Indoor seed starting can be a tough task, especially when you have so many options available at your disposal.
The answer to the million different questions in your head is simple: USDA Hardiness Zone Map. It will present you with the planting options you have available in your zone.
Let’s dive a little deeper into this and go over some solid planting options for each individual zone:
USDA Zones 1-3 (Cold Climates)
- Tomatoes: In zones 1-3, April is generally the best time to start tomato seeds indoors. Because outside conditions will be too chilly and unfavorable for growth, starting indoors and transplanting seedlings outdoors later in spring is a solid strategy.
- Peppers: Because peppers grow relatively slower compared to some of the other vegetables out there, starting seeds indoors early in wintertime is best.
- Cabbage: Cabbage you can start indoors early in April, and later in the month or early-May is generally the ideal time to move it outside when the risk of frost drops.
- Cauliflower: Cauliflower, like peppers, needs a comparatively longer growing season so it’s smart to start it early around April.
- Brussels Sprouts: Though Brussels sprouts do best in milder temperature conditions, giving them a cool start before the summer heat kicks in can be beneficial.
USDA Zones 4-5 (Cool Climates)
- Eggplant: Eggplant performs best in mild to warm temperatures, so planting outside in April definitely isn’t suitable. Start seeds indoors early, but wait till outside conditions turn favorable to transplant.
- Cucumbers: You can start your cucumbers in pots to give them a headstart. However, make sure the temperature is still cool and not warming up as, in that case, outdoor planting becomes a far better option.
- Pumpkins: Pumpkins are best transplanted when the nighttime temperature starts warming up. You want to start them early in April to protect them from frost damage, but make sure to time the transplantation right.
- Squash: Yes, both summer and winter squash varieties should be started indoors in zone 4-5 cool climates. This will result in better yields and safer long term growth without the danger of frost damage lingering overhead.
USDA Zones 6-7 (Mild Climates)
- Okra: Okra grows best in warmth, so starting indoors in April can help if outside conditions are unfavorable. However, if the heat has started setting in and the risk of frost has completely passed, there’s absolutely nothing wrong with outdoor planting.
- Melons: Melons, specifically watermelons and cantaloupes, need an early boost to grow to their fullest potential. In milder climates, you can start them early if you want, but I’d much rather plant them directly outdoors in April once the risk of frost has passed.
- Basil: Many are surprised to know that basil actually does pretty well in warmth. The fragrant herb should be planted around mid to late April, as that’s generally when mild climates provide the best growth opportunity.
USDA Zones 8-9 (Warm Climates)
- Peppers: Both hot and sweet pepper varieties prefer warm climates for the best growth. Warmth in these zones boosts early harvests and leads to fulfilling large yields.
- Tomatoes: Although tomatoes do grow well in cooler climates, warm conditions provide a second round for continuous harvesting. It’s a good idea to take advantage of varying climates and temperatures as it will most likely lead to well-rounded growth.
- Herbs: Herbs like parsley, cilantro, and oregano should be planted indoors and transplanted outside later, even if the climate is relatively warm. This is because herbs are extremely sensitive to cold and should be protected until complete warmth emerges.
USDA Zones 10-13 (Tropical & Hot Climates)
- Lettuce & Spinach: If you’re looking to start lettuce and spinach in April, it’s best to do so indoors as blasting heat is very likely to damage them. A cooler growing spot is ideal.
- Carrots: Start your carrot seeds around mid to late April in deep trays and transplant outside later to avoid extreme heat. Carrot has a reputation for growing well in cooler climates, so you just need to protect it from heat damage till conditions change.
- Microgreens: DO NOT plant microgreens outdoors around April in zones 10-13! They’re very susceptible to heat damage and should be protected at all costs. Start microgreens indoors for fresh, healthy, and easy harvests.
