You generally do not need to give up leafy greens on warfarin, but the amount of vitamin K you eat has to stay steady week to week, because suddenly loading up on greens or cutting them out can shift your INR toward either a clotting or a bleeding risk.
Warfarin is a "vitamin K antagonist" — it thins the blood by interfering with how your body uses vitamin K to form clots, and your dose is set against your usual diet. Leafy green vegetables (kale, spinach, collard/mustard/turnip greens, broccoli, Brussels sprouts, cabbage, lettuce, parsley) are the richest dietary source of vitamin K, so the amount you eat has to stay balanced against your dose. Per the CUH NHS anticoagulation leaflet and MedlinePlus, significantly increasing your vitamin K intake makes warfarin work less (INR drops, clot risk rises) while significantly decreasing it makes warfarin work more (INR rises, bleeding risk rises). That is why the guidance from every source is consistency, not elimination: MedlinePlus and CUH both state you do not need to avoid these foods, only keep your intake steady day-to-day and week-to-week and talk to your prescriber before any diet change. The labels also caution against eating unusually large amounts of green leafy vegetables, so "consistent" means a sensible steady amount, not loading up.
Watch for signs your INR has drifted toward over-thinning: unusual bruising, nosebleeds, bleeding gums, cuts that will not stop, pink/red/dark-brown urine, red or black/tarry stools, coughing or vomiting blood or "coffee-ground" material, heavier-than-normal menstrual bleeding, and headache, dizziness, or weakness (these are the exact warning signs MedlinePlus lists). Too much vitamin K (under-thinning) has no symptoms you can feel — it shows up only as a low INR and raised clot risk, which is why keeping your regular INR blood tests matters. There is no hours-based "space it apart" timing rule here — the sources give none, so none should be applied; the relevant timeframe is steady day-to-day and week-to-week intake. Talk to your prescriber or anticoagulation clinic BEFORE any major diet change — a weight-loss diet, going vegetarian/vegan, or adding daily green smoothies, green tea, or supplements — and call them if you are sick and cannot eat normally, or have ongoing vomiting, diarrhea, or fever, since that also changes your intake. Tell every provider, including your dentist, that you take warfarin.
This is general reference, not medical advice, and not a guarantee of safety. Interactions depend on your doses, health conditions, and other medicines. Always confirm with your pharmacist or doctor before combining products, and follow the dosing on each label.