above 70°F, with warm nights.
- Last Frost Date: Always plant 2-4 weeks after your average last spring frost date.
Planting too early in cold, wet soil can cause slips to rot or just sit there without growing. It’s better to wait an extra week or two for genuine warmth than to jump the gun.
Understanding Your Zone 8 Climate
USDA Hardiness Zone 8 includes a range of climates, from the Pacific Northwest to the Southeast. This affects your specific timing.
- Zone 8a: Has average minimum temperatures of 10-15°F. Spring can be a bit slower to warm. Lean toward late April or May planting.
- Zone 8b: Has average minimums of 15-20°F. Soil warms earlier. You can often plant from mid-April onward.
Your microclimate matters too. A raised bed in full sun warms faster than a ground-level plot in partial shade. Observe your own garden’s conditions each year.
Preparing for Planting: Slips vs. Store-Bought
You don’t plant sweet potatoes from a seed packet. You grow them from “slips,” which are small rooted sprouts.
How to Grow Your Own Slips
Starting your own slips is economical and ensures variety. Begin about 6-8 weeks before your planned outdoor planting date.
- Choose a healthy, organic sweet potato from the store or one saved from last year’s harvest.
- Suspend it in a jar of water using toothpicks, with the bottom half submerged.
- Place it in a warm, bright spot (like a sunny windowsill).
- In a few weeks, sprouts (slips) will emerge from the top. When they are 6-10 inches tall with roots, gently twist them off.
- Place these slips in their own shallow water to develop stronger roots before planting.
Buying Quality Slips
If you buy slips, order from a reputable nursery. They will ship them at the correct time for your zone. Have your garden ready so you can plant them as soon as they arrive, as they are perishable.
Step-by-Step Garden Preparation
Sweet potatoes need loose, well-draining soil to form nice, large tubers. Heavy clay soil will result in small, misshapen potatoes.
- Choose a Sunny Site: Select a spot that gets at least 8 hours of full sun daily.
- Loosen the Soil: Dig or till the area to a depth of 10-12 inches. Break up any hard clumps.
- Amend the Soil: Mix in 2-4 inches of compost. Avoid high-nitrogen fertilizers, which promote leafy growth instead of tubers.
- Consider Mounds or Ridges: Forming raised rows about 8 inches high improves drainage and warms the soil faster, which is a big benefit in spring.
- Soil pH: Aim for a slightly acidic pH of 5.8 to 6.2. A simple test kit can tell you if you need to adjust it.
The Planting Process
Once your slips are rooted and the soil is warm, it’s time to plant.
- Water Slips: Give your slips a good drink before transplanting.
- Space Them Out: Plant slips 12-18 inches apart in a row. Rows should be 3-4 feet apart to give the vines room to spread.
- Plant Deeply: Bury the slip so that the rooted portion and about half of the stem are underground. Leaves should be above soil.
- Water Gently: Water thoroughly after planting to settle the soil around the roots.
Caring for Your Growing Sweet Potatoes
Sweet potatoes are relatively low-maintenance once established.
Watering Schedule
Provide about 1 inch of water per week. Consistent moisture is key early on. Reduce watering during the last 3-4 weeks before harvest to help the tubers cure and develop their sweetness.
Weeding and Mulching
Weed carefully early in the season, as the young plants don’t compete well. Once the vines begin to run, they’ll shade out most weeds. Applying a light straw mulch can help retain moisture and suppress weeds.
What Not to Do: Avoid Over-Fertilizing
As mentioned, too much nitrogen is a common mistake. If your soil is poor, a balanced, low-nitrogen fertilizer or some extra compost at planting is sufficient. They really don’t need much.
When to Harvest in Zone 8
Your planting date dictates your harvest. Sweet potatoes need 90 to 120 frost-free days to mature.
- For a mid-April planting, expect to harvest from late August through September.
- For a late May planting, harvest will be in October.
The best sign is when the leaves and vines start to yellow. Always harvest before your first fall frost, as frost can damage the tubers. Use a garden fork to carefully lift them from the soil.
Curing and Storage for Longevity
This step is crucial! Freshly dug sweet potatoes are not very sweet and their skin is delicate.
- Cure: After digging, let them dry in a shady spot for a few hours. Then place them in a warm (80-85°F), humid place for 10-14 days. A greenhouse or a table in a warm bathroom works.
- Store: After curing, store them in a cool (55-60°F), dark, and well-ventilated place. Properly cured and stored sweet potatoes can last for many months.
Common Problems and Solutions in Zone 8
- Root Rot: Caused by cold, wet soil. Solution: Wait for soil warmth and ensure excellent drainage.
- Wireworms or Grubs: These pests can bore into tubers. Rotating your crops each year helps prevent infestations.
- Deer or Voles: Deer may eat the vines; fencing is the best deterrent. Voles can attack tubers; raised beds can sometimes help.
FAQ: Sweet Potato Planting in Zone 8
Can I plant sweet potatoes in July in zone 8?
It’s generally to late for a main crop, as they won’t have enough days to mature before frost. However, you could try for a crop of smaller “baby” potatoes.
What are the best sweet potato varieties for zone 8?
Popular and reliable choices include ‘Beauregard’ (fast-maturing), ‘Georgia Jet’ (good for heavier soils), ‘Centennial’, and the white-fleshed ‘O’Henry’.
Can I grow sweet potatoes in containers?
Yes! Use a large container (at least 20 gallons) with excellent drainage. A fabric grow bag is a great option. The process and timing are the same.
How do I know if my soil is warm enough?
Invest in a soil thermometer. If you don’t have one, a old rule of thumb is to wait until the nighttime air temperatures feel comfortably warm for you to be outside—not just barely above freezing.
Is it possible to plant to early in zone 8?
Absolutely. A late cold snap or planting in soil below 60°F will shock the plants, stunting growth or killing them. Patience is key for the optimal timing for planting.
By following this schedule and tips, you’ll give your sweet potatoes the best possible start. The reward is a bountiful harvest of homegrown sweetness that stores for months. Remember, the wait for warm soil is always worth it.